1
|
Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
Collapse
Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| |
Collapse
|
2
|
Talbot NP, Cheng H, Hanstock H, Smith TG, Dorrington KL, Robbins PA. Hypoxic pulmonary vasoconstriction does not limit maximal exercise capacity in healthy volunteers breathing 12% oxygen at sea level. Physiol Rep 2024; 12:e15944. [PMID: 38366054 PMCID: PMC10873163 DOI: 10.14814/phy2.15944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 02/18/2024] Open
Abstract
Maximal exercise capacity is reduced at altitude or during hypoxia at sea level. It has been suggested that this might reflect increased right ventricular afterload due to hypoxic pulmonary vasoconstriction. We have shown previously that the pulmonary vascular sensitivity to hypoxia is enhanced by sustained isocapnic hypoxia, and inhibited by intravenous iron. In this study, we tested the hypothesis that elevated pulmonary artery pressure contributes to exercise limitation during acute hypoxia. Twelve healthy volunteers performed incremental exercise tests to exhaustion breathing 12% oxygen, before and after sustained (8-h) isocapnic hypoxia at sea level. Intravenous iron sucrose (n = 6) or saline placebo (n = 6) was administered immediately before the sustained hypoxia. In the placebo group, there was a substantial (12.6 ± 1.5 mmHg) rise in systolic pulmonary artery pressure (SPAP) during sustained hypoxia, but no associated fall in maximal exercise capacity breathing 12% oxygen. In the iron group, the rise in SPAP during sustained hypoxia was markedly reduced (3.4 ± 1.0 mmHg). There was a small rise in maximal exercise capacity following sustained hypoxia within the iron group, but no overall effect of iron, compared with saline. These results do not support the hypothesis that elevated SPAP inhibits maximal exercise capacity during acute hypoxia in healthy volunteers.
Collapse
Affiliation(s)
- Nick P. Talbot
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Hung‐Yuan Cheng
- Translational Health Sciences, Bristol Medical SchoolUniversity of BristolBristolUK
| | - Helen Hanstock
- Swedish Winter Sports Research Centre, Department of Health SciencesMid Sweden UniversityÖstersundSweden
| | - Thomas G. Smith
- Centre for Human and Applied Physiological SciencesKing's College LondonLondonUK
- Guy's and St Thomas' NHS Foundation TrustLondonUK
| | | | - Peter A. Robbins
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| |
Collapse
|
3
|
O'Connor AE, Hatzenbiler DM, Flom LT, Bobadilla AC, Bruns DR, Schmitt EE. Physiological and Morphometric Differences in Resident Moderate-Altitude vs. Sea-Level Mice. Aerosp Med Hum Perform 2023; 94:887-893. [PMID: 38176033 PMCID: PMC10826331 DOI: 10.3357/amhp.6234.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
INTRODUCTION: High-altitude [>2400 m (7874 ft)] acclimatization has been well studied with physiological adaptations like reductions in body weight and exercise capacity. However, despite the significance of moderate altitude [MA, 1524-2438 m (5000-8000 ft)], acclimatization at this elevation is not well described. We aimed to investigate differences in mice reared at MA compared to sea level (SL). We hypothesized that MA mice would be smaller and leaner and voluntarily run less than SL mice.METHODS: C57BL/6 mice reared for at least three generations in Laramie, WY [2194 m (7198 ft), MA], were compared to C57BL/6J mice from Bar Harbor, ME [20 m (66 ft), SL]. We quantified body composition and exercise outputs as well as cardiopulmonary morphometrics. Subsets of MA and SL mice were analyzed to determine differences in neuronal activation after exercise.RESULTS: When body weight was normalized to tibia length, SL animals weighed 1.30 g ⋅ mm-1 while MA mice weighed 1.13 g · mm-1. Total fat % and trunk fat % were higher in MA mice with values of 41% and 39%, respectively, compared to SL mice with values of 28% and 26%, respectively. However, no differences were noted in leg fat %. MA animals had higher heart mass (119 mg) and lower lung mass (160 mg) compared to SL mice heart mass (100 mg) and lung mass (177 mg). MA mice engaged in about 40% less voluntary wheel-running activity than SL animals.DISCUSSION: Physiological differences are apparent between MA and SL mice, prompting a need to further understand larger scale implications of residence at moderate altitude.O'Connor AE, Hatzenbiler DM, Flom LT, Bobadilla A-C, Bruns DR, Schmitt EE. Physiological and morphometric differences in resident moderate-altitude vs. sea-level mice. Aerosp Med Hum Perform. 2023; 94(12):887-893.
Collapse
|
4
|
Sun Y, Zhang C, He B, Wang L, Tian D, Kang Z, Guo Y, Zhang Y, Dingda D, Zhang Q, Gao F. 7.0T cardiac magnetic resonance imaging of right ventricular function in rats with high-altitude deacclimatization. ANNALS OF TRANSLATIONAL MEDICINE 2023; 11:116. [PMID: 36819537 PMCID: PMC9929826 DOI: 10.21037/atm-22-5991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/10/2023] [Indexed: 01/31/2023]
Abstract
Background High-altitude deacclimatization syndrome (HADAS) is a severe public health issue. The study of the changes in right ventricular function caused by high-altitude deacclimatization (HADA) is of great significance for the prevention and treatment of HADAS. Methods Six-week-old, male Sprague Dawley (SD) rats were randomly divided into the plain, plateau and the HADA group. Rats in the plateau and plain group were exposed to altitudes of 3,850 and 360 m, respectively, for 12 weeks. Rats in HADA group were exposed to the plateau altitude of 3,850 m for 12 weeks and subsequently transported to the plain altitude of 360 m for 4 weeks. Right ventricular ejection fraction (RVEF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and myocardial strain parameters, including the global longitudinal strain (GLS), global radial strain (GRS), and global circumferential strain (GCS), were evaluated by 7.0T cardiac magnetic resonance (CMR). The levels of red blood cell (RBC), hemoglobin (HGB), and hematocrit (HCT) in the blood were measured, and hematoxylin-eosin (HE) staining was used to observe the pathological changes in the myocardium. Results In rats in the plateau group, the right ventricular fibrous space was slightly widened, and partial focal steatosis were observed. However, in the HADA group, only a few focal steatoses were found. Rats in the plateau group had elevated levels of RBC, HGB and HCT, increased right ventricular end-diastolic volume (RVEDV), right ventricular end-systolic volume (RVESV) and right ventricular stroke volume (RVSV), and decreased right ventricular global longitudinal strain (RVGLS), right ventricular global circumferential strain (RVGCS), and right ventricular global radial strain (RVGRS) compared to rats in the plain group (P<0.001). The RVEDV, RVGCS, and RVGRS in the HADA group basically returned to the plain state. Interestingly, the RVESV in the HADA group was higher, while the RVSV, RVEF, and RVGLS were lower than those in the other two groups. Conclusions After 12 weeks of exposure to high-altitude environment, there were some pathological changes and the whole contractile strain of the right ventricle was observed. Some pathological changes in the myocardial tissue and stroma recovered after returning to the plain for 4 weeks. However, the right ventricular systolic function and strain did not recover completely.
Collapse
Affiliation(s)
- Yanqiu Sun
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Chenhong Zhang
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Bo He
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Lei Wang
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| | - Dengfeng Tian
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Zhiqiang Kang
- Department of Radiology, Qinghai Provincial People’s Hospital, Xining, China
| | - Yong Guo
- Department of Radiology, Yushu People’s Hospital, Yushu, China
| | - Yonghai Zhang
- Department of Radiology, The Fifth People’s Hospital of Qinghai Province, Xining, China
| | - Duojie Dingda
- Department of Radiology, Yushu People’s Hospital, Yushu, China
| | - Qiang Zhang
- Department of Neurosurgery, Qinghai Provincial People’s Hospital, Xining, China
| | - Fabao Gao
- Department of Radiology, West China Hospital of Sichuan University, Chengdu, China
| |
Collapse
|
5
|
Doutreleau S, Ulliel-Roche M, Hancco I, Bailly S, Oberholzer L, Robach P, Brugniaux JV, Pichon A, Stauffer E, Perger E, Parati G, Verges S. Cardiac remodelling in the highest city in the world: effects of altitude and chronic mountain sickness. Eur J Prev Cardiol 2022; 29:2154-2162. [PMID: 35929776 DOI: 10.1093/eurjpc/zwac166] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 07/20/2022] [Accepted: 08/03/2022] [Indexed: 01/11/2023]
Abstract
AIMS A unique Andean population lives in the highest city of the world (La Rinconada, 5100 m, Peru) and frequently develops a maladaptive syndrome, termed chronic mountain sickness (CMS). Both extreme altitude and CMS are a challenge for the cardiovascular system. This study aims to evaluate cardiac remodelling and pulmonary circulation at rest and during exercise in healthy and CMS highlanders. METHODS AND RESULTS Highlanders living permanently at 3800 m (n = 23) and 5100 m (n = 55) with (n = 38) or without CMS (n = 17) were compared with 18 healthy lowlanders. Rest and exercise echocardiography were performed to describe cardiac remodelling, pulmonary artery pressure (PAP), and pulmonary vascular resistance (PVR). Total blood volume (BV) and haemoglobin mass were determined in all people. With the increase in the altitude of residency, the right heart dilated with an impairment in right ventricle systolic function, while the left heart exhibited a progressive concentric remodelling with Grade I diastolic dysfunction but without systolic dysfunction. Those modifications were greater in moderate-severe CMS patients. The mean PAP was higher both at rest and during exercise in healthy highlanders at 5100 m. The moderate-severe CMS subjects had a higher PVR at rest and a larger increase in PAP during exercise. The right heart remodelling was correlated with PAP, total BV, and SpO2. CONCLUSION Healthy dwellers at 5100 m exhibit both right heart dilatation and left ventricle concentric remodelling with diastolic dysfunction. Those modifications are even more pronounced in moderate-severe CMS subjects and could represent the limit of the heart's adaptability before progression to heart failure.
Collapse
Affiliation(s)
- Stéphane Doutreleau
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| | - Mathilde Ulliel-Roche
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| | - Ivan Hancco
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| | - Sébastien Bailly
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| | - Laura Oberholzer
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Paul Robach
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France.,National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Julien V Brugniaux
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| | - Aurélien Pichon
- Laboratoire MOVE EA 6314, Faculté des Sciences du Sport, Université de Poitiers, Poitiers, France
| | - Emeric Stauffer
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team 'Vascular Biology and Red Blood Cell', Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
| | - Elisa Perger
- Istituto Auxologico Italiano, IRCCS, Department of Cardiovascular, Neural and Metabolic Sciences, San Luca Hospital, Milan, Italy
| | - Gianfranco Parati
- Department of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy
| | - Samuel Verges
- HP2 Laboratory, Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, Avenue Kimberley, 38 434 Grenoble, France
| |
Collapse
|
6
|
Arrebola-Moreno AL, Casuso RA, Bejder J, Bonne TC, Breenfeldt Andersen A, Aragón-Vela J, Nordsborg NB, Huertas JR. Does Hypoxia and Stress Erythropoiesis Compromise Cardiac Function in Healthy Adults? A Randomized Trial. SPORTS MEDICINE - OPEN 2022; 8:137. [PMID: 36334130 PMCID: PMC9637068 DOI: 10.1186/s40798-022-00531-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 10/20/2022] [Indexed: 11/07/2022]
Abstract
OBJECTIVES To investigate whether recombinant human erythropoietin (rHuEPO) injections during an altitude training camp impact heart function. METHODS Thirty (12 women) moderately trained subjects stayed at 2320 m altitude for 4 weeks while training. Subjects were randomized to placebo (isotonic saline) or rHuEPO (20 IU/kg body weight) i.v. injections. Transthoracic echocardiography imaging was acquired 3 days after arrival to altitude and prior to the first placebo or rHuEPO injection as well as one day after the last rHuEPO injection three weeks later. RESULTS rHuEPO did not alter cardiovascular morphology parameters, systolic or diastolic function. In the placebo group, altitude exposure improved left ventricle (LV) systolic function due to an increased twist angle but rHuEPO had no additional effects. Pulmonary arterial systolic pressure was unaffected in either group. Notably, rHuEPO hampered LV untwist rate without affecting LV early filling. CONCLUSION rHuEPO provided during mild altitude exposure does not cause any major effects on heart function. The observed alteration in LV untwist induced by rHuEPO is unlikely to have a meaningful clinical effect. Trial Registration Registered on www. CLINICALTRIALS gov (NCT04227665).
Collapse
Affiliation(s)
| | - Rafael A. Casuso
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain ,grid.449008.10000 0004 1795 4150Department of Health Sciences, Universidad Loyola Andalucía, Sevilla, Spain
| | - Jacob Bejder
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Thomas Christian Bonne
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Andreas Breenfeldt Andersen
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Jerónimo Aragón-Vela
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain
| | - Nikolai B. Nordsborg
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Jesús R. Huertas
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain
| |
Collapse
|
7
|
Rieger MG, Tallon CM, Perkins DR, Smith KJ, Stembridge M, Piombo S, Radom-Aizik S, Cooper DM, Ainslie PN, McManus AM. Cardiopulmonary and cerebrovascular acclimatization in children and adults at 3800 m. J Physiol 2022; 600:4849-4863. [PMID: 36165275 DOI: 10.1113/jp283419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 09/20/2022] [Indexed: 12/24/2022] Open
Abstract
Maturational differences exist in cardiopulmonary and cerebrovascular function at sea-level, but the impact of maturation on acclimatization responses to high altitude is unknown. Ten children (9.8 ± 2.5 years) and 10 adults (34.7 ± 7.1 years) were assessed at sea-level (BL), 3000 m and twice over 4 days at 3800 m (B1, B4). Measurements included minute ventilation ( V ̇ E ${\dot{V}}_{\rm{E}}$ ), end-tidal partial pressures of oxygen ( P ETO 2 ${P}_{{\rm{ETO}}_{\rm{2}}}$ ) and carbon dioxide, echocardiographic assessment of pulmonary artery systolic pressure (PASP) and stroke volume (SV) and ultrasound assessment of blood flow through the internal carotid and vertebral arteries was performed to calculate global cerebral blood flow (gCBF). At 3000 m, V ̇ E ${\dot{V}}_{\rm{E}}$ was increased from BL by 19.6 ± 19.1% (P = 0.031) in children, but not in adults (P = 0.835); SV was reduced in children (-11 ± 13%, P = 0.020) but not adults (P = 0.827), which was compensated for by a larger increase in heart rate in children (+26 beats min-1 vs. +13 beats min-1 , P = 0.019). Between B1 and B4, adults increased V ̇ E ${\dot{V}}_{\rm{E}}$ by 38.5 ± 34.7% (P = 0.006), while V ̇ E ${\dot{V}}_{\rm{E}}$ did not increase further in children. The rise in PASP was not different between groups; however, ∆PASP from BL was related to ∆ P ETO 2 ${P}_{{\rm{ETO}}_{\rm{2}}}$ in adults (R2 = 0.288, P = 0.022), but not children. At BL, gCBF was 43% higher in children than adults (P = 0.017), and this difference was maintained at high altitude, with a similar pattern and magnitude of change in gCBF between groups (P = 0.845). Despite V ̇ E ${\dot{V}}_{\rm{E}}$ increasing in children but not adults at a lower altitude, the pulmonary vascular and cerebrovascular responses to prolonged hypoxia are similar between children and adults. KEY POINTS: Children have different ventilatory and metabolic requirements from adults, which may present differently in the pulmonary and cerebral vasculature upon ascent to high altitude. Children (ages 7-14) and adults (ages 23-44) were brought from sea level to high altitude (3000 to 3800 m) and changes in ventilation, pulmonary artery systolic pressure (PASP) and cerebral blood flow (CBF) were assessed over 1 week. Significant increases in ventilation and decreases in left ventricle stroke volume were observed at a lower altitude in children than adults. PASP and CBF increased by a similar relative amount between children and adults at 3800 m. These results help us better understand age-related differences in compensatory responses to prolonged hypoxia in children, despite similar changes in pulmonary artery pressure and CBF between children and adults.
Collapse
Affiliation(s)
- M G Rieger
- Centre for Heart, Lung & Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| | - C M Tallon
- Centre for Heart, Lung & Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| | - D R Perkins
- Cardiff School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, UK.,Youth Physical Development Centre, Cardiff School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - K J Smith
- Cerebrovascular Health, Exercise, and Environmental Research Sciences, University of Victoria, Victoria, British Columbia, Canada
| | - M Stembridge
- Cardiff School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, UK.,Youth Physical Development Centre, Cardiff School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - S Piombo
- Pediatric Exercise and Genomics Research Center, University of California Irvine School of Medicine, Irvine, CA, USA
| | - S Radom-Aizik
- Pediatric Exercise and Genomics Research Center, University of California Irvine School of Medicine, Irvine, CA, USA
| | - D M Cooper
- Pediatric Exercise and Genomics Research Center, University of California Irvine School of Medicine, Irvine, CA, USA
| | - P N Ainslie
- Centre for Heart, Lung & Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| | - A M McManus
- Centre for Heart, Lung & Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| |
Collapse
|
8
|
Williams AM, Levine BD, Stembridge M. A change of heart: mechanisms of cardiac adaptation to acute and chronic hypoxia. J Physiol 2022; 600:4089-4104. [PMID: 35930370 PMCID: PMC9544656 DOI: 10.1113/jp281724] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 07/21/2022] [Indexed: 11/20/2022] Open
Abstract
Over the last 100 years, high‐altitude researchers have amassed a comprehensive understanding of the global cardiac responses to acute, prolonged and lifelong hypoxia. When lowlanders are exposed to hypoxia, the drop in arterial oxygen content demands an increase in cardiac output, which is facilitated by an elevated heart rate at the same time as ventricular volumes are maintained. As exposure is prolonged, haemoconcentration restores arterial oxygen content, whereas left ventricular filling and stroke volume are lowered as a result of a combination of reduced blood volume and hypoxic pulmonary vasoconstriction. Populations native to high‐altitude, such as the Sherpa in Asia, exhibit unique lifelong or generational adaptations to hypoxia. For example, they have smaller left ventricular volumes compared to lowlanders despite having larger total blood volume. More recent investigations have begun to explore the mechanisms underlying such adaptive responses by combining novel imaging techniques with interventions that manipulate cardiac preload, afterload, and/or contractility. This work has revealed the contributions and interactions of (i) plasma volume constriction; (ii) sympathoexcitation; and (iii) hypoxic pulmonary vasoconstriction with respect to altering cardiac loading, or otherwise preserving or enhancing biventricular systolic and diastolic function even amongst high altitude natives with excessive erythrocytosis. Despite these advances, various areas of investigation remain understudied, including potential sex‐related differences in response to high altitude. Collectively, the available evidence supports the conclusion that the human heart successfully adapts to hypoxia over the short‐ and long‐term, without signs of myocardial dysfunction in healthy humans, except in very rare cases of maladaptation.
![]()
Collapse
Affiliation(s)
- Alexandra M Williams
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| |
Collapse
|
9
|
Chen X, Liu B, Deng Y, Yang F, Wang W, Lin X, Yu L, Pu H, Zhang P, Li Z, Zhong Q, Jia Q, Li Y, Wang X, Chen W, Burkhoff D, He K. Cardiac Adaptation to Prolonged High Altitude Migration Assessed by Speckle Tracking Echocardiography. Front Cardiovasc Med 2022; 9:856749. [PMID: 35677688 PMCID: PMC9167963 DOI: 10.3389/fcvm.2022.856749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 04/06/2022] [Indexed: 12/01/2022] Open
Abstract
Objective Exposure to high altitudes represents physiological stress that leads to significant changes in cardiovascular properties. However, long-term cardiovascular adaptions to high altitude migration of lowlanders have not been described. Accordingly, we measured changes in cardiovascular properties following prolonged hypoxic exposure in acclimatized Han migrants and Tibetans. Methods Echocardiographic features of recently adapted Han migrant (3–12 months, n = 64) and highly adapted Han migrant (5–10 years, n = 71) residence in Tibet (4,300 m) using speckle tracking echocardiography were compared to those of age-matched native Tibetans (n = 75) and Han lowlanders living at 1,400 m (n = 60). Results Short-term acclimatized migrants showed increased estimated pulmonary artery systolic pressure (PASP) (32.6 ± 5.1 mmHg vs. 21.1 ± 4.2 mmHg, p < 0.05), enlarged right ventricles (RVs), and decreased fractional area change (FAC) with decreased RV longitudinal strain (−20 ± 2.8% vs. −25.5 ± 3.9%, p < 0.05). While left ventricular ejection fraction (LVEF) was preserved, LV diameter (41.7 ± 3.1 mm vs. 49.7 ± 4.8 mm, p < 0.05) and LV longitudinal strain (−18.8 ± 3.2% vs. −22.9 ± 3.3%, p < 0.05) decreased. Compared with recent migrants, longer-term migrants had recovered RV structure and functions with slightly improved RV and LV longitudinal strain, though still lower than lowlander controls; LV size remained small with increased mass index (68.3 ± 12.7 vs. 59.3 ± 9.6, p < 0.05). In contrast, native Tibetans had slightly increased PASP (26.1 ± 3.4 mmHg vs. 21.1 ± 4.2 mmHg, p < 0.05) with minimally altered cardiac deformation compared to lowlanders. Conclusion Right ventricular systolic function is impaired in recent (<1 year) migrants to high altitudes but improved during the long-term dwelling. LV remodeling persists in long-term migrants (>5 years) but without impairment of LV systolic or diastolic function. In contrast, cardiac size, structure, and function of native Tibetans are more similar to those of lowland dwelling Hans.
Collapse
Affiliation(s)
- Xu Chen
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Bohan Liu
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Yujiao Deng
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Feifei Yang
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Wenjun Wang
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Xixiang Lin
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Liheng Yu
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Haitao Pu
- BioMind Technology, Zhongguancun Medical Engineering Center, Beijing, China
| | - Peifang Zhang
- BioMind Technology, Zhongguancun Medical Engineering Center, Beijing, China
| | - Zongren Li
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Qin Zhong
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Qian Jia
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Yao Li
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Xiao Wang
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
| | - Wei Chen
- Department of Ultrasound Diagnosis, The Seventh Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Daniel Burkhoff
- Cardiovascular Research Foundation, New York, NY, United States
| | - Kunlun He
- Beijing Key Laboratory for Precision Medicine of Chronic Heart Failure, Key Laboratory of Ministry of Industry and Information Technology of Biomedical Engineering and Translational Medicine, Translational Medicine Research Center, Medical Artificial Intelligence Research Center, Chinese PLA General Hospital, Beijing, China
- *Correspondence: Kunlun He
| |
Collapse
|
10
|
Liu G, Zhao L, Xu Q, Lang M, Xiao R. Cardiac adaptation to high altitudes after short- and long-term exposure among Chinese Han lowlanders. Echocardiography 2022; 39:465-472. [PMID: 35118707 DOI: 10.1111/echo.15317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 10/25/2021] [Accepted: 01/25/2022] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Short-term, high altitude (HA) exposure raises pulmonary artery systolic pressure (PASP) and decreases left ventricular volumes. However, relatively little is known of the long-term cardiac consequences of prolonged exposure in Chinese Han lowlanders, a highly adapted HA population. AIMS We studied cardiac structure and function by echocardiography to investigate short-term adaptation and potential long-term cardiac remodeling. METHODS This study included 301 healthy subjects of short-term exposure (STE), acclimatized Chinese Han lowlanders (AL) at HA, native Tibetans (NT), and sea level residents (SLR) with 75, 77, 69, and 80 participants, respectively. All groups underwent standard echocardiography. RESULTS Compared with SLR, systolic blood pressure (SBP) and heart rate of STE and AL did not significantly increase following HA exposure, but SBP in STE was lower than AL. In lowlanders, HA exposure enlarged right heart and pulmonary artery (PA), reduced left ventricular (LV) diastolic function. This decrease in LV diastolic function increased with exposure time. Compared with SLR, ejection fraction did not change significantly in STE, but decreased in AL. Interventricular septal end-diastolic thickness (IVSd) increased both in STE and AL compared with SLR. Compared with NT, AL population had higher SBP and the greater diameter of PA. CONCLUSIONS In Chinese Han lowlanders, exposure to HA enlarged right ventricle and decreased the diastolic function of LV. LV systolic function was preserved after short-term HA exposure but decreased after long-term HA exposure. It was possible to speculate that ethnicity contributed to the observed difference in heart.
Collapse
Affiliation(s)
- Guyue Liu
- Department of Cardiology, Chengdu Fifth People's Hospital, Sichuan, China.,Department of Ultrasound, Chengdu Office Hospital of Tibet Autonomous Region People's Government, Sichuan, China
| | - Liming Zhao
- Department of Cardiology, Chengdu Office Hospital of Tibet Autonomous Region People's Government, Sichuan, China
| | - Qing Xu
- Department of Ultrasound, Chengdu Office Hospital of Tibet Autonomous Region People's Government, Sichuan, China
| | - Mingjian Lang
- Department of Cardiology, Chengdu Fifth People's Hospital, Sichuan, China
| | - Rong Xiao
- Department of Ultrasound, Chengdu Office Hospital of Tibet Autonomous Region People's Government, Sichuan, China
| |
Collapse
|
11
|
Mamazhakypov A, Sartmyrzaeva M, Kushubakova N, Duishobaev M, Maripov A, Sydykov A, Sarybaev A. Right Ventricular Response to Acute Hypoxia Exposure: A Systematic Review. Front Physiol 2022; 12:786954. [PMID: 35095556 PMCID: PMC8791628 DOI: 10.3389/fphys.2021.786954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/02/2021] [Indexed: 11/26/2022] Open
Abstract
Background: Acute hypoxia exposure is associated with an elevation of pulmonary artery pressure (PAP), resulting in an increased hemodynamic load on the right ventricle (RV). In addition, hypoxia may exert direct effects on the RV. However, the RV responses to such challenges are not fully characterized. The aim of this systematic review was to describe the effects of acute hypoxia on the RV in healthy lowland adults. Methods: We systematically reviewed PubMed and Web of Science and article references from 2005 until May 2021 for prospective studies evaluating echocardiographic RV function and morphology in healthy lowland adults at sea level and upon exposure to simulated altitude or high-altitude. Results: We included 37 studies in this systematic review, 12 of which used simulated altitude and 25 were conducted in high-altitude field conditions. Eligible studies reported at least one of the RV variables, which were all based on transthoracic echocardiography assessing RV systolic and diastolic function and RV morphology. The design of these studies significantly differed in terms of mode of ascent to high-altitude, altitude level, duration of high-altitude stay, and timing of measurements. In the majority of the studies, echocardiographic examinations were performed within the first 10 days of high-altitude induction. Studies also differed widely by selectively reporting only a part of multiple RV parameters. Despite consistent increase in PAP documented in all studies, reports on the changes of RV function and morphology greatly differed between studies. Conclusion: This systematic review revealed that the study reports on the effects of acute hypoxia on the RV are controversial and inconclusive. This may be the result of significantly different study designs, non-compliance with international guidelines on RV function assessment and limited statistical power due to small sample sizes. Moreover, the potential impact of other factors such as gender, age, ethnicity, physical activity, mode of ascent and environmental factors such as temperature and humidity on RV responses to hypoxia remained unexplored. Thus, this comprehensive overview will promote reproducible research with improved study designs and methods for the future large-scale prospective studies, which eventually may provide important insights into the RV response to acute hypoxia exposure.
Collapse
Affiliation(s)
- Argen Mamazhakypov
- Department of Internal Medicine, Excellence Cluster Cardio-Pulmonary Institute (CPI), Member of the German Center for Lung Research (DZL), Justus Liebig University of Giessen, Giessen, Germany
| | - Meerim Sartmyrzaeva
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyzstan
| | - Nadira Kushubakova
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyzstan
| | - Melis Duishobaev
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyzstan
| | - Abdirashit Maripov
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyzstan
| | - Akylbek Sydykov
- Department of Internal Medicine, Excellence Cluster Cardio-Pulmonary Institute (CPI), Member of the German Center for Lung Research (DZL), Justus Liebig University of Giessen, Giessen, Germany
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
| | - Akpay Sarybaev
- Department of Mountain and Sleep Medicine and Pulmonary Hypertension, National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyzstan
- *Correspondence: Akpay Sarybaev
| |
Collapse
|
12
|
Naryzhnaya NV, Maslov LN, Derkachev IA, Ma H, Zhang Y, Prasad NR, Singh N, Fu F, Pei JM, Sarybaev A, Sydykov A. The effect of adaptation to hypoxia on cardiac tolerance to ischemia/reperfusion. J Biomed Res 2022:1-25. [PMID: 37183617 PMCID: PMC10387748 DOI: 10.7555/jbr.36.20220125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The acute myocardial infarction (AMI) and sudden cardiac death (SCD), both associated with acute cardiac ischemia, are one of the leading causes of adult death in economically developed countries. The development of new approaches for the treatment and prevention of AMI and SCD remains the highest priority for medicine. A study on the cardiovascular effects of chronic hypoxia (CH) may contribute to the development of these methods. Chronic hypoxia exerts both positive and adverse effects. The positive effects are the infarct-reducing, vasoprotective, and antiarrhythmic effects, which can lead to the improvement of cardiac contractility in reperfusion. The adverse effects are pulmonary hypertension and right ventricular hypertrophy. This review presents a comprehensive overview of how CH enhances cardiac tolerance to ischemia/reperfusion. It is an in-depth analysis of the published data on the underlying mechanisms, which can lead to future development of the cardioprotective effect of CH. A better understanding of the CH-activated protective signaling pathways may contribute to new therapeutic approaches in an increase of cardiac tolerance to ischemia/reperfusion.
Collapse
|
13
|
Left ventricular mechanical, cardiac autonomic and metabolic responses to a single session of high intensity interval training. Eur J Appl Physiol 2021; 122:383-394. [PMID: 34738196 DOI: 10.1007/s00421-021-04840-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/26/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE High-intensity interval training (HIIT) produces significant health benefits. However, the acute physiological responses to HIIT are poorly understood. Therefore, we aimed to measure the acute cardiac autonomic, haemodynamic, metabolic and left ventricular mechanical responses to a single HIIT session. METHODS Fifty young, healthy participants completed a single HIIT session, comprising of three 30-s maximal exercise intervals on a cycle ergometer, interspersed with 2-min active recovery. Cardiac autonomics, haemodynamics and metabolic variables were measured pre-, during and post-HIIT. Conventional and speckle tracking echocardiography was used to record standard and tissue Doppler measures of left ventricular (LV) structure, function and mechanics pre- and post-HIIT. RESULTS Following a single HIIT session, there was significant post-exercise systolic hypotension (126 ± 13 to 111 ± 10 mmHg, p < 0.05), parallel to a significant reduction in total peripheral resistance (1640 ± 365 to 639 ± 177 dyne⋅s⋅cm5, p < 0.001) and significant increases in baroreceptor reflex sensitivity and baroreceptor effectiveness index (9.2 ± 11 to 24.8 ± 16.7 ms⋅mmHg-1 and 41.8 ± 28 to 68.8 ± 16.2, respectively) during recovery compared to baseline. There was also a significant increase in the low- to high-frequency heart rate variability ratio in recovery (0.7 ± 0.48 to 1.7 ± 1, p < 0.001) and significant improvements in left ventricular global longitudinal strain (- 18.3 ± 1.2% to - 29.2 ± 2.3%, p < 0.001), and myocardial twist mechanics (1.27 ± 0.72 to 1.98 ± 0.72°·cm-1, p = 0.028) post-HIIT compared to baseline. CONCLUSION A single HIIT session is associated with acute improvements in autonomic modulation, haemodynamic cardiovascular control and left ventricular function, structure and mechanics. The acute responses to HIIT provide crucial mechanistic information, which may have significant acute and chronic clinical implications.
Collapse
|
14
|
Stembridge M, Hoiland RL, Williams AM, Howe CA, Donnelly J, Dawkins TG, Drane A, Tymko MM, Gasho C, Anholm J, Simpson LL, Moore JP, Bailey DM, MacLeod DB, Ainslie PN. The influence of hemoconcentration on hypoxic pulmonary vasoconstriction in acute, prolonged, and lifelong hypoxemia. Am J Physiol Heart Circ Physiol 2021; 321:H738-H747. [PMID: 34448634 DOI: 10.1152/ajpheart.00357.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hemoconcentration can influence hypoxic pulmonary vasoconstriction (HPV) via increased frictional force and vasoactive signaling from erythrocytes, but whether the balance of these mechanism is modified by the duration of hypoxia remains to be determined. We performed three sequential studies: 1) at sea level, in normoxia and isocapnic hypoxia with and without isovolumic hemodilution (n = 10, aged 29 ± 7 yr); 2) at altitude (6 ± 2 days acclimatization at 5,050 m), before and during hypervolumic hemodilution (n = 11, aged 27 ± 5 yr) with room air and additional hypoxia [fraction of inspired oxygen ([Formula: see text])= 0.15]; and 3) at altitude (4,340 m) in Andean high-altitude natives with excessive erythrocytosis (EE; n = 6, aged 39 ± 17 yr), before and during isovolumic hemodilution with room air and hyperoxia (end-tidal Po2 = 100 mmHg). At sea level, hemodilution mildly increased pulmonary artery systolic pressure (PASP; +1.6 ± 1.5 mmHg, P = 0.01) and pulmonary vascular resistance (PVR; +0.7 ± 0.8 wu, P = 0.04). In contrast, after acclimation to 5,050 m, hemodilution did not significantly alter PASP (22.7 ± 5.2 vs. 24.5 ± 5.2 mmHg, P = 0.14) or PVR (2.2 ± 0.9 vs. 2.3 ± 1.2 wu, P = 0.77), although both remained sensitive to additional acute hypoxia. In Andeans with EE at 4,340 m, hemodilution lowered PVR in room air (2.9 ± 0.9 vs. 2.3 ± 0.8 wu, P = 0.03), but PASP remained unchanged (31.3 ± 6.7 vs. 30.9 ± 6.9 mmHg, P = 0.80) due to an increase in cardiac output. Collectively, our series of studies reveal that HPV is modified by the duration of exposure and the prevailing hematocrit level. In application, these findings emphasize the importance of accounting for hematocrit and duration of exposure when interpreting the pulmonary vascular responses to hypoxemia.NEW & NOTEWORTHY Red blood cell concentration influences the pulmonary vasculature via direct frictional force and vasoactive signaling, but whether the magnitude of the response is modified with duration of exposure is not known. By assessing the pulmonary vascular response to hemodilution in acute normobaric and prolonged hypobaric hypoxia in lowlanders and lifelong hypobaric hypoxemia in Andean natives, we demonstrated that a reduction in red cell concentration augments the vasoconstrictive effects of hypoxia in lowlanders. In high-altitude natives, hemodilution lowered pulmonary vascular resistance, but a compensatory increase in cardiac output following hemodilution rendered PASP unchanged.
Collapse
Affiliation(s)
- Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Department of Anesthesiology, Pharmacology, and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Faculty of Medicine, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Connor A Howe
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Joseph Donnelly
- Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Aimee Drane
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.,Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, California
| | - James Anholm
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, California
| | - Lydia L Simpson
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Wales, United Kingdom
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Wales, United Kingdom
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - David B MacLeod
- Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| |
Collapse
|
15
|
Steele AR, Tymko MM, Meah VL, Simpson LL, Gasho C, Dawkins TG, Williams AM, Villafuerte FC, Vizcardo-Galindo GA, Figueroa-Mujíca RJ, Ainslie PN, Stembridge M, Moore JP, Steinback CD. Global REACH 2018: Volume regulation in high-altitude Andeans with and without chronic mountain sickness. Am J Physiol Regul Integr Comp Physiol 2021; 321:R504-R512. [PMID: 34346722 DOI: 10.1152/ajpregu.00102.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The high-altitude maladaptation syndrome known as chronic mountain sickness (CMS) is characterized by polycythemia and is associated with proteinuria despite unaltered glomerular filtration rate. However, it remains unclear if indigenous highlanders with CMS have altered volume regulatory hormones. We assessed N-terminal pro-B-type natriuretic peptide (NT pro-BNP), plasma aldosterone concentration, plasma renin activity, kidney function (urinary microalbumin, glomerular filtration rate), blood volume, and estimated pulmonary artery systolic pressure (ePASP), in Andean males without (n=14; age=39±11) and with (n=10; age=40±12) CMS at 4330 meters (Cerro de Pasco, Peru). Plasma renin activity (non-CMS: 15.8±7.9 vs. CMS: 8.7±5.4 ng/ml; p=0.025) and plasma aldosterone concentration (non-CMS: 77.5±35.5 vs. CMS: 54.2±28.9 pg/ml; p=0.018) were lower in highlanders with CMS compared to non-CMS, while NT pro-BNP was not different between groups (non-CMS: 1394.9±214.3 vs. CMS: 1451.1±327.8 pg/ml; p=0.15). Highlanders had similar total blood volume (non-CMS: 90±15 vs. CMS: 103±18 ml • kg-1; p=0.071), but Andeans with CMS had greater total red blood cell volume (non-CMS: 46±10 vs. CMS 66±14 ml • kg-1; p<0.01) and smaller plasma volume (non-CMS 43±7 vs. CMS 35±5 ml • kg-1; p=0.03) compared to non-CMS. There were no differences in ePASP between groups (non-CMS 32±9 vs. CMS 31±8 mmHg; p=0.6). A negative correlation was found between plasma renin activity and glomerular filtration rate in both groups (group: r=-0.66; p<0.01; non-CMS: r=-0.60; p=0.022; CMS: r=-0.63; p=0.049). A smaller plasma volume in Andeans with CMS may indicate an additional CMS maladaptation to high-altitude, causing potentially greater polycythemia and clinical symptoms.
Collapse
Affiliation(s)
- Andrew R Steele
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada
| | - Michael M Tymko
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada
| | - Victoria L Meah
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Canada
| | - Lydia L Simpson
- Department of Sport Science, Division of Physiology, University of Innsbruck, Austria
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, CA, United States
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Alexandra Mackenzie Williams
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, Canada
| | - Francisco C Villafuerte
- Department of Biological and Physiological Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru
| | | | - Rómulo J Figueroa-Mujíca
- Department of Biological and Physiological Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, Kelowna, Canada
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, United Kingdom
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Canada
| |
Collapse
|
16
|
Chen R, Yang J, Liu C, Ke J, Gao X, Yang Y, Shen Y, Yuan F, He C, Cheng R, Lv H, Zhang C, Gu W, Tan H, Zhang J, Huang L. Blood pressure and left ventricular function changes in different ambulatory blood pressure patterns at high altitude. J Clin Hypertens (Greenwich) 2021; 23:1133-1143. [PMID: 33677845 PMCID: PMC8678730 DOI: 10.1111/jch.14235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 02/18/2021] [Accepted: 02/25/2021] [Indexed: 11/29/2022]
Abstract
Acute high‐altitude (HA) exposure induces physiological responses of the heart and blood pressure (BP). However, few studies have investigated the responses associated with dipper and non‐dipper BP patterns. In this prospective study, 72 patients underwent echocardiography and 24‐h ambulatory BP testing at sea level and HA. Patients were divided into dipper and non‐dipper groups according to BP at sea level. Acute HA exposure elevated 24‐h systolic and diastolic BP and increased BP variability, particularly in the morning. Moreover, acute exposure increased left ventricular torsion, end‐systolic elastance, effective arterial elastance, and untwisting rate, but reduced peak early diastolic velocity/late diastolic velocity and peak early diastolic velocity/early diastolic velocity, implying enhanced left ventricular systolic function but impaired filling. Dippers showed pronounced increases in night‐time BP, while non‐dippers showed significant elevation in day‐time BP, which blunted differences in nocturnal BP fall, and lowest night‐time and evening BP. Dippers had higher global longitudinal strain, torsion, and untwisting rates after acute HA exposure. Variations in night‐time systolic BP correlated with variations in torsion and global longitudinal strain. Our study firstly demonstrates BP and cardiac function variations during acute HA exposure in different BP patterns and BP increases in dippers at night, while non‐dippers showed day‐time increases. Furthermore, enhanced left ventricular torsion and global longitudinal strain are associated with BP changes. Non‐dippers showed poor cardiac compensatory and maladaptive to acute HA exposure. However, the exact mechanisms involved need further illumination.
Collapse
Affiliation(s)
- Renzheng Chen
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jie Yang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Chuan Liu
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jingbin Ke
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Xubin Gao
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yuanqi Yang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yang Shen
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Fangzhengyuan Yuan
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Chunyan He
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Ran Cheng
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Hailin Lv
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Chen Zhang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Wenzhu Gu
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Hu Tan
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jihang Zhang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Lan Huang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, the Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| |
Collapse
|
17
|
Assessment of right atrial dyssynchrony by 2D speckle-tracking in healthy young men following high altitude exposure at 4100 m. PLoS One 2021; 16:e0247107. [PMID: 33600469 PMCID: PMC7891700 DOI: 10.1371/journal.pone.0247107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 02/01/2021] [Indexed: 11/30/2022] Open
Abstract
Background High altitude exposure induces overload of right-sided heart and may further predispose to supraventricular arrhythmia. It has been reported that atrial mechanical dyssynchrony is associated with atrial arrhythmia. Whether high altitude exposure causes higher right atrial (RA) dyssynchrony is still unknown. The aim of study was to investigate the effect of high altitude exposure on right atrial mechanical synchrony. Methods In this study, 98 healthy young men underwent clinical examination and echocardiography at sea level (400 m) and high altitude (4100 m) after an ascent within 7 days. RA dyssynchrony was defined as inhomogeneous timing to peak strain and strain rate using 2D speckle-tracking echocardiography. Results Following high altitude exposure, standard deviation of the time to peak strain (SD-TPS) [36.2 (24.5, 48.6) ms vs. 21.7 (12.9, 32.1) ms, p<0.001] and SD-TPS as percentage of R–R’ interval (4.6 ± 2.1% vs. 2.5 ± 1.8%, p<0.001) significantly increased. Additionally, subjects with higher SD-TPS (%) at high altitude presented decreased right ventricular global longitudinal strain and RA active emptying fraction, but increased RA minimal volume index, which were not observed in lower group. Multivariable analysis showed that mean pulmonary arterial pressure and tricuspid E/A were independently associated with SD-TPS (%) at high altitude. Conclusion Our data for the first time demonstrated that high altitude exposure causes RA dyssynchrony in healthy young men, which may be secondary to increased pulmonary arterial pressure. In addition, subjects with higher RA dyssynchrony presented worse RA contractile function and right ventricular performance.
Collapse
|
18
|
Atrial performance in healthy subjects following high altitude exposure at 4100 m: 2D speckle-tracking strain analysis. Int J Cardiovasc Imaging 2021; 37:1891-1902. [PMID: 33547622 PMCID: PMC8255257 DOI: 10.1007/s10554-021-02173-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/22/2021] [Indexed: 12/18/2022]
Abstract
High altitude (HA) exposure has been considered as a cardiac stress and might impair ventricular diastolic function. Atrial contraction is involved in ventricular passive filling, however the atrial performance to HA exposure is poorly understood. This study aimed to evaluate the effect of short-term HA exposure on bi-atrial function. Physiological and 2D-echocardiographic data were collected in 82 healthy men at sea level (SL, 400 m) and 4100 m after an ascent within 7 days. Atrial function was measured using volumetric and speckle-tracking analyses during reservoir, conduit and contractile phases of cardiac cycle. Following HA exposure, significant decreases of reservoir and conduit function indexes were observed in bi-atria, whereas decreases of contractile function indexes were observed in right atrium (RA), estimated via RA active emptying fraction (SL 41.7 ± 13.9% vs. HA 35.4 ± 12.2%, p = 0.001), strain during the contractile phase [SL 13.5 (11.4, 17.8) % vs. HA 12.3 (9.3, 15.9) %, p = 0.003], and peak strain rate during the contractile phase [SL − 1.76 (− 2.24, − 1.48) s−1 vs. HA − 1.57 (− 2.01, − 1.23) s−1, p = 0.002], but not in left atrium (LA). In conclusion, short-term HA exposure of healthy individuals impairs bi-atrial performance, mostly observed in RA. Especially, atrial contractile function decreases in RA rather than LA, which seems not to compensate for decreased ventricular filling after HA exposure. Our findings may provide a novel evidence for right-sided heart dysfunction to HA exposure.
Collapse
|
19
|
Gaur P, Sartmyrzaeva M, Maripov A, Muratali Uulu K, Saini S, Ray K, Kishore K, Akunov A, Sarybaev A, Kumar B, Singh SB, Vats P. Cardiac Acclimatization at High Altitude in Two Different Ethnicity Groups. High Alt Med Biol 2021; 22:58-69. [PMID: 33400909 DOI: 10.1089/ham.2020.0035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Gaur, Priya, Meerim Sartmyrzaeva, Abdirashit Maripov, Kubatbek Muratali Uulu, Supriya Saini, Koushik Ray, Krishna Kishore, Almaz Akunov, Akpay Sarybaev, Bhuvnesh Kumar, Shashi Bala Singh, and Praveen Vats. Cardiac acclimatization at high altitude in two different ethnicity groups. High Alt Med Biol. 22:58-69, 2021. Introduction: High altitude (HA) exposure causes substantial increase in pulmonary artery pressure (PAP) and resistance. However, the effects of HA hypoxia exposure on cardiac function remain incompletely understood. Studies evaluating interethnic differences in cardiac functions in response to HA exposure are lacking. We aimed to compare the cardiac performance in Indian versus Kyrgyz healthy lowland subjects over the course of a 3-week HA exposure at 4,111 m. Methodology: Ten Indians and 20 Kyrgyz subjects were studied to assess cardiac acclimatization noninvasively by echocardiography in two different ethnic groups for 3 weeks of stay at HA. Pulmonary hemodynamics, right and left ventricular functions were evaluated at basal and on days 3, 7, 14, and 21 of HA exposure and on day 3 of deinduction. Results: HA exposure significantly increased PAP, pulmonary vascular resistance, cardiac output (CO), and heart rates (HRs) in both groups. Tricuspid regurgitant gradient increased significantly in both the group at day 3 versus basal; 38.9 mmHg (31.8, 42.9) versus 21.9 mmHg (19.5, 22.6) in Kyrgyz; and 34.1 mmHg (30.2, 38.5) versus 20.4 mmHg (19.7, 21.3) in Indians. HR increased significantly in Indians at day 3 and 7, whereas in Kyrgyz throughout exposure. CO increased significantly in both groups at day 3 versus basal with 5.9 L/min (5.5, 6.4) versus 5.1 L/min (4.4, 5.9) in Kyrgyz, and 5.7 L/min (5.56, 5.98) versus 4.9 L/min (4.1, 5.3) in Indians. Both groups exhibited preserved right ventricular diastolic and systolic functions at HAs. HA exposure changed the left ventricular diastolic parameters only in Kyrgyz subjects with impaired mitral inflow E/A, but not in Indian subjects. All cardiac changes induced at HAs have been recovered fully upon deinduction in both, except lateral-septal A', which remained low in Indians. Conclusion: Although pulmonary hemodynamics responses were similar in both groups, there were differences in cardiac functional parameters between the two in response to HA exposure that may be accounted to ethnic variation.
Collapse
Affiliation(s)
- Priya Gaur
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | | | - Abdirashit Maripov
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyz Republic
| | | | - Supriya Saini
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | - Koushik Ray
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | - Krishna Kishore
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | - Almaz Akunov
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyz Republic
| | - Akpay Sarybaev
- Kyrgyz Indian Mountain Biomedical Research Center, Bishkek, Kyrgyz Republic
| | - Bhuvnesh Kumar
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | - Shashi Bala Singh
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| | - Praveen Vats
- Endocrinology and Metabolism Division, Defense Institute of Physiology and Allied Sciences, Delhi, India
| |
Collapse
|
20
|
Ewalts M, Dawkins T, Boulet LM, Thijssen D, Stembridge M. The influence of increased venous return on right ventricular dyssynchrony during acute and sustained hypoxaemia. Exp Physiol 2020; 106:925-937. [PMID: 33369788 DOI: 10.1113/ep088657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 12/19/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Right ventricular dyssynchrony is a marker of function that is elevated in healthy individuals exposed to acute hypoxia, but does it remain elevated during sustained exposure to high altitude hypoxia, and can it be normalised by augmenting venous return? What is the main finding and its importance? For the first time it is demonstrated that (i) increasing venous return in acute hypoxia restores the synchrony of right ventricular contraction and (ii) dyssynchrony is evident after acclimatisation to high altitude, and remains sensitive to changes in venous return. Therefore, the interpretation of right ventricular dyssynchrony requires consideration the prevailing haemodynamic state. ABSTRACT Regional heterogeneity in timing of right ventricular (RV) contraction (RV dyssynchrony; RVD) occurs when pulmonary artery systolic pressure (PASP) is increased during acute hypoxia. Interestingly, RVD is not observed during exercise, a stimulus that increases both PASP and venous return. Therefore, we hypothesised that RVD in healthy humans is sensitive to changes in venous return, and examined whether (i) increasing venous return in acute hypoxia lowers RVD and (ii) if RVD is further exaggerated in sustained hypoxia, given increased PASP is accompanied by decreased ventricular filling at high altitude. RVD, PASP and right ventricular end-diastolic area (RVEDA) were assessed using transthoracic two-dimensional and speckle-tracking echocardiography during acute normobaric hypoxia ( F i O 2 = 0.12) and sustained exposure (5-10 days) to hypobaric hypoxia (3800 m). Venous return was augmented with lower body positive pressure at sea level (LBPP; +10 mmHg) and saline infusion at high altitude. PASP was increased in acute hypoxia (20 ± 6 vs. 28 ± 7, P < 0.001) concomitant to an increase in RVD (18 ± 7 vs. 38 ± 10, P < 0.001); however, the addition of LBPP during hypoxia decreased RVD (38 ± 0 vs. 26 ± 10, P < 0.001). Sustained hypoxia increased PASP (20 ± 4 vs. 26 ± 5, P = 0.008) and decreased RVEDA (24 ± 4 vs. 21 ± 2, P = 0.042), with RVD augmented (14 ± 5 vs. 31 ± 12, P = 0.001). Saline infusion increased RVEDA (21 ± 2 vs. 23 ± 3, P = 0.008) and reduced RVD (31 ± 12 vs. 20 ± 9, P = 0.001). In summary, an increase in PASP secondary to acute and sustained exposure to hypoxia augments RVD, which can be at least partly reduced via increased venous return.
Collapse
Affiliation(s)
- Michiel Ewalts
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK.,Department of Physiology, Radboudumc, Nijmegen, The Netherlands
| | - Tony Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Lindsey M Boulet
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, British Columbia, Canada
| | - Dick Thijssen
- Department of Physiology, Radboudumc, Nijmegen, The Netherlands
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| |
Collapse
|
21
|
Steele AR, Tymko MM, Meah VL, Simpson LL, Gasho C, Dawkins TG, Villafuerte FC, Ainslie PN, Stembridge M, Moore JP, Steinback CD. Global REACH 2018: renal oxygen delivery is maintained during early acclimatization to 4,330 m. Am J Physiol Renal Physiol 2020; 319:F1081-F1089. [PMID: 32996319 DOI: 10.1152/ajprenal.00372.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Early acclimatization to high altitude is characterized by various respiratory, hematological, and cardiovascular adaptations that serve to restore oxygen delivery to tissue. However, less is understood about renal function and the role of renal oxygen delivery (RDO2) during high altitude acclimatization. We hypothesized that 1) RDO2 would be reduced after 12 h of high altitude exposure (high altitude day 1) but restored to sea level values after 1 wk (high altitude day 7) and 2) RDO2 would be associated with renal reactivity, an index of acid-base compensation at high altitude. Twenty-four healthy lowlander participants were tested at sea level (344 m, Kelowna, BC, Canada) and on day 1 and day 7 at high altitude (4,330 m, Cerro de Pasco, Peru). Cardiac output, renal blood flow, and arterial and venous blood sampling for renin-angiotensin-aldosterone system hormones and NH2-terminal pro-B-type natriuretic peptides were collected at each time point. Renal reactivity was calculated as follows: (Δarterial bicarbonate)/(Δarterial Pco2) between sea level and high altitude day 1 and sea level and high altitude day 7. The main findings were that 1) RDO2 was initially decreased at high altitude compared with sea level (ΔRDO2: -22 ± 17%, P < 0.001) but was restored to sea level values on high altitude day 7 (ΔRDO2: -6 ± 14%, P = 0.36). The observed improvements in RDO2 resulted from both changes in renal blood flow (Δ from high altitude day 1: +12 ± 11%, P = 0.008) and arterial oxygen content (Δ from high altitude day 1: +44.8 ± 17.7%, P = 0.006) and 2) renal reactivity was positively correlated with RDO2 on high altitude day 7 (r = 0.70, P < 0.001) but not high altitude day 1 (r = 0.26, P = 0.29). These findings characterize the temporal responses of renal function during early high altitude acclimatization and the influence of RDO2 in the regulation of acid-base balance.
Collapse
Affiliation(s)
- Andrew R Steele
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Michael M Tymko
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Victoria L Meah
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Lydia L Simpson
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, United Kingdom
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, School of Medicine, Loma Linda University, Loma Linda, California
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Francisco C Villafuerte
- Department of Biological and Physiological Sciences, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Bangor, United Kingdom
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada.,Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.,Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
22
|
Dawkins TG, Curry BA, Drane AL, Lord RN, Richards C, Brown M, Pugh CJA, Lodge F, Yousef Z, Stembridge M, Shave RE. Stimulus-specific functional remodeling of the left ventricle in endurance and resistance-trained men. Am J Physiol Heart Circ Physiol 2020; 319:H632-H641. [PMID: 32772543 DOI: 10.1152/ajpheart.00233.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Left ventricular (LV) structural remodeling following athletic training has been evidenced through training-specific changes in wall thickness and geometry. Whether the LV response to changes in hemodynamic load also adapts in a training-specific manner is unknown. Using echocardiography, we examined LV responses of endurance-trained (n = 15), resistance-trained (n = 14), and nonathletic men (n = 13) to 1) 20, 40, and 60% one repetition-maximum (1RM), leg-press exercise and 2) intravascular Gelofusine infusion (7 mL/kg) with passive leg raise. While resting heart rate was lower in endurance-trained participants versus controls (P = 0.001), blood pressure was similar between groups. Endurance-trained individuals had lower wall thickness but greater LV mass relative to body surface area versus controls, with no difference between resistance-trained individuals and controls. Leg press evoked a similar increase in blood pressure; however, resistance-trained participants preserved stroke volume (SV; -3 ± 8%) versus controls at 60% 1RM (-15 ± 7%, P = 0.001). While the maintenance of SV was related to the change in longitudinal strain across all groups (R = 0.537; P = 0.007), time-to-peak strain was maintained in resistance-trained but delayed in endurance-trained individuals (1 vs. 12% delay; P = 0.021). Volume infusion caused a similar increase in end-diastolic volume (EDV) and SV across groups, but leg raise further increased EDV only in endurance-trained individuals (5 ± 5 to 8 ± 5%; P = 0.018). Correlation analysis revealed a relationship between SV and longitudinal strain following infusion and leg raise (R = 0.334, P = 0.054); however, we observed no between-group differences in longitudinal myocardial mechanics. In conclusion, resistance-trained individuals better maintained SV during pressure loading, whereas endurance-trained individuals demonstrated greater EDV reserve during volume loading. These data provide novel evidence of training-specific LV functional remodeling.NEW & NOTEWORTHY Training-specific functional remodeling of the LV in response to different loading conditions has been recently suggested, but not experimentally tested in the same group of individuals. Our data provide novel evidence of a dichotomous, training-specific LV adaptive response to hemodynamic pressure or volume loading.
Collapse
Affiliation(s)
- Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Bryony A Curry
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Aimee L Drane
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Rachel N Lord
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Cory Richards
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Megan Brown
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Christopher J A Pugh
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Freya Lodge
- Department of Cardiology, University Hospital of Wales, Cardiff, United Kingdom
| | - Zaheer Yousef
- Department of Cardiology, University Hospital of Wales, Cardiff, United Kingdom
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Rob E Shave
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada
| |
Collapse
|
23
|
Papoušek F, Sedmera D, Neckář J, Ošťádal B, Kolář F. Left ventricular function and remodelling in rats exposed stepwise up to extreme chronic intermittent hypoxia. Respir Physiol Neurobiol 2020; 282:103526. [PMID: 32805421 DOI: 10.1016/j.resp.2020.103526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 07/20/2020] [Accepted: 08/10/2020] [Indexed: 11/30/2022]
Abstract
The main aim was to find out whether long-lasting stepwise exposure to extreme hypoxia affects left ventricular (LV) geometry and systolic function. Adult male rats were exposed to intermittent hypobaric hypoxia (8 h/day) with increasing altitude in steps of 1000 m every 3 weeks up to 8000 m. While the LV cavity diastolic diameter did not change over the whole range of hypoxia, the wall thickness increased significantly at the altitude of 8000 m. LV fractional shortening ranged between 48.1 % and 50.1 % and remained unaffected even at the most severe hypoxia. At the end of experiment, haematocrit reached 83 %, mean systemic arterial pressure 120 % and relative LV weight 154 % of normoxic values while RV systolic pressure and relative RV weight doubled. Myocyte hypertrophy and myocardial fibrosis were more pronounced in RV than in LV. In conclusion, LV systolic function was preserved after chronic stepwise exposure of rats to extreme intermittent hypoxia despite moderate concentric hypertrophy and myocardial remodelling.
Collapse
Affiliation(s)
- František Papoušek
- Laboratory of Developmental Cardiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - David Sedmera
- Laboratory of Developmental Cardiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic; Institute of Anatomy, First Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Jan Neckář
- Laboratory of Developmental Cardiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Bohuslav Ošťádal
- Laboratory of Developmental Cardiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - František Kolář
- Laboratory of Developmental Cardiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.
| |
Collapse
|
24
|
Yang Y, Liu C, Tian J, Ding X, Yu S, Bian S, Yang J, Qin Z, Zhang J, Ke J, Yuan F, Zhang C, Rao R, Huang L. Preliminary Study of Right Ventricular Dyssynchrony Under High-Altitude Exposure: Determinants and Impacts. Front Physiol 2020; 11:703. [PMID: 32714205 PMCID: PMC7343894 DOI: 10.3389/fphys.2020.00703] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 05/28/2020] [Indexed: 01/29/2023] Open
Abstract
The aims of this study were to explore the effect of high-altitude (HA) exposure on the incidence, determinants, and impacts of right ventricular dyssynchrony (RVD). In our study, 108 healthy young men were enrolled, and physiological and echocardiographic variables were recorded at both sea level and 4,100 m. By using two-dimensional speckle-tracking echocardiography, RVD was evaluated by calculating the R–R interval-corrected standard deviation of the time-to-peak systolic strain for the four mid-basal RV segments (RVSD4) and defined by RVSD4 > 18.7 ms. After HA exposure, RVSD4 was significantly increased, and the incidence of RVD was approximately 32.4%. Subjects with RVD showed lower oxygen saturation (SaO2) and RV global longitudinal strain and higher systolic pulmonary artery pressure than those without RVD. Moreover, myocardial acceleration during isovolumic contraction was increased in all subjects and those without RVD, but not in those with RVD. Multivariate logistic regression revealed that SaO2 is an independent determinant of RVD at HA (odds ratio: 0.72, 95% CI: 0.56–0.92; P = 0.009). However, the mean pulmonary artery pressure was linearly correlated with the magnitude of RVD in the presence of Notch. No changes were found in RV fractional area change, tricuspid annular motion, or tricuspid s’ velocity between subjects with and without RVD. Collectively, we demonstrated for the first time that HA exposure could induce RVD in healthy subjects, which may be mainly attributed to the decline in SaO2 as well as RV overload; the incidence of RVD was associated with reduced RV regional function and blunted myocardial acceleration.
Collapse
Affiliation(s)
- Yuanqi Yang
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Chuan Liu
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jingdu Tian
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Xiaohan Ding
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Beijing, China
| | - Shiyong Yu
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Shizhu Bian
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jie Yang
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Zhexue Qin
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jihang Zhang
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Jingbin Ke
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Fangzhengyuan Yuan
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Chen Zhang
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Rongsheng Rao
- Department of Medical Ultrasonics, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Lan Huang
- Institute of Cardiovascular Diseases of PLA, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Department of Cardiology, The Second Affiliated Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| |
Collapse
|
25
|
Williams AM, Ainslie PN, Anholm JD, Gasho C, Subedi P, Stembridge M. Left Ventricular Twist Is Augmented in Hypoxia by β 1-Adrenergic-Dependent and β 1-Adrenergic-Independent Factors, Without Evidence of Endocardial Dysfunction. Circ Cardiovasc Imaging 2020; 12:e008455. [PMID: 31060374 DOI: 10.1161/circimaging.118.008455] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Left ventricular (LV) twist mechanics are augmented with both acute and chronic hypoxemia. Although the underlying mechanisms remain unknown, sympathetic activation and a direct effect of hypoxemia on the myocardium have been proposed, the latter of which may produce subendocardial dysfunction that is masked by larger subepicardial torque. This study therefore sought to (1) determine the individual and combined influences of β1-AR (β1-adrenergic receptor) stimulation and peripheral O2 saturation (Spo2) on LV twist in acute and chronic hypoxia and (2) elucidate whether endocardial versus epicardial mechanics respond differently to hypoxia. METHODS Twelve males (27±4 years) were tested near sea level in acute hypoxia (Spo2=82±4%) and following 3 to 6 days at 5050 m (high altitude; Spo2=83±3%). In both settings, participants received infusions of β1-AR blocker esmolol and volume-matched saline (double-blind, randomized). LV mechanics were assessed with 2-dimensional speckle-tracking echocardiography, and region-specific analysis to compare subendocardial and subepicardial mechanics. RESULTS At sea level, compared with baseline (14.8±3.0°) LV twist was reduced with esmolol (11.2±3.3°; P=0.007) and augmented during hypoxia (19.6±4.9°; P<0.001), whereas esmolol+hypoxia augmented twist compared with esmolol alone (16.5±3.3°; P<0.001). At 5050 m, LV twist was increased compared with sea level (19.5±5.4°; P=0.004), and reduced with esmolol (13.0±3.8°; P<0.001) and Spo2 normalization (12.8±3.4°; P<0.001). Moreover, esmolol+normalized Spo2 lowered twist further than esmolol alone (10.5±3.1°; P=0.036). There was no mechanics-derived evidence of endocardial dysfunction with hypoxia at sea level or high altitude. CONCLUSIONS These findings suggest LV twist is augmented in hypoxia via β1-AR-dependent and β1-AR-independent mechanisms (eg, α1-AR stimulation), but does not appear to reflect endocardial dysfunction.
Collapse
Affiliation(s)
- Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, Canada (A.M.W., P.N.A.).,Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, Canada (A.M.W., P.N.A.)
| | - James D Anholm
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Chris Gasho
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Prajan Subedi
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada (A.M.W.)
| | - Mike Stembridge
- Pulmonary and Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, CA (J.D.A., C.G., P.S.)
| |
Collapse
|
26
|
Stewart GM, Wheatley-Guy CM, Morris NR, Coffman KE, Stepanek J, Carlson AR, Issa A, Schmidt MA, Johnson BD. Myocardial adaptability in young and older-aged sea-level habitants sojourning at Mt Kilimanjaro: are cardiac compensatory limits reached in older trekkers? Eur J Appl Physiol 2020; 120:799-809. [PMID: 32076831 DOI: 10.1007/s00421-020-04319-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 02/07/2020] [Indexed: 10/25/2022]
Abstract
INTRODUCTION High-altitude ascent induces left (LV) and right (RV) ventricular adaptations secondary to hypoxia-related hemodynamic and myocardial alterations. Since cardiopulmonary decrements observed with aging (e.g., decreased LV compliance and increased pulmonary vascular resistance) may limit cardiac plasticity, this study examined myocardial adaptability throughout an 11 day sojourn to 5893 m in young and older-aged trekkers. METHODS AND RESULTS Echocardiography was performed on 14 young (8 men; 32 ± 5 years) and 13 older-aged (8 men; 59 ± 5 years) subjects on non-trekking days (Day 0: 880 m; Day 3: 3100 m; Day 8: 4800 m; Day 12/post-climb: 880 m). RV systolic pressure (mmHg) was systematically higher in older-aged subjects (p < 0.01) with similar progressive increases observed during ascent for young and older subjects, respectively (Day 0: 18 ± 1 vs 20 ± 2; Day 3: 25 ± 2 vs 29 ± 3; Day 8: 30 ± 2 vs 35 ± 2). Estimates of LV filling pressure (E/E') were systematically higher in older subjects (p < 0.01) with similar progressive decreases observed during ascent for young and older-aged subjects, respectively (Day 0: 5.6 ± 0.3 vs 6.7 ± 0.5; Day 3: 5.1 ± 0.2 vs 6.1 ± 0.3; Day 8: 4.7 ± 0.3 vs 5.4 ± 0.3). Overall, RV end-diastolic and end-systolic area increased at altitude (p < 0.01), while LV end-diastolic and end-systolic volume decreased (p < 0.01). However, all RV and LV morphological measures were similar on Day 3 and Day 8 (p > 0.05), and returned to baseline post-climb (p > 0.05). Excluding mild LV dilatation in some older-aged trekkers on Day 8/Day 12 (p < 0.01), altitude-induced morphological and functional adaptations were similar for all trekkers (p > 0.05). CONCLUSION Altitude-induced myocardial adaptations are chamber specific, secondary to RV and LV hemodynamic alterations. Despite progressive hemodynamic alterations during ascent, morphological and functional cardiac perturbations plateaued, suggesting rapid myocardial adaptation which was mostly comparable in young and older-aged individuals.
Collapse
Affiliation(s)
- Glenn M Stewart
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Scottsdale, MN, 55905, USA.
| | | | - Norman R Morris
- School of Allied Health Sciences, Griffith University, Gold Coast, Australia.,Allied Health Research Collaborative, Metro North Hospital and Health Service, The Prince Charles Hospital, Brisbane, Australia.,Hopkins Centre and Menzies Health Institute, Griffith University, Gold Coast, Australia
| | - Kirsten E Coffman
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Scottsdale, MN, 55905, USA
| | - Jan Stepanek
- Aerospace Medicine Program, Mayo Clinic, Scottsdale, USA
| | - Alex R Carlson
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Scottsdale, MN, 55905, USA
| | - Amine Issa
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Scottsdale, MN, 55905, USA
| | - Michael A Schmidt
- Advanced Pattern Analysis & Countermeasures Group, Boulder, USA.,Sovaris Aerospace, Boulder, USA
| | - Bruce D Johnson
- Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Scottsdale, MN, 55905, USA
| |
Collapse
|
27
|
Bhandari S, Cavalleri GL. Population History and Altitude-Related Adaptation in the Sherpa. Front Physiol 2019; 10:1116. [PMID: 31555147 PMCID: PMC6722185 DOI: 10.3389/fphys.2019.01116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 08/12/2019] [Indexed: 12/29/2022] Open
Abstract
The first ascent of Mount Everest by Tenzing Norgay and Sir Edmund Hillary in 1953 brought global attention to the Sherpa people and human performance at altitude. The Sherpa inhabit the Khumbu Valley of Nepal, and are descendants of a population that has resided continuously on the Tibetan plateau for the past ∼25,000 to 40,000 years. The long exposure of the Sherpa to an inhospitable environment has driven genetic selection and produced distinct adaptive phenotypes. This review summarizes the population history of the Sherpa and their physiological and genetic adaptation to hypoxia. Genomic studies have identified robust signals of positive selection across EPAS1, EGLN1, and PPARA, that are associated with hemoglobin levels, which likely protect the Sherpa from altitude sickness. However, the biological underpinnings of other adaptive phenotypes such as birth weight and the increased reproductive success of Sherpa women are unknown. Further studies are required to identify additional signatures of selection and refine existing Sherpa-specific adaptive phenotypes to understand how genetic factors have underpinned adaptation in this population. By correlating known and emerging signals of genetic selection with adaptive phenotypes, we can further reveal hypoxia-related biological mechanisms of adaptation. Ultimately this work could provide valuable information regarding treatments of hypoxia-related illnesses including stroke, heart failure, lung disease and cancer.
Collapse
Affiliation(s)
- Sushil Bhandari
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Gianpiero L Cavalleri
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| |
Collapse
|
28
|
Howe CA, Ainslie PN, Tremblay JC, Carter HH, Patrician A, Stembridge M, Williams A, Drane AL, Delorme E, Rieger MG, Tymko MM, Gasho C, Santoro A, MacLeod DB, Hoiland RL. UBC-Nepal Expedition: Haemoconcentration underlies the reductions in cerebral blood flow observed during acclimatization to high altitude. Exp Physiol 2019; 104:1963-1972. [PMID: 31410899 DOI: 10.1113/ep087663] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 08/13/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the central question of this study? The aim was to evaluate the degree to which increases in haematocrit alter cerebral blood flow and cerebral oxygen delivery during acclimatization to high altitude. What is the main finding and its importance? Through haemodilution, we determined that, after 1 week of acclimatization, the primary mechanism contributing to the cerebral blood flow response during acclimatization is an increase in haemoglobin and haematocrit. The remaining contribution to the cerebral blood flow response during acclimatization is likely to be attributable to ventilatory acclimatization. ABSTRACT At high altitude, an increase in haematocrit (Hct) is achieved through altitude-induced diuresis and erythropoiesis, both of which result in increased arterial oxygen content. Given the impact of alterations in Hct on oxygen content, haemoconcentration has been hypothesized to mediate, in part, the attenuation of the initial elevation in cerebral blood flow (CBF) at high altitude. To test this hypothesis, healthy men (n = 13) ascended to 5050 m over 9 days without the aid of prophylactic acclimatization medications. After 1 week of acclimatization at 5050 m, participants were haemodiluted by rapid saline infusion (2.10 ± 0.28 l) to return Hct towards pre-acclimatization values. Arterial blood gases, Hct, global CBF (duplex ultrasound) and haemodynamic variables were measured after initial arrival at 5050 m and after 1 week of acclimatization at high altitude, before and after the haemodilution protocol. After 1 week at 5050 m, the Hct increased from 42.5 ± 2.5 to 49.6 ± 2.5% (P < 0.001), and it was subsequently reduced to 45.6 ± 2.3% (P < 0.001) after haemodilution. Global CBF decreased from 844 ± 160 to 619 ± 136 ml min-1 (P = 0.033) after 1 week of acclimatization and increased to 714 ± 204 ml min -1 (P = 0.045) after haemodilution. Despite the significant changes in Hct, and thus oxygen content, cerebral oxygen delivery was unchanged at all time points. Furthermore, these observations occurred in the absence of any changes in mean arterial blood pressure, cardiac output, arterial blood pH or oxygen saturation pre- and posthaemodilution. These data highlight the influence of Hct in the regulation of CBF and are the first to demonstrate experimentally that haemoconcentration contributes to the reduction in CBF during acclimatization to altitude.
Collapse
Affiliation(s)
- Connor A Howe
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, ON, Canada
| | - Howard H Carter
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Alex Patrician
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Alex Williams
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - Aimee L Drane
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Eric Delorme
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Mathew G Rieger
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| | - Chris Gasho
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Antoinette Santoro
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, BC, Canada
| |
Collapse
|
29
|
Maufrais C, Rupp T, Bouzat P, Estève F, Nottin S, Walther G, Verges S. Medex 2015: The key role of cardiac mechanics to maintain biventricular function at high altitude. Exp Physiol 2019; 104:667-676. [DOI: 10.1113/ep087350] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 02/19/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Claire Maufrais
- U1042INSERM F‐38000 Grenoble France
- Laboratoire HP2Grenoble Alpes University F‐38000 Grenoble France
| | - Thomas Rupp
- Laboratoire Interuniversitaire de Biologie de la MotricitéUniversité Savoie Mont Blanc EA7424 F‐73000 Chambéry France
| | - Pierre Bouzat
- EA 7442 RSRM – ID17/ESRF F‐38043 Grenoble France
- Pôle Anesthésie RéanimationCHU de Grenoble Grenoble France
- INSERM U1216Grenoble Institut des NeurosciencesGrenoble Alpes University F‐38042 Grenoble France
| | | | | | | | - Samuel Verges
- U1042INSERM F‐38000 Grenoble France
- Laboratoire HP2Grenoble Alpes University F‐38000 Grenoble France
| |
Collapse
|
30
|
Stembridge M, Levine B. Cardiac performance with chronic hypoxia: mechanisms regulating stroke volume. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2018.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
31
|
Ruggiero L, McNeil CJ. Supraspinal Fatigue and Neural-evoked Responses in Lowlanders and Sherpa at 5050 m. Med Sci Sports Exerc 2019; 51:183-192. [PMID: 30095744 DOI: 10.1249/mss.0000000000001748] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE At high altitude, Lowlanders exhibit exacerbated fatigue and impaired performance. Conversely, Sherpa (native Highlanders) are known for their outstanding performance at altitude. Presently, there are no reports comparing neuromuscular fatigue and its etiology between Lowlanders and Sherpa at altitude. METHODS At 5050 m, nine age-matched Lowlanders and Sherpa (31 ± 10 vs 30 ± 12 yr, respectively) completed a 4-min sustained isometric elbow flexion at 25% maximal voluntary contraction (MVC) torque. Mid-minute, stimuli were applied to the motor cortex and brachial plexus to elicit a motor-evoked potential and maximal compound muscle action potential (Mmax), respectively. Supraspinal fatigue was assessed as the reduction in cortical voluntary activation (cVA) from prefatigue to postfatigue. Cerebral hemoglobin concentrations and tissue oxygenation index (TOI) were measured over the prefrontal cortex by near-infrared spectroscopy. RESULTS Prefatigue, MVC torque, and cVA were significantly greater for Lowlanders than Sherpa (79.5 ± 3.6 vs 50.1 ± 11.3 N·m, and 95.4% ± 2.7% vs 88.2% ± 6.6%, respectively). With fatigue, MVC torque and cVA declined similarly for both groups (~24%-26% and ~5%-7%, respectively). During the task, motor-evoked potential area increased more and sooner for Lowlanders (1.5 min) than Sherpa (3.5 min). The Mmax area was lower than baseline throughout fatigue for Lowlanders but unchanged for Sherpa. TOI increased earlier for Lowlanders (2 min) than Sherpa (4 min). Total hemoglobin increased only for Lowlanders (2 min). Mmax was lower, whereas TOI and total hemoglobin were higher for Lowlanders than Sherpa during the second half of the protocol. CONCLUSIONS Although neither MVC torque loss nor development of supraspinal fatigue was different between groups, neural-evoked responses and cerebral oxygenation indices were less perturbed in Sherpa. This represents an advantage for maintenance of homeostasis, presumably due to bequeathed genotype and long-term altitude adaptations.
Collapse
Affiliation(s)
- Luca Ruggiero
- Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, CANADA
| | | |
Collapse
|
32
|
Sareban M, Perz T, Macholz F, Reich B, Schmidt P, Fried S, Mairbäurl H, Berger MM, Niebauer J. Impairment of left atrial mechanics does not contribute to the reduction in stroke volume after active ascent to 4559 m. Scand J Med Sci Sports 2018; 29:223-231. [PMID: 30372563 PMCID: PMC7379646 DOI: 10.1111/sms.13325] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 10/08/2018] [Accepted: 10/17/2018] [Indexed: 01/07/2023]
Abstract
Hypoxia challenges left ventricular (LV) function due to reduced energy supply. Conflicting results exist whether high‐altitude exposure impairs LV diastolic function and thus contributes to the high altitude‐induced increase in systolic pulmonary artery pressure (sPAP) and reduction in stroke volume (SV). This study aimed to assess LV diastolic function, LV end‐diastolic pressure (LVEDP), and LA mechanics using comprehensive echocardiographic imaging in healthy volunteers at 4559 m. Fifty subjects performed rapid (<20 hours) and active ascent from 1130 m to 4559 m (high). All participants underwent echocardiography during baseline examination at 424 m (low) as well as 7, 20 and 44 hours after arrival at high altitude. Heart rate (HR), sPAP, and comprehensive volumetric‐ and Doppler‐ as well as speckle tracking‐derived LA strain parameters were obtained to assess LV diastolic function, LA mechanics, and LVEDP in a multiparametric approach. Data for final analyses were available in 46 subjects. HR (low: 64 ± 11 vs high: 79 ± 14 beats/min, P < 0.001) and sPAP (low: 24.4 ± 3.8 vs high: 38.5 ± 8.2 mm Hg, P < 0.001) increased following ascent and remained elevated at high altitude. Stroke volume (low: 64.5 ± 15.0 vs high: 58.1 ± 16.4 mL, P < 0.001) and EDV decreased following ascent and remained decreased at high altitude due to decreased LV passive filling volume, whereas LA mechanics were preserved. There was no case of LV diastolic dysfunction or increased LVEDP estimates. In summary, this study shows that rapid and active ascent of healthy individuals to 4559 m impairs passive filling and SV of the LV. These alterations were not related to changes in LV and LA mechanics.
Collapse
Affiliation(s)
- Mahdi Sareban
- University Institute of Sports Medicine, Prevention and Rehabilitation and Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Tabea Perz
- University Institute of Sports Medicine, Prevention and Rehabilitation and Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Franziska Macholz
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Salzburg, Austria
| | - Bernhard Reich
- University Institute of Sports Medicine, Prevention and Rehabilitation and Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| | - Peter Schmidt
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Salzburg, Austria
| | - Sebastian Fried
- Medical Clinic VII, Sports Medicine, Translational Lung Research Center Heidelberg (TLRC-H), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Heimo Mairbäurl
- Medical Clinic VII, Sports Medicine, Translational Lung Research Center Heidelberg (TLRC-H), German Center for Lung Research (DZL), University of Heidelberg, Heidelberg, Germany
| | - Marc M Berger
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Salzburg, Austria
| | - Josef Niebauer
- University Institute of Sports Medicine, Prevention and Rehabilitation and Research Institute of Molecular Sports Medicine and Rehabilitation, Paracelsus Medical University, Salzburg, Austria
| |
Collapse
|
33
|
Ruggiero L, Hoiland RL, Hansen AB, Ainslie PN, McNeil CJ. UBC-Nepal expedition: peripheral fatigue recovers faster in Sherpa than lowlanders at high altitude. J Physiol 2018; 596:5365-5377. [PMID: 30239002 DOI: 10.1113/jp276599] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/07/2018] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS The reduced oxygen tension of high altitude compromises performance in lowlanders. In this environment, Sherpa display superior performance, but little is known on this issue. Sherpa present unique genotypic and phenotypic characteristics at the muscular level, which may enhance resistance to peripheral fatigue at high altitude compared to lowlanders. We studied the impact of gradual ascent and exposure to high altitude (5050 m) on peripheral fatigue in age-matched lowlanders and Sherpa, using intermittent electrically-evoked contractions of the knee extensors. Peripheral fatigue (force loss) was lower in Sherpa during the first part of the protocol. Post-protocol, the rate of force development and contractile impulse recovered faster in Sherpa than in lowlanders. At any time, indices of muscle oxygenation were not different between groups. Muscle contractile properties in Sherpa, independent of muscle oxygenation, were less perturbed by non-volitional fatigue. Hence, elements within the contractile machinery contribute to the superior physical performance of Sherpa at high altitude. ABSTRACT Altitude-related acclimatisation is characterised by marked muscular adaptations. Lowlanders and Sherpa differ in their muscular genotypic and phenotypic characteristics, which may influence peripheral fatigability at altitude. After gradual ascent to 5050 m, 12 lowlanders and 10 age-matched Sherpa (32 ± 10 vs. 31 ± 11 years, respectively) underwent three bouts (separated by 15 s rest) of 75 intermittent electrically-evoked contractions (12 pulses at 15 Hz, 1.6 s between train onsets) of the dominant leg quadriceps, at the intensity which initially evoked 30% of maximal voluntary force. Trains were also delivered at minutes 1, 2 and 3 after the protocol to measure recovery. Tissue oxygenation index (TOI) and total haemoglobin (tHb) were quantified by a near-infrared spectroscopy probe secured over rectus femoris. Superficial femoral artery blood flow was recorded using ultrasonography, and delivery of oxygen was estimated (eDO2 ). At the end of bout 1, peak force was greater in Sherpa than in lowlanders (91.5% vs. 84.5% baseline, respectively; P < 0.05). Peak rate of force development (pRFD), the first 200 ms of the contractile impulse (CI200 ), and half-relaxation time (HRT) recovered faster in Sherpa than in lowlanders (percentage of baseline at 1 min: pRFD: 89% vs. 74%; CI200 : 91% vs. 80%; HRT: 113% vs. 123%, respectively; P < 0.05). Vascular measures were pooled for lowlanders and Sherpa as they did not differ during fatigue or recovery (P < 0.05). Mid bout 3, TOI was decreased (90% baseline) whereas tHb was increased (109% baseline). After bout 3, eDO2 was markedly increased (1266% baseline). The skeletal muscle of Sherpa seemingly favours repeated force production at altitude for similar oxygen delivery compared to lowlanders.
Collapse
Affiliation(s)
- Luca Ruggiero
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Alexander B Hansen
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Chris J McNeil
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| |
Collapse
|
34
|
Maufrais C, Rupp T, Bouzat P, Doucende G, Verges S, Nottin S, Walther G. Heart mechanics at high altitude: 6 days on the top of Europe. Eur Heart J Cardiovasc Imaging 2018; 18:1369-1377. [PMID: 28329216 DOI: 10.1093/ehjci/jew286] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 11/10/2016] [Indexed: 12/23/2022] Open
Abstract
Aims The aim of this study was to analyse the underlying mechanisms of left and right ventricular (LV and RV) functional alterations during several days in high-altitude hypoxia. Methods and results Resting evaluations of LV and RV function and mechanics were assessed by Speckle Tracking Echocardiography on 11 subjects at sea level (SLPRE), 3 ± 2 h after helicopter transport to high altitude (D0), at day 2 (D2), day 4 (D4) and day 6 (D6) at 4350 m and 5 ± 2 h after return to sea level (SLPOST). Subjects experienced acute mountain sickness (AMS) during the first days at 4350 m. LV systolic function, RV systolic and diastolic function, LV and RV strains and LV synchrony were unchanged at high altitude. Peak twist was increased at D0, continued to increase until D6 (SLPRE: 9.0 ± 5.1deg; D6: 13.0 ± 4.0deg, P < 0.05), but was normalized at SLPOST. Early filling decreased at high altitude with a nadir at D2 (SLPRE: 78 ± 13 cm s-1; D2: 66 ± 11 cm s-1, P < 0.05). LV filling pressures index was decreased at high altitude with the minimum value obtained at D2 and remained reduced at SLPOST. Untwisting, an important factor of LV filling, was not decreased but was delayed at 4350 m. Conclusions High-altitude exposure impaired LV diastolic function with the greatest effect observed at D2, concomitantly with the occurrence of AMS. The LV early filling impairments resulted from an increased RV afterload, a decrease in LV filling pressure and a delayed LV untwist. However, the increased LV twist probably acted as a compensatory mechanism to maintain cardiac performance during high-altitude hypoxia.
Collapse
Affiliation(s)
- Claire Maufrais
- U1042, INSERM, Domaine de la Merci, F-38700, La Tronche - Grenoble, France.,Laboratoire HP2, Grenoble Alpes Université, Avenue Kimberley, F-38434, Echirolles - Grenoble, France
| | - Thomas Rupp
- U1042, INSERM, Domaine de la Merci, F-38700, La Tronche - Grenoble, France.,Laboratoire HP2, Grenoble Alpes Université, Avenue Kimberley, F-38434, Echirolles - Grenoble, France.,Laboratoire Interuniversitaire de Biologie de la Motricité, Université Savoie Mont Blanc, 27 rue Marcoz F-73000, Chambéry, France
| | - Pierre Bouzat
- Grenoble Institute of Neurosciences, INSERM U1216, Chemin Fortuné Ferrini, F-38700 La Tronche - Grenoble, France.,Pôle Anesthésie Réanimation, CHU de Grenoble, Avenue Maquis du Grésivaudan, F-38700 La Tronche - Grenoble, France
| | - Gregory Doucende
- Laboratoire Performance et Santé en Altitude, Université de Perpignan, 7 Avenue Pierre de Coubertin, F-66120, Font-Romeu, France
| | - Samuel Verges
- U1042, INSERM, Domaine de la Merci, F-38700, La Tronche - Grenoble, France.,Laboratoire HP2, Grenoble Alpes Université, Avenue Kimberley, F-38434, Echirolles - Grenoble, France
| | - Stéphane Nottin
- Avignon University, LAPEC EA4278, 74 Rue Louis Pasteur, F-84000, Avignon, France
| | - Guillaume Walther
- Avignon University, LAPEC EA4278, 74 Rue Louis Pasteur, F-84000, Avignon, France
| |
Collapse
|
35
|
O'Driscoll JM, Wright SM, Taylor KA, Coleman DA, Sharma R, Wiles JD. Cardiac autonomic and left ventricular mechanics following high intensity interval training: a randomized crossover controlled study. J Appl Physiol (1985) 2018; 125:1030-1040. [PMID: 29952247 DOI: 10.1152/japplphysiol.00056.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Physical inactivity and sedentary behavior is associated with increased cardiovascular disease risk. Short duration high-intensity interval training (HIIT) has been shown to improve important health parameters. The aim of the present study was to assess the combined adaptations of the cardiac autonomic nervous system and myocardial functional and mechanical parameters to HIIT. Forty physically inactive and highly sedentary men completed two weeks of HIIT and control period. The HIIT protocol consisted of 3 × 30-s maximal cycle ergometer sprints against a resistance of 7.5% body weight, interspersed with 2 min of active recovery. Total power spectral density (PSD) and associated low-frequency (LF) and high-frequency (HF) power spectral components of heart rate variability were recorded. Conventional and speckle tracking echocardiography recorded left ventricular (LV) structural, functional, and mechanical parameters. HIIT produced a significant increase in total log-transformed (ln) PSD and ln HF and a significant decrease in LF/HF ratio (all P < 0.05) compared with the control period. HIIT produced significant improvements in LV diastolic function, including lateral E', estimated filling pressure (E/E' ratio), E deceleration time, and isovolumetric relaxation time ( P < 0.05 for all). Fractional shortening was the only conventional marker of LV systolic function to significantly improve ( P < 0.05). In this setting, there were significant improvements in global peak systolic strain rate, early and late diastolic strain rate, and early to late diastolic strain rate ratio, as well as apical rotation, apical systolic and diastolic rotation velocity, apical radial and circumferential strain and strain rate, LV torsion, and LV systolic and diastolic torsion velocity (all P < 0.05). A short-term program of HIIT was associated with a significant increase in cardiac autonomic modulation, demonstrated by a residual increase in cardiac vagal activity as well as significantly improved cardiac function and mechanics. This study demonstrates that HIIT may be an important stimulus to reduce the health implications associated with physical inactivity and sedentary behavior. NEW & NOTEWORTHY This is the first study to measure the combined adaptations of the cardiac autonomic nervous system and myocardial function and mechanics following high-intensity interval training (HIIT). This study demonstrates that a 2-wk HIIT intervention provides significant improvements in cardiac autonomic modulation and myocardial function and mechanics in a large cohort of young physically inactive and highly sedentary individuals. HIIT may be a powerful stimulus to reduce the health implications associated with physical inactivity and sedentary behavior.
Collapse
Affiliation(s)
- Jamie M O'Driscoll
- School of Human and Life Sciences, Canterbury Christ Church University , Kent , United Kingdom.,Department of Cardiology, St. George's Healthcare National Health Service Trust , London , United Kingdom
| | - Steven M Wright
- School of Human and Life Sciences, Canterbury Christ Church University , Kent , United Kingdom
| | - Katrina A Taylor
- School of Human and Life Sciences, Canterbury Christ Church University , Kent , United Kingdom
| | - Damian A Coleman
- School of Human and Life Sciences, Canterbury Christ Church University , Kent , United Kingdom
| | - Rajan Sharma
- Department of Cardiology, St. George's Healthcare National Health Service Trust , London , United Kingdom
| | - Jonathan D Wiles
- School of Human and Life Sciences, Canterbury Christ Church University , Kent , United Kingdom
| |
Collapse
|
36
|
Stembridge M, Ainslie PN, Boulet LM, Anholm J, Subedi P, Tymko MM, Willie CK, Cooper SM, Shave R. The independent effects of hypovolaemia and pulmonary vasoconstriction on ventricular function and exercise capacity during acclimatisation to 3800 m. J Physiol 2018; 597:1059-1072. [PMID: 29808473 DOI: 10.1113/jp275278] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 04/17/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We sought to determine the isolated and combined influence of hypovolaemia and hypoxic pulmonary vasoconstriction on the decrease in left ventricular (LV) function and maximal exercise capacity observed under hypobaric hypoxia. We performed echocardiography and maximal exercise tests at sea level (344 m), and following 5-10 days at the Barcroft Laboratory (3800 m; White Mountain, California) with and without (i) plasma volume expansion to sea level values and (ii) administration of the pulmonary vasodilatator sildenafil in a double-blinded and placebo-controlled trial. The high altitude-induced reduction in LV filling and ejection was abolished by plasma volume expansion but to a lesser extent by sildenafil administration; however, neither intervention had a positive effect on maximal exercise capacity. Both hypovolaemia and hypoxic pulmonary vasoconstriction play a role in the reduction of LV filling at 3800 m, but the increase in LV filling does not influence exercise capacity at this moderate altitude. ABSTRACT We aimed to determine the isolated and combined contribution of hypovolaemia and hypoxic pulmonary vasoconstriction in limiting left ventricular (LV) function and exercise capacity under chronic hypoxaemia at high altitude. In a double-blinded, randomised and placebo-controlled design, 12 healthy participants underwent echocardiography at rest and during submaximal exercise before completing a maximal test to exhaustion at sea level (SL; 344 m) and after 5-10 days at 3800 m. Plasma volume was normalised to SL values, and hypoxic pulmonary vasoconstriction was reversed by administration of sildenafil (50 mg) to create four unique experimental conditions that were compared with SL values: high altitude (HA), Plasma Volume Expansion (HA-PVX), Sildenafil (HA-SIL) and Plasma Volume Expansion with Sildenafil (HA-PVX-SIL). High altitude exposure reduced plasma volume by 11% (P < 0.01) and increased pulmonary artery systolic pressure (19.6 ± 4.3 vs. 26.0 ± 5.4, P < 0.001); these differences were abolished by PVX and SIL respectively. LV end-diastolic volume (EDV) and stroke volume (SV) were decreased upon ascent to high altitude, but were comparable to sea level in the HA-PVX trial. LV EDV and SV were also elevated in the HA-SIL and HA-PVX-SIL trials compared to HA, but to a lesser extent. Neither PVX nor SIL had a significant effect on the LV EDV and SV response to exercise, or the maximal oxygen consumption or peak power output. In summary, at 3800 m both hypovolaemia and hypoxic pulmonary vasoconstriction contribute to the decrease in LV filling, but restoring LV filling does not confer an improvement in maximal exercise performance.
Collapse
Affiliation(s)
- Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Lindsey M Boulet
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - James Anholm
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Prajan Subedi
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Michael M Tymko
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Christopher K Willie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Stephen-Mark Cooper
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK.,Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| |
Collapse
|
37
|
Abstract
INTRODUCTION Altitude is associated with a decrease in partial pressure of oxygen. Hypoxia induces pulmonary vasoconstriction with subsequent fixed increase in pulmonary artery pressure, and eventual right heart failure. CURRENT KNOWLEDGE High altitude exposure is associated with an increase in pulmonary artery pressure that is proportional to initial vasoconstriction. Echocardiographic evaluations on a large number of subjects show that the altitude-induced increase in pulmonary pressure is generally modest and does not exceed the 25mmHg that are diagnostic of pulmonary hypertension. This does not greatly increase right ventricular afterload, so that imaging of the right ventricle only shows some alterations of indices of systolic or diastolic function, but preserved contractile reserve during exercise. In less than 1% of cases, hypoxic vasoconstriction is strong and may be a cause of severe pulmonary hypertension and right heart failure. PERSPECTIVES The prognostic relevance of altitude-induced pulmonary hypertension and associated cardiac function alterations is not known. Treatment of hypoxic pulmonary hypertension relies on evacuation to a lower altitude, oxygen and pulmonary vasodilators. These treatment strategies have not been rigorously evaluated. CONCLUSIONS Altitude may be a cause of right heart failure. This uncommon complication of altitude exposure requires further epidemiological and therapeutic studies.
Collapse
|
38
|
Pedlar CR, Brown MG, Shave RE, Otto JM, Drane A, Michaud-Finch J, Contursi M, Wasfy MM, Hutter A, Picard MH, Lewis GD, Baggish AL. Cardiovascular response to prescribed detraining among recreational athletes. J Appl Physiol (1985) 2018; 124:813-820. [DOI: 10.1152/japplphysiol.00911.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Exercise-induced cardiac remodeling (EICR) and the attendant myocardial adaptations characteristic of the athlete’s heart may regress during periods of exercise reduction or abstinence. The time course and mechanisms underlying this reverse remodeling, specifically the impact of concomitant plasma volume (PV) contraction on cardiac chamber size, remain incompletely understood. We therefore studied recreational runners ( n = 21, age 34 ± 7 yr; 48% male) who completed an 18-wk training program (~7 h/wk) culminating in the 2016 Boston Marathon after which total exercise exposure was confined to <2 h/wk (no single session >1 h) for 8 wk. Cardiac structure and function, exercise capacity, and PV were assessed at peak fitness (10–14 days before) and at 4 wk and 8 wk postmarathon. Mixed linear modeling adjusting for age, sex, V̇o2peak, and marathon finish time was used to compare data across time points. Physiological detraining was evidenced by serial reductions in treadmill performance. Two distinct phases of myocardial remodeling and hematological adaptation were observed. After 4 wk of detraining, there were significant reductions in PV (Δ −6.0%, P < 0.01), left ventricular (LV) wall thickness (Δ −8.1%, <0.05), LV mass (Δ −10.3%, P < 0.001), and right atrial area (Δ −8.2%, P < 0.001). After 8 wk of detraining, there was a significant reduction in right ventricle chamber size (end-diastolic area Δ = −8.0%, P < 0.05) without further concomitant reductions in PV or LV wall thickness. Abrupt reductions in exercise training stimulus result in a structure-specific time course of reverse cardiac remodeling that occurs largely independently of PV contraction. NEW & NOTEWORTHY Significant reverse cardiac remodeling, previously documented among competitive athletes, extends to recreational runners and occurs with a distinct time course. Initial reductions in plasma volume and left ventricular (LV) mass, driven by reductions in wall thickness, are followed by contraction of the right ventricle. Consistent with data from competitive athletes, LV chamber volumes appear less responsive to detraining and may be a more permanent adaptation to sport.
Collapse
Affiliation(s)
- Charles R. Pedlar
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
- School of Sport, Health and Applied Science, St Mary’s University, Twickenham, United Kingdom
| | - Marcel G. Brown
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Robert E. Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - James M. Otto
- Division of Surgery and Interventional Science, University College London, London, United Kingdom
| | - Aimee Drane
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Jennifer Michaud-Finch
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Miranda Contursi
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Meagan M. Wasfy
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Adolph Hutter
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Michael H. Picard
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Gregory D. Lewis
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Aaron L. Baggish
- Cardiovascular Performance Program, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| |
Collapse
|
39
|
Altered Left Ventricular Geometry and Torsional Mechanics in High Altitude-Induced Pulmonary Hypertension: A Three-Dimensional Echocardiographic Study. J Am Soc Echocardiogr 2018; 31:314-322. [DOI: 10.1016/j.echo.2017.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Indexed: 11/21/2022]
|
40
|
Stöhr EJ, Stembridge M, Shave R, Samuel TJ, Stone K, Esformes JI. Systolic and Diastolic Left Ventricular Mechanics during and after Resistance Exercise. Med Sci Sports Exerc 2018; 49:2025-2031. [PMID: 28915224 DOI: 10.1249/mss.0000000000001326] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE To improve the current understanding of the impact of resistance exercise on the heart, by examining the acute responses of left ventricular (LV) strain, twist, and untwisting rate ("LV mechanics"). METHODS LV echocardiographic images were recorded in systole and diastole before, during and immediately after (7-12 s) double-leg press exercise at two intensities (30% and 60% of maximum strength, one-repetition maximum). Speckle tracking analysis generated LV strain, twist, and untwisting rate data. Additionally, beat-by-beat blood pressure was recorded and systemic vascular resistance (SVR) and LV wall stress were calculated. RESULTS Responses in both exercise trials were statistically similar (P > 0.05). During effort, stroke volume decreased, whereas SVR and LV wall stress increased (P < 0.05). Immediately after effort, stroke volume returned to baseline, whereas SVR and wall stress decreased (P < 0.05). Similarly, acute exercise was accompanied by a significant decrease in systolic parameters of LV muscle mechanics (P < 0.05). However, diastolic parameters, including LV untwisting rate, were statistically unaltered (P > 0.05). Immediately after exercise, systolic LV mechanics returned to baseline levels (P < 0.05) but LV untwisting rate increased significantly (P < 0.05). CONCLUSIONS A single, acute bout of double-leg press resistance exercise transiently reduces systolic LV mechanics, but increases diastolic mechanics after exercise, suggesting that resistance exercise has a differential impact on systolic and diastolic heart muscle function. The findings may explain why acute resistance exercise has been associated with reduced stroke volume but chronic exercise training may result in increased LV volumes.
Collapse
Affiliation(s)
- Eric J Stöhr
- Discipline of Physiology & Health, Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UNITED KINGDOM
| | | | | | | | | | | |
Collapse
|
41
|
O'Driscoll JM, Taylor KA, Wiles JD, Coleman DA, Sharma R. Acute cardiac functional and mechanical responses to isometric exercise in prehypertensive males. Physiol Rep 2017; 5:5/7/e13236. [PMID: 28381447 PMCID: PMC5392522 DOI: 10.14814/phy2.13236] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/08/2017] [Accepted: 03/09/2017] [Indexed: 01/10/2023] Open
Abstract
Isometric exercise (IE) training has been shown to reduce resting arterial blood pressure (ABP) in hypertensive, prehypertensive, and normotensive populations. However, the acute hemodynamic response of the heart to such exercise remains unclear. We therefore performed a comprehensive assessment of cardiac structure, function, and mechanics at rest and immediately post a single IE session in 26 male (age 44.8 ± 8.4 years) prehypertensive participants. Conventional echocardiography recorded standard and tissue Doppler measures of left ventricular (LV) structure and function. Speckle tracking echocardiography was used to measure LV global longitudinal, circumferential, and radial strain and strain rate. From this data, apical and basal rotation and rotational velocities, LV twist, systolic twist velocity, untwist velocity, and torsion were determined. IE led to a significant post exercise reduction in systolic (132.6 ± 5.6 vs. 109.4 ± 19.6 mmHg, P < 0.001) and diastolic (77.6 ± 9.4 vs. 58.8 ± 17.2 mmHg, P < 0.001) blood pressure, with no significant change in heart rate (62 ± 9.4 vs. 63 ± 7.5b·min−1, P = 0.63). There were significant reductions in LV end systolic diameter (3.4 ± 0.2 vs. 3.09 ± 0.3 cm, P = 0.002), LV posterior wall thickness (0.99 ± 0.1 vs. 0.9 ± 0.1 cm, P = 0.013), relative wall thickness (0.4 ± 0.06 vs. 0.36 ± 0.05, P = 0.027) estimated filling pressure (E/E' ratio 6.08 ± 1.87 vs. 5.01 ± 0.82, P = 0.006) and proportion of participants with LV concentric remodeling (30.8% vs. 7.8%, P = 0.035), and significant increases in LV ejection fraction (60.8 ± 3 vs. 68.3 ± 4%, P < 0.001), fractional shortening (31.6 ± 4.5 vs. 39.9 ± 5%, P < 0.001), cardiac output (4.3 ± 0.7 vs. 6.1 ± 1L·min−1, P < 0.001), and stroke volume (74.6 ± 11 vs. 96.3 ± 13.5 ml, P < 0.001). In this setting, there were significant increases in global longitudinal strain (−17.8 ± 2.4 vs. −20 ± 1.8%, P = 0.002) and strain rate (−0.88 ± 0.1 vs. −1.03 ± 0.1%, P < 0.001), basal rotation (−5 ± 3.5 vs. −7.22 ± 3.3°, P = 0.047), basal systolic rotational velocity (−51 ± 21.9 vs. −79.3 ± 41.3°·s−1, P = 0.01), basal diastolic rotational velocity (48.7 ± 18.9 vs. 62.3 ± 21.4°·s−1, P = 0.042), LV twist (10.4 ± 5.8 vs. 13.8 ± 5°, P = 0.049), systolic twist velocity (69.6 ± 27.5 vs. 98.8 ± 35.8°·s−1, P = 0.006), and untwist velocity (−64.2 ± 23 vs. −92.8 ± 38°·s−1, P = 0.007). These results suggest that IE improves LV function and mechanics acutely. This may in turn be partly responsible for the observed reductions in ABP following IE training programs and may have important implications for clinical populations.
Collapse
Affiliation(s)
- Jamie M O'Driscoll
- School of Human and Life Sciences, Canterbury Christ Church University, Kent, UK .,Department of Cardiology, St George's Healthcare NHS Trust, Tooting, London, UK
| | - Katrina A Taylor
- School of Human and Life Sciences, Canterbury Christ Church University, Kent, UK
| | - Jonathan D Wiles
- School of Human and Life Sciences, Canterbury Christ Church University, Kent, UK
| | - Damian A Coleman
- School of Human and Life Sciences, Canterbury Christ Church University, Kent, UK
| | - Rajan Sharma
- Department of Cardiology, St George's Healthcare NHS Trust, Tooting, London, UK
| |
Collapse
|
42
|
Kurdziel M, Wasilewski J, Gierszewska K, Kazik A, Pytel G, Wacławski J, Krajewski A, Kurek A, Poloński L, Gąsior M. Echocardiographic Assessment of Right Ventricle Dimensions and Function After Exposure to Extreme Altitude: Is an Expedition to 8000 m Hazardous for Right Ventricular Function? High Alt Med Biol 2017; 18:330-337. [PMID: 28816526 DOI: 10.1089/ham.2017.0019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Kurdziel, Marta, Jarosław Wasilewski, Karolina Gierszewska, Anna Kazik, Gracjan Pytel, Jacek Wacławski, Adam Krajewski, Anna Kurek, Lech Poloński, and Mariusz Gąsior. Echocardiographic assessment of right ventricle dimensions and function after exposure to extreme altitude: Is an expedition to 8000 m hazardous for right ventricular function? High Alt Med Biol 18:330-337, 2017.-Although the right ventricle (RV) is under great hypoxic stress at altitude, still little is known what happens to the RV after descent. The aim of this study was to evaluate RV dimensions and function after exposure to extreme altitude. Therefore, echocardiographic examination was performed according to a protocol that focused on the RV in 11 healthy subjects participating in an expedition to K2 (8611 m) or Broad Peak (BP, 8051 m). In comparison to measurements before the expedition, after 7-8 weeks of sojourn above 2300 meters with the aim of climbing K2 and BP, the RV Tei index increased (0.5 ± 0.1 vs. 0.4 ± 0.1; p = 0.028), and RV free wall longitudinal systolic strain (RVFWLSS) decreased (-23.1% ± 2.7% vs. -25.9% ± 2.4%; p = 0.043). Decrease in peak systolic strain and strain rate was observed in the basal and mid segments of the RV free wall (respectively: -24.4% ± 4.4% vs. -30.9% ± 6.5%; -1.4 ± 0.3 s-1 vs. -1.8 ± 0.3 s-1; -28.7% ± 3.9% vs. -34% ± 3.3%; -1.5 ± 0.2 s-1 vs. -1.9 ± 0.3 s-1; p for all <0.05). The linear RV dimensions, the proximal and distal RV outflow tracks, increased (respectively: 31.3 ± 4 mm vs. 29.2 ± 3 mm, p = 0.025; 27 ± 2.7 mm vs. 24.8 ± 3 mm, p = 0.012). We found that exposure to extreme altitude may cause RV dilatation and a decrease in RV performance. The Tei index and RVFWLSS are sensitive performance indices to detect changes in RV function after the exposure to hypoxic stress. The observed alterations seem to be a manifestation of physiological adaptation to high-altitude condition in healthy individuals.
Collapse
Affiliation(s)
- Marta Kurdziel
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Jarosław Wasilewski
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Karolina Gierszewska
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Anna Kazik
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Gracjan Pytel
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Jacek Wacławski
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Adam Krajewski
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Anna Kurek
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Lech Poloński
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| | - Mariusz Gąsior
- 1 3rd Department of Cardiology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia , Katowice, Poland .,2 Silesian Center for Heart Diseases , Zabrze, Poland
| |
Collapse
|
43
|
Rieger MG, Hoiland RL, Tremblay JC, Stembridge M, Bain AR, Flück D, Subedi P, Anholm JD, Ainslie PN. One session of remote ischemic preconditioning does not improve vascular function in acute normobaric and chronic hypobaric hypoxia. Exp Physiol 2017; 102:1143-1157. [PMID: 28699679 DOI: 10.1113/ep086441] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 06/30/2017] [Indexed: 01/12/2023]
Abstract
NEW FINDINGS What is the central question of this study? It is suggested that remote ischemic preconditioning (RIPC) might offer protection against ischaemia-reperfusion injuries, but the utility of RIPC in high-altitude settings remains unclear. What is the main finding and its importance? We found that RIPC offers no vascular protection relative to pulmonary artery pressure or peripheral endothelial function during acute, normobaric hypoxia and at high altitude in young, healthy adults. However, peripheral chemosensitivity was heightened 24 h after RIPC at high altitude. Application of repeated short-duration bouts of ischaemia to the limbs, termed remote ischemic preconditioning (RIPC), is a novel technique that might have protective effects on vascular function during hypoxic exposures. In separate parallel-design studies, at sea level (SL; n = 16) and after 8-12 days at high altitude (HA; n = 12; White Mountain, 3800 m), participants underwent either a sham protocol or one session of four bouts of 5 min of dual-thigh-cuff occlusion with 5 min recovery. Brachial artery flow-mediated dilatation (FMD; ultrasound), pulmonary artery systolic pressure (PASP; echocardiography) and internal carotid artery (ICA) flow (ultrasound) were measured at SL in normoxia and isocapnic hypoxia (end-tidal PO2 maintained at 50 mmHg) and during normal breathing at HA. The hypoxic ventilatory response (HVR) was measured at each location. All measures at SL and HA were obtained at baseline (BL) and at 1, 24 and 48 h post-RIPC or sham. At SL, RIPC produced no changes in FMD, PASP, ICA flow, end-tidal gases or HVR in normoxia or hypoxia. At HA, although HVR increased 24 h post-RIPC compared with BL [2.05 ± 1.4 versus 3.21 ± 1.2 l min-1 (% arterial O2 saturation)-1 , P < 0.01], there were no significant differences in FMD, PASP, ICA flow and resting end-tidal gases. Accordingly, a single session of RIPC is insufficient to evoke changes in peripheral, pulmonary and cerebral vascular function in healthy adults. Although chemosensitivity might increase after RIPC at HA, this did not confer any vascular changes. The utility of a single RIPC session seems unremarkable during acute and chronic hypoxia.
Collapse
Affiliation(s)
- Mathew G Rieger
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Joshua C Tremblay
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UK
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada.,University of Colorado, Boulder, Department of Integrative Physiology, Integrative Vascular Biology Laboratory, Boulder, CO, USA
| | - Daniela Flück
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Prajan Subedi
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, CA, USA
| | - James D Anholm
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, CA, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| |
Collapse
|
44
|
Williams AM, Shave RE, Cheyne WS, Eves ND. The influence of adrenergic stimulation on sex differences in left ventricular twist mechanics. J Physiol 2017; 595:3973-3985. [PMID: 28188951 DOI: 10.1113/jp273368] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 02/05/2017] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Sex differences in left ventricular (LV) mechanics occur during acute physiological challenges; however, it is unknown whether sex differences in LV mechanics are fundamentally regulated by differences in adrenergic control. Using two-dimensional echocardiography and speckle tracking analysis, this study compared LV mechanics in males and females matched for LV length during post-exercise ischaemia (PEI) and β1 -adrenergic receptor blockade. Our data demonstrate that while basal rotation was increased in males, LV twist was not significantly different between the sexes during PEI. In contrast, during β1 -adrenergic receptor blockade, LV apical rotation, twist and untwisting velocity were reduced in males compared to females. Significant relationships were observed between LV twist and LV internal diameter and sphericity index in females, but not males. These findings suggest that LV twist mechanics may be more sensitive to alterations in adrenergic stimulation in males, but more highly influenced by ventricular structure and geometry in females. ABSTRACT Sex differences in left ventricular (LV) mechanics exist at rest and during acute physiological stress. Differences in cardiac autonomic and adrenergic control may contribute to sex differences in LV mechanics and LV haemodynamics. Accordingly, this study aimed to investigate sex differences in LV mechanics with altered adrenergic stimulation achieved through post-handgrip-exercise ischaemia (PEI) and β1 -adrenergic receptor (AR) blockade. Twenty males (23 ± 5 years) and 20 females (22 ± 3 years) were specifically matched for LV length (males: 8.5 ± 0.5 cm, females: 8.2 ± 0.6 cm, P = 0.163), and two-dimensional speckle-tracking echocardiography was used to assess LV structure and function at baseline, during PEI and following administration of 5 mg bisoprolol (β1 -AR antagonist). During PEI, LV end-diastolic volume and stroke volume were increased in both groups (P < 0.001), as was end-systolic wall stress (P < 0.001). LV twist and apical rotation were not altered from baseline or different between the sexes; however, basal rotation increased in males (P = 0.035). During β1 -AR blockade, LV volumes were unchanged but blood pressure and heart rate were reduced in both groups (P < 0.001). LV apical rotation (P = 0.036) and twist (P = 0.029) were reduced in males with β1 -AR blockade but not females, resulting in lower apical rotation (males: 6.8 ± 2.1 deg, females: 8.8 ± 2.3 deg, P = 0.007) and twist (males: 8.6 ± 1.9 deg, females: 10.7 ± 2.8 deg, P = 0.008), and slower untwisting velocity (males: 68.2 ± 22.1 deg s-1 , females: 82.0 ± 18.7 deg s-1 , P = 0.046) compared to females. LV twist mechanics are reduced in males compared to females during reductions to adrenergic stimulation, providing preliminary evidence that LV twist mechanics may be more sensitive to adrenergic control in males than in females.
Collapse
Affiliation(s)
- Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, University of British Columbia, Kelowna, Canada
| | - Rob E Shave
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UK
| | - William S Cheyne
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, University of British Columbia, Kelowna, Canada
| | - Neil D Eves
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, University of British Columbia, Kelowna, Canada
| |
Collapse
|
45
|
Siebenmann C, Rasmussen P, Hug M, Keiser S, Flück D, Fisher JP, Hilty MP, Maggiorini M, Lundby C. Parasympathetic withdrawal increases heart rate after 2 weeks at 3454 m altitude. J Physiol 2017; 595:1619-1626. [PMID: 27966225 DOI: 10.1113/jp273726] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 11/21/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Heart rate is increased in chronic hypoxia and we tested whether this is the result of increased sympathetic nervous activity, reduced parasympathetic nervous activity, or a non-autonomic mechanism. In seven lowlanders, heart rate was measured at sea level and after 2 weeks at high altitude after individual and combined pharmacological inhibition of sympathetic and/or parasympathetic control of the heart. Inhibition of parasympathetic control of the heart alone or in combination with inhibition of sympathetic control abolished the high altitude-induced increase in heart rate. Inhibition of sympathetic control of the heart alone did not prevent the high altitude-induced increase in heart rate. These results indicate that a reduced parasympathetic nervous activity is the main mechanism underlying the elevated heart rate in chronic hypoxia. ABSTRACT Chronic hypoxia increases resting heart rate (HR), but the underlying mechanism remains incompletely understood. We investigated the relative contributions of the sympathetic and parasympathetic nervous systems, along with potential non-autonomic mechanisms, by individual and combined pharmacological inhibition of muscarinic and/or β-adrenergic receptors. In seven healthy lowlanders, resting HR was determined at sea level (SL) and after 15-18 days of exposure to 3454 m high altitude (HA) without drug intervention (control, CONT) as well as after intravenous administration of either propranolol (PROP), or glycopyrrolate (GLYC), or PROP and GLYC in combination (PROP+GLYC). Circulating noradrenaline concentration increased from 0.9 ± 0.4 nmol l-1 at SL to 2.7 ± 1.5 nmol l-1 at HA (P = 0.03). The effect of HA on HR depended on the type of autonomic inhibition (P = 0.006). Specifically, HR was increased at HA from 64 ± 10 to 74 ± 12 beats min-1 during the CONT treatment (P = 0.007) and from 52 ± 4 to 59 ± 5 beats min-1 during the PROP treatment (P < 0.001). In contrast, HR was similar between SL and HA during the GLYC treatment (110 ± 7 and 112 ± 5 beats min-1 , P = 0.28) and PROP+GLYC treatment (83 ± 5 and 85 ± 5 beats min-1 , P = 0.25). Our results identify a reduction in cardiac parasympathetic activity as the primary mechanism underlying the elevated HR associated with 2 weeks of exposure to hypoxia. Unexpectedly, the sympathoactivation at HA that was evidenced by increased circulating noradrenaline concentration had little effect on HR, potentially reflecting down-regulation of cardiac β-adrenergic receptor function in chronic hypoxia. These effects of chronic hypoxia on autonomic control of the heart may concern not only HA dwellers, but also patients with disorders that are associated with hypoxaemia.
Collapse
Affiliation(s)
- Christoph Siebenmann
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland.,Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - Peter Rasmussen
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland.,H. Lundbeck A/S, Valby, Denmark
| | - Mike Hug
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Stefanie Keiser
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Daniela Flück
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - James P Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Matthias P Hilty
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - Marco Maggiorini
- Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland
| | - Carsten Lundby
- Centre for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland
| |
Collapse
|
46
|
Williams AM, Shave RE, Stembridge M, Eves ND. Females have greater left ventricular twist mechanics than males during acute reductions to preload. Am J Physiol Heart Circ Physiol 2016; 311:H76-84. [PMID: 27199112 DOI: 10.1152/ajpheart.00057.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 05/09/2016] [Indexed: 11/22/2022]
Abstract
Compared to males, females have smaller left ventricular (LV) dimensions and volumes, higher ejection fractions (EF), and higher LV longitudinal and circumferential strain. LV twist mechanics determine ventricular function and are preload-dependent. Therefore, the sex differences in LV structure and myocardial function may result in different mechanics when preload is altered. This study investigated sex differences in LV mechanics during acute challenges to preload. With the use of conventional and speckle-tracking echocardiography, LV structure and function were assessed in 20 males (24 ± 6.2 yr) and 20 females (23 ± 3.1 yr) at baseline and during progressive levels of lower body negative pressure (LBNP). Fourteen participants (8 males, 6 females) were also assessed following a rapid infusion of saline. LV end-diastolic volume, end-systolic volume, stroke volume (SV), and EF were reduced in both groups during LBNP (P < 0.001). While males had greater absolute volumes (P < 0.001), there were no sex differences in allometrically scaled volumes at any stage. Sex differences were not detected at baseline in basal rotation, apical rotation, or twist. Apical rotation and twist increased in both groups (P < 0.001) with LBNP. At -60 mmHg, females had greater apical rotation (P = 0.009), twist (P = 0.008), and torsion (P = 0.002) and faster untwisting velocity (P = 0.02) than males. There were no differences in mechanics following saline infusion. Females have larger LV twist and a faster untwisting velocity than males during large reductions to preload, supporting that females have a greater reliance on LV twist mechanics to maintain SV during severe reductions to preload.
Collapse
Affiliation(s)
- Alexandra M Williams
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and
| | - Rob E Shave
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Mike Stembridge
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Neil D Eves
- Centre for Heart, Lung and Vascular Health, Faculty of Health and Social Development, The University of British Columbia, Kelowna, Canada; and
| |
Collapse
|
47
|
Armstrong C, Samuel J, Yarlett A, Cooper SM, Stembridge M, Stöhr EJ. The Effects of Exercise Intensity vs. Metabolic State on the Variability and Magnitude of Left Ventricular Twist Mechanics during Exercise. PLoS One 2016; 11:e0154065. [PMID: 27100099 PMCID: PMC4839594 DOI: 10.1371/journal.pone.0154065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 04/07/2016] [Indexed: 11/18/2022] Open
Abstract
Increased left ventricular (LV) twist and untwisting rate (LV twist mechanics) are essential responses of the heart to exercise. However, previously a large variability in LV twist mechanics during exercise has been observed, which complicates the interpretation of results. This study aimed to determine some of the physiological sources of variability in LV twist mechanics during exercise. Sixteen healthy males (age: 22 ± 4 years, V˙O2peak: 45.5 ± 6.9 ml∙kg-1∙min-1, range of individual anaerobic threshold (IAT): 32–69% of V˙O2peak) were assessed at rest and during exercise at: i) the same relative exercise intensity, 40%peak, ii) at 2% above IAT, and, iii) at 40%peak with hypoxia (40%peak+HYP). LV volumes were not significantly different between exercise conditions (P > 0.05). However, the mean margin of error of LV twist was significantly lower (F2,47 = 2.08, P < 0.05) during 40%peak compared with IAT (3.0 vs. 4.1 degrees). Despite the same workload and similar LV volumes, hypoxia increased LV twist and untwisting rate (P < 0.05), but the mean margin of error remained similar to that during 40%peak (3.2 degrees, P > 0.05). Overall, LV twist mechanics were linearly related to rate pressure product. During exercise, the intra-individual variability of LV twist mechanics is smaller at the same relative exercise intensity compared with IAT. However, the absolute magnitude (degrees) of LV twist mechanics appears to be associated with the prevailing rate pressure product. Exercise tests that evaluate LV twist mechanics should be standardised by relative exercise intensity and rate pressure product be taken into account when interpreting results.
Collapse
Affiliation(s)
- Craig Armstrong
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Jake Samuel
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Andrew Yarlett
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Stephen-Mark Cooper
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Mike Stembridge
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Eric J. Stöhr
- Discipline of Physiology & Health, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
- * E-mail:
| |
Collapse
|
48
|
Boos CJ, O’Hara JP, Mellor A, Hodkinson PD, Tsakirides C, Reeve N, Gallagher L, Green NDC, Woods DR. A Four-Way Comparison of Cardiac Function with Normobaric Normoxia, Normobaric Hypoxia, Hypobaric Hypoxia and Genuine High Altitude. PLoS One 2016; 11:e0152868. [PMID: 27100313 PMCID: PMC4839767 DOI: 10.1371/journal.pone.0152868] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 03/21/2016] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND There has been considerable debate as to whether different modalities of simulated hypoxia induce similar cardiac responses. MATERIALS AND METHODS This was a prospective observational study of 14 healthy subjects aged 22-35 years. Echocardiography was performed at rest and at 15 and 120 minutes following two hours exercise under normobaric normoxia (NN) and under similar PiO2 following genuine high altitude (GHA) at 3,375 m, normobaric hypoxia (NH) and hypobaric hypoxia (HH) to simulate the equivalent hypoxic stimulus to GHA. RESULTS All 14 subjects completed the experiment at GHA, 11 at NN, 12 under NH, and 6 under HH. The four groups were similar in age, sex and baseline demographics. At baseline rest right ventricular (RV) systolic pressure (RVSP, p = 0.0002), pulmonary vascular resistance (p = 0.0002) and acute mountain sickness (AMS) scores were higher and the SpO2 lower (p<0.0001) among all three hypoxic groups (GHA, NH and HH) compared with NN. At both 15 minutes and 120 minutes post exercise, AMS scores, Cardiac output, septal S', lateral S', tricuspid S' and A' velocities and RVSP were higher and SpO2 lower with all forms of hypoxia compared with NN. On post-test analysis, among the three hypoxia groups, SpO2 was lower at baseline and 15 minutes post exercise with GHA (89.3±3.4% and 89.3±2.2%) and HH (89.0±3.1 and (89.8±5.0) compared with NH (92.9±1.7 and 93.6±2.5%). The RV Myocardial Performance (Tei) Index and RVSP were significantly higher with HH than NH at 15 and 120 minutes post exercise respectively and tricuspid A' was higher with GHA compared with NH at 15 minutes post exercise. CONCLUSIONS GHA, NH and HH produce similar cardiac adaptations over short duration rest despite lower SpO2 levels with GHA and HH compared with NH. Notable differences emerge following exercise in SpO2, RVSP and RV cardiac function.
Collapse
Affiliation(s)
- Christopher John Boos
- Department of Cardiology, Poole Hospital NHS Foundation trust, Poole, United Kingdom
- Dept of Postgraduate Medical Education, Bournemouth University, Bournemouth, United Kingdom
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
- * E-mail:
| | - John Paul O’Hara
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
| | - Adrian Mellor
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
- James Cook University Hospital, Middlesbrough, TS4 3BW, United Kingdom
- Defence Medical Services, Lichfield, United Kingdom
| | - Peter David Hodkinson
- Defence Medical Services, Lichfield, United Kingdom
- RAF Centre of Aviation Medicine, RAF Henlow, Beds, SG16 6DN, United Kingdom
- Division of Anaesthesia, University of Cambridge, Box 93, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2QQ, United Kingdom
| | - Costas Tsakirides
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
| | - Nicola Reeve
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
| | - Liam Gallagher
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
| | - Nicholas Donald Charles Green
- Defence Medical Services, Lichfield, United Kingdom
- RAF Centre of Aviation Medicine, RAF Henlow, Beds, SG16 6DN, United Kingdom
| | - David Richard Woods
- Research Institute, for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, United Kingdom
- Defence Medical Services, Lichfield, United Kingdom
- Northumbria and Newcastle NHS Trusts, Wansbeck General and Royal Victoria Infirmary, Newcastle, United Kingdom
- University of Newcastle, Newcastle upon Tyne, United Kingdom
| |
Collapse
|
49
|
van Mil ACCM, Pearson J, Drane AL, Cockcroft JR, McDonnell BJ, Stöhr EJ. Interaction between left ventricular twist mechanics and arterial haemodynamics during localised, non-metabolic hyperaemia with and without blood flow restriction. Exp Physiol 2016; 101:509-20. [DOI: 10.1113/ep085623] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 01/21/2016] [Indexed: 12/17/2022]
Affiliation(s)
| | - James Pearson
- Cardiff Metropolitan University; Cardiff UK
- University of Colorado; Colorado Springs CO USA
| | | | | | | | | |
Collapse
|
50
|
Abstract
Simonson, Tatum S. Altitude adaptation: A glimpse through various lenses. High Alt Med Biol 16:125-137, 2015.--Recent availability of genome-wide data from highland populations has enabled the identification of adaptive genomic signals. Some of the genomic signals reported thus far among Tibetan, Andean, and Ethiopian are the same, while others appear unique to each population. These genomic findings parallel observations conveyed by decades of physiological research: different continental populations, resident at high altitude for hundreds of generations, exhibit a distinct composite of traits at altitude. The most commonly reported signatures of selection emanate from genomic segments containing hypoxia-inducible factor (HIF) pathway genes. Corroborative evidence for adaptive significance stems from associations between putatively adaptive gene copies and sea-level ranges of hemoglobin concentration in Tibetan and Amhara Ethiopians, birth weights and metabolic factors in Andeans and Tibetans, maternal uterine artery diameter in Andeans, and protection from chronic mountain sickness in Andean males at altitude. While limited reports provide mechanistic insights thus far, efforts to identify and link precise genetic variants to molecular, physiological, and developmental functions are underway, and progress on the genomics front continues to provide unprecedented movement towards these goals. This combination of multiple perspectives is necessary to maximize our understanding of orchestrated biological and evolutionary processes in native highland populations, which will advance our understanding of both adaptive and non-adaptive responses to hypoxia.
Collapse
Affiliation(s)
- Tatum S Simonson
- Department of Medicine, Division of Physiology, University of California , San Diego, La Jolla, California
| |
Collapse
|