What is an AED?

An automated external defibrillator (AED) is a lightweight, portable device that delivers an electric shock through the chest to the heart. The shock can potentially stop an irregular heart beat (arrhythmia) and allow a normal rhythm to resume following sudden cardiac arrest (SCA). SCA occurs when the heart malfunctions and stops beating unexpectedly. If not treated within minutes, it quickly leads to death.

Most SCAs result from ventricular fibrillation (VF). VF is a rapid and unsynchronized heart rhythm that originates in the heart’s lower chambers (the ventricles). The heart must be “defibrillated” quickly, because a victim’s chance of surviving drops by seven to 10 percent for every minute a normal heartbeat isn’t restored.

Why are AEDs important?

AEDs make it possible for more people to respond to a medical emergency where defibrillation is required. Because AEDs are portable, they can be used by nonmedical people (lay-rescuers). They can be made part of emergency response programs that also include rapid use of 9-1-1 and prompt delivery of cardio pulmonary resuscitation (CPR). All three of these activities are vital to improving survival from SCA.

How does an AED work?

A built-in computer checks a victim’s heart rhythm through adhesive electrodes. The computer calculates whether defibrillation is needed. If it is, a recorded voice prompts the rescuer to press the shock button on the AED. This shock momentarily stuns the heart and stops all activity. It gives the heart the chance to resume beating effectively. Audible prompts guide the user through the process. AEDs advise a shock only for ventricular fibr