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The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand

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journal contribution
posted on 2023-01-24, 12:09 authored by Lindsey M. Boulet, Michael StembridgeMichael Stembridge, Michael M. Tymko, Joshua C. Tremblay, Glen E. Foster

 In humans, coronary blood flow is tightly regulated by microvessels within the myocardium to match myocardial energy demand. However, evidence regarding inherent sensitivity of the microvessels to changes in arterial partial pressure of carbon dioxide and oxygen is conflicting because of the accompanied changes in myocardial energy requirements. This study aimed to investigate the changes in coronary blood velocity while manipulating partial pressures of end-tidal CO2 (Petco2) and O2 (Peto2). It was hypothesized that an increase in Petco2 (hypercapnia) or decrease in Peto2 (hypoxia) would result in a significant increase in mean blood velocity in the left anterior descending artery (LADVmean) due to an increase in both blood gases and energy demand associated with the concomitant cardiovascular response. Cardiac energy demand was assessed through noninvasive measurement of the total left ventricular mechanical energy. Healthy subjects (n = 13) underwent a euoxic CO2 test (Petco2 = −8, −4, 0, +4, and +8 mmHg from baseline) and an isocapnic hypoxia test (Peto2 = 64, 52, and 45 mmHg). LADVmean was assessed using transthoracic Doppler echocardiography. Hypercapnia evoked a 34.6 ± 8.5% (mean ± SE; P < 0.01) increase in mean LADVmean, whereas hypoxia increased LADVmean by 51.4 ± 8.8% (P < 0.05). Multiple stepwise regressions revealed that both mechanical energy and changes in arterial blood gases are important contributors to the observed changes in LADVmean (P < 0.01). In summary, regulation of the coronary vasculature in humans is mediated by metabolic changes within the heart and an inherent sensitivity to arterial blood gases. 

History

Published in

American Journal of Physiology-Heart and Circulatory Physiology

Publisher

American Physiological Society

Version

AM (Accepted Manuscript)

Citation

Boulet, L.M., Stembridge, M., Tymko, M.M., Tremblay, J.C. and Foster, G.E. (2016) 'The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand', American Journal of Physiology-Heart and Circulatory Physiology, 311 (2), pp. 326-336

Print ISSN

0363-6135

Electronic ISSN

1522-1539

Cardiff Met Affiliation

  • Cardiff School of Sport and Health Sciences

Cardiff Met Authors

Mike Stembridge

Cardiff Met Research Centre/Group

  • Cardiovascular Physiology

Copyright Holder

© The Publisher

Language

en