Extravascular Implantable Cardioverter-Defibrillators: A Systematic Review of Emerging Evidence

Implantable cardioverter-defibrillators (ICDs) are medical devices designed to prevent sudden cardiac death caused by life-threatening ventricular arrhythmias. This review aims to investigate the most novel approach via an extravascular lead by exploring preliminary data published in the PubMed, Cochrane, and ScienceDirect databases as of October 2024. An Oxford Level of Evidence was assigned to each paper. Papers rated Level 3B or 4 were included to ensure a high level of scientific rigor, including studies with conflicting findings. This benchmark was selected because the current literature does not include any systematic reviews of the subject (Level 1-3A), and Level 5 provides a poorly supported assessment. Of the 727 initial peer-reviewed records identified, 25 were included in the final analysis: 11 articles and 14 abstracts (including relevant literature regarding preclinical investigations of animal experiments). This data includes prospective trials and observational clinical studies, patient-reported outcome studies, subsequent analyses, and retrospective studies of efficacy, safety, and complications of extravascular ICDs (EV-ICDs) and therapeutic use. This review discusses the expectations from preclinical and clinical applications of EV-ICDs (extracted from both expert opinions and reported patient outcomes) and how certain limitations may be addressed based on the literature. A comprehensive review of complex medical devices is advantageous and enables multifaceted analysis of efficacy. This systematic review revealed that EV-ICDs demonstrate effective sensing, pacing, and defibrillation with high patient acceptance and low complication risk. In comparison with transvenous and subcutaneous ICDs, EV-ICDs provide effective antiarrhythmic action through antitachycardia pacing, safe lead removal, and enhanced long-term performance.