A wearable cardioverter defibrillator (WCD), most commonly known by the brand name LifeVest, is an external device worn around the body that continuously monitors heart rhythm and can automatically deliver a defibrillation shock if a life-threatening arrhythmia is detected. Unlike an implantable cardioverter defibrillator (ICD), it does not require surgery and can be fitted and removed at any time.
How it works
The WCD consists of a garment containing electrodes that sit against the skin and a monitor unit worn on a belt. The device continuously analyses heart rhythm. If it detects ventricular fibrillation or sustained ventricular tachycardia, it delivers a warning (vibration, alert sounds, and a voice prompt) giving the patient a few seconds to press a response button if they are conscious and wish to delay or prevent the shock. If there is no response, the device delivers a shock automatically.
When it is used
The WCD is used as a temporary bridge when a patient is at elevated risk of sudden cardiac arrest but an ICD has not yet been implanted, or when it is not yet clear whether an ICD will be needed. Common scenarios include:
- The period immediately after a heart attack, when cardiac function is reduced and VF risk is temporarily elevated
- Following a diagnosis of new cardiomyopathy, while waiting to see if cardiac function improves
- After removal of a permanent ICD due to infection, while awaiting re-implantation
- When a patient is unsuitable for immediate surgery
Limitations
The WCD only works when worn correctly and continuously. It cannot treat slow rhythms (bradycardia) and does not provide pacing. Inappropriate shocks can occur if the device misdetects the rhythm, though the alert system allows conscious patients to prevent unnecessary shocks. Comfort and compliance are important considerations, as the protection offered depends on the patient wearing the device at all times except bathing.
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