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Coombs GB, Al-Khazraji BK, Suskin N, Shoemaker JK. Impact of ischemic heart disease and cardiac rehabilitation on cerebrovascular compliance. J Appl Physiol (1985) 2023; 135:753-762. [PMID: 37616337 DOI: 10.1152/japplphysiol.00654.2022] [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: 10/31/2022] [Revised: 08/18/2023] [Accepted: 08/18/2023] [Indexed: 08/26/2023] Open
Abstract
We aimed to determine the influence of ischemic heart disease (IHD) and cardiac rehabilitation (CR) on cerebrovascular compliance index (Ci). Eleven (one female) patients with IHD (mean[SD]: 61[11] yr, 29[4] kg/m2) underwent 6 mo of CR, which consisted of ≥3 sessions/wk of aerobic and resistance training (20-60 min each). Ten (three female) similarly aged controls (CON) were tested at baseline as a comparator group. Middle cerebral artery velocity (MCAv) and mean arterial pressure were monitored continuously using transcranial Doppler ultrasound and finger photoplethysmography, respectively, during a rapid sit-to-stand maneuver. A Windkessel model was used to estimate cerebrovascular Ci every five cardiac cycles for a duration of 30 s. Cerebrovascular resistance was calculated as the quotient of MAP and MCAv. Two-way ANOVAs were used to determine whether cerebrovascular variables differ during postural transitions between groups and after CR. Baseline MCAv was higher in CON versus IHD (P = 0.014) and a time × group interaction was observed (P = 0.045) where MCAv decreased more in CON after standing. Compared with the precondition, CR had no effect on MCAv (condition P = 0.950) but a main effect of time indicated that MCAv decreased from the seated position in both conditions (time P = 0.013). Baseline cerebrovascular Ci was greater in IHD versus CON (P = 0.049) and the peak cerebrovascular Ci during the transition to standing was significantly higher in IHD compared with CON (interaction P = 0.047). CR did not affect cerebrovascular compliance (P = 0.452) and no time-by-condition interaction upon standing was present (P = 0.174). Baseline cerebrovascular Ci is higher in IHD at baseline compared with CON, but 6 mo of CR did not modify the transient increase in cerebrovascular Ci during sit-to-stand maneuvers.NEW & NOTEWORTHY Post-cardiac event cognitive impairment is common and exercise-based rehabilitation may be an effective intervention to mitigate cognitive decline. Microvascular damage due to high blood pressure pulsatility entering the brain is the putative mechanism of vascular dementia. Whether patients with ischemic heart disease exhibit lower cerebrovascular compliance, and if cardiac rehabilitation can improve cerebrovascular compliance is unknown. We observed that patients with ischemic heart disease have paradoxically higher cerebrovascular compliance, which is not affected by cardiac rehabilitation.
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Affiliation(s)
- Geoff B Coombs
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Baraa K Al-Khazraji
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
| | - Neville Suskin
- Division of Cardiology, Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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2
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Olver TD, Badrov MB, Allen MD, Coverdale NS, Shoemaker JK. Acute changes in forearm vascular compliance during transient sympatho-excitation. Physiol Rep 2022; 10:e15256. [PMID: 35439367 PMCID: PMC9017978 DOI: 10.14814/phy2.15256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/07/2022] [Accepted: 03/20/2022] [Indexed: 06/14/2023] Open
Abstract
The study of vascular regulation often omits important information about the elastic properties of arteries under conditions of pulsatile flow. The purpose of this study was to examine the relationship between muscle sympathetic nerve activity (MSNA), vascular bed compliance, and peripheral blood flow responses in humans. We hypothesized that increases in MSNA would correlate with reductions in vascular compliance, and that changes in compliance would correspond with changes in peripheral blood flow during sympatho-excitation. MSNA (microneurography), blood pressure (Finopres), and brachial artery blood flow (Doppler ultrasound), were monitored in six healthy males at baseline and during the last 15 s of voluntary end-inspiratory, expiratory apneas and 5 min of static handgrip exercise (SHG; 20% maximum voluntary contraction) and 3 min of post-exercise circulatory occlusion (SHG + PECO; measured in the non-exercising arm). A lumped Windkessel model was employed to examine vascular bed compliance. During apnea, indices of MSNA were inversely related with vascular compliance, and reductions in compliance correlated with decreased brachial blood flow rate. During SHG, despite increased MSNA, compliance also increased, but was unrelated to increases in blood flow. Neither during SHG nor PECO did indices of MSNA correlate with forearm vascular compliance nor did vascular compliance correlate with brachial flow. However, during PECO, a linear combination of blood pressure and total MSNA was correlated with vascular compliance. These data indicate the elastic components of the forearm vasculature are regulated by adrenergic and myogenic mechanisms during sympatho-excitation, but in a reflex-dependent manner.
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Affiliation(s)
- T. Dylan Olver
- Biomedical SciencesWestern College of Veterinary MedicineUniversity of SaskatchewanSaskatoonSaskatchewanCanada
| | - Mark B. Badrov
- Division of CardiologyDepartment of MedicineUniversity Health Network and Sinai HealthUniversity of TorontoTorontoOntarioCanada
| | - Matti D. Allen
- Department of Physical Medicine and RehabilitationSchool of MedicineQueen's UniversityKingstonOntarioCanada
| | - Nicole S. Coverdale
- School of Kinesiology and Health StudiesQueen’s UniversityKingstonOntarioCanada
| | - J. Kevin Shoemaker
- Neurovascular Research LaboratorySchool of KinesiologyThe University of Western OntarioLondonOntarioCanada
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3
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Moir ME, Klassen SA, Zamir M, Shoemaker JK. Rapid changes in vascular compliance contribute to cerebrovascular adjustments during transient reductions in blood pressure in young, healthy adults. J Appl Physiol (1985) 2020; 129:27-35. [PMID: 32463732 DOI: 10.1152/japplphysiol.00272.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Characterization of dynamic cerebral autoregulation has focused primarily on adjustments in cerebrovascular resistance in response to blood pressure (BP) alterations. However, the role of vascular compliance in dynamic autoregulatory processes remains elusive. The present study examined changes in cerebrovascular compliance and resistance during standing-induced transient BP reductions in nine young, healthy adults (3 women). Brachial artery BP (Finometer) and middle cerebral artery blood velocity (BV; Multigon) waveforms were collected. Beginning 20 beats before standing and continuing 40 beats after standing, individual BP and BV waveforms of every second heartbeat were extracted and input into a four-element modified Windkessel model to calculate indexes of cerebrovascular resistance (Ri) and compliance (Ci). Standing elicited a transient reduction in mean BP of 20 ± 9 mmHg. In all participants, a large increase in Ci (165 ± 84%; P < 0.001 vs. seated baseline) occurred 2 ± 2 beats following standing. Reductions in Ri occurred 11 ± 3 beats after standing (Ci vs. Ri delay: P < 0.001). The increase in Ci contributed to maintained systolic BV before the decrease in Ri. The present results demonstrate rapid, large but transient increases in Ci that precede reductions in Ri, in response to standing-induced reductions in BP. Therefore, Ci represents a discreet component of cerebrovascular responses during acute decreases in BP and, consequently, dynamic autoregulation.NEW & NOTEWORTHY Historically, dynamic cerebral autoregulation has been characterized by adjustments in cerebrovascular resistance following systematic changes in blood pressure. However, with the use of Windkessel modeling approaches, this study revealed rapid and large increases in cerebrovascular compliance that preceded reductions in cerebrovascular resistance following standing-induced blood pressure reductions. Importantly, the rapid cerebrovascular compliance response contributed to preservation of systolic blood velocity during the transient hypotensive phase. These results broaden our understanding of dynamic cerebral autoregulation.
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Affiliation(s)
- M Erin Moir
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Stephen A Klassen
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Mair Zamir
- Department of Applied Mathematics, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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4
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Zamir M, Moir ME, Klassen SA, Balestrini CS, Shoemaker JK. Cerebrovascular Compliance Within the Rigid Confines of the Skull. Front Physiol 2018; 9:940. [PMID: 30065667 PMCID: PMC6056744 DOI: 10.3389/fphys.2018.00940] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/26/2018] [Indexed: 12/01/2022] Open
Abstract
Pulsatile blood flow is generally mediated by the compliance of blood vessels whereby they distend locally and momentarily to accommodate the passage of the pressure wave. This freedom of the blood vessels to exercise their compliance may be suppressed within the confines of the rigid skull. The effect of this on the mechanics of pulsatile blood flow within the cerebral circulation is not known, and the situation is compounded by experimental access difficulties. We present an approach which we have developed to overcome these difficulties in a study of the mechanics of pulsatile cerebral blood flow. The main finding is that while the innate compliance of cerebral vessels is indeed suppressed within the confines of the skull, this is compensated somewhat by compliance provided by other “extravascular” elements within the skull. The net result is what we have termed “intracranial compliance,” which we argue is more pertinent to the mechanics of pulsatile cerebral blood flow than is intracranial pressure.
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Affiliation(s)
- Mair Zamir
- Department of Applied Mathematics, The University of Western Ontario, London, ON, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada
| | - M Erin Moir
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Stephen A Klassen
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | | | - J Kevin Shoemaker
- School of Kinesiology, The University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada
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Olver TD, Reid SM, Smith AR, Zamir M, Lemon PWR, Laughlin MH, Shoemaker JK. Effects of acute and chronic interval sprint exercise performed on a manually propelled treadmill on upper limb vascular mechanics in healthy young men. Physiol Rep 2016; 4:4/13/e12861. [PMID: 27405970 PMCID: PMC4945842 DOI: 10.14814/phy2.12861] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 11/24/2022] Open
Abstract
Interval sprint exercise performed on a manually propelled treadmill, where the hands grip the handle bars, engages lower and upper limb skeletal muscle, but little is known regarding the effects of this exercise modality on the upper limb vasculature. We tested the hypotheses that an acute bout of sprint exercise and 6 weeks of training induces brachial artery (BA) and forearm vascular remodeling, favoring a more compliant system. Before and following a single bout of exercise as well as 6 weeks of training three types of vascular properties/methodologies were examined in healthy men: (1) stiffness of the entire upper limb vascular system (pulse wave velocity (PWV); (2) local stiffness of the BA; and (3) properties of the entire forearm vascular bed (determined by a modified lumped parameter Windkessel model). Following sprint exercise, PWV declined (P < 0.01), indices of BA stiffness did not change (P ≥ 0.10), and forearm vascular bed compliance increased and inertance and viscoelasticity decreased (P ≤ 0.03). Following manually propelled treadmill training, PWV remained unchanged (P = 0.31), indices of BA stiffness increased (P ≤ 0.05) and forearm vascular bed viscoelasticity declined (P = 0.02), but resistance, compliance, and inertance remained unchanged (P ≥ 0.10) compared with pretraining values. Sprint exercise induced a more compliant forearm vascular bed, without altering indices of BA stiffness. These effects were transient, as following training the forearm vascular bed was not more compliant and indices of BA stiffness increased. On the basis of these data, we conclude that adaptations to acute and chronic sprint exercise on a manually propelled treadmill are not uniform along the arterial tree in upper limb.
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Affiliation(s)
- T Dylan Olver
- Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri
| | - Steph M Reid
- Exercise Nutrition Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Alan R Smith
- Exercise Nutrition Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - Mair Zamir
- Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada Departments of Applied Mathematics and of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Peter W R Lemon
- Exercise Nutrition Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
| | - M Harold Laughlin
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
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Shoemaker JK, Badrov MB, Al-Khazraji BK, Jackson DN. Neural Control of Vascular Function in Skeletal Muscle. Compr Physiol 2015; 6:303-29. [PMID: 26756634 DOI: 10.1002/cphy.c150004] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The sympathetic nervous system represents a fundamental homeostatic system that exerts considerable control over blood pressure and the distribution of blood flow. This process has been referred to as neurovascular control. Overall, the concept of neurovascular control includes the following elements: efferent postganglionic sympathetic nerve activity, neurotransmitter release, and the end organ response. Each of these elements reflects multiple levels of control that, in turn, affect complex patterns of change in vascular contractile state. Primarily, this review discusses several of these control layers that combine to produce the integrative physiology of reflex vascular control observed in skeletal muscle. Beginning with three reflexes that provide somewhat dissimilar vascular patterns of response despite similar changes in efferent sympathetic nerve activity, namely, the baroreflex, chemoreflex, and muscle metaboreflex, the article discusses the anatomical and physiological bases of postganglionic sympathetic discharge patterns and recruitment, neurotransmitter release and management, and details of regional variations of receptor density and responses within the microvascular bed. Challenges are addressed regarding the fundamentals of measurement and how conclusions from one response or vascular segment should not be used as an indication of neurovascular control as a generalized physiological dogma. Whereas the bulk of the article focuses on the vasoconstrictor function of sympathetic neurovascular integration, attention is also given to the issues of sympathetic vasodilation as well as the impact of chronic changes in sympathetic activation and innervation on vascular health. © 2016 American Physiological Society.
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Affiliation(s)
- J K Shoemaker
- School of Kinesiology, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
| | - M B Badrov
- School of Kinesiology, Western University, London, Ontario, Canada
| | - B K Al-Khazraji
- Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - D N Jackson
- Department of Medical Biophysics, Western University, London, Ontario, Canada
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Nelson ES, Mulugeta L, Myers JG. Microgravity-induced fluid shift and ophthalmic changes. Life (Basel) 2014; 4:621-65. [PMID: 25387162 PMCID: PMC4284461 DOI: 10.3390/life4040621] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 09/17/2014] [Accepted: 10/17/2014] [Indexed: 11/16/2022] Open
Abstract
Although changes to visual acuity in spaceflight have been observed in some astronauts since the early days of the space program, the impact to the crew was considered minor. Since that time, missions to the International Space Station have extended the typical duration of time spent in microgravity from a few days or weeks to many months. This has been accompanied by the emergence of a variety of ophthalmic pathologies in a significant proportion of long-duration crewmembers, including globe flattening, choroidal folding, optic disc edema, and optic nerve kinking, among others. The clinical findings of affected astronauts are reminiscent of terrestrial pathologies such as idiopathic intracranial hypertension that are characterized by high intracranial pressure. As a result, NASA has placed an emphasis on determining the relevant factors and their interactions that are responsible for detrimental ophthalmic response to space. This article will describe the Visual Impairment and Intracranial Pressure syndrome, link it to key factors in physiological adaptation to the microgravity environment, particularly a cephalad shifting of bodily fluids, and discuss the implications for ocular biomechanics and physiological function in long-duration spaceflight.
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Affiliation(s)
- Emily S Nelson
- NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135, USA.
| | - Lealem Mulugeta
- Universities Space Research Association, Division of Space Life Sciences, 3600 Bay Area Boulevard, Houston, TX 77058, USA.
| | - Jerry G Myers
- NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135, USA.
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Faturechi R, Hashemi A, Abolfathi N. A tensile machine with a novel optical load cell for soft biological tissues application. J Med Eng Technol 2014; 38:411-5. [DOI: 10.3109/03091902.2014.968677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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9
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Nielson CA, Frances MF, Fitzgeorge L, Prapavessis H, Zamir M, Shoemaker JK. Impact of a smoking cessation lifestyle intervention on vascular mechanics in young women. Appl Physiol Nutr Metab 2014; 39:572-80. [DOI: 10.1139/apnm-2013-0272] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypotheses that smoking-induced changes in vascular mechanics would be detected earlier in the lumped properties of peripheral vascular beds, which include the properties of microvasculature, than in the local properties of central conduits, and that such changes are reversible with lifestyle changes that include smoking cessation and exercise. Vascular measures were made in 53 young (18–40 years) female smokers and 25 age-matched non-smokers. Twenty-two of the smokers were tested before and after a 14-week smoking cessation program and, of these, 13 were tested again after 52 weeks of smoking cessation. Compared with non-smokers, lumped forearm vascular bed compliance (C: mL/mm Hg) was lower, while lumped viscoelasticity (K: mm Hg/(mL·min)) and resistance (R: mm Hg/(mL·min)) were higher in the smoker group. Neither the carotid-to-toe pulse wave velocity nor local carotid artery elasticity indices were different between groups. Compared with non-smokers, brachial artery distensibility was less, and other markers of stiffness higher, in the smoker group. At 14 and 52 weeks of smoking cessation, forearm vascular R was reduced and C was increased while K was unchanged. The changes in C and R occurred while maintaining a constant R×C value, which represents a dynamic time constant. Thus, early changes in K were observed in the forearm vascular bed of smokers, which were not reflected in the local properties of central conduit vessels. Forearm C, but not K, was reversed following smoking cessation, a finding that may represent a persistent effect of smoking on the intercellular matrix of the vessel wall.
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Affiliation(s)
- Chantelle A. Nielson
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, ON N6A 3K7, Canada
| | - Maria F. Frances
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, ON N6A 3K7, Canada
| | - Lyndsay Fitzgeorge
- Exercise and Health Psychology Laboratory, School of Kinesiology, Western University, London, ON N6A 3K7, Canada
| | - Harry Prapavessis
- Exercise and Health Psychology Laboratory, School of Kinesiology, Western University, London, ON N6A 3K7, Canada
| | - Mair Zamir
- Departments of Applied Mathematics and of Medical Biophysics, Western University, London, ON N6A 3K7, Canada
| | - J. Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, Western University, London, ON N6A 3K7, Canada
- Department of Physiology and Pharmacology, Western University, London, ON N6A 3K7, Canada
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Noble E, Melling J, Shoemaker K, Tikkanen H, Peltonen J, Stuckey M, Petrella RJ. Innovation to Reduce Cardiovascular Complications of Diabetes at the Intersection of Discovery, Prevention and Knowledge Exchange. Can J Diabetes 2013; 37:282-93. [DOI: 10.1016/j.jcjd.2013.07.061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/27/2013] [Accepted: 07/29/2013] [Indexed: 01/20/2023]
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Frances MF, Goswami R, Rachinsky M, Craen R, Kiviniemi AM, Fleischhauer A, Steinback CD, Zamir M, Shoemaker JK. Adrenergic and myogenic regulation of viscoelasticity in the vascular bed of the human forearm. Exp Physiol 2011; 96:1129-37. [DOI: 10.1113/expphysiol.2011.059188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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