WEDNESDAY, Dec. 4, 2002 (HealthDayNews) -- When the heart develops an abnormal and potentially dangerous rhythm, it seems logical that treatment should concentrate on restoring the normal heartbeat.
Not so, say two new major studies, one here and one in Europe. For many patients, it's better to focus on the rate at which the heart beats.
Atrial fibrillation is a condition that affects an estimated 2 million Americans. It occurs when the upper chambers of the heart -- called the atria -- begin to flutter rather than beat rhythmically. It's the most common heart rhythm abnormality, and its incidence increases with age, so that it occurs in at least 6 percent of people 80 and older.
The studies found that overly aggressive efforts to restore the normal rhythm of the atria can sometimes be damaging, and even fatal.
The American AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management) study enrolled 4,060 patients, whose average age was just under 70. The death rate for those given rhythm-control medication was 23.8 percent, compared to 21.3 percent for those given medication aimed at controlling the rate at which the ventricles, the lower chambers of the heart, beat, says a report in tomorrow's issue of The New England Journal of Medicine.
"More patients in the rhythm-control group than in the rate-control group were hospitalized, and there were more adverse drug affects in the rhythm-control group as well," the journal report says.
The European study got comparable results for the 522 patients it enrolled. "Rate control is not inferior to rhythm control for the prevention of death and mortality," says a report in the same issue of the journal.
The two studies will go a long way toward settling "a controversy about how aggressive one should be in trying to maintain regular rhythm," says Dr. Robert O. Bonow, a professor of medicine at Northwestern University and president of the American Heart Association.
As Bonow interprets the studies, a cardiologist should still make an initial effort to restore normal atrial rhythm. If that doesn't work, the next treatment for patients with no underlying condition, such as valve disease or heart failure, would be "a simple approach to restoring normal heart rate," he says.
The problem with an aggressive effort that concentrates on atrial rhythm is that many of the drugs used for that purpose can have serious side effects, says Dr. Rodney H. Falk, a professor of medicine at Boston University School of Medicine and author of an accompanying editorial in the journal.
"In some cases they can cause weakness of the heart muscle, and in a small percentage of cases they can provoke a rhythm disturbance in the ventricle, so there is a small chance that they might kill the patient," Falk says.
Medications designed to restore the normal rate of beating of the ventricles, which can go over 100 beats a minute because of atrial fibrillation, have fewer side effects and are easier to manage, Falk and Bonow say.
"In many cases, it appears that slowing the heart rate may be the only thing needed, in terms of short-term and medium-term outcome," Falk says.
One more lesson to be taken from the U.S. study concerns an entirely different class of drugs -- anticoagulants, given to prevent blood clots that can block an artery to the brain, causing a stroke.
Atrial fibrillation can cause blood to pool in the heart, increasing the risk of such a clot, and doctors routinely prescribe anticoagulants to prevent that from happening.
However, the study showed that anticoagulant therapy often is not administered long enough, Falk says. In both groups of patients -- those given treatment for rhythm control and those treated for rate control -- most of the strokes occurred after the patients left the hospital, when anticoagulant treatment was stopped, the study found.
"There was a tendency to stop anticoagulant treatment too soon," Falk says. "This shows it needs to be continued longer than previously thought."
What To Do
A primer on atrial fibrillation is offered by the American Heart Association. For more on anticoagulant therapy, visit the European Stroke Initiative.
