The new, automated heart-shocking devices saved nearly half of all victims in the two studies. That is 10 times the usual survival rate of 5 percent for people who suffer cardiac arrest outside a hospital.
"These articles prove minimal training is enough to step in and save someone's life," said Dr. Michael A. Jaker, director of emergency medicine at the University of Medicine and Dentistry of New Jersey in Newark.
About 250,000 Americans die each year of cardiac arrest, which is usually caused by a heart rhythm disturbance called ventricular fibrillation. For each minute that passes without a defibrillator shocking the heart back into a normal rhythm, the chance of surviving drops 10 percent.
Despite that, many police and fire department vehicles, ambulances and nursing homes are not equipped with the laptop-size devices, which give an EKG readout just like a hospital monitor and tell the operator whether the person needs a shock, how to apply the pads and when to press the button.
The devices are so simple to use that an earlier study of simulated cardiac arrest cases found that sixth-graders, once trained, needed only 27 seconds more than paramedics to accomplish defibrillation.
With wider use of such defibrillators, "it should certainly be possible for us to improve survival rates across the country to 20 to 30 percent," said Dr. Rose Marie Robertson, president of the American Heart Association. "That would save 50,000 lives a year."
The two new studies appear in Thursday's issue of the New England Journal of Medicine.
In one, defibrillator-trained security guards at 32 Nevada and Mississippi casinos places that attract lots of senior citizens tried to save patrons whose hearts and breathing had stopped.
In the 90 cases where ventricular fibrillation was to blame and the patients' collapse was witnessed so personnel could determine how long it took until they were shocked, 59 percent were resuscitated and survived to go home from the hospital.
Seventy-four percent of those shocked within three minutes survived, compared with 49 percent of those who had to wait longer, said Dr. Terence D. Valenzuela, a professor of emergency medicine at the University of Arizona who led the study.
In the other study, researchers examined the use of defibrillators from 1997 through 1999 by American Airlines, the first airline to put the devices, and attendants trained to use them, on every flight.
In 13 cases where the device indicated a passenger was in ventricular fibrillation and the person was shocked, every one was resuscitated. Forty percent survived to leave the hospital later.
The device never incorrectly indicated someone should be shocked, aid Dr. Richard L. Page, an associate professor of internal medicine at University of Texas Southwestern Medical Center, who led the study.
In any case, he said, shocking a patient who is not in ventricular defibrillation generally causes no harm.
In dozens of other cases, the defibrillator helped volunteer doctors on a flight monitor the condition of fellow passengers with other heart or breathing problems, sometimes averting costly flight diversions.
Nearly all large casinos are now equipped with defibrillators and most major airlines have them on all flights or plan to do so, according to associations representing those industries.
The heart association last year started a campaign to make the defibrillators more widely available and already has about 100 communities working on getting the devices and trained operators in malls, stadiums, offices, retirement villages, airports, theme parks and other busy places. The devices cost about $3,000 but will probably get cheaper.
"It doesn't sound like much to save someone's life," Jaker said.
Page said airlines should weigh the cost against that of a lawsuit for not having a defibrillator aboard a flight where a passenger died of cardiac arrest.