This study is designed to rigorously evaluate the safety and effectiveness of Stereotactic Body Radiotherapy (SBRT) as an innovative, non-invasive treatment for Hypertrophic Obstructive Cardiomyopathy (HOCM). HOCM, a prevalent cardiac condition, is primarily characterized by asymmetric septal hypertrophy, which results in the obstruction of the left ventricular outflow tract. This obstruction significantly compromises patient quality of life and is associated with severe risks, including arrhythmias and sudden cardiac death. While current treatments like medications, surgical septal myectomy, and percutaneous transluminal septal myocardial ablation (PTSMA) have proven to be effective, they are not without limitations. SBRT, a recent development in non-invasive cardiac radioablation, has shown encouraging results in early-stage studies, suggesting its potential as a safe and feasible option for HOCM treatment.

In this study, participants will be randomly assigned to either the SBRT treatment group or a control group receiving a sham procedure. The primary objective is to measure the change in the left ventricular outflow tract pressure gradient under provoked conditions, using cardiac ultrasound at a 6-month follow-up. This will provide a clear assessment of the direct impact of SBRT on the primary physiological complication of HOCM.

The study also sets forth several secondary objectives to provide a holistic view of the treatment's impact. These include evaluating changes in NYHA functional classification and KCCQ scores to assess improvements in symptom severity and quality of life, respectively. Additionally, we will monitor physical capacity through the 6-minute walk test, and biomarkers like NT-proBNP and cTNT for cardiac stress and damage. The effect of SBRT on QRS duration will be analyzed to understand its impact on cardiac electrical activity. The incidence of major adverse cardiac events (MACEs) within 6 months post-treatment will be recorded to evaluate safety, and the need for invasive septal reduction therapy post-treatment will be assessed to gauge long-term efficacy.

This study aims to provide a comprehensive understanding of the potential of SBRT as a treatment alternative for HOCM. By comparing its outcomes with those of traditional therapies, the study seeks to establish SBRT's role in symptom alleviation, quality of life enhancement, and risk reduction in HOCM management.

Inclusion Criteria:

• Adults aged 18 years or older.
• Confirmed diagnosis of Hypertrophic Obstructive Cardiomyopathy (HOCM) with a left ventricular outflow tract resting pressure gradient of 50mmHg or greater, as evidenced by cardiac ultrasound or Cardiac MRI.
• Willingness and consent to undergo non-invasive cardiac radioablation technology for the treatment of HOCM.
• Provision of informed consent, indicating voluntary participation in the study.
• Capability to read, understand, and communicate in Chinese for study-related procedures and consent.

Exclusion Criteria:

• Participation in any interventional clinical trial within 30 days prior to enrollment in this study, excluding participation in non-interventional and diagnostic reagent studies.
• Previous receipt of any invasive treatment options for HOCM.
• Advanced heart failure characterized by NYHA functional class IV.
• A left Ventricular Ejection Fraction (LVEF) of less than 30%.
• Concurrent severe illnesses that are life-limiting with an expected lifespan of less than one year.
• Planned or requirement for any form of surgical intervention.
• Pregnancy or currently breastfeeding.
• Involvement in the execution or implementation of this study, including study staff and their immediate family members.