By Lisa Rapaport

(Reuters Health) – More patients with heart rhythm problems that put them at high risk for stroke are taking daily pills to prevent clotting – and they’re having fewer strokes as a result, a Swedish study suggests.

Most strokes occur when a clot blocks an artery carrying blood to the brain, known as an ischemic stroke. Atrial fibrillation, a common form of irregular rapid heartbeat, can lead to these kinds of clots and stroke.

For the new study, researchers studied two groups of patients with atrial fibrillation to see how often they had strokes and whether they took the older blood thinning pill warfarin (Coumadin) or newer oral anticoagulants (NOACs) that have a lower risk of bleeding and serious complications.

Researchers assessed the first group of about 41,000 patients in 2012, before warfarin alternatives were widely used, and found 52 percent of them took anti-clotting pills. This group had an annual stroke rate of 2.1 for every 100,000 patients.

Then, researchers assessed a second group of more than 49,000 patients in 2017, after NOACs were widely available. In this group, 74 percent of patients took anti-clotting pills and the annual stroke rate was 1.17 for every 100,000 patients.

“The introduction of NOACs has provided more alternatives for stroke prevention in atrial fibrillation,” said lead study author Dr. Tomas Forslund of the Karolinska Institutet in Stockholm.

“An increased use of NOAC or warfarin in an entire real-world atrial fibrillation population comprised of many old, frail and other high risk patients … was associated with a decreased risk for stroke without increasing the risk for severe (bleeding),” Forslund said by email.

In atrial fibrillation, electrical impulses in the upper chambers of the heart are chaotic, and the atrial walls quiver rather than contracting normally. As a result, blood doesn’t move as well to the heart’s lower chambers. This can lead to the formation of clots that can travel through the arteries. Atrial fibrillation patients have up to seven times the stroke risk of people without the disorder.

While warfarin can prevent strokes, long-term use of this older blood thinner can increase the risk of severe bleeding, and it’s inconvenient because it requires frequent lab tests and check-ups to ensure that patients have the right dose.

Even as use of blood thinners increased during the study period, bleeding didn’t become more common, even among people at especially high risk for bleeding, the study found.

That may be at least in part because more people took NOACs instead of warfarin as time went on, researchers conclude in Stroke.

The study wasn’t a controlled experiment designed to prove whether or how one type of anti-clotting drug might be better at stroke prevention than another.

It’s also possible that changes in other aspects of stroke prevention beyond just medication might have contributed to the decline in strokes among atrial fibrillation patients, said Tom Marshall, a researcher at the University of Birmingham in the U.K. who wasn’t involved in the study.

“Increased use of any anticoagulants will reduce incidence of stroke,” Marshall said by email. “NOACs may have some modest advantages over warfarin, but NOACs have mainly contributed to the recent increase largely because pharmaceutical companies have a strong incentive to educate physicians about the need to prescribe anticoagulants and to promote the use of NOACs and this chimes with the desire of physicians to prevent strokes.”

Drug companies have an incentive to promote the newer drugs, becomes they command premium prices compared to older generic medicines like warfarin, Marshall noted.

Patients may also prefer NOACs and stick with this treatment more than they did with warfarin, said Dr. Wesley O’Neal, a researcher at Emory University School of Medicine in Atlanta who wasn’t involved in the study.

“NOACs have fewer drug interactions, less dietary restrictions, and more favorable bleeding profiles compared with warfarin,” O’Neal said by email. “The reduced risk of stroke observed in this study was directly related to the higher proportion of patients who used antithrombotic agents, and the higher rate of antithrombotic agent use occurred with the introduction of NOACs as an option for patients with atrial fibrillation.”

SOURCE: Stroke, online August 28, 2018.