[Left ventricular outflow tract obstruction caused by accessory mitral valve tissue].

An asymptomatic 15-year-old woman was studied because of a systolic ejection murmur. The echocardiogram showed a mobile, leaflet-like structure attached to the ventricular surface of the anterior mitral leaflet, chordae tendineae and papillary muscle. This structure moved to the left ventricular outflow tract during systole occupying the subaortic area. Conventional Doppler examination revealed left ventricular outflow obstruction caused by the accessory mitral valve tissue that produced a pressure gradient of 25 mmHg between the aorta and left ventricle. The diagnosis was not obvious clinically and was based on the echocardiographic data.