Understanding Outcomes with the S-ICD in Primary Prevention Patients with Low EF Study (UNTOUCHED): Clinical characteristics and perioperative results.

Abstract

BACKGROUND\nThe subcutaneous implantable cardioverter-defibrillator (S-ICD) has shown favorable outcomes in large registries with broad inclusion criteria. The cohorts reported had less heart disease and fewer comorbidities than standard ICD populations.\n\n\nOBJECTIVE\nThe purpose of this study is to characterize acute performance for primary prevention patients with a left ventricular ejection fraction (LVEF) ≤35% (primary prevention ≤35%).\n\n\nMETHODS\nPrimary prevention ≤35% patients with no prior documented sustained ventricular tachycardia (VT), pacing indication, end-stage heart failure, or advanced renal failure were prospectively enrolled. Analyses included descriptive statistics, Kaplan-Meier time to event, and multivariable logistic regression.\n\n\nRESULTS\nIn 1112 of 1116 patients, an S-ICD was successfully implanted (99.6%). Predictors for longer procedure time included 3-incision technique, higher body mass index (BMI), performing defibrillation testing (DFT), imaging, younger age, black race, and European vs North American centers. Patients undergoing DFT (82%) were successfully converted (99.2%; 94.3% converting at ≤65 J). Higher BMI was predictive of failing DFT at ≤65 J. The rate of 30-day freedom from complications was 95.8%. Most complications involved postoperative healing (45%) or interventions after DFT or impedance check (19%).\n\n\nCONCLUSION\nThe procedural outcome data of UNTOUCHED reinforce that S-ICD therapy has low perioperative complication rates and high conversion efficacy of induced ventricular fibrillation, even in a higher-risk cohort with low LVEF and more comorbidities than previous S-ICD studies. Higher BMI warrants more careful attention to implant technique.