AEDs Aplenty: What Does Their Proliferation Mean for EMS?

Sudden cardiac arrest--it's not just an EMS thing anymore. As AEDs have proliferated in public places and become ever-easier to use, minimally trained laypersons have assumed the job of defibrillating many victims of SCA. Now, as the devices make their way into private homes, spouses and children will begin serving as de facto first responders when their loved ones start arresting. By most people's accounts, this is a good thing. But what does it mean for EMS?

A Safety Device

The latest turn on the AED's road to ubiquity was a landmark decision last fall by the U.S. Food and Drug Administration (FDA). Following a July recommendation from its Circulatory Systems Devices Panel, the FDA approved Philips' HeartStart Home Defibrillator for over-the-counter sales without the prescription previously required. Anyone can buy one now, which likely means the home HeartStart will begin penetrating private residences in what could be significant numbers.

Most people will tell you this is great news.

"The majority of people who suffer sudden cardiac arrest have no previously recognized symptoms, and less than 5% survive, largely because a defibrillator doesn't arrive in time," says Wendy Katzman, business director for Philips' HeartStart Home Defibrillator efforts. "Yet when you look at the literature on public-access defibrillation, when you can defibrillate quickly, the survival rate goes up."

Time is the most significant factor in treating SCA, which claims an estimated 340,000 Americans a year. And AEDs are an effective answer for ventricular fibrillation (VF), the most common type of SCA. If a shock is delivered within the first five minutes following an arrest, the victim's chances of survival are roughly 50-50. With each additional minute that passes, those odds decrease by 10%. After nine minutes--not an uncommon time frame for the arrival of EMS in some locales--there's just a 10% likelihood of living.

This is why, as Katzman notes, public-access defibrillation programs work: Having the devices available immediately, rather than waiting even a few minutes for EMS to arrive, reduces the victim's time to shock, thus increasing their odds of survival.

Scientific literature indicates fairly strongly that PAD programs decrease mortality. Most recently, the results of the well-known Public Access Defibrillation Trial conducted from 2000--2002, featured in the August 2004 New England Journal of Medicine, showed a higher rate of survival to hospital discharge among victims of witnessed public arrests treated with CPR and AEDs than among those treated with CPR alone. In an Italian study from 2002, SCA survival improved from 2.9% when the victim waited for EMS intervention to 11.1% when trained laypersons utilized AEDs instead. Other examples abound, and the wide consensus is that shortening the time to defibrillation through the wide availability of AEDs can only help SCA victims.

"The benefits are enormous," concluded PAD researchers from the Medical College of Wisconsin in a study published in 2002. "Reported VF survival rates can approach 50% or higher...PAD provides the potential opportunity to transform cardiac arrest into a survivable event for most victims by making the community the ultimate coronary care unit."

So, if it works that well in the public environment, how can it not save lives in private homes, where up to 80% of SCAs occur?

"We know that immediate defibrillation saves lives," says Mary Newman, executive director of the National Center for Early Defibrillation at the University of Pittsburgh. "Basically, we consider an AED a safety device, like a smoke alarm, and we believe Americans ought to be able to buy safety devices for their homes."

"It's Not the Box on the Wall..."

Not so fast, say some.

"Data are limited on the number of times a cardiac arrest in the home is witnessed and who is most at risk," the American Heart Association (AHA) warned in a statement following the FDA's decision. "In the absence of scientific evidence of effectiveness, the American Heart Association cannot recommend broad adoption of the home use of AEDs."