Accessory mitral valve: a rare cause of asymptomatic severe left ventricular outflow tract obstruction.

Accessory mitral valve (AMV) is an extremely uncommon congenital cardiac anomaly and it is a rare cause of left ventricular outflow tract (LVOT) obstruction. Identification of asymptomatic patients with LVOT obstruction is uncommon since the symptoms usually become manifest when the gradient across the LVOT rises. We describe a rare case of asymptomatic AMV with severe LVOT obstruction in a 10-year old child with no other congenital or acquired cardiac defects who successful underwent surgery. This case emphasizes the importance of early surgical indication also in absence of symptoms when significant LVOT obstruction occurs.