Myocardial Oxygen Consumption and Autoregulation of the Coronary Vascular Bed

Abstract

The local control of vascular resistance is characterized by a relatively constant coronary flow during changes in perfusion pressure (autoregulation) and the ability of coronary flow to match increased metabolic requirements (metabolic regulation). Generally it is assumed that perfusion pressure does not affect heart metabolism (Feigl, 1983) although there is some evidence of the contrary (Gregg, 1963; Arnold et al., 1970). Under physiological conditions with aortic pressure as perfusion pressure of the coronary vascular bed, changes in mean aortic pressure (exercise, hypertension) cause significant changes in coronary blood flow via both myocardial oxygen consumption and perfusion pressure (Bugni et al., 1980). Relating coronary flow exclusively to oxygen consumption (Rubio & Berne, 1975; Eckenhoff et al., 1947) ignores the possible direct effect of perfusion pressure on flow. The oxygen hypothesis as formulated by Laird (Laird & Spaan, 1981; Drake-Holland et al., 1984) predicts a linear relation between coronary flow and both perfusion pressure and oxygen consumption. The aim of this study was to test this hypothesis applying multiple linear regression analysis to experimental data obtained from the in situ cannulated coronary bed of anaesthetised open chest dog and goat.