(Reuters Health) - Even when the heart rhythm disorder known as atrial fibrillation goes away after treatment, patients’ risk of stroke may still be higher than average, a large UK study suggests.

Researchers examined health records collected between 2000 and 2016 for 15,059 people with ongoing atrial fibrillation, 11,159 people with “resolved” atrial fibrillation whose heart rhythm had returned to normal, and a control group of 22,266 people who were never diagnosed with the heart rhythm disorder.

People with resolved atrial fibrillation were 24 percent less likely to have a stroke than patients with continued arrhythmia, the study found. But people with resolved atrial fibrillation were still 63 percent more likely to have a stroke than individuals who had never been diagnosed with the condition.

“This may be because the atrial fibrillation had not really gone away and just became more intermittent, or it may be because it had gone away but recurred,” said senior study author Tom Marshall of the University of Birmingham.

“Patients recorded as having resolved atrial fibrillation may therefore benefit from continued anticoagulant therapy, but our results show that few of these patients are prescribed anticoagulants,” Marshall said by email.

In atrial fibrillation, electrical impulses in the upper chambers of the heart are chaotic, causing that part of the heart muscle to quiver rather than contracting normally. As a result, blood doesn’t move as well to the heart’s lower chambers, which can lead to the formation of clots that travel through the arteries and sometimes cause strokes.

Many patients with atrial fibrillation are prescribed anticoagulants, also known as blood thinners, such as warfarin (Coumadin), that lengthen the time it takes for clots to form in the blood. Warfarin can increase the risk of severe bleeding, and patients may also take newer alternatives like dabigatran (Pradaxa), rivaroxaban (Xarelto) or apixaban (Eliquis).

Patients in the study with resolved atrial fibrillation, however, were one fifth as likely to receive anticoagulants as people with ongoing rhythm irregularities, researchers report in The BMJ.

People with resolved atrial fibrillation were 40 percent less likely to die during the study period as patients with ongoing arrhythmia, but they were 13 percent more likely to die than individuals who had never been diagnosed with the heart rhythm disorder.

The study wasn’t a controlled experiment designed to prove whether or how past atrial fibrillation might cause strokes. Another limitation is that the study focused on primary care patients, and it’s possible some people receive treatment from specialists.

Still, the results suggest that patients should be cautious about stopping anticoagulants even when atrial fibrillation is considered resolved, said Dr. Wesley O’Neal, a researcher at Emory University School of Medicine in Atlanta who wasn’t involved in the study.

“The take home message here is that all forms of atrial fibrillation carry an important risk of stroke that can be reduced through the use of oral anticoagulant agents,” O’Neal said by email.

Blood thinners can help even when they don’t prevent strokes, said Dr. Ying Xian, a neurology researcher at Duke University Medical Center in Durham, North Carolina, who wasn’t involved in the study.

“Anticoagulants protect against stroke and reduce the risk of stroke by almost two-thirds,” Xian said by email. “Even if strokes occur while on these medications, those strokes tend to be less severe and less deadly.”

SOURCE: bit.ly/2yqTvB1 The BMJ, online May 9, 2018.