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Drug, Pacemaker Fight Irregular Heartbeat

Studies suggest new weapons against dangerous atrial fibrillation

WEDNESDAY, Sept. 5 (HealthDay News) -- Cardiac researchers say a new drug may help treat the abnormal heartbeat called atrial fibrillation.

The drug, dronedarone, is not yet approved by the U.S. Food and Drug Administration but has proven effective in two major trials, with fewer side effects than existing medications, according to a report in the Sept. 6 issue of the New England Journal of Medicine.

And in the same issue of the journal, researchers say a special pacemaker can help prevent the development of atrial fibrillation in people with sinus-node disease -- a dysfunction of the cardiac region controlling heartbeat.

The American Heart Association estimates that 2.2 million Americans, many of them elderly, have atrial fibrillation, in which the two upper chambers of the heart lose their regular rhythm.

The condition increases the risk of dangerous clots forming as blood pools in the heart. Atrial fibrillation is treated with drugs that prevent clot formation and also with medications that restore the heart's normal rhythm.

The two trials -- which were funded by Sanofi-Aventis, the maker of dronedarone -- included more than 1,200 participants with atrial fibrillation.

In one European trial, the heartbeat remained normal for an average of 96 days in those getting dronedarone, compared to 41 days in those getting a placebo. In the other trial, conducted in the United States and several other countries, the heartbeat remained normal for an average of 158 days for those getting dronaderone and 59 days in those getting placebo.

Most important, the incidence of dangerous side effects -- such as occur with an approved drug, amiodarone -- was low in the dronedarone trial, said lead researcher Dr. Bramah N. Singh, a professor of medicine at the University of California at Los Angeles. Amiodarone can affect the thyroid, liver and lungs.

"Up to this time, there have been no cases of pulmonary fibrosis [associated with dronedarone], which is the most deadly complication that a patient can have," Singh noted.

Because the incidence of pulmonary fibrosis is low, participants in the trials will continue to be monitored for some time, he said. "But the issue can be resolved relatively quickly," Singh said. "There is a morbidity and mortality trial coming close to being completed, with 4,600 patients. We should have results in six to seven months."

It's also necessary to have a direct comparison of dronedarone vs. amiodarone, he said. "They have not been compared directly in the same population." Singh said. "Until that is actually done, we cannot with confidence say that dronedarone is less effective or more effective."

Direct comparison studies are underway, he said, "and those usually are quickly done, in 12 months or so."

The second atrial fibrillation study, done by a group led by Dr. Michael O. Sweeney, an electrophysiologist at Brigham and Women's Hospital in Boston, included 1,065 participants who had pacemakers installed because of sinus-node disease.

Some 10 percent to 15 percent of Americans over 65 have the condition, Sweeney said, and many have been given pacemakers that stimulate regular beating of the heart's chambers.

The idea behind pacemaking is to speed the abnormally slow heartbeat that occurs with sinus-node disease. However, the conventional pacemaker can boost the risk of atrial fibrillation by increasing the heart rate until the chamber flutters, rather than pumping blood, Sweeney explained.

Some participants in the trial got pacemakers that acted on just the ventricles, the lower chambers of the heart. Atrial fibrillation developed in 7.9 percent of them, compared to 12.7 percent of those with conventional pacemakers.

The study was supported by medical device maker Medtronic.

"This is the first time this technology has been validated in a clinical trial," Sweeney said. "Hopefully it will change the approach to sinus-node disease."

The technique can even be applied to people who already have pacemakers implanted, Sweeney said, since those pacemakers can be reprogrammed. "Patients might want to ask their physicians about the management of ventricular pacing," he said.

More information

There's more on atrial fibrillation at the American Heart Association.

SOURCES: Bramah N. Singh, M.D., professor, medicine, University of California at Los Angeles; Michael O. Sweeney, M.D., electrophysiologist, Brigham and Women's Hospital, Boston; Sept. 6, 2007, New England Journal of Medicine

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