Septal radioablation therapy for patients with hypertrophic obstructive cardiomyopathy: first-in-human study.

Aims: There is still no non-invasive septal reduction therapy for patients with hypertrophic obstructive cardiomyopathy (HOCM). This study aimed to investigate the feasibility, safety, and efficacy of stereotactic body radiotherapy (SBRT) in patients with drug-refractory symptomatic HOCM.

Methods and results: The radiation target of ventricular septum was determined by multiple anatomical imaging. Stereotactic body radiotherapy was performed with standard techniques. Patients were treated with a single fraction of 25 Gy, followed up at 1, 3, 6, and 12 months by clinical visit. Five patients were enrolled and completed the 12 months follow-up. The mean radioablation time was 21.6 min, and the mean target volume was 10.5 cm³. All five patients survived and showed improvements in symptoms after SBRT. At 12 months post-SBRT, the echocardiography-derived left ventricular outflow tract gradient decreased from 88 mmHg (range, 63-105) to 52 mmHg (range, 36-66) at rest and from 101 mmHg (range, 72-121) to 74 mmHg (range, 65-100) after Valsalva. The end-diastolic thickness of the targeted septum reduced from 23.7 mm (range, 20.3-29) to 22.4 mm (range, 19.7-26.5); 6 min walking distance increased from 190.4 m (range, 50-370) to 412.0 m (range, 320-480). All patients presented with new fibrosis in the irradiated septum area. No radiation-related complications were observed during SBRT and up to 12 months post procedure.

Conclusion: The current study suggests that SBRT might be a feasible radioablation therapeutic option for patients with drug-refractory symptomatic HOCM.

Trial registration: ClinicalTrials.gov Identifier: NCT04686487.