A defibrillator vest is an external medical device used to provide emergency treatment for the dangerous heart conditions of ventricular fibrillation and pulseless ventricular tachycardia. Like other defibrillators, it functions by delivering an electrical charge into the heart in response to a detected abnormality in heartbeat. A defibrillator vest's distinguishing feature is that it is worn continuously on the body like a garment in order to provide immediate emergency defibrillation for the user, unlike implanted defibrillators inside the patient's body or conventional defibrillator machines that are entirely separate from the patient and operated by another person.
Heartbeat is caused by electrical impulses that travel through the heart. Abnormalities in the production or transmission of these electrical signals result in abnormal heartbeat, called arrhythmia or dysrhythmia. Some types of arrhythmia are minor, but ventricular fibrillation and ventricular tachycardia are both potentially fatal.
Ventricular fibrillation is a condition in which the ventricles of the heart are not properly coordinated when they contract with each heartbeat, leaving the heart unable to pump blood back into the circulatory system. In pulseless ventricular tachycardia, the ventricles contract too quickly, resulting in heartbeats that are very rapid but fail to actually circulate blood. Both are lethal within minutes if allowed to continue. Defibrillators restore normal heartbeat by sending an electric current into the heart. This temporarily depolarizes the heart's cells, halting the abnormal heartbeat and allowing the heart to establish a more normal rhythm.
Defibrillation must be done quickly, because it is used to treat health threats that kill almost immediately. Thus, the purpose of a defibrillator vest is to allow people with heart conditions that can cause sudden cardiac arrest to more safely participate in normal life instead of remaining under constant medical supervision. It is usually a temporary measure prior to the permanent surgical implantation of an implantable defibrillator. Defibrillator vests are used by patients in the assessment period after a suffering heart attack, or by patients with a temporary condition, such as an infection, that requires implantation surgery to be delayed.
Worn beneath the user's clothing, a defibrillator vest is connected to a monitoring and recording device carried by the user in a shoulder strap. It uses electrodes to continuously monitor the patient's heartbeat for abnormalities. In the event of a dangerous arrhythmia, it gives a warning signal to the wearer before releasing an electrically conductive gel over its electrodes, discharging a defibrillating electric shock into the wearer's heart. The shock can be manually overridden by the patient after the warning signal is given if he or she desires, but unless directly countermanded, the defibrillator will activate on its own once the arrhythmia is detected. This allows the vest to perform its function even if the wearer is alone and has lost consciousness.