Studies on Starling's Law of the Heart

Abstract

The acute circulatory responses to impeding venous return to the heart by the inflation of a balloon in the inferior vena cava were determined in 14 patients undergoing left heart catheterization. In the five patients without clinical or hemodynamic evidence of impaired left ventricular function, left ventricular end-diastolic pressure fell, and the decrease was accompanied by reductions in the cardiac index, left ventricular stroke volume, and left ventricular stroke work. In nine patients with impaired left ventricular function, directionally similar responses were noted, although the left ventricular function curves relating left ventricular end-diastolic pressure to left ventricular stroke work were generally flatter and lower than those in the patients without left ventricular disease. In none of the patients did a significant increase in cardiac index, stroke volume, or left ventricular stroke work occur during inflation of the balloon. It is concluded that the Starling relationship appears to operate in a directionally similar manner both in the normal and the depressed human left ventricle, and that the left ventricles of patients with impaired function are not on a descending limb of the curve. However, a descending limb of the left ventricular Starling curve may become apparent when an additional work load is imposed on the diseased ventricle.