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Right ventricular pacing triggers heart failure: pacemaker users had 44% higher rate of HF death, hospitalization.

PHILADELPHIA -- Single-chamber right ventricular pacing may be producing many new cases of heart failure by causing ventricular dyssynchrony.

New evidence for this hypothesis came from a study with more than 23,000 paced patients and controls, showing that patients with pacemakers were 44% more likely to have heart failure (HF) death or hospitalization than matched patients without pacemakers, Ronald Freudenberger, M.D., reported at the annual meeting of the International Society for Heart and Lung Transplantation.

"This is the first population-based study to show that right ventricular pacing in patients without heart failure is bad," said Dr. Freudenberger, director of the heart failure and transplant cardiology program at Robert Wood Johnson Medical School in New Brunswick, N.J. A link between single-chamber pacing and HF also has been noted in several recent intervention studies.

"The way we've practiced cardiac pacing for the last 3 decades must be abandoned," said Michael O. Sweeney, M.D., director of cardiac pacing and implantable-device therapies at Brigham and Women's Hospital, Boston.

Although Dr. Freudenberger stressed that his findings do not prove that single-chamber pacing causes HF, the results are suggestive enough that physicians should immediately minimize their use of single-chamber right ventricular pacing as much as possible. One way is to set pacing rates so that patients are paced only when their heart rates make pacing necessary, he told this newspaper.

It's also possible that right-atrial pacing may avoid producing the dyssynchrony and QRS-interval widening that is probably causing HF in patients who have right ventricular pacing. But superior safety of right-atrial pacing must still be proven in prospective studies.

One such study, led by Dr. Sweeney, is testing "the first new mode of cardiac pacing in 35 years," using a device that provides "managed ventricular pacing." This device can produce dual- or single-chamber pacing, depending on conduction activity. When normal conduction is present, it automatically switches to pacing the right atrium only, minimizing right ventricular pacing. The study, being done at about 100 centers in the United States, Canada, and Europe, is on track to finish enrollment this year and produce results in 2007, Dr. Sweeney told this newspaper.

The case-control study involved more than 3 million patients discharged alive from 85 acute-care hospitals in New Jersey during 1997-1999. Records for these patients were in the Myocardial Infarction Data Acquisition System. There were 11,426 patients who had received pacemakers for the first time and had no record of HF either at the time of pacemaker implantation or in the prior year. A group of 11,656 control patients without pacemakers or HF were selected from the same database. The two groups were matched by demographic and clinical measures including age, sex, and history of MI, hypertension, and diabetes.

Subsequent records for these patients were reviewed at a median follow-up of 33 months to determine the incidence of HF death and hospitalization.

In a multivariate analysis controlling for known variables, patients with a pacemaker had a 44% increased risk of subsequent HF hospitalization or HF death, compared with controls. Patients with a single-chamber pacemaker had a 59% increased risk of HF hospitalization of HF death. Patients with a dual-chamber pacemaker had a 36% increased risk of these outcomes, suggesting that pacing both the right atrium and ventricle may be less hazardous than pacing the right ventricle alone.

Another possible interpretation is that the findings simply show that patients who require pacing have worse outcomes than patients who don't, with no causal link between pacing and the subsequent development of heart failure, said Mariell Jessup, M.D., medical director of the heart failure and cardiac transplantation program at the University of Pennsylvania, Philadelphia.

This probably does not explain the findings, because control patients were carefully matched for other HF risk factors, such as coronary artery disease, hypertension, and diabetes, Dr. Freudenberger said. The main difference between the two study groups was the use of pacing. This, plus the long follow-up and the large number of patients, makes it more likely that the association is real, he said.

BY MITCHEL L. ZOLER

Philadelphia Bureau
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Title Annotation:Cardiovascular Medicine
Author:Zoler, Mitchel L.
Publication:Internal Medicine News
Geographic Code:1USA
Date:Jul 1, 2005
Words:679
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