Warfarin, Aspirin Provide Similar Stroke Prevention

(National Institutes of Health)

In a six-year, 11-country clinical trial, researchers at Columbia University found aspirin and the anti-clotting drug warfarin to offer about equal protection against death and strokes in heart failure patients with normal heart rhythms. The findings of the study led by Columbia medical school professor Shunichi Homma were presented at the International Stroke Conference in New Orleans.

The Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction (WARCEF) trial tracked 2,305 patients with heart failure and normal heart rhythm for up to six years, with participants followed on average for 3.5 years.  Patients averaged 61 years of age and had left-ventricle pumping capacity or ejection fraction of less than 35 percent; normal ejection fraction is 55 percent or higher.

Patients with heart failure in general are at increased risk of death, blood clots, and strokes. Of the patients in the trial, 13 percent experienced a stroke or transient ischemic attack — i.e. mini-stroke, where the blockage breaks up quickly and with no lasting brain damage — and were at heightened risk of recurrence.

Patients were randomly assigned to receive either 325 milligrams (mg) per day of aspirin or warfarin doses calibrated to a pre-specified level of blood thinning. Warfarin therapy requires frequent blood testing to monitor its dosage in order to achieve the desired level of blood thinning. In order to avoid bias, all patients had blood drawn on the same schedule and their pills adjusted so neither the patients nor their treating physicians knew which regimen they were taking.

The study looked at the occurrence of ischemic stroke — the kind caused by blockage of an artery feeding the brain — or bleeding inside the brain known as intracerebral hemorrhage, or death. These events happened to 7.5 percent of warfarin patients, compared to 7.9 percent of patients taking aspirin, a difference not statistically significant.

Warfarin did perform better than aspirin among patients followed for more than three years. Over the entire six-year study period, patients receiving warfarin were about half as likely to develop a stroke as those taking aspirin. Nonetheless, the rates of stroke were low: 0.72 percent per year in patients assigned to warfarin and 1.36 percent per year for those taking aspirin.

The trial also studied the safety of the two therapies, specifically major bleeding events other than intracerebral hemorrhage, which was one of the effectiveness measures. Some 1.8 percent of warfarin patients had these major bleeding events, compared to 0.9 percent of aspirin patients, a statistically significant difference. Intracerebral hemorrhage — bleeding inside the brain and the kind of bleeding many patients fear — occurred rarely in both groups: 0.12 percent per year in the warfarin group and 0.05 percent per year in the aspirin group.

“Given that there is no overall difference between the two treatments and that possible benefit of warfarin does not start until after 4 years of treatment,” says Homma, “there is no compelling reason to use warfarin, especially considering the bleeding risk.”

Disclosure: The author is on a prescribed aspirin regimen for a heart condition.

Read More: Trial Finds New Drug Better Than Common Blood Thinner

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