ORLANDO, FLA. - Duke University Medical Center cardiologists have shown that patients with an abnormal heart rhythm known as atrial fibrillation, and who also have congestive heart failure (CHF), have similar mortality rates when treated with drugs that control the heart's rhythm compared to treatment with drugs that control the heart's rate.
The findings, which support the results of an earlier study, are important because the use of drugs to restore the heart's normal rhythm has been on the increase over the past decade, despite the fact these drugs have more negative side effects than those controlling the heart's rate, the researchers said. They added that further prospective studies should be conducted to weigh the mortality and quality-of-life issues for each of the two strategies for patients with atrial fibrillation and CHF.
Duke cardiologist Sana Al-Khatib, M.D., presented the results of the Duke analysis today (Nov. 10, 2003) at the 76th annual scientific sessions of the American Heart Association.
In atrial fibrillation the upper chambers of the heart, known as the atria, contract extremely rapidly. This causes the pumping chambers of the heart, the ventricles, to pump erratically and inefficiently. The other condition, CHF, is marked by the inability of the heart muscle to pump enough oxygen and nutrients to the body's tissues. Once diagnosed with CHF, about 50 percent of patients die within five years.
For patients with atrial fibrillation, physicians can control the rate of ventricular contraction with drugs such as digoxin or beta-blockers. In contrast, the rhythm strategy tries to correct underlying electrical abnormalities either by electric shock (electrical cardioversion) and/or with drugs (pharmacologic cardioversion) such as amiodarone or sotalol. Many atrial fibrillation patients also receive the blood-thinning agent coumadin, since they are at a high risk of developing clots that can lead to a stroke.
The results of the Duke study confirmed a recently completed trial of more than 4,000 patients treated at 213 sites in the U.S. and Canada. Dubbed AFFIRM (Atrial Fibrillation Follow-up Investigation of Rhythm Management), that National Institutes of Health-funded study found that rhythm control is not associated with improved survival when compared to rate control, although it had higher rates of drug-related side effects.
"However, AFFIRM did not definitively address the important issue of how these two strategies affect the outcome of patients who have CHF as well as atrial fibrillation," said Al-Khatib, a member of the Duke Clinical Research Institute. "This is an important subgroup of patients since CHF puts them at a higher risk of dying and having a stroke.
"Only 23 percent of patients enrolled in AFFIRM had a history of CHF," Al-Khatib continued. "Thus it was not determined whether rhythm-control therapy is superior to rate-control therapy for this group of patients."
Al-Khatib examined clinical records on all the patients entered into the Duke Cardiovascular Disease Databank with atrial fibrillation and CHF since 1995 to determine whether there was any difference in outcomes. The Duke database has collected long-term clinical data on every patient who has received a cardiac catheterization procedure at Duke since 1969.
Al-Khatib's search identified 1,009 patients who had CHF, a weakened pumping chamber and a history of atrial fibrillation. Forty-nine percent of these patients received an anti-arrhythmic medication. They tended to be younger and less likely to have advanced coronary artery disease. Interestingly, Al-Khatib also found that the use of anti-arrhythmic medications increased from 30.3 percent in 1995 to 67.5 percent in 2002.
"While our data show the use of anti-arrhythmic drugs becoming more widespread, there remains some controversy over the best way to medically treat atrial fibrillation," Al-Khatib said. "When we adjusted for the baseline variables, we found no difference in survival between the two strategies."
Al-Khatib said that while there haven't been any large randomized trials that could settle the rhythm vs. rate control debate in patients with CHF, an ongoing clinical trial could provide the definitive answer.
The Atrial Fibrillation and Congestive Heart Failure (AF-CHF) trial plans to enroll 1,450 patients at more than 100 centers in the U.S., Canada, South American and Europe. The trial, being run by the Cardiology Institute of Montreal, will compare mortality rates for the two approaches.
"Finding answers to these questions will become increasingly important because with the aging of the American population, clinicians will see more patients with atrial fibrillation," Al-Khatib said. "We not only want to be able to improve the life expectancy for these patients, but also to take into account their quality of life."
Al-Khatib's analysis was funded by a peer-reviewed grant from the GlaxoSmithKline Research and Education Foundation for Cardiovascular Disease.
Duke colleagues in the study were Linda Shaw, MS Monica Shah, M.D., Christopher O'Connor, M.D., and Robert Califf, M.D.