Accessory mitral valve causing left ventricular outflow tract obstruction.

We studied the clinical characteristics and operative treatment of left ventricular outflow tract obstruction (LVOTO) caused by a congenital accessory mitral valve (AMV). Two patients were admitted to our department. Preoperatively, case 1 was diagnosed as congenital heart disease with severe LVOTO and an anterior mitral valve cleft. The patient in case 2 had a congenital atrial septal defect combined with AMV and mild LVOTO, as well as mild mitral valve regurgitation. In case 1, LVOTO was caused by a type I (fixed) AMV. In case 2, the AMV was type II (mobile type). Both AMV were resected, and the concomitant cardiac disorders were treated simultaneously. The operations were successful, and the LVOTO almost disappeared. Patients with LVOTO caused by AMV should undergo operation for removal of the accessory valve. These patients should be followed up and observed periodically by Doppler echocardiography to identify any aggravation of the LVOTO.