Differences in direction-dependent shortening of the left ventricular wall in hypertrophic cardiomyopathy and in systemic hypertension

To determine whether patients with hypertrophic cardiomyopathy (HC) have an altered mode of contraction of the left ventricular (LV) wall related to underlying myocardial abnormalities, geometric changes in the LV wall were analyzed at 2 points of the cardiac cycle (end-diastole and end-systole) using 2-dimensional echocardiography. The relations between meridional and circumferential shortening of the LV midwall, mean wall thickening, and the changes in the short-axis cross-sectional area of the LV wall at the level of chordae tendineae were determined in 18 patients with nonobstructive HC, and were compared with those in 31 normal subjects and 19 patients with essential systemic hypertension. In normal subjects, no significant difference was observed between meridional (16.3 ± 2.4%) and circumferential (17.1 ± 4.0%) shortening, whereas cross-sectional LV wall area increased significantly at end-systole (p < 0.001). In patients with hypertension, all measured indexes were not different from those in normal subjects. In contrast, patients with HC had significantly reduced meridional shortening (p < 0.001) and mean wall thickening (p < 0.01). Consequently, a striking difference was observed between meridional (8.9 ± 2.4%) and circumferential (16.9 ± 3.2%) shortening (p < 0.001). Furthermore, no increase in cross-sectional LV wall area was observed at end-systole. Thus, echocardiographic detection of direction-dependent contraction can be a useful index for distinguishing HC from systemic hypertension.