Age-related differences and associated mid-term outcomes of subcutaneous implantable cardioverter defibrillators: a propensity-matched analysis from a multicenter European registry

Background: A few limited case series have shown that the S-ICD system is safe in teenagers and young adults, but a large-scale analysis is currently lacking. Objectives: To compare mid-term device-associated outcomes in a large real-world cohort of S-ICD patients, stratified by age at implantation. Methods: Two propensity-matched cohorts of teenagers + young adults (≤ 30-year-old) and adults (> 30-year-old) were retrieved from the ELISIR registry. The primary outcome was the comparison of the inappropriate shock rate; complications, freedom from sustained ventricular arrhythmias, overall and cardiovascular mortality were deemed secondary outcomes. Results: Teenagers + young adults represented 11.0% of the entire cohort. Two propensity-matched groups of 161 patients each were used for the analysis; median follow-up was 23.1 [13.2-40.5] months. 15.2% patients experienced inappropriate shocks and 9.3% device related complications were observed, with no age-related differences in inappropriate shocks (16.1% vs 14.3%; p=0.642) and complication rates (9.9% vs 8.7%; p=0.701). At univariate analysis, young age was not associated with increased rates of inappropriate shocks (HR 1.204 [0.675-2.148]: p=0.529). At multivariate analysis, the use of SMART pass algorithm was associated to a strong reduction in inappropriate shocks (aHR 0.292 [0.161-0.525]; p<0.001), while ARVC was associated with higher rates of inappropriate shocks (aHR 2.380 [1.205-4.697]; p=0.012). Conclusion: In a large multicentered registry of propensity-matched patients, the use of S-ICD in teenagers/young adults resulted safe and effective. The rates of inappropriate shocks and complications between cohorts were not significantly different. The only predictor of increased inappropriate shocks was a diagnosis of ARVC