International Experience With Implantable Cardioverter Defibrillators for the Prevention of Sudden Death in High-Risk Patients With Hypertrophic Cardiomyopathy

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BACKGROUND: Implanted cardioverter-defibrillators (ICDs) have been used in patients with hypertrophic cardiomyopathy (HCM) to prevent sudden death, and have proven lifesaving for many patients. However, experience with ICD therapy has largely been derived from relatively small HCM cohorts confined to specific countries or regions of the world. Therefore, we sought to determine the effectiveness of ICDs in preventing sudden death due to life-threatening ventricular arrhythmias in a large international multicenter HCM population. METHODS: Databases from 25 HCM centers (8 in the United States, 9 in Europe, 4 in Asia, and 1 each in Australia, Africa, Mexico, and South America) were retrospectively interrogated to identify consecutive patients with HCM with ICDs (1992 to 2024) followed for 7±6 years (up to 32 years) for clinical outcomes. RESULTS: A total of 3387 patients were identified (63% men). They had a mean left ventricular thickness of 22±7 mm. The participants had received ICDs at a mean age of 47±17 years. Over follow-up, 550 patients (16%) experienced ≥1 appropriate ICD therapy (2.6%/y), including 86 of the 247 implanted for secondary prevention (35% [6.4%/y]) and 464 of the 3140 implanted for primary prevention (15% [2.2%/y]). Appropriate therapy occurred in the 464 primary prevention patients at a mean age of 49±17 years, with a median time to first appropriate therapy of 4 years after ICD implantation; 16% of these received their first appropriate therapy ≥10 years after implantation, and 47% experienced multiple interventions. Independent predictors of appropriate ICD therapy included unexplained syncope, left ventricular apical aneurysms, left ventricular systolic dysfunction, and nonsustained ventricular tachycardia on ambulatory monitoring. Of the 3140 primary prevention patients, 2946 survived (94%) and 194 died (6%) (0.8%/y), including 68 due to HCM (0.3%/y), predominantly of end-stage heart failure (n=43) or stroke (n=9). In contrast, 11 patients (0.4%) died suddenly, with device failures occurring in 2.4% of those with life-threatening ventricular tachyarrhythmias. Survival free from HCM-related mortality at 10 and 20 years was 97% and 91%, respectively. CONCLUSIONS: In this international multicenter study, the largest to date, including >3300 consecutive patients with HCM and ICDs, device therapy terminated potentially lethal ventricular tachyarrhythmias in 1 of 6 patients, with low HCM-related mortality rates for patients with ICDs. These novel data demonstrate the effectiveness of the ICD initiative, which has probably favorably altered the natural history of many patients with HCM worldwide.

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