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'Silent' Heart Arrhythmias More Common Than Thought

Researchers say anticoagulant therapy should be continued

WEDNESDAY, Jan. 7, 2004 (HealthDayNews) -- Episodes of atrial fibrillation, a dangerous heart condition found in 2 million Americans, are more common than experts thought in patients for whom drugs seemed to correct the problem.

Drug treatment with warfarin, an anticoagulant, should be continued in these patients who have these so-called "silent" episodes of atrial fibrillation, conclude a team of German researchers who report their finding in the Jan. 7 issue of the Journal of the American College of Cardiology.

The researchers recommend that doctors continue treatment with warfarin (known under the brand name Coumadin) even if patients appear to be free of heart rhythm problems for more than three months. Standard practice is to treat episodes of atrial fibrillation with rhythm-correcting drugs and with anticoagulants -- usually warfarin -- and to halt the therapy when a patient has not had a repeat occurrence of atrial fibrillation for three months.

In atrial fibrillation, the heart's two small upper chambers, called the atria, quiver instead of beating effectively. The blood isn't pumped completely out of the chambers and may pool and clot, and if a piece of the clot travels to an artery in the brain, a stroke results.

In the German study, researchers followed 110 patients with the condition who had implantable pacemakers that recorded their heart rhythms constantly. They found that 38 percent of those who did not report any symptoms of atrial fibrillation (which can include an irregular or rapid heartbeat felt by the patient) actually had a recurrence of atrial fibrillation lasting longer than 48 hours.

This so-called silent fibrillation should be treated, according to the researchers, if the patient has one other risk factor for stroke, such as high blood pressure, diabetes or advanced age.

The new study confirms what several previous studies have also suggested, according to an expert who co-authored an editorial accompanying the study. "This is one of several recent studies suggesting that patients put on anti-arrhythmia drugs who their doctors think are OK have 'silent' episodes of atrial fibrillation," says Dr. Albert L. Waldo, the Walter H. Pritchard professor of cardiology and professor of medicine at Case Western University in Cleveland.

"With silent episodes of atrial fibrillation, the risk of stroke returns," Waldo adds.

Warfarin is not an easy drug to stay on, he notes, because it interacts with foods and medications such as antibiotics. It's also difficult to keep the blood level of warfarin steady enough to be constantly effective, Waldo says.

But he and other experts expect a new medication to be approved soon by the U.S. Food and Drug Administration that will do the same job as warfarin but be easier to take.

Meanwhile, even with its downsides, "warfarin is very, very effective," Waldo says. "It impacts the risk of stroke." Patients on it must be monitored closely by their doctors, he emphasizes.

Waldo offers this advice for patients: "If they have a history of atrial fibrillation and are at risk for stroke, they need to take an anticoagulant."

More information

To learn more about atrial fibrillation, click on the American Heart Association. For frequently asked questions about the condition, go to the British Heart Foundation.

SOURCES: Albert L. Waldo, M.D., professor, cardiology and medicine, Case Western Reserve University, Cleveland; Jan. 7, 2004, Journal of the American College of Cardiology
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