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 cm(3). 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