Subcutaneous ICD therapy after sternotomy: feasibility and long-term outcomes in a propensity-matched analysis from a national registry

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established alternative to transvenous ICD for the prevention of sudden cardiac death. In patients with a history of sternotomy, however, the presence of sternal wires may challenge optimal lead positioning and could theoretically interfere with sensing or defibrillation performance. Evidence supporting S-ICD use in this setting is currently limited. Objectives To evaluate the feasibility of S-ICD implantation and device outcomes in patients with prior sternotomy. Methods Within the framework of the prospective "Rhythm Detect" registry, we analyzed consecutive patients who had undergone S-ICD implantation across 33 Italian centers between 2014 to 2024. Patients with a history of median sternotomy were propensity-matched to patients without sternotomy, and outcomes were compared between groups. Results Among 2,123 S-ICD implants, 259 patients (12%) had prior sternotomy, after 1:1 propensity matching, 518 patients were included (259 with vs 259 without sternotomy). Defibrillation testing was performed in 325 patients (63%), with successful conversion ≤65 J in 314 patients (97%; Sternotomy Group 98% vs Non-sternotomy Group 95%, p=0.228). A PRAETORIAN score <90 was observed in 99% of the Sternotomy Group vs 96% of the Non- sternotomy Group (p=0.214). Over a median follow-up of 43 months (IQR 22–71), the annualized rates of device-related complications (1.4%/year vs 1.1%/year, HR 1.21, p=0.650) and inappropriate shocks (2.2%/year vs 1.8%/year, HR 1.08, p=0.811) were similar between groups (Kaplan–Meier survival curves are shown in the Figure). No oversensing related to sternal wires was observed. The annualized rate of appropriate shocks was 2.2% /year in both groups, with first-therapy success in 95% and 100% final conversion in both groups. Conclusions In patients with previous cardiac surgery, the S-ICD provided safe and effective protection from ventricular arrhythmias. These findings support the S-ICD as a valid treatment option in this population.