Transapical beating-heart septal myectomy for obstructive hypertrophic cardiomyopathy with anomalous papillary muscle insertion

OBJECTIVES Anomalous papillary muscles directly inserted into the anterior mitral valve constitute an infrequent anomaly in obstructive hypertrophic cardiomyopathy. This study sought to evaluate the efficacy and safety of a novel approach with transapical beating-heart septal myectomy to relieve obstruction while avoiding abnormal papillary muscle manipulation. METHODS Among 439 patients with obstructive hypertrophic cardiomyopathy from March 2023 to February 2024, 27 patients (6.2%) were diagnosed with anomalous papillary muscle directly inserted into the anterior mitral leaflet. Isolated myectomy without papillary muscle intervention was performed in these patients with a transapical beating-heart septal myectomy approach. RESULTS The median age of patients was 54 (47–60) years. The abnormal papillary muscle insertion into the body (Type I/II) and only the free edge (Type III) of anterior mitral valve leaflet were 21 and 6 patients, respectively. There was no operative death, septal perforation, conversion to sternotomy, blood transfusion and no patients with preoperative normal conduction required a pacemaker. The resting left ventricular outflow tract gradient decreased from 110 (70–121) mmHg at baseline to 10 (8–21) mmHg at 12 months. Reduction to a mitral regurgitation grade ≤ 1+ was achieved in 25 (92.6%) patients at 12 months. At follow-up 25 (92.6%) patients returned to NYHA class I. CONCLUSIONS In selected patients with sufficient septal thickness and no intrinsic mitral valve pathology, transapical beating-heart septal myectomy may provide obstruction and mitral regurgitation relief without direct papillary muscle intervention. This new approach without sternotomy or cardiopulmonary bypass increases the options for this infrequent condition. Clinical registration number NCT05332691