- Mina K Chung, MD
Mina K Chung, MD
- Professor of Medicine
- Cleveland Clinic Lerner College of Medicine of Case Western Reserve University
The implantable cardioverter-defibrillator (ICD) has been shown to improve survival from sudden cardiac arrest and to improve overall survival in several populations at high risk for sudden cardiac death (SCD). However, there remain situations in which implantation of an ICD is immediately not feasible (eg, patients with an active infection), may be of uncertain benefit, may not be covered by third-party payers (eg, early post-myocardial infarction, patients with limited life expectancy or new onset systolic heart failure), or when an ICD must be removed (eg, infection).
In cases where ICD implantation must be deferred, a wearable cardioverter-defibrillator (WCD) offers an alternative approach for the prevention of sudden cardiac death. The WCD (LifeVest) is an external device capable of automatic detection and defibrillation of ventricular tachycardia and ventricular fibrillation (picture 1). While the WCD can be worn for years, typically the device is used for several months as temporary protection against SCD.
The indications, efficacy, and limitations of the wearable cardioverter-defibrillator will be discussed here. Detailed discussions of the roles of the ICD are presented separately. (See "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy" and "Primary prevention of sudden cardiac death in heart failure and cardiomyopathy".)
DESCRIPTION AND FUNCTIONS OF THE WCD
The wearable cardioverter-defibrillator (WCD) is an external device capable of automatic detection and defibrillation of ventricular tachycardia (VT) or ventricular fibrillation (VF). As of June 2015, the approved devices do not have pacing capabilities and therefore are unable to provide therapy for bradycardic events or antitachycardic pacing.
Wearing the WCD — The WCD is composed of four dry, nonadhesive monitoring electrodes, three defibrillation electrodes incorporated into a chest strap assembly, and a defibrillation unit carried on a waist belt (picture 1). The monitoring electrodes are positioned circumferentially around the chest, held in place by tension from an elastic belt, and provide two surface electrocardiogram leads. The defibrillation electrodes are positioned in a vest assembly for apex-posterior defibrillation. Proper fitting is required to achieve adequate skin contact to avoid noise and frequent alarms.
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- DESCRIPTION AND FUNCTIONS OF THE WCD
- Wearing the WCD
- Detection and delivery of shocks
- Efficacy in terminating VT/VF
- Avoiding inappropriate shocks
- Storage of ECGs and compliance data
- Bridge to indicated or interrupted ICD therapy
- Early post-MI patients with LV dysfunction
- Patients with LV dysfunction early after coronary revascularization
- Newly diagnosed nonischemic cardiomyopathy
- Bridge to heart transplant
- - WCD in patients with VADs
- LIMITATIONS OF THE WCD
- Patient size
- Lack of pacemaker functionality
- Inappropriate shocks
- Patient compliance and complaints
- USE OF THE WCD IN CHILDREN
- SUMMARY AND RECOMMENDATIONS