Abstract
A method is described which permitted separate, simultaneous measurement of blood flow in the left and right coronary arteries while the performance of the left or right ventricles was altered. As long as neither ventricle was overdistended and when arterial oxygen tension and pH were constant, blood flow in the right or the left coronary tree was a linear function of the right or left coronary driving pressure. When the right ventricle was overdistended so that abnormally high pressures existed in it, vasomotor tonus in both coronary trees was markedly diminished, although the performance of the left heart did not vary appreciably.