New blood thinner reduces stroke risk in patients with atrial fibrillation

Patients with high-risk atrial fibrillation, or AFib, often require one drug to regulate heart rhythm and a second drug to thin their blood and reduce the risk of stroke. A recent study led by a University of Missouri School of Medicine cardiologist found that use of a newer blood thinner significantly decreased the risk of strokes for patients with AFib who require both types of medication.

Although the anticoagulant warfarin has been the standard of care since the 1940s, more recent advancements in blood-thinning medication led to the development of the drug apixaban. The 2011 ARISTOTLE trial, conducted internationally, found that patients with atrial fibrillation taking apixaban had fewer strokes than those taking warfarin.

Greg Flaker, M.D., the Wes and Simone Sorenson Chair in Cardiovascular Research at the MU School of Medicine, directed a team of researchers who recently reviewed data from the ARISTOTLE trial.

Flaker's study indicated that the rate of stroke or blood clot to the body was 39 percent lower in those patients taking the amiodrarone-apixiban drug combination, compared to taking the amiodarone-warfarin combination.

"Although warfarin works very well for most patients who take it, we know that it can be a difficult medication to regulate ? especially when combining it with another drug," Flaker said. "About 30 percent of patients taking warfarin experience fluctuations in blood thickness, depending on how warfarin is metabolized by the individual. Interaction with another drug, such as amiodarone, also affects how warfarin is metabolized."

"Amiodarone is a common and effective drug used to normalize irregular heart rhythm caused by atrial fibrillation," Flaker said. "However, because clotting is a complication associated with the condition, an anticoagulant or blood thinner is frequently used to reduce that possibility. Warfarin has been used as a blood thinner in this capacity for quite some time."

Flaker, a member of the Steering Committee for the earlier ARISTOTLE clinical trial, and his research team reviewed data from that trial in their study.

"Our study mirrored the ARISTOTLE trial in that apixaban proved to be a better blood -thinning medication for all patients with atrial fibrillation," Flaker said. "We looked at the specific drug combination of apixaban and amiodarone. We found that if you had atrial fibrillation and were taking amiodarone to control your heart rhythm, your stroke risk would be higher if you took warfarin than if you took apixaban."

"Certainly there are factors such as cost, physician preference and patient decision-making that affect what drug we use to reduce stroke risks," Flaker said. "The good news for AFib patients is that there is a very good alternative to warfarin for their physicians to consider when developing care strategies for patients with high-risk atrial fibrillation."