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Heart Disease Health Center

Pacemaker Study Stopped for Safety

Patients with Implanted Defibrillators Should Have Older-Style Pacemaker
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Dec. 20, 2002 -- Most heart patients who receive implantable defibrillators now also have their heart rhythms regulated with a pacemaker, but a new study finds that depending on the type of pacemaker, it might cause a worse effect on the heart with increased hospitalization, worsening heart failure, and death.

While no one questions the value of defibrillators like the one Vice President Dick Cheney received last year for patients with dangerously fast heart rhythms, the new research suggests that pacing the rhythm of two chambers of the heart instead of one is not needed in the vast majority of patients.

Researchers at the Cleveland Clinic stopped their study of these newer dual-chamber pacemaker-defibrillators early after determining that patients were dying much faster than those with the older single-chamber pacemakers. This newer type of pacemaker stimulates both chambers of the heart to not only fill the heart but pump blood out. A single-chamber pacemaker only stimulates the chamber that pumps blood out.

Their findings are published in the Dec. 25 issue of the Journal of the American Medical Association.

The study's lead researcher says patients who have the newer dual-chamber pacemaker-defibrillators should talk to their doctor about reprogramming the device so that the pacemaker function does not stimulate both chambers.

Bruce Wilkoff, MD, tells WebMD that fewer than 20% of patients who need defibrillators for irregular heart rhythms actually need pacemakers, which are primarily used to treat patients with slow heartbeats. Defibrillators sense abnormal heart rhythms and deliver an electric shock when such rhythms are determined to be dangerous. Dual-chamber pacemakers supply electrical impulses to both the upper and lower chambers of the heart.

"This year there were between 80,000 and 100,000 defibrillators implanted worldwide, and up to three-fourths of them were the dual-chamber devices and most are being programmed to the dual-pacing mode," he says.

The Cleveland Clinic study included 506 patients with heart disease or previous heart attacks who received the dual-chamber defibrillator-pacemakers. Half were programmed to stimulate the heart to pump at a rate of 70 beats per minute, and the other were programmed to have the pacemaker activated if the pumping capacity of the heart fell below 40 beats per minute, similar to a backup system for the pumping function of the heart should it fail.

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