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Karim S, Chahal A, Khanji MY, Petersen SE, Somers V. Autonomic Cardiovascular Control in Health and Disease. Compr Physiol 2023; 13:4493-4511. [PMID: 36994768 PMCID: PMC10406398 DOI: 10.1002/cphy.c210037] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Autonomic neural control of the cardiovascular system is formed of complex and dynamic processes able to adjust rapidly to mitigate perturbations in hemodynamics and maintain homeostasis. Alterations in autonomic control feature in the development or progression of a multitude of diseases with wide-ranging physiological implications given the neural system's responsibility for controlling inotropy, chronotropy, lusitropy, and dromotropy. Imbalances in sympathetic and parasympathetic neural control are also implicated in the development of arrhythmia in several cardiovascular conditions sparking interest in autonomic modulation as a form of treatment. A number of measures of autonomic function have shown prognostic significance in health and in pathological states and have undergone varying degrees of refinement, yet adoption into clinical practice remains extremely limited. The focus of this contemporary narrative review is to summarize the anatomy, physiology, and pathophysiology of the cardiovascular autonomic nervous system and describe the merits and shortfalls of testing modalities available. © 2023 American Physiological Society. Compr Physiol 13:4493-4511, 2023.
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Affiliation(s)
- Shahid Karim
- Mayo Clinic, Rochester, Minnesota, USA
- William Harvey Research Institute, NIHR Barts Biomedical Centre, Queen Mary University London, UK
| | - Anwar Chahal
- Mayo Clinic, Rochester, Minnesota, USA
- University of Pennsylvania, Pennsylvania, USA
- William Harvey Research Institute, NIHR Barts Biomedical Centre, Queen Mary University London, UK
| | - Mohammed Y. Khanji
- William Harvey Research Institute, NIHR Barts Biomedical Centre, Queen Mary University London, UK
- Barts Heart Centre, St Bartholomew’s Hospital, Barts Health NHS Trust, London, UK
- Newham University Hospital, Barts Health NHS Trust, London, UK
| | - Steffen E. Petersen
- William Harvey Research Institute, NIHR Barts Biomedical Centre, Queen Mary University London, UK
- Barts Heart Centre, St Bartholomew’s Hospital, Barts Health NHS Trust, London, UK
- Health Data Research UK, London, UK
- Alan Turing Institute, London, UK
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2
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Banodhe GK, Badhwar S, Sharma HB, Deepak KK. Assessment of baroreflex sensitivity during isometric handgrip exercise and oscillatory lower body negative pressure. J Taibah Univ Med Sci 2023; 18:868-875. [PMID: 36852235 PMCID: PMC9957788 DOI: 10.1016/j.jtumed.2023.01.007] [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: 10/10/2022] [Revised: 12/10/2022] [Accepted: 01/06/2023] [Indexed: 01/19/2023] Open
Abstract
Objectives Baroreflex sensitivity (BRS) is an estimate of autonomic control of cardiovascular system via the baroreflex arc. It has been suggested that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain, which facilitates the simultaneous rise in blood pressure (BP) and heart rate during the exercise. This study investigated the effects of isometric handgrip exercise (IHE) on baroreflex gain and frequency dependence of baroreflex sensitivity while fluctuations in arterial BP were generated. Methods Thirteen healthy men performed IHE at 20% and 30% of their maximum voluntary contraction (MVC), while oscillatory lower body negative pressure (OLBNP) of 40 mmHg was applied in 0.1 and 0.25 Hz frequencies. Results Compared to the OLBNP at 0.25 Hz frequency alone, the baroreflex gain for diastolic BP (DBP) was significantly reduced with the addition of IHE at 20% and 30% of MVC in the high frequency band. At rest (without IHE and OLBNP) the baroreflex gain was significantly more in the high frequency band for DBP, but the baroreflex gain for DBP was not significantly different when IHE + OLBNP were applied at 20% and 30% of MVC in both frequencies. Conclusions The significant reduction of DBP baroreflex gain with the addition of graded IHE might indicate that exercise pressure reflex and muscle metaboreflex override baroreflex during exercise to decrease baroreflex gain at a high frequency band (0.25 Hz). The frequency-dependent phenomenon of BRS was altered when IHE and OLBNP were applied, meaning that the frequency dependence of BRS was nullified during IHE.
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Affiliation(s)
- Gagan K. Banodhe
- Department of Physiology, All India Institute of Medical Science, Room no. 3106, Tatibandh, Raipur, Chhattisgarh 492001, India,Corresponding address: Department of Physiology, AIIMS, Raipur, India.
| | - Smriti Badhwar
- Women's Cardiovascular Health Lab, York University, Toronto, Canada
| | | | - Kishore K. Deepak
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
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Abbariki F, Roy M, Labrecque L, Drapeau A, Imhoff S, Smirl JD, Brassard P. Influence of high-intensity interval training to exhaustion on the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men. Physiol Rep 2022; 10:e15384. [PMID: 35822439 PMCID: PMC9277516 DOI: 10.14814/phy2.15384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023] Open
Abstract
We previously reported subtle dynamic cerebral autoregulation (dCA) alterations following 6 weeks of high-intensity interval training (HIIT) to exhaustion using transfer function analysis (TFA) on forced mean arterial pressure (MAP) oscillations in young endurance-trained men. However, accumulating evidence suggests the cerebrovasculature better buffers cerebral blood flow changes when MAP acutely increases compared to when MAP acutely decreases. Whether HIIT affects the directional sensitivity of the cerebral pressure-flow relationship in these athletes is unknown. In 18 endurance-trained men (age: 27 ± 6 years, VO2 max: 55.5 ± 4.7 ml·kg-1 ·min-1 ), we evaluated the impact of 6 weeks of HIIT to exhaustion on dCA directionality using induced MAP oscillations during 5-min 0.05 and 0.10 Hz repeated squat-stands. We calculated time-adjusted changes in middle cerebral artery mean blood velocity (MCAv) per change in MAP (ΔMCAvT /ΔMAPT ) for each squat transition. Then, we compared averaged ΔMCAvT /ΔMAPT during MAP increases and decreases. Before HIIT, ΔMCAvT /ΔMAPT was comparable between MAP increases and decreases during 0.05 Hz repeated squat-stands (p = 0.518). During 0.10 Hz repeated squat-stands, ΔMCAvT /ΔMAPT was lower during MAP increases versus decreases (0.87 ± 0.17 vs. 0.99 ± 0.23 cm·s-1 ·mmHg-1 , p = 0.030). Following HIIT, ΔMCAvT /ΔMAPT was superior during MAP increases over decreases during 0.05 Hz repeated squat-stands (0.97 ± 0.38 vs. 0.77 ± 0.35 cm·s-1 ·mmHg-1 , p = 0.002). During 0.10 Hz repeated squat-stands, dCA directional sensitivity disappeared (p = 0.359). These results suggest the potential for HIIT to influence the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men.
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Affiliation(s)
- Faezeh Abbariki
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Marc‐Antoine Roy
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Jonathan D. Smirl
- Cerebrovascular Concussion Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Sport Injury Prevention Research Centre, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Hotchkiss Brain InstituteUniversity of CalgaryCalgaryAlbertaCanada
- Integrated Concussion Research ProgramUniversity of CalgaryCalgaryAlbertaCanada
- Alberta Children's Hospital Research InstituteUniversity of CalgaryCalgaryAlbertaCanada
- Libin Cardiovascular Institute of AlbertaUniversity of CalgaryAlbertaCanada
- Concussion Research Laboratory, Faculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBritish ColumbiaCanada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
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Yamasaki F, Sato T, Sato K, Diedrich A. Analytic and Integrative Framework for Understanding Human Sympathetic Arterial Baroreflex Function: Equilibrium Diagram of Arterial Pressure and Plasma Norepinephrine Level. Front Neurosci 2021; 15:707345. [PMID: 34335177 PMCID: PMC8322947 DOI: 10.3389/fnins.2021.707345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 06/24/2021] [Indexed: 11/15/2022] Open
Abstract
Background The sympathetic arterial baroreflex is a closed-loop feedback system for stabilizing arterial pressure (AP). Identification of unique functions of the closed system in humans is a challenge. Here we propose an analytic and integrative framework for identifying a static operating point and open-loop gain to characterize sympathetic arterial baroreflex in humans. Methods and Results An equilibrium diagram with two crossing functions of mechanoneural (MN) and neuromechanical (NM) arcs was analyzed during graded tilt maneuvers in seven healthy subjects. AP and plasma norepinephrine level (PNE), as a surrogate for sympathetic nerve activity, and were recorded after vagal modulation of heart function was blocked by atropine. The MN-arc curve was described as a locus of operating points during –7, 0, 15, and 60° head-up tilting (HUT) on a PNE-AP plane. The NM-arc curve was drawn as a line between operating points before and after ganglionic blockade (trimethaphan, 0.1 mg⋅ml–1⋅kg–1) during 0° or 15° HUT. Gain values were estimated from the slopes of these functional curves. Finally, an open-loop gain, which is a most important index for performance of arterial baroreflex, was given by a product of the gain values of MN (GMN) and NM arcs (GNM). Gain values of MN was 8.92 ± 3.07 pg⋅ml−1⋅mmHg−1; and GNM at 0° and 15° HUT were 0.61 ± 0.08 and 0.36 ± 0.05 mmHg⋅ml⋅pg–1, respectively. A postural change from supine to 15° HUT significantly reduced the open-loop gain from 5.62 ± 0.98 to 3.75 ± 0.62. The effects of HUT on the NM arc and open-loop gain seemed to be similar to those of blood loss observed in our previous animal studies. Conclusion An equilibrium-diagram analysis contributes to a quantitative and integrative understanding of function of human sympathetic arterial baroreflex.
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Affiliation(s)
- Fumiyasu Yamasaki
- Department of Clinical Laboratory, Kochi Medical School, Nankoku, Japan
| | - Takayuki Sato
- Department of Cardiovascular Control, Kochi Medical School, Nankoku, Japan
| | - Kyoko Sato
- Department of Clinical Laboratory, Kochi Medical School, Nankoku, Japan
| | - André Diedrich
- Department of Biomedical Engineering, Autonomic Dysfunction Center, Vanderbilt University Medical Center, Vanderbilt University, Nashville, TN, United States
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Akerman AP, Meade RD, Notley SR, Rutherford MM, Kenny GP. Myths and methodologies: Reliability of non-invasive estimates of cardiac autonomic modulation during whole-body passive heating. Exp Physiol 2020; 106:593-614. [PMID: 33197089 DOI: 10.1113/ep089069] [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: 09/06/2020] [Accepted: 11/10/2020] [Indexed: 12/16/2022]
Abstract
Observed individual variability in cardiac baroreflex sensitivity (cBRS) and heart rate variability (HRV) is extensive, especially during exposure to stressors such as heat. A large part of the observed variation may be related to the reliability (consistency) of the measurement. We therefore examined the test-retest reliability of cBRS and HRV measurements on three separate occasions in 14 young men (age: 24 (SD 5) years), at rest and during whole-body heating (water-perfused suit) to raise and clamp oesophageal temperature 0.6°C, 1.2°C and 1.8°C above baseline. Beat-to-beat measurements of RR interval and systolic blood pressure (BP) were obtained for deriving HRV (from RR), and cBRS calculated via (i) the spontaneous method, α coefficients and transfer function analysis at each level of heat strain, and (ii) during forced oscillations via squat-stand manoeuvres (0.1 Hz) before and after heating. Absolute values and changes in all cBRS estimates were variable but generally consistent with reductions in parasympathetic activity. cBRS estimates demonstrated poor absolute reliability (coefficient of variation ≥25%), but relative reliability (intraclass correlation coefficient; ICC) of some frequency estimates was acceptable (ICC ≥0.70) during low-heat strain (ICC: 0.56-0.74). After heating, forced oscillations in BP demonstrated more favourable responses than spontaneous oscillations (better reliability, lower minimum detectable change). Absolute reliability of HRV estimates were poor, but relative reliability estimates were often acceptable (≥0.70). Our findings illustrate how measurement consistency of cardiac autonomic modulation estimates are altered during heat stress, and we demonstrate the possible implications on research design and data interpretation.
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Affiliation(s)
- Ashley P Akerman
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Robert D Meade
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Sean R Notley
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Maura M Rutherford
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Ontario, Canada
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Shahzad T, Saleem S, Usman S, Mirza J, Islam QU, Ouahada K, Marwala T. System dynamics of active and passive postural changes: Insights from principal dynamic modes analysis of baroreflex loop. Comput Biol Med 2018; 100:27-35. [PMID: 29975851 DOI: 10.1016/j.compbiomed.2018.06.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 06/21/2018] [Accepted: 06/22/2018] [Indexed: 10/28/2022]
Abstract
The baroreflex being a key modulator of cardiovascular control ensures adequate blood pressure regulation under orthostatic stress which otherwise may cause severe hypotension. Contrary to conventional baroreflex sensitivity indices derived across a-priori traditional frequency bands, the present study is aimed at proposing new indices for the assessment of baroreflex drive which follows active (supine to stand-up) and passive (supine to head-up tilt) postural changes. To achieve this, a novel system identification approach of principal dynamic modes (PDM) was utilized to extract data-adaptive frequency components of closed-loop interactions between beat-to-beat interval and systolic blood pressure recorded from 10 healthy humans. We observed that the gain of low-pass global PDM of cardiac arm (:feedback reflex loop, mediated by pressure sensors to adjust heart rate in response to arterial blood pressure), and 0.2 Hz global PDM of mechanical arm (:feed-forward pathways, originating changes in arterial blood pressure in response to heart rate variations) may function as potential markers to distinguish active and passive orthostatic tests in healthy subjects.
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Affiliation(s)
- Tariq Shahzad
- Department of Electrical and Electronic Engineering Science, University of Johannesburg, South Africa.
| | - Saqib Saleem
- Department of Electrical Engineering, COMSATS University Islamabad, Sahiwal Campus, Sahiwal, Pakistan.
| | - Saeeda Usman
- Department of Electrical Engineering, COMSATS University Islamabad, Sahiwal Campus, Sahiwal, Pakistan.
| | - Jawad Mirza
- Department of Electrical Engineering, COMSATS University Islamabad, Islamabad, Pakistan.
| | - Qamar-Ul Islam
- Department of Space Science, Institute of Space Technology, Islamabad, Pakistan.
| | - Khmaies Ouahada
- Department of Electrical and Electronic Engineering Science, University of Johannesburg, South Africa.
| | - Tshilidzi Marwala
- Department of Electrical and Electronic Engineering Science, University of Johannesburg, South Africa.
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Horsman HM, Peebles KC, Tzeng YC. Interactions between breathing rate and low-frequency fluctuations in blood pressure and cardiac intervals. J Appl Physiol (1985) 2015. [PMID: 26205543 DOI: 10.1152/japplphysiol.00525.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evidence derived from spontaneous measures of cardiovagal baroreflex sensitivity (BRS) suggests that slow breathing at 6 breaths/min augments BRS. However, increases in BRS associated with slow breathing may simply reflect the frequency-dependent nature of the baroreflex rather than the modulation of baroreflex function by changes in breathing rate per se. To test this hypothesis we employed a crossover study design (n = 14) wherein breathing rate and systolic arterial blood pressure (SAP) oscillation induced via the application of oscillating lower body negative pressure (OLBNP) were independently varied at fixed frequencies. Breathing rate was controlled at 6 or 10 breaths/min with the aid of a metronome, and SAP oscillations were driven at 0.06 Hz and 0.1 Hz using OLBNP. The magnitudes of SAP and R-R interval (cardiac period) oscillations were quantified using power spectral analysis, and the transfer function gain between SAP and R-R interval was used to estimate BRS. Linear mixed-effects models were used to examine the main effects and interactions between breathing rate and OLBNP frequency. There was no statistical interaction between breathing and OLBNP frequency (P = 0.59), indicating that the effect of breathing rate on BRS did not differ according to OLBNP frequency (and vice versa). Additionally, there was no main effect for breathing rate (P = 0.28). However, we observed a significant main effect for OLBNP frequency (P = 0.01) consistent with the frequency-dependent nature of baroreflex. These findings suggest that increases in spectral indices of BRS reflect the frequency dependence of the baroreflex and are not due to slow breathing per se.
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Affiliation(s)
- H M Horsman
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - K C Peebles
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand; Department of Physiology, University of Otago, Dunedin, New Zealand; and Department of Health Professions, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Y C Tzeng
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand;
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Optimal Testing Intervals in the Squatting Test to Determine Baroreflex Sensitivity. NEUROPHYSIOLOGY+ 2015. [DOI: 10.1007/s11062-015-9479-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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9
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Horsman HM, Tzeng YC, Galletly DC, Peebles KC. The repeated sit-to-stand maneuver is a superior method for cardiac baroreflex assessment: a comparison with the modified Oxford method and Valsalva maneuver. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1345-52. [DOI: 10.1152/ajpregu.00376.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Baroreflex assessment has diagnostic and prognostic utility in the clinical and research environments, and there is a need for a reliable, simple, noninvasive method of assessment. The repeated sit-to-stand method induces oscillatory changes in blood pressure (BP) at a desired frequency and is suitable for assessing dynamic baroreflex sensitivity (BRS). However, little is known about the reliability of this method and its ability to discern fundamental properties of the baroreflex. In this study we sought to: 1) evaluate the reliability of the sit-to-stand method for assessing BRS and compare its performance against two established methods (Oxford method and Valsalva maneuver), and 2) examine whether the frequency of the sit-to-stand method influences hysteresis. Sixteen healthy participants underwent three trials of each method. For the sit-to-stand method, which was performed at 0.1 and 0.05 Hz, BRS was quantified as an integrated response (BRSINT) and in response to falling and rising BP (BRSDOWN and BRSUP, respectively). Test retest reliability was assessed using the intraclass correlation coefficient (ICC). Irrespective of frequency, the ICC for BRSINT during the sit-to-stand method was ≥0.88. The ICC for a rising BP evoked by phenylephrine (PEGAIN) in the Oxford method was 0.78 and ≤0.5 for the remaining measures. During the sit-to-stand method, hysteresis was apparent in all participants at 0.1 Hz but was absent at 0.05 Hz. These findings indicate the sit-to-stand method is a statistically reliable BRS assessment tool and suitable for the examination of baroreflex hysteresis. Using this approach we showed that baroreflex hysteresis is a frequency-dependent phenomenon.
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Affiliation(s)
- H. M. Horsman
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Y. C. Tzeng
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - D. C. Galletly
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - K. C. Peebles
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
- Department of Physiology, University of Otago, Dunedin, New Zealand; and
- Department of Human Sciences, Macquarie University, Sydney, Australia
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Smirl JD, Haykowsky MJ, Nelson MD, Tzeng YC, Marsden KR, Jones H, Ainslie PN. Relationship Between Cerebral Blood Flow and Blood Pressure in Long-Term Heart Transplant Recipients. Hypertension 2014; 64:1314-20. [DOI: 10.1161/hypertensionaha.114.04236] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Heart transplant recipients are at an increased risk for cerebral hemorrhage and ischemic stroke; yet, the exact mechanism for this derangement remains unclear. We hypothesized that alterations in cerebrovascular regulation is principally involved. To test this hypothesis, we studied cerebral pressure-flow dynamics in 8 clinically stable male heart transplant recipients (62±8 years of age and 9±7 years post transplant, mean±SD), 9 male age-matched controls (63±8 years), and 10 male donor controls (27±5 years). To increase blood pressure variability and improve assessment of the pressure-flow dynamics, subjects performed squat–stand maneuvers at 0.05 and 0.10 Hz. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal carbon dioxide were continuously measured during 5 minutes of seated rest and throughout the squat–stand maneuvers. Cardiac baroreceptor sensitivity gain and cerebral pressure-flow responses were assessed with linear transfer function analysis. Heart transplant recipients had reductions in R-R interval power and baroreceptor sensitivity low frequency gain (
P
<0.01) compared with both control groups; however, these changes were unrelated to transfer function metrics. Thus, in contrast to our hypothesis, the increased risk of cerebrovascular complication after heart transplantation does not seem to be related to alterations in cerebral pressure-flow dynamics. Future research is, therefore, warranted.
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Affiliation(s)
- Jonathan D. Smirl
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Mark J. Haykowsky
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Michael D. Nelson
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Yu-Chieh Tzeng
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Katelyn R. Marsden
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Helen Jones
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Philip N. Ainslie
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
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