Response of the Left Ventricle to Changes in Output

Abstract

Previous studies on the mammalian heart have demonstrated that both the diastolic and systolic volumes increase with an increase in total output, mean arterial pressure remaining constant. (Patterson, Piper and Starling, Wiggers and Katz). Kozawa, working with the turtle's heart found that only the diastolic volume varied. The present study was made on dogs using the modified heart lung preparation of Dusser de Barenne in conjunction with an apparatus designed to maintain physical conditions as constant as possible regardless of variations in output. A cannula of large diameter was inserted into the aorta. The pulmonary artery was cannulated twice, one cannula toward the right ventricle and the other toward the lungs. The right ventricle pumped only blood flowing from the coronary system, while the left ventricle that which was allowed to return from the venous reservoir. Fig. 1 shows the result obtained by rapidly increasing the input to the left ventricle. The changes in volume of the ventricles, were recorded so that systole produced a downward movement of the piston-recorder lever. Prior to (1) no blood was returning to the left ventricle from the venous reservoir, the right ventricle pumping only the coronary blood flow. At (1) blood from the venous reservoir was allowed to return to the left ventricle by way of the lungs. The diastolic volume rapidly increased to a plateau at (6). The systolic volume decreased with one exception to (2). From (3) to (4) the output of the left ventricle was about 1000 cc. per minute. The venous return to the left ventricle was blocked at (4). At (5) the volume changes of the heart were again approximately the same as at (1). Heart rate was constant and mean blood pressure increased only about one mm. Hg. during the peak of the flow, as indicated at (4).