WEDNESDAY, Dec. 8, 2004 (HealthDayNews) -- People who've had a heart attack and are at a high risk for irregular heartbeats called arrhythmias may have to wait at least a month before they can get an implantable defibrillator.
That's because a new study failed to find any reduction in overall mortality when these devices were implanted between six days and 40 days after a heart attack.
These findings for early implantation, reported in the Dec. 9 issue of the New England Journal of Medicine, sharply contrast the findings from studies done on later implantation. When these devices are implanted after the heart has had time to heal, the survival benefit is clear.
"Defibrillators are wonderful medical devices, and when used in the right patients they have an indisputable survival benefit," said Dr. Sandeep Jauhar, director of the heart failure program at Long Island Jewish Medical Center in New Hyde Park, N.Y.
"In this group, where the heart is not yet healed, there appeared to be no survival benefit for ICDs," said Jauhar, who wrote an editorial accompanying the study.
ICD is short for implantable cardioverter defibrillator. These devices, which are about the size of a pager, constantly monitor the heart's rhythm. If an abnormal heart rhythm is detected, the device sends a shock to the heart to restore a normal rhythm. Vice President Dick Cheney had well-publicized surgery to receive an ICD in 2001.
Because previous trials have looked at ICD use months and sometimes even years after a heart attack, the current study was designed to see if people who had just had a heart attack and were at risk for arrhythmias could benefit from this therapy.
Three-hundred-thirty two people who received ICDs between six days and 40 days after having a heart attack were compared to a control group of 342 people who had just had heart attacks but did not receive ICDs.
While the study participants were randomized into either the treatment or control group, the study was not blinded, so both the doctors and the participants knew who had which treatment.
The researchers followed the volunteers for up to four years, with an average follow-up time of 30 months. During that time, 120 people died. Sixty-two were from the ICD group and 58 were from the control group.
Twelve people in the ICD group died from arrhythmias compared to 29 in the control group. However, 50 people in the ICD group died from other causes, while only 29 from the control group did.
"Although ICD therapy was associated with a reduction in the rate of death due to arrhythmia, that was offset by an increase in the rate of death from nonarrhythmic causes," wrote the authors.
"If by preventing one type of cardiac death you leave the patient alive and he or she is still sick, they can die of another cause. That seemed to be the case here, at least at first glance," said Dr. James Reiffel, a cardiologist at New York-Presbyterian Hospital/Columbia Medical Center in New York, N.Y.
Reiffel pointed out the authors' acknowledgement that the control group was more likely to receive treatment with an antiarrhythmic medication called amiodarone. The authors believe the use of this medication didn't affect the study results, but Reiffel said it makes him wonder what other treatment differences there were between the two groups.
"The data that's missing in this trial is any differences in the way the patients may have been treated. Patients on higher doses of beta blockers and ACE inhibitors may do better," he said, adding that since the study wasn't blinded, doctors may have given patients who didn't receive an ICD more medication.
Reiffel said the standard of care now is to wait at least a month after a heart attack before implanting a defibrillator, but he said this can be very frustrating for patients who then have to come back to the hospital to have the surgery. That's why, he said, doctors had hoped this trial would show an early benefit.
"This study doesn't change what we do," he said, adding that even if a patient wanted to have the surgery earlier, insurance companies won't reimburse for the cost until a month has passed after a heart attack.
To learn more about implantable cardioverter defibrillators, go to the U.S. Food and Drug Administration.