THE EVALUATION OF THE WORK OF THE HEART

Abstract

The following were computed from central pressure pulses typical of a wide variety of conditions, and from arterial dis-tensibility measurements: the curve of cardiac ejection; the change in aortic cross-section during systole; the velocity curve during systole (a/b); the curve of kinetic work during [image] ; and the variations in pressure work 2 g during systole (a times pressure in aorta). The kinetic work is of the order of 2% of the total work except when the stroke volume is abnormally large and the diastolic pressure is abnormally low. The pressure work is underestimated by 0 to 12% by multiplying the total ejection by the mean pressure during systole. The work done by the heart in raising the pressure of the blood is 10-40% more than that done at the periphery in forcing blood through the peripheral resistance. Energy in this amt. is lost as the aortic standing wave is damped out.