Use of the Wearable Cardioverter Defibrillator in High-Risk Populations

The United States Food and Drug Administration has approved the wearable cardioverter defibrillator (WCD) for use in patients who are at high risk for sudden cardiac arrest (SCA) and who do not yet have an established indication for an implantation cardioverter defibrillator (ICD) or have contraindications for device implantation for various reasons. The WCD is typically used for primary prevention in (1) high-risk patients with reduced left ventricular ejection fraction (LVEF) ≤35 % after recent acute myocardial infarction (MI) during the 40-day ICD waiting period, (2) before and after coronary artery bypass graft or percutaneous coronary intervention during the 90-day ICD waiting period, (3) after recently diagnosed nonischemic dilated cardiomyopathy (NICM) during the 3- to 9-month medical therapy optimization period, or (4) for those with inherited proarrhythmic conditions such as long QT syndrome or hypertrophic cardiomyopathy. Unlike the automatic external defibrillator, the WCD does not require assistance from bystanders for therapy and conscious patients can delay or avert therapy with the use of response buttons. The WCD exhibits a small risk of inappropriate shock, mostly due to supraventricular tachycardia and/or electrical noise. Multiple non-randomized observational studies have shown high efficacy in detection and appropriate shock therapy for sustained ventricular tachyarrhythmias. This paper discusses the use of the WCD for prevention of SCA in patients with various cardiac substrates.