WEDNESDAY, March 9 (HealthDay News) -- The blood pressure-lowering drug Avapro doesn't seem to prevent heart disease and stroke in patients suffering from the irregular heartbeat called atrial fibrillation, a new Canadian study finds.

People with atrial fibrillation are at risk for heart disease and stroke, and lowering blood pressure is one way of staving off these potential problems. Avapro (irbesartan) is an angiotensin-receptor blocker, which lowers blood pressure by helping blood vessels dilate.

"Atrial fibrillation affects between 2 and 6 million men and women in the United States," said Dr. Gregg Fonarow, a spokesman for the American Heart Association and a professor of cardiology at the University of California, Los Angeles.

"Individuals with atrial fibrillation have substantially increased risk for stroke, other cardiovascular events, hospitalizations, and health-care expenditures," he added.

It has been "widely speculated" that angiotensin-receptor blockers might reduce the likelihood of recurrent atrial fibrillation and reduce the risk of cardiovascular events, Fonarow explained.

Earlier studies have suggested that angiotensin-receptor blockers benefit patients with atrial fibrillation, he added.

The latest report is published in the March 10 issue of the New England Journal of Medicine.

For the study, Dr. Salim Yusuf, from McMaster University in Hamilton, and colleagues randomly assigned 9,016 patients with atrial fibrillation to daily doses of Avapro or a placebo. Over about four years of follow-up, the researchers looked for incidents of stroke, heart attack, death and heart failure.

The researchers found that even though people taking Avapro had lower blood pressure than those taking placebo, people in both groups suffered a stroke, heart attack or died at the same rate over the four years.

In addition, those taking Avapro or placebo suffered heart failure at about the same rate, but those taking Avapro had a lower rate of hospitalization for heart failure, the researchers said. Also, there was no benefit from the drug among patients with a normal heart rhythm at the start of the study when it came to preventing hospitalization for atrial fibrillation.

The researchers also found more patients taking Avapro had blood pressure that was too low and more had kidney failure than did those receiving a placebo.

"This study demonstrates Avapro, despite a modest reduction in blood pressure, does not prevent recurrent episodes of atrial fibrillation or prevent cardiovascular events overall," Fonarow said. "There were no differences in heart attacks, cardiovascular deaths or deaths from any cause. There were modestly lower rates of hospitalization for heart failure and any cardiovascular hospitalization."

When this new trial is considered together with an earlier trial, it's evident that this class of blood pressure drugs has no effect in preventing episodes of atrial fibrillation in patients with intermittent atrial fibrillation, he added.

"In the absence of other indications, routine use of angiotensin-receptor blockers in patients with atrial fibrillation does not appear to be warranted," Fonarow said.

More information

For more on atrial fibrillation, visit the American Heart Association.