Accessory mitral valve without left ventricular outflow tract obstruction in an adult.

Accessory mitral valve is a rare congenital abnormality and an unusual cause of subvalvular obstruction of the left ventricular outflow tract. Accessory mitral valves are usually detected in children due to symptomatic obstruction; isolated nonobstructive accessory mitral valve is rarely seen in adults. We describe the echocardiographic diagnosis of accessory mitral valve as an isolated congenital anomaly not associated with a substantial degree of obstruction of the left ventricular outflow tract in an asymptomatic adult patient. This case highlights the importance of transthoracic and transesophageal echocardiography in the diagnosis and follow-up of this uncommon congenital anomaly.