ICD benefit in hypertrophic cardiomyopathy: a real-world analysis

Introduction

Sudden cardiac death (SCD) remains a major challenge in the management of hypertrophic cardiomyopathy (HCM). While the ESC HCM-Risk-SCD score aids implantable cardiac-defibrillator (ICD) decision-making, considerable uncertainty persists in patients at intermediate risk, raising concerns about over-implantation and device-related complications. Improved risk stratification to identify patients most likely to benefit from ICD therapy remains an unmet clinical need.

Aim

To identify clinical predictors of appropriate ICD therapies in patients with HCM undergoing ICD implantation for primary-prevention.

Methods

We performed a single-centre observational study of patients with HCM who received a primary-prevention ICD between 2018 and 2024. Appropriate ICD therapy was defined as ATP or shock for sustained ventricular arrhythmias. Patients were compared according to the occurrence of appropriate therapies. Event-free survival was analysed using Kaplan–Meier methods, with time to first appropriate ICD intervention as the primary endpoint.

Results

From a cohort of 156 HCM patients, 34 underwent primary-prevention ICD implantation and were included in the analysis (mean age 54±4 years, 50% male). Among these patients, 7 patients (21%) had MYBPC3 mutations and 4 patients (12%) had MYH7 mutations. In 15 patients (44%) genetic test was negative. 12% of patients carried more than one sarcomeric mutation. A family history of SCD was present in 30%. At baseline, 9 patients (27%) were classified as high risk and 13 (38%) as intermediate risk according to the ESC HCM-Risk-SCD score.

Over a mean follow-up of 4±0.6 years, 9 patients (26%) received at least one appropriate ICD therapy. In univariable analysis, these patients had higher HCM-Risk-SCD scores at implantation (6%±1 vs 4%±0.3; p=0.043) and larger left atrial diameter (62 [55–67] vs 42 [38–48] mm; p=0.050). No significant differences were found for age, sarcomeric mutation status, maximal LV wall thickness or LVOT gradient.

In multivariable logistic regression, prior syncope was the only independent predictor of appropriate ICD therapy (OR 17.2, 95% CI 1.63–181.1; p=0.018). Appropriate ICD therapy was also independently associated with cardiovascular hospitalization (OR 7.24, 95% CI 1.25–41.8; p=0.027). Kaplan–Meier analysis showed a median time to first therapy of 5 years (95% CI 4.1–5.9), with an estimated mean event-free survival of 7.7 years (95% CI 5.1–10.3) (Figure 1). Finally, only 1 patient in this cohort had an inappropriate ICD therapy due to atrial fibrillation.

Conclusion

In this cohort, prior syncope appeared to be the most informative marker for subsequent appropriate ICD therapies, while conventional risk factors showed limited discriminatory value. These findings suggest that current stratification may not fully identify those most likely to benefit, highlighting the need for further refinement in primary-prevention ICD selection.For image description, please refer to the figure legend and surrounding text.