The rhythm of the heartbeat is controlled by the internal electrical system of the heart. The problems can cause abnormal heart rhythms, called arrhythmias. There are many types of arrhythmia. During an arrhythmia, the heart may beat too fast or too slow, or may stop beating. Sudden cardiac arrest occurs when the heart develops an arrhythmia that stops it from beating. This differs from a heart attack in which the heart usually beats, but the flow of blood to the heart is blocked.
There are many possible reasons for cardiac arrest. These include ischemic heart disease, physical stress, and some inherited diseases. Sometimes there is no known cause for sudden cardiac arrest. Without medical help, the person dies in a few minutes. People die less often if defibrillated early. Defibrillation discharges the current to restore the heart rate. You must give the sudden cardiac arrest person cardiopulmonary resuscitation (CPR) until defibrillation.