Ventricular septal defect of the atrioventricular canal type--report of a surgically treated case.

A 19-month-old male infant with Down syndrome was referred for investigation of heart murmur. An electrocardiogram showed normal axis (+100 degrees) of the QRS complex, incomplete right bundle branch block, and biventricular hypertrophy. Echocardiography revealed a ventricular septal defect (VSD) and a cleft of the anterior mitral leaflet with mild value regurgitation. The anterior mitral leaflet and the septal tricuspid leaflet attached to the same level of the ventricular septum were also delineated, however, no atrial septal defects were detected. Cardiac catheterization demonstrated pulmonary hypertension and a left to right shunt at the right ventricle. During operation, no defects in the atrial septum and no cleft of the septal tricuspid leaflet were found. Cleft of the anterior mitral leaflet, continuity between the mitral anterior leaflet and the tricuspid septal leaflet, and a VSD of the atrioventricular canal type were confirmed. The cleft of the anterior mitral leaflet and the VSD were repaired with the aid of cardiopulmonary bypass. The patient recovered uneventfully.