Relationship Between Ventricular Pressures and Right and Left Myocardial Blood Flow

The effects of constriction of the pulmonary artery and aorta on myocardial blood flow, measured as local hydrogen clearances, in the anterior parts of the right and the left myocardium have been studied in open chest dogs. The increase in myocardial flow that by progressive constriction rarely exceeded 100 percent of control values was in most experiments confined to the ventricle‐ under increased pressure load. Plots of relative flows and pressures yielded regression lines of similar slopes for both ventricles without significant differences between systolic and mean ventricular pressures as indices of myocardial flow. Left myocardial flow remained unchanged when outflow resistance from the right ventriclc incrcased until aortic pressure fell. The effect of increased aortic pressure on right myocardial flow was more variable. Increase of systolic left ventricular pressure to 250 mm Hg. had slight or no effect on right myocardial flow. More severe aortic constriction which donbled mean left ventricular pressure increased right and left myocardial flow similarly. It is concluded that the relationship between relative flow and ventricular pressure variations previously demonstrated fur the left ventricle also applies to the right ventricle and that myocardial flow is regulnted independently for the two ventricles. except at extreme perfusion pressures.