• Jeff S Healey, Andrew D Krahn, Jamil Bashir, Guy Amit, François Philippon, William F McIntyre, Bernice Tsang, Jacqueline Joza, Derek V Exner, David H Birnie, Mouhannad Sadek, Darryl P Leong, Markus Sikkel, Victoria Korley, John L Sapp, Jean-Francois Roux, Shun Fu Lee, Gloria Wong, Angie Djuric, Danna Spears, Sandra Carroll, Eugene Crystal, Tom Hruczkowski, Stuart J Connolly, Blandine Mondesert, and ATLAS Investigators.
• Population Health Research Institute, Hamilton, Ontario, Canada (J.S.H., W.F.M., D.P.L., S.F.L., G.W., A.D., S.J.C.).
• Ann. Intern. Med. 2022 Dec 1; 175 (12): 165816651658-1665.

BackgroundImplantable cardioverter defibrillators (ICDs) improve survival in patients at risk for cardiac arrest, but are associated with intravascular lead-related complications. The subcutaneous ICD (S-ICD), with no intravascular components, was developed to minimize lead-related complications.ObjectiveTo assess key ICD performance measures related to delivery of ICD therapy, including inappropriate ICD shocks (delivered in absence of life-threatening arrhythmia) and failed ICD shocks (which did not terminate ventricular arrhythmia).DesignRandomized, multicenter trial. (ClinicalTrials.gov: NCT02881255).SettingThe ATLAS trial.Patients544 eligible patients (141 female) with a primary or secondary prevention indication for an ICD who were younger than age 60 years, had a cardiogenetic phenotype, or had prespecified risk factors for lead complications were electrocardiographically screened and 503 randomly assigned to S-ICD (251 patients) or transvenous ICD (TV-ICD) (252 patients). Mean follow-up was 2.5 years (SD, 1.1). Mean age was 49.0 years (SD, 11.5).MeasurementsThe primary outcome was perioperative major lead-related complications.ResultsThere was a statistically significant reduction in perioperative, lead-related complications, which occurred in 1 patient (0.4%) with an S-ICD and in 12 patients (4.8%) with TV-ICD (-4.4%; 95% CI, -6.9 to -1.9; P = 0.001). There was a trend for more inappropriate shocks with the S-ICD (hazard ratio [HR], 2.37; 95% CI, 0.98 to 5.77), but no increase in failed appropriate ICD shocks (HR, 0.61 (0.15 to 2.57). Patients in the S-ICD group had more ICD site pain, measured on a 10-point numeric rating scale, on the day of implant (4.2 ± 2.8 vs. 2.9 ± 2.2; P < 0.001) and 1 month later (1.3 ± 1.8 vs. 0.9 ± 1.5; P = 0.035).LimitationAt present, the ATLAS trial is underpowered to detect differences in clinical shock outcomes; however, extended follow-up is ongoing.ConclusionThe S-ICD reduces perioperative, lead-related complications without significantly compromising the effectiveness of ICD shocks, but with more early postoperative pain and a trend for more inappropriate shocks.Primary Funding SourceBoston Scientific.

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