Abstract
Time course of the changes in left ventricular pressure-volume coefficient in a cardiac cycle, defined as e (t) =p (t) /v (t), where t=time from the beginning of the cardiac cycle, p (t) = systolic intraventricular pressure and v(t) = systolic intraventricular volume, is studied on anesthetized and thoracotomized dogs. For actual computation, v (t) = (1-ρ) -1·vs-∫t0i (t)dt, where ρ=residual volume ratio of the left ventricle measured by a thermodilution method, vs= stroke volume and i(t) = ascending aortic blood flow by an electromagnetic flowmeter. It is demonstrated that e(t) is approximately independent from intraventricular end-diastolic volume and from conditions of the arterial system, but is characteristically dependent on the strength of cardiac sympathetic stimulation and heart rate.
A model of the left ventricular pumping is proposed with e(t), and the results of its theoretical analysis are in satisfactory agreement with many investigated relationships among circulatory variables in cardiovascular physiology.
