BOSTON - Implanted defibrillators that zap the heart out of cardiac arrest could cut the risk of death in half for 65,000 Americans who survive heart attacks each year, a study suggests.
Last May, the U.S. Food and Drug Administration greatly expanded the recommended use of battery-powered implanted defibrillators. The details of the study that persuaded the agency to make this change were published in Thursday's New England Journal of Medicine.
Critics of the study that was funded by a defibrillator manufacturer said the device should be used only by heart attack survivors at the highest risk of death from cardiac arrest.
Dr. Arthur J. Moss and colleagues from the University of Rochester Medical Center estimate that perhaps 5 percent of the 1.3 million U.S. heart attack survivors annually could substantially improve their chance of avoiding death from cardiac arrest if they received the defibrillators.
They calculate that if all 65,000 potential defibrillator patients actually got them, they could stop about 9,000 deaths over the following two years.
Implanted defibrillators - like the external ones that are used so often on TV hospital shows - shock the heart back into normal rhythm during cardiac arrest. The implanted versions are about the size of a cassette tape and automatically fire whenever they detect dangerously abnormal heartbeats.
The devices were previously approved for patients who had survived at least one cardiac arrest or had recurring rapid heartbeat that did not respond to medical therapy. Now, however, the devices are recommended for a much larger group - patients who have survived heart attacks but have no symptoms other than erratic heart rhythms that show up on electrocardiograms.
Moss' team tested the defibrillators on 196 heart attack survivors. Among those getting defibrillators, 15 died during two years of follow up, 11 of them from cardiac causes. By comparison, 39 patients who did not get the devices died during the same period, 27 of them from their heart conditions. From this, the researchers concluded that the devices cut the risk of death in half for these patients.
The study was financed by CPI/Guidant Corp. of St. Paul, Minn., which makes the device tested.
However, a skeptically worded editorial in the journal by Drs. Peter L. Friedman and William G. Stevenson of Brigham and Women's Hospital in Boston questioned whether the study's seemingly impressive results should be believed.
The critics noted that about 10 percent of the patients were receiving drugs that could have triggered their cardiac arrests. They said the drugs, not the defibrillators, could have accounted for the difference in survival between the two groups.
Moss countered that both those who received defibrillators and those who did not received the drugs, so they are unlikely to have influenced the results.
"That didn't make any sense to me at all," he said.
The editorial also questioned the cost of such wide use of the devices. The doctors calculate that even if only 16,000 patients actually got them, that would cost more than $1 billion annually - or more than $60,000 per patient.
Moss countered that if the defibrillators became so widely used, the cost would surely come down.
"Our job is not to try to save costs for insurance companies," Moss said.
The editorial writers recommended that the devices be reserved "for a carefully selected subgroup" of heart attack survivors who are at highest risk of dying from cardiac arrest.