Using an automated external defibrillator (AED) on a person who is having sudden cardiac arrest (SCA) may save the person’s life.

The most common cause of SCA is an arrhythmia called ventricular fibrillation (v-fib). In v-fib, the ventricles (the heart’s lower chambers) don’t beat normally. Instead, they quiver very rapidly and irregularly.

Another arrhythmia that can lead to SCA is ventricular tachycardia. This is a fast, regular beating of the ventricles that may last for a few seconds or much longer.

In people who have either of these arrhythmias, an electric shock from an AED can restore the heart’s normal rhythm (if done within minutes of the onset of SCA).

What Are the Signs of Sudden Cardiac Arrest?

If someone is having SCA, you may see him or her suddenly collapse and lose consciousness. Or, you may find the person unconscious and unable to respond when you call or shake him or her.

The person may not be breathing, or he or she may have an abnormal breathing pattern. If you check, you usually can’t find a pulse. The person’s skin also may become dark or blue from lack of oxygen. Also, the person may not move, or his or her movements may look like a seizure (spasms).

An AED can check the person’s heart rhythm and determine whether an electric shock is needed to try to restore a normal rhythm.

We also offer a free certificate of completion. To receive the certificate you must pass a 50-question test with a score of 70 or higher. Check our Basic First Aid Certificate of Completion page for more information.