Accessory mitral valve tissue: an unusual cause of congenital mitral stenosis

Accessory mitral valve tissue (AMVT) is a rare congenital anomaly of endocardial cushion. Usually, it arises from the anterior mitral leaflet and causes the left ventricular outflow tract obstruction. We report here the first and a rarest presentation of the AMVT in a 19-year old female patient diagnosed to have double outlet right ventricle, ventricular septal defect (VSD), infundibular stenosis and congenital mitral stenosis (MS). She presented with a history of shortness of breath and chest pain over 3 years. Diagnosis was made by chest X-ray, transthoracic and transoesophageal echocardiography, which was confirmed by cardiac catheterization, and angiography. A successful closure of the VSD with excision of the right ventricular bundle and excision of the AMVT was done. Post-operative course was uneventful and an echocardiogram before the discharge showed no residual shunt, no right ventricular outflow gradient or mitral regurgitation, and the gradient across the mitral valve was 5/3 mmHg. We emphasize that, although AMVT commonly produces left ventricular outflow tract obstruction, it should be considered a rare but an important cause of congenital MS.