Sudden cardiac death, or cardiac arrest, is usually caused by cardiac arrhythmia. The most common arrhythmias that result in cardiac arrest are ventricular fibrillation (VF) and ventricular tachycardia (VT). VF is an erratic, disorganized firing of impulses from the ventricles that affect the heart's pumping and contracting ability, thereby cutting off blood flow to the brain and other vital organs. VT is a rapid heartbeat initiated within the ventricles, characterized by three or more consecutive premature ventricular beats that critically reduce the heart's ability to effectively pump blood throughout the body.
The treatment for VF and VT is defibrillation, a process in which an electronic device (defibrillator) gives an electric shock to the heart. The electric shock resets the electrical state of the heart, thereby enabling the heart to beat to a rhythm controlled by its own natural pacemaker cells. Defibrillation helps re-establish normal contraction rhythms in a heart that has a dangerous arrhythmia or is in cardiac arrest. Left untreated, VF and VT can lead to cardiac arrest that is fatal within minutes. Studies have shown that individuals who survive severe cardiac arrhythmias do so because defibrillation is performed almost immediately.
Although the focus of this policy is automatic (automated) external defibrillators (AEDs), it should be noted that for most individuals at high risk for cardiac arrhythmias, an implantable cardioverter-defibrillator (ICD) is the treatment of choice. The surgically implanted ICD is designed to constantly monitor an individual's heart rate, recognize VF or VT, and deliver an electric shock to terminate these arrhythmias in order to reduce the risk of sudden death. When an ICD is not an option for an individual at risk for sudden death due to cardiac arrhythmias, an AED is necessary.
An AED is a wearable or nonwearable device that monitors cardiac rhythms. AEDs are used to treat potentially lethal dysrhythmias by delivering an electric shock to the heart through monitoring electrodes that are attached to an affected individual's chest. The AED collects information about the heart's rhythm that is immediately analyzed. If the analyzed rhythm is interpreted to be VF or VT, the AED can automatically or manually deliver a defibrillating shock to restore normal heart rhythm.
A wearable AED is a vest-like garment (worn under clothing) that automatically defibrillates an individual's heart. A nonwearable AED is a portable device that is used by someone other than the affected individual to effect defibrillation. Both types of AEDs consist of a monitor, electrodes, and a small alarm module.
The US Food and Drug Administration (FDA) has approved several AEDs that can be used by individuals outside of a health care facility. On May 2, 2001, the FDA approved the first external defibrillators to be used on children who experience cardiac arrest. The device, known as the Heartstream HeartStart FR2 AED (Agilent Technologies, Inc., Santa Clara, CA), is equipped with pediatric-sized attenuated electrode pads and cables that emit a shock suitable for children. Both the American Heart Association (AHA) and the Pediatric Advanced Life Support Task Force of the International Liaison Committee on Resuscitation (ILCOR) have recommended using an AED only when it can deliver a pediatric dose and when the child is between 1 and 8 years of age who have no signs of circulation. According to the ILCOR, an AED should not be used on children under 1 year of age.
Other manufacturers, such as Welch Allyn, maker of the Pediatric Energy Reducer for AED 10®, provide the pediatric attenuator as a separate accessory. According to the manufacturer, the Energy Reducer for AED 10® facilitates the use of less costly nonattenuating electrodes for all individuals, eliminating the potential to confuse attenuating electrodes with nonattenuating electrodes, as well as the need to ensure sufficient stock of the two styles of electrodes.
On December 18, 2001, the FDA approved the Wearable Cardioverter Defibrillator (WCD®) 2000 LifeVest (Lifecor, Inc., Pittsburgh, PA) for individuals over 18 years of age. The WCD® is an external device, worn 24 hours a day (except when bathing or showering) that functions like an ICD. It is a noninvasive, vest-like garment (worn under clothing) that consists of a monitor, electrodes, and a small alarm module that constantly checks and analyzes heart rhythm. If an abnormal shockable heart rhythm (i.e., VT or VF) is detected, a shock will be delivered. The device displays a message prior to delivering the shock, and an individual is able to prevent the shock by holding and pressing the response buttons. But if the individual loses consciousness while holding the buttons, the release of the buttons will automatically trigger the defibrillator to deliver the shock in an attempt to restore normal heart rhythm.
On December 17, 2015, the FDA approved a new indication for the LifeVest (Zoll Manufacturing Corporation, Pittsburgh, PA) wearable cardioverter defibrillator. The LifeVest is approved for children who are at risk for sudden cardiac arrest but who are not candidates for an implantable defibrillator due to certain medical conditions or lack of parental consent.
Weighing less than 2 pounds, the LifeVest consists of two main components: an electrode belt and garment that surround the patient’s chest, and a monitor that the patient wears around his or her waist. This device is intended only for children that weigh at least 41 pounds and have a chest size of 26 inches or more (about the size of an average 8 year old).
The pediatric approval was based on published studies and a company registery containing clinical information from 248 patients, ages 3 to 17, at risk for sudden cardiac arrest. No additional safety concerns were identified during the study. Four individuals who experienced sudden cardiac arrest received a shock that successfully restored a life-sustaining heartbeat.
On July 28, 2021, the FDA approved the ASSURE® Wearable Cardioverter Defibrillator (WCD) System for adult individuals at risk for sudden cardiac arrest who are not candidates for (or refuse) an ICD. (Kestra Medical Technologies, Inc., Kirkland, WA).
Cardiopulmonary resuscitation and the use of a portable AED are emergency techniques that assist an individual in the management of cardiac arrest until emergency personnel arrive. It is advisable that any individual potentially using these techniques have formal training in the use of the device and in basic life support.