Patterns of systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: assessment by two-dimensional echocardiography.

A variety of patterns of systolic anterior motion (SAM) of the mitral valve were identified by realtime, 2-dimensional echocardiography in 62 patients with hypertrophic cardiomyopathy. In 36 patients (58%), both the anterior and posterior mitral leaflets appeared to participate importantly in SAM, although the anterior leaflet actually contacted or most closely approached the ventricular septum during systole because of its anterior anatomic position. In 19 patients (31%), SAM was produced selectively by the posterior mitral leaflet. In only 6 patients (10%) was the anterior leaflet alone responsible for SAM. In just 1 patient did the chordae tendineae appear to be primarily responsible for the SAM. In 51 patients (82%), only the distal portion of the anterior or posterior mitral leaflet (and possibly the attached proximal chordae tendineae) approached or contacted the septum in systole; in 10 patients both the body and tip regions of the anterior leaflet produced mitral-septal apposition. Hence, in obstructive hypertrophic cardiomyopathy, (1) the morphologic structures responsible for moderate to severe SAM are not identical in all patients, and a variety of patterns of SAM occur; (2) the posterior mitral leaflet plays an important role in SAM in almost 90% of patients, either by producing SAM alone (31%) or by moving anteriorly in concert with the anterior leaflet (58%); (3) SAM produced selectively by the anterior mitral leaflet is relatively uncommon; and (4) SAM is usually produced primarily by the distal portions of the mitral leaflets (with or without the attached chordae tendineae).