Evaluation of subcutaneous implantable cardioverter-defibrillator performance in patients with ion channelopathies from the EFFORTLESS cohort and comparison with a meta-analysis of transvenous ICD outcomes

BACKGROUND The subcutaneous implantable cardioverterdefibrillator (S-ICD) is an alternative to conventional transvenous ICD (TV-ICD) therapy to reduce lead complications. OBJECTIVE To evaluate outcomes in channelopathy vs patients with structural heart disease in the EFFORTLESS-SICD Registry and with a previously reported TV-ICD meta-analysis in channnelopathies. METHODS The EFFORTLESS registry includes 199 patients with channelopathies (Brugada syndrome 83, long QT syndrome 24, idiopathic ventricular fibrillation 78, others 14) and 786 patients with structural heart disease. RESULTS Channelopathy patients were younger (39 +/- 14 years vs 51 +/- 17 years; P < .001) with left ventricular ejection fraction 59% +/- 9% vs 41% +/- 18% (P < .001). The complication rate (follow-up: 3.2 +/- 1.5 years vs 3.0 +/- 1.5 years) was similar: 13.6% vs 11.2% (P 5.42). Appropriate shocks rates were 9.5% vs 10.8% (P = .70), with shocks for monomorphic ventricular tachycardia being 2.0% vs 6.9% (P < .02) and for polymorphic ventricular tachycardia/ ventricular fibrillation (VT/VF) 8.0% vs 5.7% (P = .30). Conversion effectiveness of VT/VF episodes was similar: 36 of 37 (97.3%) vs 151 of 155 (97.4%, P 5.59). VT/VF storm event (2% vs 0.9%, P = .33) and lower inappropriate shock (IAS) (8.5% vs 12.5%, P = .12) rates were statistically similar between channelopathy and non-channelopathy patients, with 45.5% channelopathy vs 31.4% non-channelopathy patients managed with a conditional zone. 200 beats per minute (P 5.0002). Annualized appropriate shock, IAS, and complication rates appear to be lower for the S-ICD vs meta-analysis TV-ICD patients, particularly lead complications. CONCLUSION EFFORTLESS demonstrates similar S-ICD efficacy and a nonsignificant, lower rate of IAS in channelopathy patients as compared to structural heart disease. Comparable IAS rates were achieved with the device programmed to higher rates for channelopathy patients.