Echocardiographic studies of mitral valve motion. Genesis of the opening snap in mitral stenosis

Abstract

In an effort to delineate the origin of the mitral opening snap, 29 patients with rheumatic mitral stenosis and audible opening snaps were studied by means of simultaneous external recordings including phonocardiography, mitral echocardiography, and apex cardiography. Comparison was made with 10 normal volunteer subjects. Discrepancies were noted when the apex cardiogram was utilized to time the opening snap or isovolumic relaxation of the left ventricle. This method, however, remains a useful tool for differentiation of heart sounds. Echocardiographic timing of the opening snap is more precise than heretofore available reference methods. Opening snap and completion of anterior mitral leaflet opening movement were simultaneous within the error of measurement, 5 msec., in all patients with clinically pure mitral stenosis and in 74 per cent of those with mixed or bivalvular lesions. In the remainder of the latter group these events occurred within 10 msec. apart. This study supports the hypothesis that opening snap originates from the diseased mitral leaflets as they reach completion of their opening movement.