1974 Volume 112 Issue 1 Pages 89-100
Effects of heart rate on ventricular performance, myocardial contractile state and coronary circulation were studied under constant cardiac output in right heart by-passed anesthetized dogs. Myocardial contractile state (Vmax) was elevated as heart rate increased, and this was considered to play an important role in impeding further increase of systolic time ratio which would have occurred unless this elevation had occurred. Myocardial oxygen consumption (MVO2) was mainly influenced by heart rate, left ventricular systolic peak pressure and the contractile state of the left ventricle, but neither by stroke volume of the left ventricle nor left ventricular work. After administration of propranolol, the left ventricle was deteriorated at tachycardia more than 210 beats per minute, and Vmax did not rise at such a tachycardia. These results suggest that adrenergic beta-receptor plays an important role in augmenting the contractile state of the left ventricle and in preventing it from being deteriorated at tachycardia.
