Age-related differences and associated outcomes of S-ICD: insights from a large, european, multicenter, real-world registry
Authors: Schiavone M , Gasperetti A , Gulletta S , Steffel J , Kaiser L , Mitacchione G , Lavalle C , Badenco N , Dello Russo A , Olivotto I , Tondo C , Kuschyk J , Biffi M , Tilz R , Forleo GB 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Young patients often represent the most suitable candidates for an entirely subcutaenous implantable cardioverter defibrillator (S-ICD) system, since they have to face a lifetime of device therapy and they rarely have a pre-existing or concurrent pacing or cardiac resynchronization therapy (CRT) indication. Moreover, S-ICD offers lower rate and a safer management of lead and major procedure-related complications. To date, a few limited case series and experiences with S-ICD in teenagers and young adults have shown that the S-ICD system is safe and feasible in this population, with a rate of inappropriate shocks (IS) comparable to transvenous (TV) ICD, but focused analysis on a large scale are currently lacking in this setting.

Purpose
The aim of the current study was to compare the age-related differences observed in patient selection, baseline characteristics, and device long-term associated outcomes in a large real world cohort of S-ICD recipients. The primary outcome of the study was defined as the comparisons of the IS rate observed during the entirety of follow up in the teenagers/young adult vs the adult populations. Rate of complications, freedom from sustained ventricular arrhythmic events, overall and cardiovascular mortality were also assessed in the two cohorts and assessed as secondary outcomes.

Methods
All S-ICD recipients in the ELISIR project were enrolled in the current study. Patients were classified into teenagers + young adults (≤ 30 years old) vs adults (&gt; 30 years old), depending from patient age at device implantation (Figure 1). Rates of device-related complications and IS were compared between the cohorts.

Results
A total of 1349 patients were extracted from the ELISIR project. Teenagers and young adults represented 12.4% of the registry (n=56 teenagers; n=112 young adults). Patients were followed-up for a median of 23.1 [12.6–37.9] months. Overall, 117 (8.7%) patients experienced inappropriate S-ICD shocks and 100 (7.4%) device related complications were observed, with no age-related differences. IS resulted more frequent in the teenager and young adult cohort (14.3% vs 7.9%; p=0.006). Figure 2 reports Kaplan Meier curves for the occurrence of IS. At univariate analysis, young age was associated with IS, but after correcting for differences in arrhythmic substrate, this association resulted non-significant (aHR: 1.428 [0.883–2.331]; p=0.146). The use of SMART pass algorithm was instead associated to a strong reduction in IS (aHR 0.367 [0.245–0.548]; p&lt;0.001).

Conclusion
The use of S-ICD in teenagers/young adults resulted safe and effective. Indeed, the rate of complications between teenagers/young adults and adults was not significantly different. Although a higher rate of IS was observed in the teenagers/young adults, when accounting for differences in baseline substrate and comorbidities, young age did not result associated with an increased risk of IS.