TUESDAY, Jan. 6 (HealthDay News) -- Implanted cardioverter defibrillators (ICDs), which deliver an electric shock to prevent sudden death when a heart stops beating properly, improve survival in people 75 and older, new research suggests.

The finding contradicts several earlier studies, notably a 2007 report from Canada that said the benefits of ICDs were limited for older people.

"Their discussion looked at defibrillators in patients who were older and sicker," said Dr. Paul Chan, an assistant professor of medicine at the University of Missouri in Kansas City, and lead author of the new report. "It found use of defibrillators was limited, because they were more likely to die. But there was no control group, no comparison with a group of similar patients who did not get defibrillators."

The new study did have such a control group. It looked at results for 500 people who got ICDs because their left ventricles, which pump blood to the body, were functioning at no more than 35 percent of capacity. The study compared those results to those for a similar number of people with the same condition who did not get ICDs.

"We found that older people were more likely to die," Chan said, "but in this older group of patients, we still found they got a benefit from the defibrillator, similar to that seen in the other age groups."

Over the course of the six-year study, the overall death rate was 26.7 percent for the non-ICD group and 21.6 percent for the ICD group. This 30 percent reduction in deaths was the same for people 75 and older as well as younger recipients.

The results, published in the Jan. 7 issue of the journal Circulation: Cardiovascular Quality and Outcomes , indicate that "we shouldn't be denying defibrillators that may be life-saving specifically because of age," Chan said.

He acknowledged that the finding "needs to be validated in other studies with larger populations."

Another factor that must be considered is whether the potential recipient has already experienced a life-threatening heart arrhythmia (irregular heartbeat) or similar event, said Dr. Gordon F. Tomaselli, a professor of medicine at Johns Hopkins University School of Medicine, and a spokesman for the American Heart Association.

"If there has been a life-threatening arrhythmia, and the patient is otherwise healthy, I would be much more inclined to recommend a defibrillator," Tomaselli said. "For primary prevention, when no such event has yet occurred, I would be a lot more cautious about people in their eighth and ninth decades of life, and would carefully consider their comorbidities (more than one illness)".

"Age and comorbidities are the key factors I consider when a patient might require a defibrillator," he said.

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• Arrhythmia
• Pacemakers and Implantable Defibrillators
• Seniors' Health