Performance and Safety of the Extravascular Implantable Cardioverter-Defibrillator in Patients With Hypertrophic Cardiomyopathy

Background: The automatic implantable cardioverter-defibrillator (ICD) is effective in preventing arrhythmic sudden cardiac death in patients with hypertrophic cardiomyopathy (HCM). The extravascular (EV) ICD provides antitachycardia pacing and defibrillation capabilities while avoiding transvenous lead complications. Objectives: This study sought to evaluate the safety and performance of the novel EV-ICD in patients with HCM. Methods: This analysis was derived from the Pivotal EV-ICD Study, an international, multicenter, interventional trial evaluating the EV-ICD in patients with guideline-based indications for ICD therapy. Patients were classified according to the presence of a diagnosis of HCM at baseline. The main efficacy endpoint was successful defibrillation testing at implantation. The main safety endpoint was freedom from system- or procedure-related major complications through 3 years of follow-up. Results: A total of 316 patients (mean age 53.8 ± 13.1 years, 25% female, 41 [13%] with HCM) underwent attempted EV-ICD placement. The implantation success rate was 92.7% in HCM patients and 94.9% in non-HCM patients (P = 0.47). Defibrillation testing was successful in 100% and 98.5% of HCM and non-HCM patients, respectively (P = 1.00). During a mean follow-up of 30.6 ± 8.5 months, 1 (2.6%) HCM patient received appropriate ICD therapy (shock for ventricular fibrillation), compared with 23 (8.8%) non-HCM patients (log-rank P = 0.20). Inappropriate ICD therapies occurred in 7 (18.4%) HCM and 41 (15.7%) non-HCM patients (log-rank P = 0.80). System- and procedure-related major complications occurred in 12.2% of HCM and 8.7% of non-HCM patients (log-rank P = 0.44). Conclusions: In patients with HCM, the EV-ICD demonstrated high defibrillation success and a safety profile similar to what was observed in non-HCM patients.