Latent Left Ventricular Outflow Tract Obstruction Due to Accessory Mitral Valve in a 12-Year-Old Boy.

Accessory mitral valve (AMV) is a rare congenital anomaly which can cause left ventricular outflow tract (LVOT) obstruction. Patients with isolated AMV usually present with exertional dyspnea, chest pain, or syncope during the first ten years of life. In patients with AMV, detection of latent LVOT obstruction can be clinically challenging. We here present a case of AMV causing latent LVOT obstruction in an adolescent, which was diagnosed by echocardiography with dobutamine provocation and finally treated by successful surgical resection.