Time trends in ICD recommendations and predictors of device activation hypertrophic cardiomyopathy: a real-world cohort study.

Background: Sudden cardiac death (SCD) remains a major concern in hypertrophic cardiomyopathy (HCM). Over recent years, European Society of Cardiology (ESC) guidelines have broadened recommendations for implantable cardioverter defibrillator (ICD) implantation in primary prevention. We aimed to evaluate clinical outcomes and event detection in an HCM primary prevention cohort, while assessing how these evolving criteria translate into real-world ICD eligibility and event detection. Methods: We conducted a single-centre retrospective study including 52 consecutive HCM patients who received an ICD for primary prevention between 2014 and 2024. Baseline clinical, imaging, and follow-up data were collected. The primary endpoint was appropriate ICD therapy for ventricular tachycardia or fibrillation. Patients were classified according to the 2014, 2022, and 2023 ESC guidelines. Time-to-event analyses using univariate Cox regression were performed to identify predictors of ICD activation. Results: Over a median follow-up of 2.2 years, 6 patients (12%) experienced appropriate ICD therapy. According to ESC classifications, the 2022/2023 guidelines would have increased ICD eligibility by about 50% compared with the 2014 guideline, mainly due to the inclusion of extensive late gadolinium enhancement on CMR and reduced LVEF (<50%) as risk enhancers. However, no guideline set identified all patients who developed ventricular arrhythmias, and a subset of patients with events would not have been eligible for ICD implantation under any ESC recommendation. Lower LVEF was associated with higher risk of ICD activation. Conclusions: Successive ESC guidelines have lowered the threshold for ICD implantation in HCM, increasing eligibility but also implantations in event-free patients. Persistent event occurrence in ineligible individuals highlights the need for refined prediction models and individualized clinical judgment, including complementary tools such as ILR monitoring.