CALGARY, Alberta, Dec. 4 (UPI) -- Medications used to return abnormal heart rhythms back to normal -- the gold standard for treating irregular heartbeat -- might not be as effective as once thought and fail to protect adequately against complications such as stroke, a new study released Wednesday concludes.
Researchers led by Dr. D. George Wyse, chairman of the Atrial Fibrillation Follow-up Investigation of Rhythm Management steering committee and professor of cardiology at the University of Calgary, said the so-called rhythm method, used for the last few decades to treat atrial fibrillation or irregular heartbeat, does not appear to be as effective as it should.
The trial compared the rhythm technique to restore regular heart rhythm, which involves using the drugs amidarone, satolol and propefenone, to an alternative approach called heart rate control strategy, which aims to control the rate of the lower heart chambers or ventricles, while allowing the atria or upper chambers to fluctuate. The heart rate control strategy uses the so-called beta blocking drugs, as well as calcium channel blockers and digitalis.
The study involved 4,060 patients at 213 treatment sites in the United States and Canada between 1995 and 1999. Patients were 65 or older, had hypertension, diabetes or congestive heart failure, all risk factors for stroke. They were assigned randomly to either the rhythm control technique or the heart rate strategy and followed the patients for an average of three-and-a-half years. Both groups also were treated with warfarin, a blood thinner.
Study results showed 365 patients in the rhythm control group died compared to 310 in the heart rate group. There were no differences in rates of stroke between the two groups. Among the rhythm control group, 1,374 were hospitalized compared to 1,220 of the heart rate strategy patients.
Side effects were more common among the rhythm control group, researchers report in the Dec. 5 issue of The New England Journal of Medicine, including abnormally low heart rate and lung problems.
"It challenges the dogma of rhythm control being the way you should treat these patients," Wyse told United Press International. The rhythm control approach "was not based on direct evidence. It was based on the presumption that if you restored normal (heart) rhythm, patients would be better."
Atrial fibrillation occurs when the upper heart chambers or atria become overloaded with electrical activity and fail to contract properly. Patients do not feel this, Wyse explained. The reason there is such a high risk for stroke is when atrial fibrillation occurs, the blood stops flowing properly. This increases the risk for clotting and, consequently, for stroke. At the same time, Wyse said, the lower heart chambers or ventricles can be driven to go faster when the atria gets stuck forcing the ventricles to flutter. Patients then start to feel their heart racing. "That's what makes them feel dizzy and short of breath," Wyse said.
Conventional thinking had been to restore the atria to stop the arrhythmia or irregularity, but Wyse said doctors should focus on controlling the ventricles instead.
"We'll have to wait and see how physicians accept these things," Wyse said.
Dr. Nieca Goldberg, a cardiologist at Lenox Hill Hospital in New York and a spokeswoman for the American Heart Association said these findings dust off old ways of thinking about atrial fibrillation.
"The results of this trial are very interesting and contradict the commonly held theory that rhythm control is better, because of reduced risk of stroke," Goldberg told UPI. "In this study, rate and rhythm control had the same stroke rate."
Goldberg added, "Unfortunately this study also shows that the medications we have for maintaining regular rhythm are ineffective because many of the patients in the rhythm group ended up on medications for rate control because they went back into atrial fibrillation. The most effective way to reduce stroke risk in patients who have atrial fibrillation is to use the blood thinner coumadin with the rate control medications."
The study was funded by National Heart, Lung, and Blood Institute, a division of the U.S. National Institutes of Health.
(Reported by Katrina Woznicki, UPI Science News, in Washington)
