A review of safety data raises questions about the reliability of the heart zappers that hang on the walls of airports, shopping malls and health clubs.
Harvard Medical School researchers found that over the past decade, one in five automated external defibrillators were recalled because of the potential for malfunction, and devices that failed were associated with 370 deaths.
Nevertheless, the devices have saved tens of thousands of lives, and the benefits outweigh the risk of malfunctions, said study author Dr. William Maisel.
"The number of malfunctions may be alarming to some, but you have to take it in the context of the large number of patients saved by these devices," he said.
He said the study — the first comprehensive look at safety data on the devices — underscores the importance of properly maintaining the defibrillators.
The American Heart Association estimates that 900 Americans die each day from sudden cardiac arrest. Defibrillators are meant to revive people by delivering a shock that restores a normal heart rhythm. Combined with cardiopulmonary resuscitation, the easy-to-use devices can keep victims alive until emergency crews arrive.
Devices help increase survival
In a 2004 study, the devices helped raise the cardiac arrest survival rate to 23 percent, compared with 14 percent with CPR alone.
Some states have passed laws requiring defibrillators in public buildings, and Congress has approved money for rural communities to buy them. The lunchbox-size devices cost around $700 to $1,200; almost 200,000 are distributed a year.
The study found that most of the recalls were for electrical or software problems. The findings are based reports to the Food and Drug Administration from 1996 through 2005. The FDA issued 52 advisories about automated external defibrillators or crucial components during that period. Those advisories applied to 385,922 devices.
One malfunction report to the FDA read: "While attempting to defibrillate a patient in cardiac arrest, the device made a loud `bang' sound and displayed an error message. The device was then unable to charge or discharge energy."
The study appears in Wednesday's Journal of the American Medical Association.
Regular maintenance, training needed
Schools, casinos and sports arenas are among the places that now have the devices and the responsibility for keeping them in working order.
"I do not feel that AEDs are like fire extinguishers, that you put them out there and then you're done," said Dr. Lance Becker of the University of Pennsylvania and a longtime leader in the American Heart Association. He said businesses that install defibrillators should offer CPR training, maintain the devices and plan drills.
Rob Clark, spokesman for Medtronic Inc., one of the top manufacturers of the devices, said Medtronic tracks all of its devices and sends word of recalls and safety alerts by certified letter, sometimes following up with phone calls and service visits, and reaches well over 90 percent of device owners.
"The thousands of lives these have saved clearly outweigh the small risk in terms of malfunction," Clark said.