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Ishii K, Idesako M, Asahara R, Liang N, Matsukawa K. Central command suppresses pressor-evoked bradycardia at the onset of voluntary standing up in conscious cats. Exp Physiol 2023; 108:28-37. [PMID: 36404613 PMCID: PMC10103771 DOI: 10.1113/ep090718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 11/01/2022] [Indexed: 11/22/2022]
Abstract
NEW FINDINGS What is the central question of this study? Standing up can cause hypotension and tachycardia. Accumulated evidence poses the simple question, does the cardiac baroreflex operate at the onset of standing up? If the cardiac baroreflex is suppressed, what mechanism is responsible for baroreflex inhibition? What is the main finding and its importance? In cats, we found blunting of cardiac baroreflex sensitivity in the pressor range at the onset of voluntary hindlimb standing, but not of passive hindlimb standing. This finding suggests that central command suppresses pressor-evoked bradycardia at the onset of standing up, probably in advance, to prevent or buffer orthostatic hypotension. ABSTRACT It remains unclear whether cardiac baroreflex function is preserved or suppressed at the onset of standing up. To answer the question and, if cardiac baroreflex is suppressed, to investigate the mechanism responsible for the suppression, we compared the sensitivity of the arterial cardiac baroreflex at the onset of voluntary and passive hindlimb standing in conscious cats. Cardiac baroreflex sensitivity was estimated from the maximal slope of the baroreflex curve between the responses of systolic arterial blood pressure and heart rate to a brief occlusion of the abdominal aorta. The systolic arterial blood pressure response to standing up without aortic occlusion was greater in the voluntary case than in the passive case. Cardiac baroreflex sensitivity was clearly decreased at the onset of voluntary standing up compared with rest (P = 0.005) and the onset of passive standing up (P = 0.007). The cardiac baroreflex sensitivity at the onset of passive standing up was similar to that at rest (P = 0.909). The findings suggest that central command would transmit a modulatory signal to the cardiac baroreflex system during the voluntary initiation of standing up. Furthermore, the present data tempt speculation on a close relationship between central inhibition of the cardiac baroreflex and the centrally induced tachycardiac response to standing up.
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Affiliation(s)
- Kei Ishii
- Human Informatics and Interaction Research InstituteNational Institute of Advanced Industrial Science and TechnologyTsukubaIbarakiJapan
- Department of Integrative PhysiologyGraduate School of Biomedical and Health SciencesHiroshima UniversityMinami‐kuHiroshimaJapan
| | - Mitsuhiro Idesako
- Department of Integrative PhysiologyGraduate School of Biomedical and Health SciencesHiroshima UniversityMinami‐kuHiroshimaJapan
| | - Ryota Asahara
- Human Informatics and Interaction Research InstituteNational Institute of Advanced Industrial Science and TechnologyTsukubaIbarakiJapan
- Department of Integrative PhysiologyGraduate School of Biomedical and Health SciencesHiroshima UniversityMinami‐kuHiroshimaJapan
| | - Nan Liang
- Department of Integrative PhysiologyGraduate School of Biomedical and Health SciencesHiroshima UniversityMinami‐kuHiroshimaJapan
- Cognitive Motor Neuroscience, Human Health SciencesGraduate School of MedicineKyoto UniversitySakyo‐kuKyotoJapan
| | - Kanji Matsukawa
- Department of Integrative PhysiologyGraduate School of Biomedical and Health SciencesHiroshima UniversityMinami‐kuHiroshimaJapan
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2
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van der Ster BJP, Kim YS, Westerhof BE, van Lieshout JJ. Central Hypovolemia Detection During Environmental Stress-A Role for Artificial Intelligence? Front Physiol 2021; 12:784413. [PMID: 34975538 PMCID: PMC8715014 DOI: 10.3389/fphys.2021.784413] [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: 09/27/2021] [Accepted: 11/18/2021] [Indexed: 11/19/2022] Open
Abstract
The first step to exercise is preceded by the required assumption of the upright body position, which itself involves physical activity. The gravitational displacement of blood from the chest to the lower parts of the body elicits a fall in central blood volume (CBV), which corresponds to the fraction of thoracic blood volume directly available to the left ventricle. The reduction in CBV and stroke volume (SV) in response to postural stress, post-exercise, or to blood loss results in reduced left ventricular filling, which may manifest as orthostatic intolerance. When termination of exercise removes the leg muscle pump function, CBV is no longer maintained. The resulting imbalance between a reduced cardiac output (CO) and a still enhanced peripheral vascular conductance may provoke post-exercise hypotension (PEH). Instruments that quantify CBV are not readily available and to express which magnitude of the CBV in a healthy subject should remains difficult. In the physiological laboratory, the CBV can be modified by making use of postural stressors, such as lower body "negative" or sub-atmospheric pressure (LBNP) or passive head-up tilt (HUT), while quantifying relevant biomedical parameters of blood flow and oxygenation. Several approaches, such as wearable sensors and advanced machine-learning techniques, have been followed in an attempt to improve methodologies for better prediction of outcomes and to guide treatment in civil patients and on the battlefield. In the recent decade, efforts have been made to develop algorithms and apply artificial intelligence (AI) in the field of hemodynamic monitoring. Advances in quantifying and monitoring CBV during environmental stress from exercise to hemorrhage and understanding the analogy between postural stress and central hypovolemia during anesthesia offer great relevance for healthy subjects and clinical populations.
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Affiliation(s)
- Björn J. P. van der Ster
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Anesthesiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Yu-Sok Kim
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Internal Medicine, Medisch Centrum Leeuwarden, Leeuwarden, Netherlands
| | - Berend E. Westerhof
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Pulmonary Medicine, Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Johannes J. van Lieshout
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Medical Research Council Versus Arthritis Centre for Musculoskeletal Ageing Research, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, The Medical School, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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3
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Frandsen MN, Mehlsen J, Bang Foss N, Kehlet H. Pre-operative autonomic nervous system function - a missing link for post-induction hypotension? Anaesthesia 2021; 77:139-142. [PMID: 34291821 DOI: 10.1111/anae.15546] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2021] [Indexed: 01/07/2023]
Affiliation(s)
- M N Frandsen
- Section of Surgical Pathophysiology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - J Mehlsen
- Section of Surgical Pathophysiology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - N Bang Foss
- Department of Anaesthesiology, Hvidovre University Hospital, Hvidore, Denmark
| | - H Kehlet
- Section of Surgical Pathophysiology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
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4
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Ogoh S, Washio T, Paton JFR, Fisher JP, Petersen LG. Gravitational effects on intracranial pressure and blood flow regulation in young men: a potential shunting role for the external carotid artery. J Appl Physiol (1985) 2020; 129:901-908. [PMID: 32816640 DOI: 10.1152/japplphysiol.00369.2020] [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: 12/11/2022] Open
Abstract
We sought to determine whether gravity-induced changes in intracranial pressure influence cerebral blood flow regulation. Accordingly, nine young healthy men were studied while supine (0°) and during mild changes in hydrostatic pressure induced by head-up tilt at +20° and +10° (HUT+20 and HUT+10) and head-down tilt at -20° and -10° (HDT-20, HDT-10). Blood flows were measured in the internal and external carotid and vertebral arteries (ICA, ECA, and VA). Intraocular pressure (IOP) was measured as an indicator of hydrostatic changes in intracranial pressure. A posture change from HUT+20 to HDT-20 increased IOP by +5.1 ± 1.9 mmHg (P < 0.001) and ECA blood flow (from 61.7 ± 26.1 to 87.6 ± 46.4 mL/min, P = 0.004) but did not affect ICA (P = 0.528) or VA (P = 0.101) blood flow. The increase in ECA flow correlated with the tilt angle and resultant changes in intracranial pressures (by IOP), thus indicating a passive hydrostatic gravitational dependence (r = 0.371, P = 0.012). On the contrary, ICA flow remained constant and thus well protected against moderate orthostatic stress. When ICA flow was corrected for the gravitational changes in intracranial pressures (by IOP), it demonstrated the same magnitude of gravitational dependence as ECA. These findings suggest that passive hydrostatic increases in intracranial pressure outbalance the concurrent increase in arterial feeding pressure to the brain and thus prevent cerebral hyperperfusion during HDT. The mechanism for maintaining constant cerebral flow was by increased ECA flow, thus supporting the role of these vascular beds as a shunting pathway.NEW & NOTEWORTHY We investigated whether gravity-induced changes in intracranial pressure influence cerebral blood flow regulation in young men. We recorded extra- and intracerebral blood flow during changes in posture, and data indicate that the external carotid artery may serve as an overflow pathway to prevent cerebral hyperperfusion during increases in cerebral arterial blood pressure.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Takuro Washio
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Lonnie G Petersen
- Department of Biomedical Science, Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark.,Department of Radiology, University of California, San Diego, California.,Department of Mechanical and Aerospace Engineering, University of California, San Diego, California
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5
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Raimundo Fernades ÉM, de Moura SS, Silva RO, Totou NL, Baleeiro RDS, de Oliveira EC, Coelho DB, Cardoso LM, Becker LK. Acute volume expansion decreased baroreflex response after swimming but not after running exercise training in hypertensive rats. Clin Exp Hypertens 2019; 42:460-468. [DOI: 10.1080/10641963.2019.1693588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
| | - Samara Silva de Moura
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
| | | | - Nádia Lúcia Totou
- Research Center in Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | | | - Emerson Cruz de Oliveira
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Daniel Barbosa Coelho
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Leonardo Máximo Cardoso
- Research Center in Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Lenice Kappes Becker
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
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6
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Alessandro C, Sarabadani Tafreshi A, Riener R. Cardiovascular responses to leg muscle loading during head-down tilt at rest and after dynamic exercises. Sci Rep 2019; 9:2804. [PMID: 30808948 PMCID: PMC6391465 DOI: 10.1038/s41598-019-39360-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/18/2019] [Indexed: 01/09/2023] Open
Abstract
The physiological processes underlying hemodynamic homeostasis can be modulated by muscle activity and gravitational loading. The effects of leg muscle activity on cardiovascular regulation have been observed during orthostatic stress. Here, we evaluated such effects during head-down tilt (HDT). In this posture, the gravitational gradient along the body is different than in upright position, leading to increased central blood volume and reduced venous pooling. We compared the cardiovascular signals obtained with and without leg muscle loading during HDT in healthy human subjects, both at rest and during recovery from leg-press exercises using a robotic device. Further, we compared such cardiovascular responses to those obtained during upright position. Loading leg muscles during HDT at rest led to significantly higher values of arterial blood pressure than without muscle loading, and restored systolic values to those observed during upright posture. Maintaining muscle loading post-exercise altered the short-term cardiovascular responses, but not the values of the signals five minutes after the exercise. These results suggest that leg muscle activity modulates cardiovascular regulation during HDT. This modulation should therefore be considered when interpreting cardiovascular responses to conditions that affect both gravity loading and muscle activity, for example bed rest or microgravity.
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Affiliation(s)
- Cristiano Alessandro
- Northwestern University, Feinberg School of Medicine, Department of Physiology, Chicago, USA.
- ETH Zurich, Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, Zurich, Switzerland.
| | - Amirehsan Sarabadani Tafreshi
- ETH Zurich, Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, Zurich, Switzerland
| | - Robert Riener
- ETH Zurich, Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, Zurich, Switzerland
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7
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Totou NL, Moura SS, Coelho DB, Oliveira EC, Becker LK, Lima WG. Swimming exercise demonstrates advantages over running exercise in reducing proteinuria and glomerulosclerosis in spontaneously hypertensive rats. Physiol Int 2018; 105:76-85. [PMID: 29602293 DOI: 10.1556/2060.105.2018.1.7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Experimental studies in animal models have described the benefits of physical exercise (PE) to kidney diseases associated with hypertension. Land- and water-based exercises induce different responses in renal function. Our aim was to evaluate the renal alterations induced by different environments of PE in spontaneously hypertensive rats (SHRs). The SHRs were divided into sedentary (S), swimming exercise (SE), and running exercise (RE) groups, and were trained for 8 weeks under similar intensities (60 min/day). Arterial pressure (AP) and heart rate (HR) were recorded. The renal function was evaluated through urinary volume at each week of training; sodium and potassium excretions, plasma and urinary osmolarities, glomerular filtration rate (GFR), levels of proteinuria, and renal damage were determined. SE and RE rats presented reduced mean AP, systolic blood pressure, and HR in comparison with S group. SE and RE rats showed higher urine osmolarity compared with S. SE rats showed higher free water clearance (P < 0.01), lower urinary density (P < 0.0001), and increased weekly urine volume (P < 0.05) in comparison with RE and S groups. GFR was increased in both SE and RE rats. The proteinuria of SE (7.0 ± 0.8 mg/24 h) rats was decreased at the 8th week of the PE in comparison with RE (9.6 ± 0.8 mg/24 h) and S (9.8 ± 0.5 mg/24 h) groups. The glomerulosclerosis was reduced in SE rats (P < 0.02). SE produced different response in renal function in comparison with RE, in which only swimming-trained rats had better profile for proteinuria and glomerulosclerosis.
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Affiliation(s)
- N L Totou
- 1 Department of Biological Sciences (DECBI), Federal University of Ouro Preto , Minas Gerais, Brazil
| | - S S Moura
- 2 Sports Center (CEDUFOP), Federal University of Ouro Preto , Minas Gerais, Brazil
| | - D B Coelho
- 2 Sports Center (CEDUFOP), Federal University of Ouro Preto , Minas Gerais, Brazil
| | - E C Oliveira
- 2 Sports Center (CEDUFOP), Federal University of Ouro Preto , Minas Gerais, Brazil
| | - L K Becker
- 2 Sports Center (CEDUFOP), Federal University of Ouro Preto , Minas Gerais, Brazil
| | - W G Lima
- 1 Department of Biological Sciences (DECBI), Federal University of Ouro Preto , Minas Gerais, Brazil
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8
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Ogoh S, Marais M, Lericollais R, Denise P, Raven PB, Normand H. Interaction between graviception and carotid baroreflex function in humans during parabolic flight-induced microgravity. J Appl Physiol (1985) 2018; 125:634-641. [PMID: 29745800 DOI: 10.1152/japplphysiol.00198.2018] [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] [Indexed: 01/04/2023] Open
Abstract
The aim of the present study was to assess carotid baroreflex (CBR) function during acute changes in otolithic activity in humans. To address this question, we designed a set of experiments to identify the modulatory effects of microgravity on CBR function at a tilt angle of -2°, which was identified to minimize changes in central blood volume during parabolic flight. During parabolic flight at 0 and 1 g, CBR function curves were modeled from the heart rate (HR) and mean arterial pressure (MAP) responses to rapid pulse trains of neck pressure and neck suction ranging from +40 to -80 Torr; CBR control of HR (carotid-HR) and MAP (carotid-MAP) function curves, respectively. The maximal gain of both carotid-HR and carotid-MAP baroreflex function curves were augmented during microgravity compared with 1 g (carotid-HR, -0.53 to -0.80 beats·min-1·mmHg-1, P < 0.05; carotid-MAP, -0.24 to -0.30 mmHg/mmHg, P < 0.05). These findings suggest that parabolic flight-induced acute change of otolithic activity may modify CBR function and identifies that the vestibular system contributes to blood pressure regulation under fluctuations in gravitational forces. NEW & NOTEWORTHY The effect of acute changes in vestibular activity on arterial baroreflex function remains unclear. In the present study, we assessed carotid baroreflex function without changes in central blood volume during parabolic flight, which causes acute changes in otolithic activity. The sensitivity of both carotid heart rate and carotid mean arterial pressure baroreflex function was augmented in microgravity compared with 1 g, suggesting that the vestibular system contributes to blood pressure regulation in humans on Earth.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University , Saitama , Japan
| | - Michaël Marais
- Normandie University , France.,UNICAEN, COMETE, Caen , France.,INSERM, U 1075 COMETE, Caen , France
| | - Romain Lericollais
- Normandie University , France.,UNICAEN, COMETE, Caen , France.,INSERM, U 1075 COMETE, Caen , France.,CHU de Caen, Department of Clinical Physiology , Caen , France
| | - Pierre Denise
- Normandie University , France.,UNICAEN, COMETE, Caen , France.,INSERM, U 1075 COMETE, Caen , France.,CHU de Caen, Department of Clinical Physiology , Caen , France
| | - Peter B Raven
- Department of Integrative Physiology, University of North Texas, Health Science Center , Fort Worth, Texas
| | - Hervé Normand
- Normandie University , France.,UNICAEN, COMETE, Caen , France.,INSERM, U 1075 COMETE, Caen , France.,CHU de Caen, Department of Clinical Physiology , Caen , France
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9
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Chalghoum A, Noichri Y, Dandana A, Baudin B, Miled A, Ferchichi S. Pathological interactions between the endothelin-1 and the angiotensin- converting enzyme among Tunisian coronary patients. BMC Cardiovasc Disord 2016; 16:244. [PMID: 27894250 PMCID: PMC5127035 DOI: 10.1186/s12872-016-0417-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 11/16/2016] [Indexed: 11/29/2022] Open
Abstract
Background The correct understanding of the biochemical and metabolic interactions between coronary risk factors contribute to the exploration of cardiovascular pathophysiology and improves therapeutic care. The aim of this study was to explore the endothelin-1 (ET-1) concentration and the angiotensin converting enzyme (ACE) activity among Tunisian patients with coronary heart disease, and to investigate the metabolic relationships between these two markers,… and to assess the possible relationship between them and the different risk factors. In this present study, ET-1 concentration was determined by an analytical method (High Performance Chromatography, coupled by Mass Spectrometry), ACE activity was measured by a kinetic method for patients and healthy controls. These subjects (157 patients and 142 controls) beneficed also by a biochemical exploration (lipid, apolipoproteins and glucose profiles) to quantify cardiovascular risk. Results A statistically significant increase of the ET-1 concentration was found among patients compared to healthy controls (15.2 ± 5.3 nM vs 7.1 ± 2.7 nM, p < 0,00001). For the ACE activity, in spite the treatment of the majority of patients (97%) with ACE inhibitors, this activity was statistically elevated in patients compared to healthy subjects (86.7 ± 25.4 IU/L vs 42.8 ± 12.1 IU/L, p < 0.00001). Furthermore, a statistically positive correlation was identified between these two cardiac markers (r = 0.68 p < 0.00001). Conclusion The study of the metabolic relationship between the ET-1 and ACE among coronary patients reveals other therapeutics targets.
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Affiliation(s)
- Abdelkader Chalghoum
- Laboratory of Biochemistry, Farhat HACHED Hospital, Street Doctor Moreau, 4000, Sousse, Tunisia. .,Valorization and Technology Transfer Space, Center of Biotechnology of Borj Cedria, 2050, HamamLif, Tunisia.
| | - Yosri Noichri
- Laboratory of Biochemistry, Farhat HACHED Hospital, Street Doctor Moreau, 4000, Sousse, Tunisia
| | - Azza Dandana
- Laboratory of Biochemistry, Farhat HACHED Hospital, Street Doctor Moreau, 4000, Sousse, Tunisia
| | - Bruno Baudin
- Department of Biochemistry, Saint-Antoine Hospital, 184 Street Faubourg Saint-Antoine, 75571, Paris, Cedex 12, France
| | - Abdelhédi Miled
- Laboratory of Biochemistry, Farhat HACHED Hospital, Street Doctor Moreau, 4000, Sousse, Tunisia
| | - Salima Ferchichi
- Laboratory of Biochemistry, Farhat HACHED Hospital, Street Doctor Moreau, 4000, Sousse, Tunisia
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10
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Oliveira MF, Alencar MC, Arbex F, Souza A, Sperandio P, Medina L, Medeiros WM, Hirai DM, O'Donnell DE, Neder JA. Effects of heart failure on cerebral blood flow in COPD: Rest and exercise. Respir Physiol Neurobiol 2016; 221:41-8. [DOI: 10.1016/j.resp.2015.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 10/07/2015] [Accepted: 10/10/2015] [Indexed: 12/13/2022]
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11
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Cardiovascular Reflexes Activity and Their Interaction during Exercise. BIOMED RESEARCH INTERNATIONAL 2015; 2015:394183. [PMID: 26557662 PMCID: PMC4628760 DOI: 10.1155/2015/394183] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/26/2015] [Accepted: 07/28/2015] [Indexed: 02/07/2023]
Abstract
Cardiac output and arterial blood pressure increase during dynamic exercise notwithstanding the exercise-induced vasodilation due to functional sympatholysis. These cardiovascular adjustments are regulated in part by neural reflexes which operate to guarantee adequate oxygen supply and by-products washout of the exercising muscles. Moreover, they maintain adequate perfusion of the vital organs and prevent excessive increments in blood pressure. In this review, we briefly summarize neural reflexes operating during dynamic exercise with particular emphasis on their interaction.
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12
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Ogoh S, Hirasawa A, Sugawara J, Nakahara H, Ueda S, Shoemaker JK, Miyamoto T. The effect of an acute increase in central blood volume on the response of cerebral blood flow to acute hypotension. J Appl Physiol (1985) 2015; 119:527-33. [DOI: 10.1152/japplphysiol.00277.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 07/07/2015] [Indexed: 11/22/2022] Open
Abstract
The purpose of the present study was to examine whether the response of cerebral blood flow to an acute change in perfusion pressure is modified by an acute increase in central blood volume. Nine young, healthy subjects voluntarily participated in this study. To measure dynamic cerebral autoregulation during normocapnic and hypercapnic (5%) conditions, the change in middle cerebral artery mean blood flow velocity was analyzed during acute hypotension caused by two methods: 1) thigh-cuff occlusion release (without change in central blood volume); and 2) during the recovery phase immediately following release of lower body negative pressure (LBNP; −50 mmHg) that initiated an acute increase in central blood volume. In the thigh-cuff occlusion release protocol, as expected, hypercapnia decreased the rate of regulation, as an index of dynamic cerebral autoregulation (0.236 ± 0.018 and 0.167 ± 0.025 s−1, P = 0.024). Compared with the cuff-occlusion release, the acute increase in central blood volume (relative to the LBNP condition) with LBNP release attenuated dynamic cerebral autoregulation ( P = 0.009). Therefore, the hypercapnia-induced attenuation of dynamic cerebral autoregulation was not observed in the LBNP release protocol ( P = 0.574). These findings suggest that an acute change in systemic blood distribution modifies dynamic cerebral autoregulation during acute hypotension.
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Affiliation(s)
| | | | - Jun Sugawara
- National Institute of Advanced Industrial Science and Technology, Ibaraki Japan
| | | | - Shinya Ueda
- Morinomiya University of Medical Sciences, Osaka, Japan; and
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13
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Michelini LC, O'Leary DS, Raven PB, Nóbrega ACL. Neural control of circulation and exercise: a translational approach disclosing interactions between central command, arterial baroreflex, and muscle metaboreflex. Am J Physiol Heart Circ Physiol 2015; 309:H381-92. [PMID: 26024683 PMCID: PMC4631530 DOI: 10.1152/ajpheart.00077.2015] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 05/18/2015] [Indexed: 01/13/2023]
Abstract
The last 100 years witnessed a rapid and progressive development of the body of knowledge concerning the neural control of the cardiovascular system in health and disease. The understanding of the complexity and the relevance of the neuroregulatory system continues to evolve and as a result raises new questions. The purpose of this review is to articulate results from studies involving experimental models in animals as well as in humans concerning the interaction between the neural mechanisms mediating the hemodynamic responses during exercise. The review describes the arterial baroreflex, the pivotal mechanism controlling mean arterial blood pressure and its fluctuations along with the two main activation mechanisms to exercise: central command (parallel activation of central somatomotor and autonomic descending pathways) and the muscle metaboreflex, the metabolic component of exercise pressor reflex (feedback from ergoreceptors within contracting skeletal muscles). In addition, the role of the cardiopulmonary baroreceptors in modulating the resetting of arterial baroreflex is identified, and the mechanisms in the central nervous system involved with the resetting of baroreflex function during dynamic exercise are also described. Approaching a very relevant clinical condition, the review also presents the concept that the impaired arterial baroreflex function is an integral component of the metaboreflex-mediated exaggerated sympathetic tone in subjects with heart failure. This increased sympathetic activity has a major role in causing the depressed ventricular function observed during submaximal dynamic exercise in these patients. The potential contribution of a metaboreflex arising from respiratory muscles is also considered.
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Affiliation(s)
- Lisete C Michelini
- Department of Physiology and Biophysics, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil
| | - Donal S O'Leary
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Peter B Raven
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas; and
| | - Antonio C L Nóbrega
- Department of Physiology and Pharmacology, Fluminense Federal University, Niteroi, Brazil
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Narayan J, Amatoury J, Cho JG, Verma M, Kairaitis K, Wheatley J, Amis T. Snoring effects on the baroreflex: an animal model. Respir Physiol Neurobiol 2012; 180:342-51. [PMID: 22244879 DOI: 10.1016/j.resp.2011.12.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 10/14/2022]
Abstract
Baroreflex sensitivity (BRS) is reduced in humans during snoring, however the mechanisms are unknown. We used an anaesthetised rabbit induced snoring (IS) model, to test: (1) whether IS was associated with reduced BRS; and (2) if snoring related vibration transmission to peri-carotid tissues influenced BRS levels. BRS was quantified using the spontaneous sequence technique. During IS, BRS fell by 40%, without any associated change in blood pressure (BP) but accompanied by an increase in heart rate (HR). Direct application of a snore frequency and intensity matched vibratory stimulus to the peri-carotid tissues of non-snoring tracheostomised rabbits had no effect on BRS, HR or BP. In conclusion, IS induced depression of BRS is likely mediated via a HR driven change in BRS operating point that is unrelated to snoring-related vibration transmission to carotid baroreceptors. The anaesthetised IS rabbit provides a model in which mechanistic interactions between snoring and BRS can be further explored.
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Affiliation(s)
- Jyotishna Narayan
- Ludwig Engel Centre for Respiratory Research, Sydney, NSW, Australia.
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15
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Fadel PJ, Raven PB. Human investigations into the arterial and cardiopulmonary baroreflexes during exercise. Exp Physiol 2011; 97:39-50. [PMID: 22002871 DOI: 10.1113/expphysiol.2011.057554] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
After considerable debate and key experimental evidence, the importance of the arterial baroreflex in contributing to and maintaining the appropriate neural cardiovascular adjustments to exercise is now well accepted. Indeed, the arterial baroreflex resets during exercise in an intensity-dependent manner to continue to regulate blood pressure as effectively as at rest. Studies have indicated that the exercise resetting of the arterial baroreflex is mediated by both the feedforward mechanism of central command and the feedback mechanism associated with skeletal muscle afferents (the exercise pressor reflex). Another perhaps less appreciated neural mechanism involved in evoking and maintaining neural cardiovascular responses to exercise is the cardiopulmonary baroreflex. The limited information available regarding the cardiopulmonary baroreflex during exercise provides evidence for a role in mediating sympathetic nerve activity and blood pressure responses. In addition, recent investigations have demonstrated an interaction between cardiopulmonary baroreceptors and the arterial baroreflex during dynamic exercise, which contributes to the magnitude of exercise-induced increases in blood pressure as well as the resetting of the arterial baroreflex. Furthermore, neural inputs from the cardiopulmonary baroreceptors appear to play an important role in establishing the operating point of the arterial baroreflex. This symposium review highlights recent studies in these important areas indicating that the interactions of four neural mechanisms (central command, the exercise pressor reflex, the arterial baroreflex and cardiopulmonary baroreflex) are integral in mediating the neural cardiovascular adjustments to exercise.
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Affiliation(s)
- Paul J Fadel
- Department of Medical Pharmacology and Physiology, MA415 Medical Sciences Building, University of Missouri, Columbia, MO 65212, USA.
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16
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Kim YS, Davis SC, Truijen J, Stok WJ, Secher NH, van Lieshout JJ. Intensive Blood Pressure Control Affects Cerebral Blood Flow in Type 2 Diabetes Mellitus Patients. Hypertension 2011; 57:738-45. [DOI: 10.1161/hypertensionaha.110.160523] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Type 2 diabetes mellitus is associated with microvascular complications, hypertension, and impaired dynamic cerebral autoregulation. Intensive blood pressure (BP) control in hypertensive type 2 diabetic patients reduces their risk of stroke but may affect cerebral perfusion. Systemic hemodynamic variables and transcranial Doppler-determined cerebral blood flow velocity (CBFV), cerebral CO
2
responsiveness, and cognitive function were determined after 3 and 6 months of intensive BP control in 17 type 2 diabetic patients with microvascular complications (T2DM+), in 18 diabetic patients without (T2DM−) microvascular complications, and in 16 nondiabetic hypertensive patients. Cerebrovascular reserve capacity was lower in T2DM+ versus T2DM− and nondiabetic hypertensive patients (4.6±1.1 versus 6.0±1.6 [
P
<0.05] and 6.6±1.7 [
P
<0.01], Δ%mean CBFV/mm Hg). After 6 months, the attained BP was comparable among the 3 groups. However, in contrast to nondiabetic hypertensive patients, intensive BP control reduced CBFV in T2DM− (58±9 to 54±12 cm · s
−1
) and T2DM+ (57±13 to 52±11 cm · s
−1
) at 3 months, but CBFV returned to baseline at 6 months only in T2DM−, whereas the reduction in CBFV progressed in T2DM+ (to 48±8 cm · s
−1
). Cognitive function did not change during the 6 months. Static cerebrovascular autoregulation appears to be impaired in type 2 diabetes mellitus, with a transient reduction in CBFV in uncomplicated diabetic patients on tight BP control, but with a progressive reduction in CBFV in diabetic patients with microvascular complications, indicating that maintenance of cerebral perfusion during BP treatment depends on the progression of microvascular disease. We suggest that BP treatment should be individualized, aiming at a balance between BP reduction and maintenance of CBFV.
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Affiliation(s)
- Yu-Sok Kim
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Shyrin C.A.T. Davis
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Jasper Truijen
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Wim J. Stok
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Niels H. Secher
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Johannes J. van Lieshout
- From the Departments of Internal Medicine (Y.-S.K., J.T., J.J.v.L.) and Physiology (W.J.S.), Academic Medical Center and Laboratory for Clinical Cardiovascular Physiology, Academic Medical Center, Center for Heart Failure Research (Y.-S.K., S.C.A.T.D., J.T., W.J.S., J.J.v.L.), University of Amsterdam, Amsterdam, The Netherlands; Department of Anesthesia (N.H.S.), Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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17
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Hart EC, Rasmussen P, Secher NH, George KP, Cable NT, Volianitis S, Shave R. The carotid baroreflex is reset following prolonged exercise in humans. Acta Physiol (Oxf) 2010; 200:291-9. [PMID: 20608902 DOI: 10.1111/j.1748-1716.2010.02160.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Alterations in the carotid baroreflex (CBR) control of arterial pressure may explain the reduction in arterial pressure and left ventricular (LV) function after prolonged exercise. We examined the CBR control of heart rate (HR) and mean arterial pressure (MAP), in addition to changes in LV function, pre- to post-exercise. METHODS Seven males (age, mean ± SEM; 29 ± 4 years) completed 4 h of ergometer rowing at a workload of 10-15% below the lactate threshold. The CBR control of HR and MAP was assessed via the rapid neck-suction/pressure protocol. LV systolic function was measured by echocardiography, where ejection fraction (EF), the ratio of systolic blood pressure to end systolic volume (SBP/ESV) and stroke volume (SV) were estimated. RESULTS Following exercise MAP was reduced (12 ± 3%) and HR was elevated (35 ± 5%; P < 0.05). Furthermore, CBR control of MAP was relocated to the left on the stimulus-response curve (P < 0.05) demonstrating that the CBR operated around a lower arterial pressure. Concomitantly, LV systolic function was reduced, indicated by a decrease in EF (22 ± 2%), SBP/ESV (32 ± 14%) and SV (25 ± 5%, P < 0.05). The reduced EF and SBP/ESV were associated with the decreased MAP operating point (r² = 0.71 and r² = 0.47, respectively, P < 0.05). CONCLUSION The CBR is reset after prolonged exercise to a lower prevailing arterial pressure. This resetting of the CBR may contribute to the reduction arterial pressure and LV function after exercise.
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Affiliation(s)
- E C Hart
- Centre for Sports Medicine and Human Performance, Brunel University, London, UK.
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18
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Vorluni L, Volianitis S. Interaction of cardiac and muscle mechanical afferents on baroreflex control of the sinus node during dynamic exercise. Scand J Med Sci Sports 2009; 20:434-40. [DOI: 10.1111/j.1600-0838.2009.00902.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Bell-shaped relationship between central blood volume and spontaneous baroreflex function. Auton Neurosci 2008; 143:46-52. [DOI: 10.1016/j.autneu.2008.07.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Revised: 06/24/2008] [Accepted: 07/29/2008] [Indexed: 11/19/2022]
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20
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Levine BD, Zhang R. Comments on Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. J Appl Physiol (1985) 2008; 105:1373. [DOI: 10.1152/japplphysiol.zdg-8199.pcpcomm.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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21
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Guimaraes GV, d'Avila VM, Pires P, Bacal F, Stolf N, Bocchi E. Acute effects of a single dose of phosphodiesterase type 5 inhibitor (sildenafil) on systemic arterial blood pressure during exercise and 24-hour ambulatory blood pressure monitoring in heart transplant recipients. Transplant Proc 2008; 39:3142-9. [PMID: 18089340 DOI: 10.1016/j.transproceed.2007.04.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 04/30/2007] [Indexed: 10/22/2022]
Abstract
BACKGROUND Arterial systemic hypertension (SH) can be associated with a decrease in endothelium-dependent nitric oxide (NO). Sildenafil increases cyclic guanosine monophosphate (cGMP), a mediator of NO. However, little is known about the effects of PDE5 inhibition on 24-hour ambulatory pressure (ABP) and exercise blood pressure, noreprinephrine (Nor), and exercise capacity, especially after orthotopic heart transplantation (OHT). METHODS We studied 22 OHT patients who on the 1st day underwent a cardiopulmonary (CP) self-controlled treadmill 6' walk test (6') and, then, an ECG monitored CP treadmill maximal exercise test (Ex) within 60 and 90 minutes after oral Sildenafil (Sil; 50 mg) or placebo (Pl) given at random, and ABP. We determined at basal position (b), in the last minute of the 6' and at the peak Ex, the HR (bpm), Systolic blood pressure (SBP), and diastolic blood pressure (DBP), (mm Hg), VO2 (mL/kg/min), Slope VE/VCO2, exercise time (ET, min), distance (D; miles), and Nor (pg/mL). Also, after CP tests, 24-h SBP and DBP, the measurements were repeated on the 2nd day when the cross-over was done. RESULTS Sil significantly reduced blood pressure in the basal position and during exercise. It also promoted a significant reduction in SBP and DBP during 24 hours, daytime and nighttime. Sil did not change exercise capacity. CONCLUSION The NO-cGMP pathway seems to play a role in blood pressure control in OHT. In addition to antihypertensive therapy, PDE5 inhibition may have potential beneficial effects on hypertensive OHT.
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Masuki S, Eisenach JH, Schrage WG, Dietz NM, Johnson CP, Wilkins BW, Dierkhising RA, Sandroni P, Low PA, Joyner MJ. Arterial baroreflex control of heart rate during exercise in postural tachycardia syndrome. J Appl Physiol (1985) 2007; 103:1136-42. [PMID: 17673566 DOI: 10.1152/japplphysiol.00176.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Patients with postural tachycardia syndrome (POTS) have excessive tachycardia without hypotension during orthostasis as well as exercise. We tested the hypothesis that excessive tachycardia during exercise in POTS is not related to abnormal baroreflex control of heart rate (HR). Patients (n = 13) and healthy controls (n = 10) performed graded cycle exercise at 25, 50, and 75 W in both supine and upright positions while arterial pressure (arterial catheter) and HR (ECG) were measured. Baroreflex sensitivity of HR was assessed by bolus intravenous infusion of phenylephrine at each workload. In both positions, HR was higher in the patients than the controls during exercise. Supine baroreflex sensitivity (HR/systolic pressure) in POTS patients was -1.3 +/- 0.1 beats.min(-1).mmHg(-1) at rest and decreased to -0.6 +/- 0.1 beats.min(-1).mmHg(-1) during 75-W exercise, neither significantly different from the controls (P > 0.6). In the upright position, baroreflex sensitivity in POTS patients at rest (-1.4 +/- 0.1 beats.min(-1).mmHg(-1)) was higher than the controls (-1.0 +/- 0.1 beats.min(-1).mmHg(-1)) (P < 0.05), and it decreased to -0.1 +/- 0.04 beats.min(-1).mmHg(-1) during 75-W exercise, lower than the controls (-0.3 +/- 0.09 beats.min(-1).mmHg(-1)) (P < 0.05). The reduced arterial baroreflex sensitivity of HR during upright exercise was accompanied by greater fluctuations in systolic and pulse pressure in the patients than in the controls with 56 and 90% higher coefficient of variations, respectively (P < 0.01). However, when baroreflex control of HR was corrected for differences in HR, it was similar between the patients and controls during upright exercise. These results suggest that the tachycardia during exercise in POTS was not due to abnormal baroreflex control of HR.
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Affiliation(s)
- Shizue Masuki
- Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, MN 55905, USA
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23
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Ogoh S, Fisher JP, Fadel PJ, Raven PB. Increases in central blood volume modulate carotid baroreflex resetting during dynamic exercise in humans. J Physiol 2007; 581:405-18. [PMID: 17317751 PMCID: PMC2075218 DOI: 10.1113/jphysiol.2006.125112] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We sought to determine if resetting of the carotid-vasomotor baroreflex function curve during exercise is modulated by changes in central blood volume (CBV). CBV was increased during exercise by altering: (1) subject posture (supine versus upright) and (2) pedal frequency (80 versus 60 revolutions min(-1) (r.p.m.)); while oxygen uptake ( ) was kept constant. Eight male subjects performed three exercise trials: upright cycling at 60 r.p.m. (control); supine cycling at 60 r.p.m. (SupEX) and upright cycling at 80 r.p.m. to enhance the muscle pump (80EX). During each condition, carotid baroreflex (CBR) function was determined using the rapid neck pressure (NP) and neck suction (NS) protocol. Although mean arterial pressure (MAP) was significantly elevated from rest (88 +/- 2 mmHg) during all exercise conditions (P < 0.001), the increase in MAP was lower during SupEX (94 +/- 2 mmHg) and 80EX (95 +/- 2 mmHg) compared with control (105 +/- 2 mmHg, P < 0.05). Importantly, the blood pressure responses to NP and NS were maintained around these changed operating points of MAP. However, in comparison to control, the carotid-vasomotor baroreflex function curve was relocated downward and leftward when CBV was increased during SupEX and 80EX. These alterations in CBR resetting occurred without any differences in or heart rate between the exercise conditions. Thus, increasing CBV and loading the cardiopulmonary baroreflex reduces the magnitude of exercise-induced increases in MAP and CBR resetting. These findings suggest that changes in cardiopulmonary baroreceptor load influence carotid baroreflex resetting during dynamic exercise.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Integrative Physiology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA.
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Licker M, Sierra J, Kalangos A, Panos A, Diaper J, Ellenberger C. Cardioprotective effects of acute normovolemic hemodilution in patients with severe aortic stenosis undergoing valve replacement. Transfusion 2007; 47:341-50. [PMID: 17302782 DOI: 10.1111/j.1537-2995.2007.01111.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND After acute normovolemic hemodilution (ANH), improvement of the rheologic conditions may contribute to optimize tissue oxygen delivery and attenuate ischemia-reperfusion injuries. It was hypothesized that ANH would confer additional cardioprotection in patients with ventricular hypertrophy undergoing open heart surgery. STUDY DESIGN AND METHODS This study was a randomized controlled trial. Forty patients scheduled for elective aortic valve replacement were randomly assigned to a control group (standard care) or an ANH group (target hematocrit level of 28%). All patients were managed with standard myocardial preservation techniques (cold blood cardioplegia, anesthetic preconditioning). The outcome measures included the release of myocardial enzymes, perioperative hemodynamic changes, the need for pharmacologic cardiovascular support, and cardiac complications. RESULTS In the ANH group, the postoperative release of troponin I (mean peak plasma concentrations, 1.7 ng/mL; 95% confidence interval, 1.4-2.1 ng/mL) and myocardial fraction of creatine kinase (22 U/L; range, 18-24 U/L) was significantly lower than in the control group (3.6 [range, 3.0-4.2] ng/mL and 45 [range, 39-51] U/L, respectively). In addition, requirement for inotropic support was significantly lower and fewer hemodiluted patients presented adverse cardiac events. After ANH, there was a significant decrease in heart rate (-11 +/- 6%) and rate-pressure product (-16 +/- 8%) until the aortic cross-clamping time and, at the end of surgery, the circulating levels of erythropoietin (EPO) were higher than in control patients (13.6 +/- 4.2 mUI/mL vs. 7.3 +/- 2.4 mUI/mL; p < 0.05). CONCLUSIONS Besides conventional cardiac preservation techniques, preoperative ANH further attenuates myocardial injuries. Optimization of preischemic myocardial oxygen delivery and/or consumption and the postconditioning effects of endogenous EPO are potential mechanisms for ANH-induced cardioprotection.
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Affiliation(s)
- Marc Licker
- Department of Anesthesiology, Pharmacology and Surgical Intensive Care, University Hospital of Geneva, Geneva, Switzerland.
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