Stereotactic body radiation therapy led to improvements in left ventricular diastolic function as well as symptoms, exercise capacity, and clinical outcomes in patients with hypertrophic obstructive cardiomyopathy in a small pilot study. Study findings were presented at the American Society of Echocardiography (ASE) 2025 Scientific Sessions and published as an abstract (PC1-37) in the Journal of the American Society of Echocardiography.
Background and Study Methods
Results from a previous first-in-human study of septal radioablation therapy in patients with hypertrophic obstructive cardiomyopathy suggested that radioablation was a feasible therapeutic option for patients with drug-refractory symptomatic hypertrophic obstructive cardiomyopathy.
In this study, investigators further explored the potential for radiation therapy in this population. Researchers, including Na Liu, Bo Peng, Qiming Liu, and ShengHua Zhou, from the Second Xiangya Hospital of Central South University in Changsha, China, explored symptoms and outcomes among 10 patients with hypertrophic cardiomyopathy all treated at similar times by the Department of Cardiovascular Medicine at the Second Xiangya Hospital.
They looked specifically at five patients with hypertrophic cardiomyopathy who were treated with stereotactic body radiation therapy and five matched control patients with drug-refractory symptomatic hypertrophic cardiomyopathy who were treated by medication only, to compare the results. There were two female and 3 male patients in each cohort; patients in the radiation therapy group had a mean age of 52.4 years vs 50.6 years in the medication group.
The researchers used serial transthoracic echocardiography to assess interventricular septal thickness, left ventricular outflow tract diameter, peak pressure gradient, and diastolic function in each cohort. They assessed these parameters prior to treatment as well as at 1, 3, and 6 months after treatment in both cohorts. The researchers also examined symptoms, laboratory test results, results of 6-minute walking tests, New York Heart Association function heart classifications, and scores from the Kansas City Cardiomyopathy Questionnaire both prior to treatment and at 6 months after treatment.
Echocardiographic Outcome Findings
Stereotactic body radiation therapy was associated with significant improvements in mitral valve systolic anterior motion as well as reductions in left ventricular outflow tract pressure gradients. Compared with baseline measurements, resting left ventricular outflow tract pressure gradients reduced after treatment to –39.5% at 1 month post–radiation therapy, –38.9% at 3 months post treatment, and –34.3% at 6 months post treatment (P < .05). Reductions in Valsalva gradients were also observed by –34.3% at 1 month post–radiation treatment and by –33.5% at 3 months post treatment (P < .05).
Septal hypertrophy also regressed in the radiation group, with significant decreases in interventricular septal thickness noted by 6 months after treatment (P < .05). Global longitudinal strain improvements were considered more significant in the radiation group than the treatment group at 6 months post treatment (P < .05).
Clinical Outcomes
At 6 months post treatment, patients in the radiation cohort showed improvements in clinical parameters, specifically including increases in the 6-minute walking test and the Kansas City Cardiomyopathy Questionnaire scores, from baseline metrics (P < .05). These improvements were not seen in the medication control cohort (P > .05).
Greater Clinical Context
In this early experience, stereotactic body radiation therapy appeared to achieve reductions in left ventricular outflow tract pressure noninvasively in symptomatic patients with hypertrophic obstructive cardiomyopathy refractory to medical treatments. This makes stereotactic body radiation therapy a possible alternative treatment modality of great interest for patients with hypertrophic obstructive cardiomyopathy unsuitable for invasive intervention or following drug resistance.
However, due to the small sample size and short follow-up of this study, further and larger studies are needed to confirm the safety and efficacy of stereotactic body radiation therapy for patients with symptomatic hypertrophic obstructive cardiomyopathy.
Disclosures were not available at press time.
