The mode of left ventricular pumping: is there an outer contour change in addition to the atrioventricular plane displacement?

The outer contour of the heart has in some studies been shown to be constan t during the heart cycle and the epicardial apex almost stationary whilst t he base of the ventricles moves towards apex during systole. The base of th e left ventricle has been regarded as a cylinder with constant cross-sectio nal area with changes in height during the heart cycle, the latter correspo nding to the amplitude of mitral annulus motion (MAM). In this echocardiogr aphic study, including 20 healthy adults, the stroke volume calculated by t he cylinder model was significantly lower than by a reference method (modif ied Simpson's rule). MAM explained 82% of the stroke volume and 18% must, t herefore, be explained by an inward motion of the outer left: ventricular w all. A mean outer diameter shortening of about 3% (about 2 mm) was calculat ed.