Indications and use of the wearable cardiac defibrillator

Abstract

The implantable cardiac defibrillator (ICD) has been an effective tool for prevention of sudden cardiac death (SCD) in populations at high risk for life-threatening sustained ventricular tachycardia (VT) and ventricular fibrillation (VF). However, ICD implantation is dependent on defining ventricular substrate, evaluating the future risk of SCD and estimation of the patient's overall survival. The ability to predict risk of SCD is often difficult. If ventricular dysfunction (a surrogate marker for the risk of SCD) improves, ICD therapy may not be indicated. The wearable cardiac defibrillator (WCD) provides an option for protection during this vulnerable period when the risk of SCD is unclear. It combines an electrocardiogram-monitoring system with an external automatic defibrillator. The WCD can be a safe and effective tool for prevention of VT/VF related SCD events and is used in a variety of clinical situations where the risk of SCD is changing. Such situations include the early phase after acute myocardial infarction with poor left ventricular function (35%), after acute coronary revascularization procedures and reduced left ventricular ejection fraction (35%), acute heart failure and non-ischemic cardiomyopathy of uncertain duration and prior to medical therapy initiation. The WCD also has a role in patients waiting for heart transplantation or who need a ventricular-assist device and those who have an acute contra-indication to implantation such as active infection. This review discusses the technical aspects of the WCD, its potential clinical application and summarizes the currently available data on the WCD in different populations and future directions.