Patterns of Mitral Valve Systolic Anterior Motion in Obstructive Hypertrophic Cardiomyopathy

Background. The morphological determinants of mitral valve systolic anterior motion (SAM) and obstruction to left ventricular outflow in patients within the broad clinical spectrum of hypertrophic cardiomyopathy (HCM) are not completely understood, particularl the contribution of mitral leaflet length and size. Methods and Results. To clarify this issue, mitral valve specimens from 43 patients with HCM and basal outflow obstruction were used to relate morphometric measurements of leaflet area to certain morphological and functional assessments of left ventricular outflow tract geometry and valvular motion obtained from echocardiograms in the same patients. Twenty-four patients (56%) had mitral valves of normal size (leaflet area < 12.0 cm2) and 19 patients (44%) had enlarged and elongated valves (area >12.0 cm2). Compared with normal-sized mitral valves, the enlarged valves were situated more posteriorly in a larger left ventricular outflow tract (cross-sectional area, 3.3±1.0 versus 1.9±0.7 cm2 for normal-sized valves; p<0.001) and also had greater systolic excursion of the anterior leaflet