A cardiac vest, formally known as a Wearable Cardioverter Defibrillator (WCD), is a non-invasive medical technology designed to protect individuals at risk of sudden cardiac death. This external device functions as a temporary safeguard, continuously monitoring the heart’s electrical activity for dangerous, rapid rhythms. The WCD provides a protective measure for patients whose risk of cardiac arrest is high but potentially reversible or temporary. It allows medical professionals time to assess the patient’s long-term heart health and determine the most appropriate permanent treatment plan. The WCD automatically delivers a life-saving electrical shock if a life-threatening heart rhythm occurs, without requiring intervention.
Defining the Wearable Defibrillator
The WCD is an external device worn directly against the skin, unlike an Implantable Cardioverter Defibrillator (ICD) which requires surgery. The system consists of three primary components: a lightweight fabric garment, an electrode belt, and a monitor unit. The garment, resembling a vest or bra, is worn beneath the patient’s clothing and holds the electrode belt securely in place around the torso.
The electrode belt contains four dry sensing electrodes that continuously record the heart’s electrical signals, similar to an electrocardiogram (ECG). It also houses three defibrillation electrodes—one on the front of the chest and two on the back—which deliver the therapeutic electrical current. The monitor unit, often worn on a waist belt or shoulder strap, processes the heart rhythm data and houses the battery and alarm system.
How the Vest Delivers Therapy
The WCD mechanism is a three-step process initiated by detecting a life-threatening arrhythmia. Sensing electrodes constantly analyze the heart’s rhythm for rapid, chaotic patterns, specifically ventricular tachycardia (VT) or ventricular fibrillation (VF). If the device identifies one of these dangerous rhythms, it immediately initiates an alert sequence to determine the patient’s consciousness.
The first alert is a vibration against the skin, followed by an audible alarm and voice prompts instructing the patient to press response buttons. If the patient is conscious and the rhythm is a false alarm, pressing these buttons delays the treatment shock. If the patient does not respond by pressing the buttons within a short time, the device assumes the patient is unconscious and proceeds to treatment. A conductive gel is then released onto the skin over the therapy electrodes to ensure efficient electrical transfer and minimize skin injury. The device automatically delivers a calibrated electrical shock, or defibrillation, aimed at resetting the heart’s electrical system to a normal rhythm.
Medical Conditions Requiring Use
A WCD is prescribed for patients with an elevated, temporary risk of sudden cardiac death while their underlying condition is being evaluated or treated. One common scenario is immediately following a heart attack (acute myocardial infarction), particularly when the heart’s pumping function (ejection fraction) is 35% or lower. Guidelines recommend a 40-day waiting period after an MI before considering a permanent ICD, and the WCD covers this time of heightened risk.
Patients who have recently undergone a coronary revascularization procedure, such as bypass surgery, may also be at high risk for up to 90 days while the heart muscle recovers. The vest is also utilized for newly diagnosed cases of non-ischemic cardiomyopathy (NICM), a condition where the heart muscle is weakened for reasons other than coronary artery disease. In these cases, the WCD offers protection during the initial 90-day period as doctors start guideline-directed medical therapy, allowing time to see if heart function improves. Furthermore, the WCD functions as a bridge-to-care for patients awaiting a heart transplant or for those who need their permanent ICD removed due to an infection, requiring temporary external protection until a new device can be safely implanted.
Living With and Maintaining the Device
Wearing the WCD requires patient compliance, as the device must be worn for nearly 24 hours a day to provide continuous protection. Patients are instructed to wear the vest even while sleeping, removing it only for brief periods of personal hygiene. The main exception for removal is for a short shower or bath, and patients are often advised to have a family member or caregiver present during this time.
Proper maintenance involves regular care of the non-electronic components to ensure the device functions correctly. The fabric garment, which can become soiled from constant wear, must be washed frequently, typically every one to two days. However, the patient must first carefully remove the electrode belt and monitor unit, as these electronic components cannot get wet and would be damaged by washing. Patients are also responsible for managing the rechargeable batteries, needing to swap them out and charge them daily to ensure the monitor is constantly powered.