Despite expanding indication of the subcutaneous implantable cardioverter defibrillator (S-ICD) in clinical practice, limited data exists on safety and efficacy of S-ICD in arrhythmogenic right ventricular cardiomyopathy (ARVC) patients. The aim of this multicenter study was to evaluate the safety and efficacy of S-ICD in ARVC patients. The study population included 44 consecutive patients with definite ARVC diagnosis according to the 2010 ITF criteria (57% male, mean age 37 ± 17 years [range 10-75 years]) who received an S-ICD. Eighteen (41%) patients were implanted for secondary prevention. At implant, all inducible patients (34/44) had conversion of ventricular fibrillation at 65 J. No early complications occurred. During a median follow-up of 12 months (7-19), 3 (6.8%) patients experienced complications requiring surgical revision. No local or systemic device-related infections were observed. Six patients (14%) received a total of 61 appropriate and successful shocks on ventricular arrhythmias. Six (14%) patients experienced 8 inappropriate shocks for oversensing of cardiac signal (4 cases) and non-cardiac signal (4 cases) with one patient requiring device explantation. No patients had the device explanted due to the need for antitachycardia pacing. The study shows that S-ICD provides safe and effective therapy for termination of both induced and spontaneous malignant ventricular tachyarrhythmias with high energy shocks in ARVC patients, but the risk of inappropriate shocks and complications needing surgical revision should be considered.

A previous randomized study demonstrated that the subcutaneous implantable cardioverter defibrillator (S-ICD) was noninferior to transvenous ICD with respect to device-related complications and inappropriate shocks. However, that was performed prior to the widespread adoption of pulse generator implantation in the intermuscular (IM) space instead of the traditional subcutaneous (SC) pocket. The aim of this analysis was to compare survival from device-related complications and inappropriate shocks between patients who underwent S-ICD implantation with the generator positioned in an IM position in comparison with an SC pocket. We analysed 1577 consecutive patients who had undergone S-ICD implantation from 2013 to 2021 and were followed up until December 2021. Subcutaneous patients (n = 290) were propensity matched with patients of the IM group (n = 290), and their outcomes were compared. : During a median follow-up of 28 months, device-related complications were reported in 28 (4.8%) patients and inappropriate shocks were reported in 37 (6.4%) patients. The risk of complication was lower in the matched IM group than in the SC group [hazard ratio 0.41, 95% confidence interval (CI) 0.17–0.99, P = 0.041], as well as the composite of complications and inappropriate shocks (hazard ratio 0.50, 95% CI 0.30–0.86, P = 0.013). The risk of appropriate shocks was similar between groups (hazard ratio 0.90, 95% CI 0.50–1.61, P = 0.721). There was no significant interaction between generator positioning and variables such as gender, age, body mass index, and ejection fraction. Our data showed the superiority of the IM S-ICD generator positioning in reducing device-related complications and inappropriate shocks. Clinical Trial Registration: ClinicalTrials.gov; NCT02275637.

Patients with cardiomyopathies and channelopathies are usually younger and have a predominantly arrhythmia-related prognosis; they have nearly normal life expectancy thanks to the protection against sudden cardiac death provided by the implantable cardioverter defibrillator (ICD). The subcutaneous ICD (S-ICD) is an effective alternative to the transvenous ICD and has evolved over the years. This study aimed to evaluate the rate of inappropriate shocks (IS), appropriate therapies, and device-related complications in patients with cardiomyopathies and channelopathies who underwent modern S-ICD implantation. We enrolled consecutive patients with cardiomyopathies and channelopathies who had undergone implantation of a modern S-ICD from January 2016 to December 2020 and who were followed up until December 2022. A total of 1338 S-ICD implantations were performed within the observation period. Of these patients, 628 had cardiomyopathies or channelopathies. The rate of IS at 12 months was 4.6% [95% confidence interval (CI): 2.8–6.9] in patients with cardiomyopathies and 1.1% (95% CI: 0.1–3.8) in patients with channelopathies (P = 0.032). No significant differences were noted over a median follow-up of 43 months [hazard ratio (HR): 0.76; 95% CI: 0.45–1.31; P = 0.351]. The rate of appropriate shocks at 12 months was 2.3% (95% CI: 1.1–4.1) in patients with cardiomyopathies and 2.1% (95% CI: 0.6–5.3) in patients with channelopathies (P = 1.0). The rate of device-related complications was 0.9% (95% CI: 0.3–2.3) and 3.2% (95% CI: 1.2–6.8), respectively (P = 0.074). No significant differences were noted over the entire follow-up. The need for pacing was low, occurring in 0.8% of patients. Modern S-ICDs may be a valuable alternative to transvenous ICDs in patients with cardiomyopathies and channelopathies. Our findings suggest that modern S-ICD therapy carries a low rate of IS. URL: http://clinicaltrials.gov/Identifier: NCT02275637.

The implantable cardioverter-defibrillator (ICD) is a life-saving therapy in patients with hypertrophic cardiomyopathy (HCM) at risk of sudden cardiac death. Implantable cardioverter-defibrillator complications are of concern. The subcutaneous ICD (S-ICD) does not use transvenous leads and is expected to reduce complications. However, it does not provide bradycardia and anti-tachycardia pacing (ATP). The aim of this study was to compare appropriate and inappropriate ICD interventions, complications, disease-related adverse events and mortality between HCM patients implanted with a S- or transvenous (TV)-ICD. Consecutive HCM patients implanted with a S- (n = 216) or TV-ICD (n = 211) were enrolled. Propensity-adjusted cumulative Kaplan–Meier curves and multivariate Cox proportional hazard ratios were used to compare 5-year event-free survival and the risk of events. The S-ICD patients had lower 5-year risk of appropriate (HR: 0.32; 95%CI: 0.15–0.65; P = 0.002) and inappropriate (HR: 0.44; 95%CI: 0.20–0.95; P = 0.038) ICD interventions, driven by a high incidence of ATP therapy in the TV-ICD group. The S- and TV-ICD patients experienced similar 5-year rate of device-related complications, albeit the risk of major lead-related complications was lower in S-ICD patients (HR: 0.17; 95%CI: 0.038–0.79; P = 0.023). The TV- and S-ICD patients displayed similar risk of disease-related complications (HR: 0.64; 95%CI: 0.27–1.52; P = 0.309) and mortality (HR: 0.74; 95%CI: 0.29–1.87; P = 0.521). Hypertrophic cardiomyopathy patients implanted with a S-ICD had lower 5-year risk of appropriate and inappropriate ICD therapies as well as of major lead-related complications as compared to those implanted with a TV-ICD. Long-term comparative follow-up studies will clarify whether the lower incidence of major lead-related complications will translate into a morbidity or survival benefit.