Myocardial perfusion during exercise in endurance-trained and untrained humans

Laaksonen, Marko S.; Kalliokoski, Kari K.; Luotolahti, Matti; Kemppainen, Jukka; Teräs, Mika; Kyröläinen, Heikki; Nuutila, Pirjo; Knuuti, Juhani

doi:10.1152/ajpregu.00771.2006

Cited by 34 publications

(18 citation statements)

References 37 publications

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“…During exercise, the threefold increase in MBF in our study reflects the upward shift of the autoregulation plateau induced by metabolic and flow-mediated vasodilatory factors (14). The present exercise data are in accordance to previous studies (6,14,24,27). The blood flow increase was not only achieved by accelerating erythrocyte passage through the capillary network (increased ␤) but also by increasing myocardial blood volume.…”

Section: Discussionsupporting

confidence: 91%

Microvascular response to metabolic and pressure challenge in the human coronary circulation

Marchi

Gloekler

Rimoldi

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

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de Marchi SF, Gloekler S, Rimoldi SF, Rölli P, Steck H, Seiler C. Microvascular response to metabolic and pressure challenge in the human coronary circulation. Am J Physiol Heart Circ Physiol 301: H434-H441, 2011. First published May 13, 2011; doi:10.1152/ajpheart.01283.2010.-In vivo observations of microcirculatory behavior during autoregulation and adaptation to varying myocardial oxygen demand are scarce in the human coronary system. This study assessed microvascular reactions to controlled metabolic and pressure provocation [bicycle exercise and external counterpulsation (ECP)]. In 20 healthy subjects, quantitative myocardial contrast echocardiography and arterial applanation tonometry were performed during increasing ECP levels, as well as before and during bicycle exercise. Myocardial blood flow (MBF; ml·min Ϫ1 ·g Ϫ1 ), the relative blood volume (rBV; ml/ml), the coronary vascular resistance index (CVRI; dyn·s·cm Ϫ5 /g), the pressure-work index (PWI), and the pressure-rate product (mmHg/min) were assessed. MBF remained unchanged during ECP (1.08 Ϯ 0.44 at baseline to 0.92 Ϯ 0.38 at high-level ECP). Bicycle exercise led to an increase in MBF from 1.03 Ϯ 0.39 to 3.42 Ϯ 1.11 (P Ͻ 0.001). The rBV remained unchanged during ECP, whereas it increased under exercise from 0.13 Ϯ 0.033 to 0.22 Ϯ 0.07 (P Ͻ 0.001). The CVRI showed a marked increase under ECP from 7.40 Ϯ 3.38 to 11.05 Ϯ 5.43 and significantly dropped under exercise from 7.40 Ϯ 2.78 to 2.21 Ϯ 0.87 (both P Ͻ 0.001). There was a significant correlation between PWI and MBF in the pooled exercise data (slope: ϩ0.162). During ECP, the relationship remained similar (slope: ϩ0.153). Whereas physical exercise decreases coronary vascular resistance and induces considerable functional capillary recruitment, diastolic pressure transients up to 140 mmHg trigger arteriolar vasoconstriction, keeping MBF and functional capillary density constant. Demandsupply matching was maintained over the entire ECP pressure range. myogenic vasoconstriction; autoregulation; myocardial microcirculation; external counterpulsation; contrast echocardiography; applanation tonometry CORONARY AUTOREGULATION DESCRIBES the ability of the coronary circulation to keep blood flow matched to myocardial needs despite pressure challenges that accidentally occur during life (37). The small arteriolar resistance vessels are the effectors in both autoregulation activity and adaptation to varying myocardial oxygen demand. The numerous types of challenges that the coronary circulation must face are expected to affect the capillary system as well. These interactions, however, are poorly understood, and in vivo observations in humans are scarce.External counterpulsation (ECP) is a physical therapeutic method that has emerged in the last years. It is intended to stimulate myocardial perfusion in coronary artery disease (CAD) and congestive heart failure (CHF) patients. The adjustable diastolic pressure transients that can be produced by ECP offer the unique opportunity to investigate the coronary respons...

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Section: Discussionsupporting

confidence: 91%

Microvascular response to metabolic and pressure challenge in the human coronary circulation

Marchi

Gloekler

Rimoldi

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

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“…In this context, blood flow to cardiac muscle in the left ventricle can equal ϳ500 ml·min Ϫ1 ·100 g Ϫ1 in equines during heavy exercise (12,296,298,351) with values of 300 -400 ml·min Ϫ1 ·100 g Ϫ1 seen in other species including humans (150,204,264,519). Estimates of skin blood flow equal to 6 -8 l/min distributed in perhaps 2 kg of skin in heated humans would also seem to rival the per 100 g values seen in skeletal and cardiac muscle (389).…”

Section: F Is There a Maximum Value For Skeletalmentioning

confidence: 99%

Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs

Joyner

Casey

2015

Physiological Reviews

564

513

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LJoyner MJ, Casey DP. Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs. Physiol Rev 95: 549 -601, 2015; doi:10.1152/physrev.00035.2013.-This review focuses on how blood flow to contracting skeletal muscles is regulated during exercise in humans. The idea is that blood flow to the contracting muscles links oxygen in the atmosphere with the contracting muscles where it is consumed. In this context, we take a top down approach and review the basics of oxygen consumption at rest and during exercise in humans, how these values change with training, and the systemic hemodynamic adaptations that support them. We highlight the very high muscle blood flow responses to exercise discovered in the 1980s. We also discuss the vasodilating factors in the contracting muscles responsible for these very high flows. Finally, the competition between demand for blood flow by contracting muscles and maximum systemic cardiac output is discussed as a potential challenge to blood pressure regulation during heavy large muscle mass or whole body exercise in humans. At this time, no one dominant dilator mechanism accounts for exercise hyperemia. Additionally, complex interactions between the sympathetic nervous system and the microcirculation facilitate high levels of systemic oxygen extraction and permit just enough sympathetic control of blood flow to contracting muscles to regulate blood pressure during large muscle mass exercise in humans.

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“…77 Finally, in young, healthy humans performing supine bicycle exercise while in the PET scanner ( ) individuals although as expected trained subjects had lower resting HR (44±6 bpm) versus untrained subject (58±6 bpm) but similar MAP (78±6 versus 76±4 mm Hg, respectively). 78 In summary, therefore, across a range of experimental designs and species, including humans (Tables 1-4), exercise levels to ≈10 to 13 METs have been associated with measured MBF of 2 to 4 mL·min…”

Section: Coronary Physiology and Absolute Measurements Of Mbfmentioning

confidence: 91%

“…Factors that may play a role include physical fitness 78 and genetic and other factors (eg, myocyte oxidative stress) that may affect the efficiency of myocardial oxygen utilization both in mitochondrial production of ATP 80 and in generation of external mechanical work. 81 Individual variation notwithstanding, stress MBF levels <1.9 mL·min −1 ·g −1 in a given coronary territory are likely to render it vulnerable to effort-induced ischemia, perhaps not life-threatening or severe but ischemia nonetheless (and potentially life-threatening if engendering ventricular tachycardia/ventricular fibrillation), particularly as effort exceeds 9 METs.…”

Section: ·Gmentioning

confidence: 99%

“…44,46 The MFR ratio, however, is heavily dependent of the level of rest MBF and thus may be misleading in certain cases. Data reviewed above indicate that myocardial oxygen demand in the range of 9 to 10 METs clearly cannot be met by stress MBF in the range of 0.4 to 1.0 mL·min [75][76][77][78] often regarded as within the range of normal rest MBF. 85,87 Although it has been reported anecdotally that such patients may do well clinically if MFR is ≥1.7X, 42 this likely reflects the combination of sedentary lifestyle and β-blocker therapy, which limit MVo 2 and make such low levels of stress MBF adequate to the patient's needs.…”

Section: ·Gmentioning

confidence: 99%

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Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease

Gewirtz

Dilsizian

2016

Circulation

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In the >40 years since planar myocardial imaging with 43 K-potassium was introduced into clinical research and management of patients with coronary artery disease (CAD), diagnosis and treatment have undergone profound scientific and technological changes. One such innovation is the current state-of-the-art hardware and software for positron emission tomography myocardial perfusion imaging, which has advanced it from a strictly research-oriented modality to a clinically valuable tool. This review traces the evolving role of quantitative positron emission tomography measurements of myocardial blood flow in the evaluation and management of patients with CAD. It presents methodology, currently or soon to be available, that offers a paradigm shift in CAD management. Heretofore, radionuclide myocardial perfusion imaging has been primarily qualitative or at best semiquantitative in nature, assessing regional perfusion in relative terms. Thus, unlike so many facets of modern cardiovascular practice and CAD management, which depend, for example, on absolute values of key parameters such as arterial and left ventricular pressures, serum lipoprotein, and other biomarker levels, the absolute levels of rest and maximal myocardial blood flow have yet to be incorporated into routine clinical practice even in most positron emission tomography centers where the potential to do so exists. Accordingly, this review focuses on potential value added for improving clinical CAD practice by measuring the absolute level of rest and maximal myocardial blood flow. Physiological principles and imaging fundamentals necessary to understand how positron emission tomography makes robust, quantitative measurements of myocardial blood flow possible are highlighted.

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Myocardial perfusion during exercise in endurance-trained and untrained humans

Cited by 34 publications

References 37 publications

Microvascular response to metabolic and pressure challenge in the human coronary circulation

Microvascular response to metabolic and pressure challenge in the human coronary circulation

Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs

Integration of Quantitative Positron Emission Tomography Absolute Myocardial Blood Flow Measurements in the Clinical Management of Coronary Artery Disease

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