Transapical Beating-Heart Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy With Anomalous Papillary Muscle Insertion.

Objectives: Anomalous papillary muscles (PMs) directly inserted into the anterior mitral valve (MV) constitute an infrequent anomaly in obstructive hypertrophic cardiomyopathy (HCM). 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 PM manipulation.

Methods: Among 439 patients with obstructive HCM from March 2023 to February 2024, 27 patients (6.2%) were diagnosed with anomalous PM directly inserted into the anterior mitral leaflet. Isolated myectomy without PMs 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 PMs insertion into the body (type I/II) and only the free edge (type III) of anterior MV 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) mm Hg at baseline to 10 (8-21) mm Hg at 12 months. Reduction to a mitral regurgitation (MR) grade ≤ 1+ was achieved in 25 (92.6%) patients at 12 months. At follow-up, 25 (92.6%) patients returned to New York Heart Association (NYHA) class I.

Conclusions: In selected patients with sufficient septal thickness and no intrinsic MV pathology, transapical beating-heart septal myectomy may provide obstruction and MR relief without direct PMs intervention. This new approach without sternotomy or cardiopulmonary bypass increases the options for this infrequent condition.

Clinical registration number: NCT05332691.