A screen displays a patient's vital signs at the University of Maryland Medical Center in Baltimore, on Nov. 28, 2016. THE CANADIAN PRESS/AP-Patrick Semansky

By The Canadian Press

Blood thinners no longer needed for many with irregular heatbeats, study suggests

Nov 8, 2025 | 2:45 PM

Those who have undergone successful corrective procedures for irregular heart beats may no longer need to commit to long-term blood thinning therapy, an international study co-led by Canadian researchers suggests.

Researchers behind the study published in the New England Journal of Medicine say the discovery could potentially alter the clinical care of millions of people around the world.

The randomized study involved more than 1,200 patients who had undergone an ablation for atrial fibrillation, a procedure that involves altering the electrical signals in the heart through the use of a catheter. The randomized trial then compared how one group reacted to taking rivaroxaban, a commonly prescribed anticoagulant, with another prescribed low doses of aspirin.

“The guidelines have said that even if your doctor does an ablation and feels it’s successful, you should continue your blood thinners for life,” said Dr. Atul Verma, a senior cardiovascular scientist based at the McGill University Health Centre in Montreal who co-led the trial. “We decided to do this trial to see if this was actually necessary.”

Atrial fibrillation is the most common form of cardiac arrhythmia and affects one per cent of all Canadians, and five per cent of those above the age of 65, he said.

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After following the patients over the course of three years, researchers found there was no significant difference in the rates of stroke and embolism, the obstruction or blockage of blood vessels, between the two groups.

“We were a little surprised by the results,” Verma said. “It appears that atrial fibrillation ablation, when successful, not only lowers the amount of atrial fibrillation, but also seems to drastically lower the risk of stroke.”

Brain MRIs were also conducted on patients at the beginning of the study and the end three years later to look for signs of silent strokes, he said, which revealed low rates between both groups.

“The rate of stroke or silent stroke in these patients was really, really low,” Verma said. “It was so low that we could not detect any difference between continuing blood thinners or going on aspirin.”

That brain imaging revealed that after three years, 96 per cent of patients showed no signs of silent strokes, he highlighted.

Anticoagulants, also known as blood thinners, work to prevent blood clots from forming, but have been known to cause bleeding. That could include excessive bleeding from cuts, blood in the urine, or heavy menstrual bleeding.

Verma said many patients are eager to get off them, since the bleeding they can cause, say in the instance of an accident, can be life-threatening.

“The first thing they ask is, can I stop this blood thinner? I like to go skiing, I like to work in my garage, I’m at risk of bleeding by taking these things,” Verma said. “And now for a certain substantial portion of those patients, I think we can say, yes you can.”

Dr. David Birnie, a professor in the Department of Medicine at the University of Ottawa, and the division head of cardiology at its Ottawa Heart Institute, which was involved in the study, called the findings a “game-changer.”

“Our results show that one year after a successful ablation, the risk of stroke is so low that the downsides of continuing blood thinners outweigh the benefits, meaning many patients can safely stop,” Birnie, who also co-led the trial, said through a press release.

Over 50 cardiovascular research centres across Canada, Europe, China and Australia were involved, a collaboration coordinated by Dr. George Wells, the director of cardiovascular research at the Ottawa Heart Institute.

This report by The Canadian Press was first published Nov. 8, 2025.

Jean-Benoit Legault, The Canadian Press