Reducing the risks of atrial fibrillation in patients with heart failure

Encouraging results from a study conducted by the Montreal Heart Institute (MHI) and recently published in the peer-reviewed journal Circulation, showed that enalapril, a drug used to treat hypertension and heart failure, markedly reduces the risk of developing atrial fibrillation in patients suffering from heart failure. Atrial fibrillation increases the risk of cardiovascular hospitalization and death by 76 percent for patients suffering from congestive heart failure.

Researchers at the MHI found that enalapril is associated with a 77.8 per cent relative risk reduction of developing atrial fibrillation compared to placebo.

“Our study brings to light a new and additional benefit of enalapril, an ACE inhibitor, in patients with heart failure – the prevention of atrial fibrillation. With over 200,000 people in Canada suffering from atrial fibrillation and the devastating health risks posed by this condition for patients with heart failure, it is very good news,” said Dr. Anique Ducharme, joint principal investigator and director of the Heart Failure Clinic at the Montreal Heart Institute.

Atrial fibrillation is caused when the upper chambers of the heart (the atria) start quivering instead of beating. This quivering occurs when the electrical activity in the atria is totally disorganized and very rapid, resulting in 350 to 600 contractions per minute as opposed to 60 to 80 per minute, the normal heart rhythm. In patients with congestive heart failure, this type of fibrillation can be deadly. Heart failure promotes the occurrence of atrial fibrillation and gets worse as the heart failure condition becomes increasingly severe.

The MHI study involved 374 patients who had previously been enrolled in the Study On Left Ventricular Dysfunction trials (SOLVD), a randomized, double-blind, placebo controlled study. The purpose of this trial was to determine the effect of enalapril (an angiotensin-converting enzyme inhibitor ACEi) on the survival of patients presenting left ventricular dysfunction. Of these 374 patients, 156 received enalapril and 188 a placebo. The patients were followed during an average of 2.9 years. A total of 1491 electro-cardiograms were examined by a single cardiologist, who was not informed of which patients had received enalapril or the placebo. The objective was to determine if there was a difference between the two groups of patients in terms of developing atrial fibrillation.

Study results showed that out of all patients tested, 55 of them had one or more episodes of atrial fibrillation during the 2.9 year follow-up period. Only ten (or 5.4 per cent) of those being treated with enalapril had a fibrillation episode compared to 45 (or 24%) patients in the placebo group.

“This study is significant as it illustrates that using enalapril lowers the risk of atrial fibrillation of patients suffering from a poorly contracting ventricle. The results achieved by enalapril and its protective effect against atrial fibrillation, even in patients without overt heart failure, are very encouraging,” said Dr. Jean-Claude Tardif, joint principal investigator and Director of Clinical Research at the Montreal Heart Institute. “In fact, they demonstrate that we need to treat five patients with enalapril for just under three years to prevent one episode of atrial fibrillation.”