Subcutaneous ICD Therapy in Patients with Monomorphic Ventricular Tachycardia: Arrhythmia Recurrence, Shock Rate, and Management Strategies

Background: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is recommended for patients at risk of sudden cardiac death who do not require pacing or antitachycardia pacing (ATP). However, patients with a history of monomorphic ventricular tachycardia (MVT), which is often amenable with ATP, are underrepresented in clinical studies dealing with S-ICD. Objectives: To evaluate outcomes of S-ICD therapy in patients with prior MVT and describe subsequent management strategies in clinical practice. Methods: From 2,164 consecutive de novo S-ICD implantations, we identified 210 patients (10%) with a history of sustained MVT. Clinical characteristics, procedural data, and outcomes were analyzed. The endpoints of the study included the rates of sustained MVT and S-ICD shocks for all ventricular arrhythmias. Results: During a median follow-up of 43 months (IQR 21-70), 21 patients (10%) experienced 66 MVT episodes (60 isolated, 6 storms), and a total of 98 ventricular arrhythmic episodes, all successfully terminated by shocks. The annualized rate of MVT was 2.8% /year, and the rate of appropriate shocks was 4.9% /year. First-shock efficacy was 93% for both MVT and polymorphic VT/ventricular fibrillation. Approximately half of patients with recurrent MVT underwent ablation, with high procedural success. No patient required S-ICD explantation or conversion to a transvenous ICD for ATP delivery. The complication rate was 2.3% /year and the inappropriate shock rate 2.8% /year. Conclusions: In patients with prior MVT, the S-ICD provided safe and effective protection from ventricular arrhythmias. Ablation was the preferred management strategy, and no patients required conversion to a transvenous device. These findings support the use of the S-ICD as a viable option in this patient population.