Accessory mitral papillary muscle causing severe aortic insufficiency

Accessory mitral papillary muscle originating from the interventricular septum is a rare congenital anomaly. A 20-year-old male patient presented with a complaint of exertional dyspnea. On cardiac examination, a grade 3/4 diastolic murmur was heard over the right upper parasternal area, and the apical pulsations were easily palpable over the precordium. Transthoracic echocardiography showed severe aortic regurgitation, dilatation of the left ventricle, and an accessory papillary muscle with its chordae, extending from the interventricular septum to the anterior mitral leaflet in the left ventricular outflow tract (LVOT). There was no mitral regurgitation. Color Doppler imaging showed turbulence set up by the abnormal mitral attachment and an associated mild pressure gradient of 20 mmHg across the LVOT. At surgery for aortic valve replacement, degenerative changes in the aortic leaflets were noted. The accessory papillary muscle was spared to maintain mitral valve functions and an aortic bileaflet mechanical prosthetic valve was implanted. During eight months of follow-up, he was well without any signs of left ventricular systolic dysfunction and mitral regurgitation, with a functioning prosthetic valve.