Subcutaneous implantable cardioverter defibrillator in pediatric and young adults: an analysis from the European SIDECAR Registry

Subcutaneous implantable cardioverter defibrillators (S-ICDs) are preferred for younger patients who face extended lifetime risks from complications associated with traditional transvenous ICD systems. However, data on the safety and efficacy of S-ICDs in paediatric and young adult- with congenital heart disease (ACHD)- populations remain limited. This study aims to describe current European practices regarding S-ICD therapy in these population, tracking its evolution over time and associated outcomes

Pediatric and ACHD patients receiving S-ICDs for primary or secondary prevention of sudden cardiac death at 12 European centers were enrolled in the multicenter, observational, retrospective, non-randomized, standard-of-care SIDECAR registry from 2010 to 2024. We analyzed baseline and procedural data, as well as acute efficacy and safety outcomes

A total of 212 patients (54% with cardiomyopathies, 17% with congenital heart diseases, 14% with inherited arrhythmias, and 15% with idiopathic ventricular fibrillation), with a median age of 15 years [IQR: 13–17], BMI 21.7 ± 3.9 kg/m², underwent S-ICD implantation (57% for primary prevention). The generator was placed in an intermuscular pocket in 137 (65%) patients, and the two-incision technique was used in 186 (88%) procedures. The median procedure duration was 60 minutes [IQR: 45–91].

With increasing experience at the centers, the use of the intermuscular technique expanded from 59% in early implantations (first tertile of procedures in each center) to 73% in later ones (last tertile). Similarly, the adoption of the two-incision technique increased from 74% to 99% (P < 0.001), and procedural times significantly decreased from 66 minutes [IQR: 50–100] to 55 minutes [IQR: 43–90] (P = 0.04). Defibrillation testing was performed in 171 (81%) patients, achieving a 98% success rate at ≤65J and 100% at ≤80J, with the success rate remaining consistently high. Defibrillation testing omission remained stable at 19% across implantation cohorts (tertiles of procedures). No intraoperative complications were reported. At implantation, the median programmed conditional zone cut-off was 220 bpm [IQR: 200–220], and the shock zone cut-off was 250 bpm [IQR: 240–250]. While the conditional zone cut-off rate did not change, the shock zone cut-off increased from 240 bpm [IQR: 235–250] to 250 bpm [IQR: 240–250].

This multicenter European experience confirms that S-ICD is an effective and safe therapeutic option for paediatric and adult patients. European clinical practice in these populations has evolved, incorporating more efficient implantation techniques, which have shortened procedure times while maintaining high efficacy and safety. Long-term outcome analyses from SIDECAR registry data are ongoing.