the ailment that a defibrillator does treat is very often preceded by one or more heart attacks. Because part of the heart muscle dies during the buildup to a heart attack, the dead cells and tissue that result can cause problems with electrical conductivity within the heart. This is a key factor in the ailment treated by a defibrillator and the reason a defibrillator is so effective.

Sudden cardiac arrest is caused by an electrical fault, or short-circuit, in the lower ventricles, or chambers, of the heart. It causes the heart to literally and suddenly stop beating. instead quivering chaotically and weakly. This is known as ventricular fibrillationOnce ventricular fibrillation has occurred, there is a cessation of blood flow and oxygen to the vital body organs and the brain. Unless CPR is administered, or better yet a defibrillator is used on the victim, brain and body death will begin somewhere between four and six minutes after the event; death is almost certain by 10 minutes if the victim is not defibrillated