By Lisa Rapaport

(Reuters Health) – Patients with atrial fibrillation, a common heart rhythm disorder, should take newer blood thinners to prevent stroke instead of the old standby drug warfarin, U.S. doctors recommend.

Atrial fibrillation patients have up to seven times the stroke risk of people without the disorder.

“Stroke due to atrial fibrillation tends to be quite severe,” said Dr. Craig January of the University of Wisconsin-Madison, who helped draft the new guidelines published in Circulation.

In atrial fibrillation, electrical impulses in the upper chambers of the heart are chaotic, causing the heart muscle to quiver rather than contracting normally. As a result, blood doesn’t flow through the heart as well. This can lead to the formation of clots that can then travel through the arteries to the brain.

Even though doctors have long recommended blood thinners to prevent stroke in atrial fibrillation patients, many people who need these drugs don’t take them. Warfarin, once the drug of choice for this purpose, carries a risk of severe bleeding and is inconvenient, requiring frequent lab tests and checkups to ensure patients have the right dose.

Instead of warfarin, the new guidelines advise that most people with atrial fibrillation take newer blood thinners known as non-vitamin K oral anticoagulants (NOACs). NOACs include dabigatran, rivaroxaban, apixaban and edoxaban.

“Clinical trials have suggested that there is less bleeding risk with NOACs compared to warfarin, and at least some NOACs also may be slightly better at preventing blood clots, (blood vessel obstruction) and stroke,” January said by email.

Another potential advantage of NOACs is that their effects can be reversed more easily than warfarin if patients do develop severe bleeding or need emergency surgery. Newer drugs, so-called reversal agents, can work within hours to halt anti-clotting activity of NOACs, while warfarin may take a day or more to reverse.

NOACs might also be used in people at lower risk of stroke than previously thought, doctors note in the new guidelines. Although the evidence for this recommendation is not yet definitive, emerging research suggests that the potential for stroke prevention may outweigh the potential risks of taking NOACs for more people than have traditionally been advised to take blood thinners.

Two groups of atrial fibrillation patients shouldn’t take NOACs, the guidelines stress. People with mechanical heart valves should take warfarin, and so should people with mitral stenosis, a narrowed valve opening that restricts blood flow between the left chambers of the heart.

The newer drugs haven’t been well studied in mitral stenosis patients and some evidence suggests they might not work as well as warfarin in people with mechanical valves, January said.

“The take home message for patients is that we have oral anticoagulants that are associated with a similar reduction in stroke risk compared with warfarin, but a much safer profile with regards to bleeding risk,” said Dr. Wesley O’Neal, a cardiologist at Emory University School of Medicine in Atlanta who wasn’t involved in the recommendations.

“Your physician is able to determine your individualized risk of stroke, and to recommend one of these medications if your stroke risk is deemed high enough to benefit from oral anticoagulation,” O’Neal said by email.

The new guidelines were issued jointly by the American Heart Association, American College of Cardiology, and Heart Rhythm Society to update recommendations from 2014 that still favored warfarin.

In addition to endorsing NOACs, the new guidelines also urge weight loss for atrial fibrillation patients who are overweight. Losing weight can reduce the health risks associated with atrial fibrillation and can also help lower high blood pressure.

SOURCE: Circulation, online January 28, 2019.