Key result
Myocardial oxygen consumption is the major determinant of coronary blood flow, while autoregulation is reduced in ischemic hearts with atheromatous occlusion.
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This review highlights that myocardial oxygen consumption primarily drives coronary blood flow, a mechanism that becomes impaired in ischemic heart disease where flow relies more heavily on pressure gradients.
Phasic changes in intramyocardial tension during the cardiac cycle interrupt coronary blood flow (CBF) so that most of the nutrient flow to the ventricular myocardium occurs in ventricular diastole. Rapid changes in mean arterial pressure cause transient changes in CBF before autoregulatory factors return flow toward previous levels. Myocardial oxygen consumption (MVo2) appears to the major determinant of CBF and the factors determining MVo, (mainly developed tension and contractile state) are, therefore, major determinants of CBF. The direct effects of autonomic excitation on CBF appear relatively minor, however; the vagus, sympathetic nerves and adrenal medullary hormones profoundly alter CBF indirectly through changes in MVor In the ischaemic heart with atheromatous occlusion of large vessels there Is a reduced capacity for autoregulation, and nutrient flow is more dependent on pressure gradient. Hypertension and valvular disorders are often associated with raised MVo2 but associated abnormalities in pressure gradient and resistance to flow often hinder the supply of CBF needed to meet high demands.
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White et al. (1973) conducted a review in Coronary blood flow regulation in normal and diseased heart. Myocardial oxygen consumption is the major determinant of coronary blood flow, while autoregulation is reduced in ischemic hearts with atheromatous occlusion.
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