Modern Subcutaneous Implantable Defibrillator Therapy in Patients with Cardiomyopathies and Channelopathies: data from a large multicenter registry

Background: 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. Objective: 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. Methods: 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. Results: 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%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 (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 0.7% of patients. Conclusions: 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.