Combating arrhythmia by controlling heart rate

Many people with a common heart rhythm abnormality may not be getting the most effective treatment.

The first step in treating atrial fibrillation, especially among elderly patients, should be controlling the rate at which the heart beats, rather than trying to correct the rhythm, a large comparison study has concluded.

Patients getting either treatment felt better, but those given rhythm-correcting medications or a heart-shocking procedure called cardioversion had more hospitalizations and medication side effects than those taking drugs to control their heart rate, researchers found.

The study of 4,060 U.S. and Canadian patients, published in the Dec. 5 issue of the New England Journal of Medicine, along with a smaller European study in the same issue, is likely to change the way doctors treat atrial fibrillation, which affects 2.3 million Americans and is expected to affect as many as 6 million by 2040 as the baby boomers age.

“In older folks, I think a lot more of them are going to get rate control,” said Dr. D. George Wyse, a cardiology professor at the University of Calgary in Canada.

With atrial fibrillation, the upper chambers of the heart, called the atria, contract so quickly that they quiver. As a result, they don’t pump blood properly into the lower chambers, called the ventricles. The heartbeat becomes erratic and blood flow can become stagnant, increasing the risk that clots will form and travel to the brain, resulting in a stroke. Although some patients report no symptoms, others experience heart palpitations, shortness of breath and dizziness.

The problem is chronic; even when fibrillation is brought under control, “it’s going to come back,” Wyse said.

The new data finally give doctors information upon which to base their treatment decisions, which changed with the arrival of anti-arrhythmia drugs in the late 1970s and 1980s. For the first time, there were drugs “that had a reasonable chance of getting you back into a normal rhythm,” Wyse said. Consequently, most doctors moved away from the older strategy of going after the heart rate with drugs such as digitalis, beta blockers and calcium channel blockers.

“This is a back-to-the-future story, a less-is-more story,” said Wyse, who chaired the steering committee for the study, called Atrial Fibrillation Follow-up Investigation of Rhythm Management, sponsored by the National Heart, Lung and Blood Institute of the National Institutes of Health. With the anti-arrhythmic drugs, “everybody just assumed there were a lot of advantages; if you were in a normal rhythm, you’d feel better.”

But the reality was that the newer drugs, such as amiodarone, which can cause a potentially fatal condition called pulmonary fibrosis, were tough on patients, and many of them still had recurrences of their fibrillation.

The study also demonstrated the importance of patients with the rhythm disorder taking an anticoagulant, such as warfarin. Although rhythm control treatments were supposed to let patients stop taking warfarin, Wyse said, “what we found is you can’t stop warfarin: Most strokes in both groups occur when they stop the warfarin or when the dose is too low.”