Sudden cardiac arrest (SCA) is a life-threatening emergency that occurs when the heart suddenly stops beating. It strikes people of all ages who may seem to be healthy, including children, teens, and young adults. When SCA happens, the person collapses and doesn’t respond or breathe normally. They may gasp or shake as if having a seizure. SCA leads to death in minutes if the person does not get help right away. Survival depends on people nearby NOT JUST calling 911, but also starting CPR and using an automated external defibrillator (AED) as soon as possible.