In 1990, the American Heart Association developed the Chain of Survival. This protocol addresses the fact that most Sudden Cardiac Arrest (SCA) episodes occur outside of a hospital, with death occurring within minutes of onset. For the Chain to be effective, quick execution of each and every link is critical. With each minute that passes, the likelihood of survival decreases 7-10%.

Time After Onset of Attack	Survival Chances
With every minute	Chances are reduced by 7 - 10%
Within 4 - 6 minutes	Permanent brain damage starts  to occur with possible death
After 10 minutes	Few attempts at resuscitation  succeed

To provide the best opportunity for survival, each of these four links must be put into motion within the first few minutes of SCA onset:

1. Early Access to Emergency Care must be provided by calling 911.
2. Early CPR should be started and maintained until emergency medical services (EMS) arrive.
3. Early Defibrillation is the only one that can re-start the heart function of a person with ventricular fibrillation (VF). If an automated external defibrillator (AED) is available, a trained operator should administer defibrillation as quickly as possible until EMS personnel arrive.
4. Early Advanced Care, the final link, can then be administered as needed by EMS personnel.

When each link in the chain works successfully, the chance of surviving SCA increases greatly.