Accessory mitral valve tissue: an increasingly recognized cause of left ventricular outflow tract obstruction.

Subvalvar left ventricular outflow tract obstruction (LVOTO) may be secondary to congenital abnormalities of the mitral valve, including abnormal attachments of the anterior leaflet of the mitral valve, parachute mitral valve, and accessory valve tissue. Successful correction of LVOTO due to accessory mitral valve tissue is reported in a 44-year-old man. Twenty-five patients with LVOTO due to accessory mitral valve tissue have been previously reported; however, only a few have been recognized preoperatively. A high index of suspicion is necessary for preoperative and intra-operative recognition and correction of the abnormality.