First-in-Human Chronic Implant Experience of the Substernal Extravascular Implantable Cardioverter-Defibrillator

OBJECTIVES The aim of this study was to evaluate the safety and performance of an extravascutar (EV) implantable cardioverter-defibrillator (ICD).BACKGROUND Limitations of existing transvenous and subcutaneous ICD systems include lead reliability and morbidity issues associated with ICD lead implantation in the vasculature or tack of pacing therapies (e.g., antitachycardia pacing) in subcutaneous systems. The EV defibrillator uses a novel substemat lead placement to address these limitations.METHODS This was a prospective, nonrandomized, chronic pilot study conducted at 4 centers in Australia and New Zealand. Participants were 21 patients referred for ICD implantation. Patients received EV ICD systems. Data collection included major systemic and procedural adverse events, defibrillation testing at implantation, and sensing and pacing thresholds.RESULTS Among 20 patients who underwent successful implantation, the median defibrillation threshold was 15 J, and 90% passed defibrillation testing with a >= 10-1 safety margin. Mean R-wave amplitude was 3.4 +/- 2.0 mV, mean ventricular fibrillation amplitude was 2.8 +/- 1.7 mV, and pacing was successful in 95% at <= 10 V. There were no intraprocedurat complications. Two patients have undergone elective chronic system removal since hospital discharge. In the 15 patients presently implanted, the systems are stable in long-term follow-up.CONCLUSIONS This first-in-human evaluation of an EV ICD demonstrated the feasibility of substemal lead placement, defibrillation, and paring with a chronically implanted system. There were no acute major complications, and pacing, defibrillation, and sensing performance at implantation were successful in most patients. (C) 2020 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation.