Dimensional Changes of the Human Left Ventricle Prior to Aortic Valve Opening

Abstract

Previous studies of the dynamic geometry of the left ventricle have yielded conflicting results concerning shape changes during the preejection period. Accordingly, left ventricular dimensional changes prior to aortic valve opening in man were analyzed using high-speed biplane cineradiograms exposed in the frontal and lateral projections. In each projection the long axis and three chords perpendicular to it were measured. In six patients without left ventricular disease there was a mean decrease in equatorial diameter of approximately 1 mm before aortic valve opening ( P < 0.05), without significant change in the long axis, causing an apparent volume decrease of 4.0 ml or 2.8% of end-diastolic volume (EDV). In five patients with wall motion disorders secondary to coronary artery disease the equatorial diameter decreased by an average of 1.5 mm and volume was diminished by 8.3 ml or 3.9% of EDV. In four of seven patients with primary myocardial disease, an increase in the equatorial diameter and a basal chord occurred, while the apical chord decreased, suggesting nonhomogeneous myocardial involvement. In eight patients with mitral regurgitation, the reduction in equatorial diameter averaged 2.8 mm and volume decreased by 16.7 ml or 8.0% of EDV. In normal patients the occurrence of circumferential fiber shortening prior to aortic valve opening under basal conditions can result in as much as a 9% underestimation of contractile element velocity calculated from dp/dt, whereas in patients with mitral regurgitation this figure may be as high as 31%. These studies indicate that, in man, expansion at the minor equator during the preejection period occurs only under highly abnormal conditions. They further suggest that the reductions in shape and volume prior to aortic valve opening may be significant relative to mechanical analyses of this phase of contraction.