Percutaneous Intramyocardial Septal Radiofrequency Ablation in Patients With Drug-Refractory Hypertrophic Obstructive Cardiomyopathy.

Importance: Patients with hypertrophic obstructive cardiomyopathy (HOCM) and drug-refractory symptoms and outflow gradients have limited nonsurgical treatment options. The feasibility of percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) has been reported previously; however, procedural and medium-term outcomes are unknown. Objective: To describe the safety and medium-term outcomes of PIMSRA in a large patient cohort with drug-refractory HOCM. Design, Setting, and Participants: This was a single-arm, open-label study of PIMSRA in patients with drug-refractory HOCM. Patients presenting to the Xijing Hospital in Xi'an, China, between October 2016 to June 2020 with hypertrophic cardiomyopathy. Of 1314 patients presenting with HOCM, 244 fulfilled inclusion criteria of severe resting/provoked outflow gradients of 50 mm Hg or higher, and symptoms of New York Heart Association functional class of II or higher refractory to maximum tolerated medications. After discussion among the heart team, 40 patients underwent surgical or alcohol septal reduction therapy and 4 required treatment of significant coronary artery disease. Interventions: PIMSRA performed in patients. Main Outcomes and Measures: The primary outcome was 30-day major adverse clinical events: death, emergency surgery, severe effusion requiring intervention, procedure-related stroke, bleeding, and stroke. Secondary outcomes included 30-day technical success and 90-day improvement in outflow obstruction. Results: The mean (SD) age of 200 patients was 46.9 (14.0) years, and 125 (62.5%) were men. Resting or provoked left ventricular outflow tract gradients were 50 mm Hg or higher. The median (IQR) follow-up for all patients was 19 (6-50) months. Thirty-day major adverse clinical events rate was 10.5% (n = 21): there were 2 in-hospital/30-day deaths (1.0%), 7 patients (3.5%) with pericardial effusion requiring mini-thoracotomy, 12 patients (6%) with pericardial effusion requiring pericardiocentesis, and no bleeding or strokes. Other periprocedural complications included permanent right bundle branch block in 5 patients (2.5%), resuscitated ventricular fibrillation in 2 (1.0%), and septal branch aneurysm in 2 (1.0%). There were no permanent pacemaker implantations. At follow-up, maximum septal thickness was reduced from a mean (SD) of 24.0 (5.1) mm to 17.3 (4.4) mm (P < .001), and left ventricular outflow tract gradient was decreased from a mean (SD) of 79.0 (53.0) mm Hg to 14.0 (24.0) mm Hg (P < .001). Overall, 190 patients (96%) with HOCM were in New York Heart Association functional class I or II at last follow-up. Conclusions and Relevance: This study found that PIMSRA in patients with drug-refractory HOCM may be an effective procedure for relief of left ventricular outflow tract obstruction and symptoms with acceptable complication rates. These results are encouraging and support the design of a randomized clinical trial against well-established septal reduction therapies.