A Contemporary Review of Subcutaneous and Extravascular Implantable Cardiac Defibrillators

Implantable cardioverter-defibrillators (ICDs) are life-saving devices used to prevent sudden cardiac death. Two newer types of ICDs-the extravascular ICD (EV-ICD) and the subcutaneous ICD (S-ICD)-offer alternatives to traditional transvenous ICDs. Additionally, efforts are being made to introduce defibrillation and pacing interventions through a single device called the modular cardiac rhythm management system (mCRM). This review compares the EV-ICD and S-ICD based on currently available clinical data, focusing on their safety and performance. Additionally, we review modular ICD systems, which integrate leadless pacing with defibrillation. We conducted a comprehensive literature search of PubMed and ScienceDirect, focusing on articles demonstrating the clinical outcomes of EV-ICDs and S-ICDs as well as modular systems. However, we found that sufficient studies are not available to determine the clinical efficacy and safety outcomes of EV-ICDs and the mCRM. Additionally, comparative studies between EV-ICDs and S-ICDs are still required to determine their relative roles in the field of electrophysiology, with the goal of empowering clinicians to understand these emerging technologies to support better patient care decision-making.