Clinical impact of defibrillation testing in a real-world S-ICD population: data from the ELISIR registry.

Background Current guidelines recommend defibrillation testing (DT) performance in patients with a subcutaneous implantable cardioverter defibrillator (S-ICD), theoretically to reduce the amount of ineffective shocks. DT however, has been proven unnecessary in transvenous ICD and real-world data show a growing trend in avoidance of DT after S-ICD implantation. Methods All patients undergoing S-ICD implant at nine associated Italian centers joining in the ELISIR registry (ClinicalTrials.gov Identifier: NCT04373876) were enrolled and classified upon DT performance. Long term follow-up events were recorded and compared to report the long-term efficacy and safety of S-ICD implantations without DT in a real-world setting. Results A total of 420 patients (54.0±15.5 years, 80.0% male) were enrolled in the study. A DT was performed in 254 (60.5%) patients (DT+ group), while in 166 (39.5%) was avoided (DT- group). Over a median follow-up of 19 [11-31] months, a very low rate (0.7%) of ineffective shocks was observed, and no significant differences in the primary combined arrhythmic outcome were observed between the two groups (p = 0.656). At regression analysis, the only clinical predictor associated with the primary combined outcome was S-ICD placement for primary prevention (OR: 0.42; p = 0.013); DT performance instead was not associated with a reduction in primary outcome (p= 0.375). Conclusion Implanting a S-ICD without DT does not appear to impact the safety of defibrillation therapy and overall patients' survival. This article is protected by copyright. All rights reserved.