Incidence of Defibrillator Shocks After Elective Generator Exchange Following Uneventful First Battery Life

Background A significant number of implantable cardioverter‐defibrillator ( ICD ) patients do not experience shocks after ICD implant. Elective generator exchange ( GE ) has been associated with increased risk of infection and ICD lead failure. There is a paucity of contemporary data reporting on shock incidence with replacement devices. Methods and Results Patients undergoing elective GE (n=24 203) who transmit data remotely via a remote monitoring system were analyzed to determine the incidence of ICD shocks after GE . A total of 16 230 patients (67%) did not experience a shock with the first ICD (group A), and 7973 (33%) received at least 1 shock (group B). Patients in group A were older (71.3 versus 68.8 years, P <0.001) and more often female (71% versus 77% male, P <0.001). Over an average follow‐up of 1.9±1.2 years after GE , the proportion of patients with shocks and risk of ICD shocks was lower for those who did not receive a shock during the first battery life (group A: 9.9% versus 27.7%, hazard ratio 0.36, 95% CI 0.34 to 0.38, P <0.001). The cumulative rate of ICD shocks at 5 years after GE was 25.7% in group A and 51.1% in group B. Conclusions In this large cohort of ICD patients implanted across the United States, two thirds did not receive ICD shock therapy prior to GE . The occurrence of ICD shocks prior to GE is an important predictor of shocks after GE ; however, even among those without shocks during first battery life, the incidence of shocks at 5 years following GE is >25%. These data should support informed decision making for patients and physicians at the time of ICD generator end of service.