Wearable Cardioverter-Defibrillators

Since its introduction >3 decades ago, the implantable cardioverter-defibrillator (ICD) has been used extensively to enhance the survival of patients at high risk for sudden cardiac death resulting from life-threatening ventricular tachyarrhythmias (VTs; ie, sustained VT and ventricular fibrillation [VF]).1,2 Nevertheless, the invasive nature of the implantation procedure, cost issues, and potential complications related to an in-dwelling intravascular device (eg, inappropriate shocks, infection, thrombosis) have limited the use of ICD therapy to patients whose risk of sudden cardiac death is considered to be both very high and permanent. Consequently, patients undergoing diagnostic workups for underlying causes of VT/VF or those with reversible causes of sudden death frequently remain unprotected against cardiac arrest for time periods of variable duration. Similarly, patients awaiting ICD implantation and those with contraindications to implantation may also go unprotected for significant time periods. The recent emergence of the wearable cardioverter-defibrillator provides a new prophylactic strategy for patients who are at significant risk for VT/VF but are not immediate candidates for ICD implantation. The patient population who is likely to derive the most benefit from the wearable defibrillator remains to be defined. We provide an in-depth review of the evidence base and role of wearable defibrillator therapy and clinical indications for its use.The only commercially available wearable defibrillator to date is the LifeVest manufactured by ZOLL and approved by the Food and Drug Administration (FDA) in 2002. It consists of an elastic belt and shoulder straps (Figure 1) that carry 4 dry, nonadhesive sensing electrodes and 3 defibrillator electrodes. The electrodes exude gel automatically just before delivery of a shock. This way, the discomfort related to the exposure to large amounts of gel during long-term ambulatory use of the wearable defibrillator is avoided. The monitor is worn on a holster around the waist …