Localization of left ventricular outflow obstruction by cross-sectional echocardiography.

Cross-sectional echocardiographic studies were performed using a high resolution real time mechanical sector scanner in 70 patients with left ventricular outflow obstruction. Seven separate obstructive patterns were recorded in these patients. An area of aortic narrowing just distal to the aortic valve at the superior border of the left atrium was noted with supravalvular aortic stenosis. With congenital valvular aortic stenosis there was an increase in echo production by the thickened aortic leaflets. During systole these prominent leaflet echoes curved inward toward the center of the aortic root reflecting the systolic doming of the valve. With calcific aortic stenosis, the calcification produced an area of dense linear echoes attached in varying degrees to either the anterior or posterior border of the aortic root. At the subvalvular level three obstructive patterns were recorded; with a discrete subvalvular obstructive membrane two linear echoes apparently produced by the inner margins of the obstructing membrane were recorded in the outflow tract. With more extensive fibromuscular narrowing of the subvalvular area, there was inward bowing of the echoes from both the anterior and posterior walls of the outflow tract. In one case this was a dense shelf-like mass of echoes extending downward from the basal portion of the interventricular septum toward the mid-portion of the anterior mitral leaflet with corresponding systolic anterior motion of the mitral leaflet. In patients with idiopathic hypertrophic subaortic stenosis there was systolic anterior motion of the anterior mitral leaflet beginning just distal to the point of coaptation of the mitral leaflets and extending distally toward the papillary muscles. This report suggests that the enlarged field of vision and spatial orientation provided by the cross-sectional echocardiographic technic should improve our ability to record and characterize areas of obstruction to left ventricular outflow.