Interrelation Between Cardiac Oxygen Consumption and Coronary Blood Flow

Abstract

Determinants of the coronary flow in the anesthetized dog with the heart in situ were studied under controlled conditions. The following conclusions were reached. The coronary flow is not related to the cardiac output. Mean aortic pressure affects the coronary flow but at the same time produces significant changes in O2 consumption. Within the limits of these experiments, the pure mechanical effect of aortic pressure on coronary flow, independent of its O2 consumption effect, is slight. O2 consumption appears to be the most important factor determining coronary flow. A nomogram showing the relation between coronary flow, mean aortic pressure and O2 consumption is presented in which the dominant determining role of O2 consumption on the quantity of coronary flow is clearly shown. Because of this relationship, it is suggested that if experimental values of coronary flow are to have meaning they must first be related to the level of O2 consumption existing at the moment. With increasing O2 consumption, a coronary vasodilatation occurs to meet the O2 needs of the myocardium. Thus the availability of O2 parallels the need for it. An increase in mean aortic pressure produces a. slowing of the heart and an increase in coronary flow. However, this does not result in a decreased O2 consumption by the myocardium.