Geometric changes allow normal ejection fraction despite depressed myocardial shortening in hypertensive left ventricular hypertrophy

Abstract

This study of hypertensive left ventricular hypertrophy 1) assessed myocardial shortening in both the circumferential and long-axis planes, and 2) investigated the relation between geometry and systolic function. In hypertensive left ventricular hypertrophy, whole-heart studies have suggested normal systolic function on the basis of ejection fraction-systolic stress relations. By contrast, isolated muscle data show that contractility is depressed. It occurred to use that this discrepancy could be related to geometric factors (relative wall thickness). We studied 43 patients with hypertensive left ventricular hypertrophy and normal ejection fraction (mean +/- SD 69 +/- 13%) and 50 clinically normal subjects. By echocardiography, percent myocardial shortening was measured in two orthogonal planes; circumferential shortening was measured at the endocardium and at the midwall, and long-axis shortening was derived from mitral annular motion (apical four-chamber view). Circumferential shortening was related to end-systolic circumferential stress and long-axis shortening to meridional stress. Endocardial circumferential shortening was higher than normal (42 +/- 10% vs. 37 +/- 5%, p < 0.01) and midwall circumferential shortening lower than normal in the left ventricular hypertrophy group (18 +/- 3% vs. 21 +/- 3%, p < 0.01). Differences between endocardial and midwall circumferential shortening are directly related to differences in relative wall thickness. Long-axis shortening was also depressed in the left ventricular hypertrophy group (18 +/- 6% in the left ventricular hypertrophy group, 21 +/- 5% in control subjects, p < 0.05). Midwall circumferential shortening and end-systolic circumferential stress relations in the normal group showed the expected inverse relation; those for approximately 33% of the left ventricular hypertrophy group were > 2 SD of normal relations, indicating depressed myocardial function. There was no significant relation between long-axis shortening and meridional stress, indicating that factors other than afterload influence shortening in this plane. High relative wall thickness allows preserved ejection fraction and normal circumferential shortening at the endocardium despite depressed myocardial shortening in two orthogonal planes.