In about 50% of Double orifice mitral valve (DOMV) cases, valvular function is normal, others present with stenosis or regurgitation. In most cases, a larger orifice is accompanied by a small eccentric accessory orifice, and some show duplicated mitral valves. Embryologically, the lesion results from abnormal leaflet fusion and persistence of the left part of the common atrio-ventricular canal.