Surgery for Anomalous Papillary Muscle Directly Into the Anterior Mitral Leaflet

Background: The anomalous insertion of papillary muscle directly into the anterior mitral leaflet is a rare congenital anomaly concomitant with hypertrophic cardiomyopathy. We herein report our surgical technique, which is designed to relieve left ventricular obstruction and preserve the mitral valve and subvalvular apparatus. Methods: Among 38 patients who underwent septal myectomy from 2007 to 2020, 4 had an anomalous mitral subvalvular apparatus with papillary muscle with direct insertion into the anterior mitral leaflets. In all cases, mitral valve repair was accomplished with excision and reconstruction of all anomalous papillary muscles, concomitant with septal myectomy. In another 34 patients, 20 cases needed mitral valve repair with regard to systolic anterior motion by hypertrophic cardiomyopathy. The comparison study was conducted between the anomalous papillary muscle group (group A) and the others (group B). Results: There was no early or late death in group A, and there were 3 early deaths and 2 late deaths in group B. The mean peak gradient in the left ventricle was significantly decreased in both groups. Mitral valve regurgitation grade was also significantly decreased from 3 to 0.5 without valve replacement in group A, and from 2 to 0.6 in group B. Six patients needed mitral valve replacement because of the thickness of anterior mitral leaflet in group B. Conclusions: Hypertrophic obstructive cardiomyopathy associated with the anomalous insertion of papillary muscle can be successfully treated without mitral valve replacement. Excision and reconstruction with the anomalous papillary muscle seems to be a feasible operation to reduce mitral regurgitation and relieve outflow tract obstruction.