A cardiac vest, formally known as a Wearable Cardioverter Defibrillator (WCD), is a non-invasive, external device designed to protect patients at risk of Sudden Cardiac Arrest (SCA). It is worn directly against the body, typically underneath clothing, and provides continuous monitoring of the heart’s electrical activity. It acts as a temporary safeguard, intervening automatically if a life-threatening heart rhythm is detected. The vest’s primary purpose is to deliver a controlled electrical shock to restore a normal heartbeat.
How the Wearable Defibrillator Works
The WCD system has two main parts: a garment with integrated electrodes and a separate monitoring unit worn on a belt. The garment contains sensing electrodes that constantly record the heart’s rhythm, similar to an electrocardiogram (ECG). This data is transmitted to the monitor, which is a battery-powered device containing the detection and defibrillation technology. The system is specifically programmed to recognize life-threatening arrhythmias, primarily ventricular tachycardia (VT) and ventricular fibrillation (VF).
When a dangerous rhythm is identified, the device initiates a three-step response sequence that takes place in less than a minute. First, it alerts the patient and nearby individuals with a series of audible alarms and strong vibrations. This warning phase is crucial, as it allows a conscious patient to respond and prevent an unnecessary shock. If the patient remains unresponsive, the device proceeds to the second step, which involves releasing a conductive gel onto the skin from integrated pads to ensure proper electrical contact.
In the final step, if the life-threatening rhythm persists and the patient has not pressed the response buttons, the device automatically delivers a calculated electrical shock (defibrillation). This therapeutic shock is intended to reset the heart’s electrical system and restore a stable rhythm.
Medical Situations Requiring a Cardiac Vest
The cardiac vest is prescribed as a temporary measure, acting as a “bridge” for patients whose risk of sudden cardiac death is elevated. One common indication is for patients who have recently suffered a myocardial infarction (heart attack) and have severely reduced left ventricular function, often defined as an ejection fraction of 35% or less. Medical guidelines suggest a waiting period after a heart event to see if the heart muscle recovers with medication before considering a permanent device.
The WCD provides protection during this recovery period, which can last up to three months. It is also used for patients with a new diagnosis of severe heart failure or cardiomyopathy, where the cause of the weakened heart is not yet fully understood or treated. For individuals awaiting a heart transplant or other definitive long-term treatment, the vest offers a safety net against fatal arrhythmias. Furthermore, the device is used when a patient already has an indication for a permanent Implantable Cardioverter Defibrillator (ICD) but has a temporary medical contraindication, such as an active infection that prevents immediate surgery.
Practicalities of Wearing the Device
For the cardiac vest to be effective, consistent wear is necessary, with physicians recommending it be worn for almost 24 hours a day, including while sleeping. The only time a patient should remove the device is for brief periods, such as when taking a shower or bath. During these short breaks, a caregiver should be present, if possible, to monitor the patient.
Daily maintenance involves managing the battery, requiring regular charging and swapping out batteries to ensure continuous function. The vest itself is worn beneath clothing and must fit properly against the skin to allow the electrodes to accurately sense the heart rhythm. Patient adherence to the wearing schedule is a major factor in the device’s protective capability.
A feature allowing the patient to interact with the device is the response button, which can temporarily override the shock delivery during the warning phase. If the patient is conscious and the alarm sounds, they can press these buttons to indicate they are alert and prevent a shock, which can sometimes be triggered by non-life-threatening rhythms or motion artifacts.