Accessory mitral valve tissue causing left ventricular outflow tract obstruction: case reports and literature review

Accessory mitral valve (AMV) tissue is a rare congenital malformation causing left ventricular outflow tract obstruction (LVOTO). We present three patients with AMV tissue undergoing surgery. A 60-year old man presented with an AMV leaflet, mild LVOTO and coronary artery disease and underwent accessory leaflet excision and coronary revascularization. A 24-year old man presented with an AMV leaflet, LVOTO and interatrial septal defect and underwent defect closure and accessory leaflet resection. An 8-month-old girl underwent interventricular septal closure and AMV leaflet resection but died on postoperative day 5 from progressive heart failure. Another 87 cases with AMV tissue were identified in the literature The anomaly was classified as: Type I (fixed: A = nodular, B = Membranous), and type II (mobile: A = pedunculated, B = leaflet like). Type IIB was further subdivided as rudimentary chordae and developed chordae. Patients with AMV tissue causing LVOTO may undergo mass removal with acceptable postoperative outcome. Prophylactic removal of AMV tissue should not be attempted in patients with no or mild LVOTO and no other associated heart defects. These patients should be followed and observed periodically by Doppler echocardiography to identify any progression in LVOTO.