Long-Term Outcome in High-Risk Patients With Hypertrophic Cardiomyopathy After Primary Prevention Defibrillator Implants

Background: The implantable cardioverter-defibrillator (ICD) is effective for preventing sudden death in patients with hypertrophic cardiomyopathy. However, data on performance and complications of implanted ICDs over particularly long time periods to inform clinical practice is presently incomplete. Methods: The study cohort comprises 217 consecutive hypertrophic cardiomyopathy patients with primary prevention ICDs implanted before 2008 and followed for ≥10 years (mean 12±4; range to 31). Results: Patients were 38±17 years at implant and 45 (21%) experienced appropriate interventions terminating ventricular tachycardia/ventricular fibrillation. The majority of ICD discharges occurred ≥5 years after implant (29 patients; 64%), including ≥10 years in 16 patients (36%). Initial device therapy increased in frequency from 2.3% of patients at <1 year to 8.5% of patients at ≥10-years after implant (P=0.005). Inappropriate ICD shocks in 39 patients occurred most commonly <5 years after implant (54%) and decreased in frequency with increasing time from implant (from 9.7% of patients at <5 years to 3.8% at ≥10 years, P=0.02). Other major device complications including infection and lead fractures and dislodgement occurred in 27 patients (12%) but did not increase in frequency over follow-up after implant (P=0.47). There were no arrhythmic sudden death events among the 217 patients with ICD. Conclusions: In hypertrophic cardiomyopathy, after a primary prevention implant, ICD therapy often followed prolonged periods of device dormancy and increased progressively in frequency over time, including one-third of patients with initial therapy after 5 to 9 years, and an additional one-third of patients at ≥10 years. Frequency of inappropriate shocks decreased over follow-up, likely reflecting standard changes in device programming, while occurrence of device complications, such as lead fractures/infection, did not increase during follow-up.