Echocardiographic studies to explain opening snaps in presence of nonstenotic mitral valves

Abstract

An opening snap is most often associated with either mitral or tricuspid valvular stenosis. A study using the simultaneous graphic recording of mitral valve motion by echocardiography along with the phonocardiogram and the left ventricular apex cardiogram has provided evidence supporting the existence of a mitral valve opening snap in the following cardiac conditions: (1) tricuspid atresia with a large atrial septal defect; (2) idiopathic second and third degree heart block; (3) ventricular septal defect; (4) mitral regurgitation; (5) thyrotoxicosis; and (6) tetralogy of Fallot occurring after a Blalock-Taussig procedure. In each condition the opening snap occurred 90 to 110 msec after appearance of the aortic component of the second heart sound on the phonocardiogram, and it coincided with the point of maximal descent of the anterior leaflet of the mitral valve as shown by the echocardiogram and the 0 point on the apex cardiogram. The pulmonic closure sound was identified in each case as a separate sound. An exaggerated third heart sound was thought not to be the cause of this high to mid-frequency diastolic sound since it consistently occurred before the peak of the rapid filling wave. None of the patients had mitral stenosis, as determined by cardiac catheterization in 2 patients and by echocardiography in 4. The common hemodynamic factor responsible for the abnormal sound seemed to be excessive blood flow across the mitral valve into a normal left ventricle. This study confirms previous impressions that opening snaps may be found in a variety of apparently unrelated cardiac conditions, and it demonstrates yet another use for echocardiography.