Evaluation Of The Two Types Of Cardiac Pacemakers Indicates Only Modest Differences In Value

April 16, 1998

Implanted cardiac pacemakers have been used to treat people with slow heart rates for more than two decades. But until recently there had never been a comprehensive evaluation made of the quality of life associated with the two different forms of the therapy.

As a result, discretion on which to use has been left to individual institutions or physicians.

Now, in the April 16 issue of The New England Journal of Medicine, researchers representing 10 different institutions report the results of a large-scale, multi-institutional clinical trial assessing the relative merits of the two forms of treatment--the single chamber (ventricular) pacemaker and the dual chamber (ventricular and atrial) pacemaker. Lee Goldman, MD, UCSF professor of medicine and chairman of the Department of Medicine, was the senior author of the study, which was led by Gervasio A. Lamas, MD, chief of the Division of Cardiology at Mount Sinai Medical Center in Miami Beach, Fla., and the University of Miami.

Not surprisingly, the researchers say, both pacemakers dramatically improved the health-related quality of life of patients. Unexpectedly, however, the researchers also determined that the slightly higher quality of life traditionally associated with dual chamber pacing was detectable only in a group of patients with a heart condition known as sinus node dysfunction. "Our study shows that both types of pacemaker make people feel much better," said Goldman. "And, when there are quality of life benefits from the more complicated dual chamber pacemakers, they are seen only in people with sinus node dysfunction. And even there, the degree of improvement is considerably more modest than we had expected."

In the study, 407 patients aged 65 and older and 60 percent male, were assessed for health-related quality of life, as measured by social function, physical ability, emotional mental health and energy, cardiac functional status and long-term cardiac function.

The researchers did see better long-term cardiac functional status in patients with dual chamber pacemakers, but this observation, they say, demonstrates the complexities inherent in measuring quality of life in the elderly. "While it is clear from our results that dual chamber pacing is associated with long-term improvements in cardiovascular function of over time," said Goldman, "aging and the development or worsening of other diseases may overwhelm the modest improvements in cardiovascular functional class and minimize the long-term effect on generic quality of life."

The pacemakers have traditionally been associated with different advantages. The single chamber ventricular pacemaker is less expensive, easier to implant, and has a longer service life than the dual chamber pacemaker; most important, there often are fewer complications associated with the pacemaker itself. Dual chamber pacemakers, on the other hand, offer the theoretical benefit of mimicking the normal electrical sequence of the heart, pacing the atrium first and the ventricular chamber second.

"The question," said Goldman, "has been whether the benefit of the dual chamber pacemaker in terms of heart function and other complications warrants the extra difficulty in placement, shorter battery life and potential risk of complications for the pacemaker itself, as well as the extra cost. The answer seems to be that in many cases it is not."

The 29-center study, called the Pacemaker Selection in the Elderly Trial, involved patients diagnosed with either sinus node dysfunction, a condition in which the heart beat is not initiated at the appropriate rate, or atrial-ventricular block, in which the heart beat is initiated at the appropriate rate but does not make it through the electrical system. Patients were assessed at three, nine and 18 months after enrollment in the study.
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University of California - San Francisco

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