An AED assists during a cardiac emergency by analyzing the victim's heart rhythm through adhesive electrode pads placed on the chest. The device determines whether the heart is in a shockable rhythm, such as ventricular fibrillation or pulseless ventricular tachycardia. If a shock is needed, the AED will prompt the user to deliver it, or in some models, automatically administer the shock.

 

The electrical shock briefly stops the heart’s abnormal activity, giving it a chance to reset into a normal rhythm. This process, called defibrillation, is most effective when performed quickly after the onset of cardiac arrest. In conjunction with high-quality CPR, the AED helps maintain circulation to vital organs and gives the person the best chance of recovery before emergency medical services arrive.