Clinical Evaluation of Defibrillation Testing in an Unselected Population of 2,120 Consecutive Patients Undergoing First Implantable Cardioverter-Defibrillator Implant

Study Questions:

Does defibrillation testing (DT) at the time of implantation improve outcomes in patients with an implantable cardioverter-defibrillator (ICD)?


In this prospective, multicenter, observational study, 2,120 patients (mean age 67 years) underwent ICD implantation with (n = 836) or without (n = 1,284) DT, based on operator preference. Follow-up was performed every 6 months for 2 years. The primary endpoint was a composite of complications at the time of ICD implantation and sudden death or ineffective appropriate ICD shocks.


A defibrillation safety margin ≥10 J was present in 93% of 695 patients in the DT group, for which complete DT data were available. There was not a significant difference in the annual incidence of the primary endpoint between the DT group (1.15%) and the non-DT group (0.68%). No primary endpoint events occurred in patients with a safety margin <10 J. Appropriate shocks that were ineffective occurred in 13 patients (0.6%) overall, with no significant difference between the two groups.


The investigators concluded that DT at the time of ICD implantation does not affect outcomes.


The main purpose of DT is to minimize the risk of ineffective ICD shocks. Yet in this study, ineffective appropriate shocks were not any less likely to occur among patients who underwent DT than among those who did not. These results suggest that DT is not necessary at the time of ICD implantation. However, the study was not randomized and a definitive assessment of DT awaits completion of a large, randomized, multicenter trial that is currently in progress (SIMPLE).

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Prostheses and Implants, Defibrillators, Follow-Up Studies, Death, Shock, Ventricular Fibrillation, Electric Countershock, Disease Management, Tachycardia

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