What are the guidelines for the use of an external wearable cardiac defibrillator (Automated External Defibrillator - AED)?

From the Guidelines

External wearable cardiac defibrillators (WCDs) are recommended for patients at temporary high risk of sudden cardiac death who are not immediate candidates for implantable cardioverter-defibrillators (ICDs). The primary candidates include patients with recent myocardial infarction with ejection fraction ≤35%, newly diagnosed non-ischemic cardiomyopathy with ejection fraction ≤35%, patients awaiting heart transplantation, those with myocarditis, and patients who had an ICD removed due to infection 1.

Key Considerations

• The WCD should be worn continuously except during bathing or showering, typically for 1-3 months while awaiting improvement in cardiac function or definitive treatment.
• Proper skin care is essential, with daily cleaning of the electrode areas and repositioning of electrodes to prevent skin irritation.
• Patients must be trained to respond to alarms, allow the device to deliver shock when necessary, and perform regular device checks.

Effectiveness and Compliance

The effectiveness of WCDs is based on their ability to detect ventricular arrhythmias and deliver timely defibrillation, with studies showing 90-98% first-shock success rates 1. Compliance is crucial for effectiveness, and patients should understand that the WCD is typically a temporary bridge rather than a permanent solution.

Recommendations

According to the guidelines, in patients with an ICD and a history of SCA or sustained VA in whom removal of the ICD is required, the wearable cardioverter-defibrillator is reasonable for the prevention of SCD (Class IIa, LOE B-NR) 1. Additionally, in patients at an increased risk of SCD but who are not ineligible for an ICD, the wearable cardioverter-defibrillator may be reasonable (Class IIb, LOE B-NR) 1.

From the Research

Guidelines for Use of External Wearable Cardiac Defibrillator

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

Patient Selection

• Left ventricular ejection fraction alone is unlikely to be sufficient for effective sudden cardiac death risk prediction, due to low sensitivity and specificity 3.
• ICDs confer a significant survival benefit only in high-risk patients with ischemic cardiomyopathy and left ventricular ejection fraction of ≤35% due to a remote myocardial infarction 3.
• The benefits of ICDs in the elderly as well as in women are not established 3.
• Assessment of ejection fraction remains the most important step to identify patients at risk of sudden cardiac death who would benefit from ICD implantation 4.

Device Selection and Outcome

• Multiple randomized multicentre clinical trials have established the role of the implantable cardioverter-defibrillator (ICD) as the mainstay in the treatment of ventricular tachyarrhythmias and sudden cardiac death (SCD) prevention 5.
• The wearable cardioverter-defibrillator (WCD) is an alternative antiarrhythmic device that provides continuous cardiac monitoring and defibrillation capabilities through a noninvasive, electrode-based system 6.
• The WCD has been shown to be highly effective at restoration of sinus rhythm in patients with a ventricular tachyarrhythmia 6.