An automated external defibrillator (AED) is a battery-operated light, portable device (slighlty smaller than a shoe box) that analysis the heart rhythm and can send an electric shock to the heart to try to restore a normal rhythm. AEDs are used to treat Sudden Cardiac Arrest (SCA). SCA is a condition in which the heart suddenly and unexpectedly stops beating. The most common cause of SCA’s are myocardial infarctions or “heart attacks” as these are more commonly known.