An automated external defibrillator (AED) is a device that can detect and correct a type of abnormal heart rhythm called ventricular fibrillation. Ventricular fibrillation causes cardiac arrest.

AEDs are easy to use. The American Red Cross and other organizations provide training sessions on the use of AEDs. Most training sessions take only a few hours; but it is possible to use an AED even if you have never participated in a training course. Different AEDs have somewhat different instructions for use. The instructions are written on the AED, and most modern AEDs also use voice prompts to direct the user in each step. AEDs are available in many public gathering places, such as stadiums, airports, and concert halls. People who are told by their doctor that they are likely to develop ventricular fibrillation but who do not have an implanted defibrillator may want to purchase an AED for home use by family members, who should be trained in its use.