What is Sudden Cardiac Arrest? Each year, sudden cardiac arrest (SCA) strikes about 220,000 Americans. Unlike a heart attack, in which blood flow to the heart muscle is temporarily blocked, the primary cause of sudden cardiac arrest is ventricular fibrillation, a life-threatening condition in which the heart's normal electrical signals become erratic, causing the heart to cease pumping blood effectively. When this occurs, the victim immediately becomes unresponsive, stops breathing, has no detectable pulse and-without intervention-will die within minutes. Defibrillation, or restoring the heart's natural rhythm by applying an electrical shock, is the only definitive treatment for SCA.

What causes SCA? The underlying cause of SCA is not well understood. Many victims have no history of heart disease, or, if heart disease is present, it has not functionally impaired them. SCA strikes both men and women, with the average age of victims being 65, but with many being in their 30s or 40s. In addition, it often strikes without warning. Cardiopulmonary resuscitation (CPR) and early defibrillation are the most critical factors in determining survival of SCA. Published studies indicate that survival rates from ventricular fibrillation can exceed 70 percent if defibrillation is administered within the first few minutes of SCA.

Why is it critical to have access to an AED? It has been reported that the chance of survival decreases by approximately ten percent with each minute that passes after the time of attack (Cummins, RO et al, Annals of Emergency Medicine, 1989; 18:1269–1275). However, response times for paramedics or emergency medical technicians to arrive on site with a defibrillator are often more than ten minutes, resulting in average SCA survival rates in the United States of less than five percent. Widespread deployment of automated external defibrillators (AEDs) is the only feasible method of achieving early defibrillation. Public access proponents estimate that the broad deployment of AEDs among trained responders could prevent an estimated 45,000-50,000 unnecessary deaths each year in the United States

Cardiac Chain of Survival Early defibrillation is an important step in the cardiac "Chain of Survival" –a series of four critical steps for resuscitation:

AEDs are now available in a wide range of settings, including airplanes, office buildings, industrial plants, casinos, golf courses, ski resorts, cruise ships and health clubs. With the widespread availability of AEDs, a critical and logical step in strengthening the sudden cardiac arrest "Chain of Survival" is now available. A break in any of the four links in the chain can compromise the victim's chance for survival; however, CPR and early defibrillation are recognized as the most critical steps in restoring an effective cardiac rhythm and resuscitating a victim of SCA. The likelihood of successful resuscitation following SCA decreases by approximately ten percent with each minute that passes before defibrillation. After ten minutes, few attempts are successful.