An AED is an external medical device that delivers an electrical shock to the heart to restore a normal heart rhythm in people who have suffered a specific type of cardiac arrest, known as sudden cardiac arrest (SCA). SCA is not the equivalent of a heart attack, nor are AEDs used to treat all heart conditions. Rather, AEDs are only indicated for the treatment of sudden cardiac arrest.
In the majority of cases, SCA is caused by ventricular fibrillation (VF), which is a complete lack of heartbeat that can be fatal within minutes. However, SCA can also result from ventricular tachycardia (VT), a rapid heartbeat that can occur after fever, exercise, or nervous excitement.
Sudden cardiac arrest can strike people of any age, race, or gender. For example, electrocution, drowning, choking, and trauma can all disturb the heart’s normal rhythm. Although certain individuals are genetically predisposed to SCA, most people who have this condition have no prior symptoms or warning. Often, when you read about an apparently healthy young athlete collapsing during a game, SCA is the cause. Still, the majority of SCAs do occur in older adult males.
An AED is the appropriate emergency treatment in those cases when an electrical malfunction of the heart has stopped its normal rhythm. In these cases, a shock must be delivered via the AED within the first ten minutes of the SCA to restore a regular pulse.
Defibrillation can restore the heart’s normal rhythm if it’s done within minutes of the arrest. According to the American Heart Association, every minute that passes without defibrillation decreases the victim’s chances of survival by 10 percent. This is significant when you consider how long it can take for emergency medical services (EMS) to respond to treat a victim of SCA.
According to researchers who evaluate public access defibrillation programs, the average EMS response time from call to shock interval in the United States is likely to be greater than five minutes. Response times vary greatly and can be longer in very urban settings with heavy traffic or in more isolated rural settings.
Effectiveness of AEDs
According to a recent study that looked at survival rates in Las Vegas casinos, which were among the first establishments to implement the use of AEDs, these devices have been demonstrated to be effective. The study, published in the October 2000 issue of the New England Journal of Medicine, found that the overall survival rate for patients with ventricular fibrillation (VF) was 53 percent. This finding is most impressive when you compare their success to victims who don’t receive defibrillation. Most studies show survival rates for ventricular fibrillation/ventricular tachycardia to be about 10 percent. Having rapid access to an AED could improve survival rates by as much as 40 percent. In plain terms, that is four more lives saved for every ten people afflicted.
The American Heart Association recommends that AEDs be available wherever large numbers of people congregate. Such places include airports, convention centers, sports stadiums and arenas, large industrial buildings, high-rise offices, and large health and fitness facilities.