Implantation and follow-up of totally subcutaneous versus conventional implantable cardioverter-defibrillators: a multicenter case-control study

Background: The approval of an entirely subcutaneous implantable-cardioverter defibrillator (ICD) system (S-ICD) has raised attention about this promising technology. It was developed to overcome lead failure and infection problems of conventional transvenous ICD systems. Nevertheless, lead migration of the initial design and inappropriate shock rates have raised concerns regarding its reliability and safety.

Objective: The purpose of this study was to report the largest multicenter series to date of patients with the new device in comparison with a matched conventional transvenous ICD collective with focus on perioperative complications, conversion of induced ventricular fibrillation (VF), and short-term follow-up.

Methods/results: Sixty-nine patients (50 male and 19 female; mean age 45.7 ± 15.7 years) received an S-ICD in three German centers and were randomly assigned to 69 sex- and age-matched conventional ICD patients. The indication was primary prevention in 41 patients (59.4%) without difference between groups (34 control patients; P = .268). The predominant underlying heart disease was ischemic cardiomyopathy in 11 (15.9%), dilated cardiomyopathy in 25 (36.2%), and hypertrophic cardiomyopathy in 10 (14.5%) in the S-ICD group. Mean implantation time was 70.8 ± 27.9 minutes (P = .398). Conversion rates of induced VF were 89.5% for 65 J (15-J safety margin) and 95.5% including reversed shock polarity (15-J safety margin) in the study group. Termination of induced VF was successful in 90.8% (10-J safety margin, device dependent) of the control patients (P = .815). Procedural complications were similar between the 2 groups. Mean follow-up was 217 ± 138 days. During follow-up, 3 patients with S-ICD were appropriately treated for ventricular arrhythmias. Three inappropriate episodes (5.2%) occurred in 3 S-ICD patients due to T-wave oversensing, whereas atrial fibrillation with rapid conduction was the predominant reason for inappropriate therapy in conventional devices (P = .745).

Conclusion: The novel S-ICD system can be implanted safely with similar perioperative adverse events compared with standard transvenous devices. Our case-control study demonstrates a 10.4% failure of conversion of induced VF with the S-ICD set to standard polarity and 15-J safety margin and comparable inappropriate shock rates during short-term follow-up.