The Rate of Change of Left Ventricular Volume in Man

Abstract

The rate of left ventricular volume change (dV/dt) is by definition left ventricular ejection rate during systole and filling rate during diastole, and in the absence of valvular regurgitation or intracardiac shunts, is equal to systolic aortic valve flow and diastolic mitral valve flow respectively. A computerized technique for the calculation of instantaneous left ventricular dV/dt from cineangiographically measured left ventricular volume is presented. Curve smoothing was accomplished by passing a second degree polynomial through nine consecutive volume points using the least squares technique. Validity of this technique was demonstrated by the high degree of correlation of systolic dV/dt with instantaneous ascending aortic blood velocity (flow) measured simultaneously with an electromagnetic catheter-tip velocity transducer in ten patients. Peak left ventricular systolic ejection rate (S dV/dt) was calculated from single plane cineangiographically measured left ventricular volumes in 113 adult patients and related to other measures of cardiovascular function. Mean S dV/dt for the group of 29 normal patients was 427 ± 129 cc per second and was not significantly different in patients with coronary artery disease (21), aortic stenosis (13), mitral stenosis (11), or cardiomyopathy (9), but was increased significantly in patients with valvular regurgitation (19). S dV/dt correlates poorly with the ejection fraction and with left ventricular end-diastolic pressure (LVEDP) and is not a reliable measure of left ventricular function. The primary determinant of S dV/dt appears to be total left ventricular stroke volume. When S dV/dt is divided by end-diastolic volume (EDV), the resultant S dV/dt/EDV correlates well with peak normalized circumferential fiber shortening rate ( r = 0.89, P < 0.01) and with ejection fraction ( r = 0.69, P < 0.01). The correlation coefficient of S dV/dt/DV with LVEDP was r = 0.36 ( P < 0.01) and with arterio-venous oxygen difference, r = 0.38 ( P < 0.01). Thus, S dV/dt/EDV appears to be a measure of ventricular function. S dV/dt occurs in midsystole in normal subjects and in patients with mitral regurgitation and is not delayed in patients with aortic stenosis. The three patients with idiopathic hypertrophic subaortic stenosis appeared to have characteristic changes in the left ventricular ejection rate curve with an increase in S dV/dt (and especially S dV/dt/EDV), with S dV/dt occurring earlier in systole than normal.