Research Highlights:

  • In a large study of adults with implanted heart devices that detected short, symptomless bouts of irregular heart rhythm, known as subclinical atrial fibrillation, those who took the anti-clotting medication apixaban were 37% less likely to have a stroke or blood clot compared to adults taking daily aspirin.
  • While the anti-clotting medication was linked with more bleeding, most bleeding did not result in any serious or permanent consequences.
  • For many patients with brief, symptomless, subclinical atrial fibrillation, the benefits of apixaban likely outweigh risks, researcher said.

Embargoed until 8:45 a.m. ET, Sunday, Nov. 12, 2023

PHILADELPHIA, Nov. 12, 2023 — The anti-clotting medication apixaban reduced the rate of stroke and blood clots, among adults with implanted heart devices experiencing short bouts of asymptomatic, irregular heart rhythms compared to adults who took aspirin, according to late-breaking science presented today at the American Heart Association’s Scientific Sessions 2023. The meeting, Nov. 11-13, in Philadelphia, is a premier global exchange of the latest scientific advancements, research and evidence-based clinical practice updates in cardiovascular science. The full manuscript is also simultaneously published today in The New England Journal of Medicine.

The medication was associated with major bleeding; however, it was not life-threatening.

Atrial fibrillation, or AFib, is an irregular heartbeat that can lead to blood clots, strokeheart failure or other heart-related complications. It can occur without symptoms or be so brief that it is difficult to detect. Subclinical atrial fibrillation is brief, asymptomatic AFib that is detected by pacemakers, implantable defibrillators and cardiac monitors that record people’s heart rates continuously and detect these short bouts of irregular heartbeats.

Previous research has indicated that treatment with oral anti-clotting medications (also known as anticoagulants) may prevent up to two-thirds of strokes in people diagnosed with atrial fibrillation. However, anti-clotting medications including apixaban cause an increased risk of major bleeding, including blood in stool or in urine, and/or trauma-related bleeding.

“We have observed in previous research that the magnitude of stroke risk associated with short duration, asymptomatic, subclinical atrial fibrillation was lower than what was seen in people with longer-lasting symptomatic atrial fibrillation,” said study author Jeff Healey, M.D., M.S., cardiology division director and professor of medicine at McMaster University in Hamilton, Ontario, Canada. “So that’s a different risk-benefit consideration for prescribing anticoagulants.”

This phase 4 clinical trial, called “Apixaban for the Reduction of Thrombo-Embolism in patients with device-detected Subclinical Atrial fibrillation trial (ARTESIA),” examined the risk-benefit considerations of treating asymptomatic atrial fibrillation. Researchers enrolled more than 4,000 adults from 16 countries in North America and Europe who had an implanted pacemaker, defibrillator or cardiac monitor that detected asymptomatic atrial fibrillation.

Half of the participants were randomly assigned to receive an anticoagulant (the standard treatment for patients with stroke risk factors who have clinical atrial fibrillation); specifically, 5 mg of apixaban, twice daily or 2.5 mg twice daily in patients meeting a pre-set criteria for dose reduction such as being over age 80 or weighing less than 132 pounds). The other half of the participants received 81 mg of aspirin daily. Neither participants nor researchers knew which medication participants were taking. Researchers monitored study participants for an average of 3.5 years for stroke, blood clots and/or major bleeding.

The investigation found:

  • People in the apixaban-treatment group had a 37% overall reduction in incidence of stroke or blood clots, driven mainly by a 51% reduction in fatal or disabling strokes.
  • Among patients actively taking study medication, the risk of major bleeding was 74% higher in the apixaban group compared to the aspirin group (1.69% per year vs. 0.96% per year).
  • Nominally fewer major bleeds in the apixaban arm presented with neurological symptoms or critically low blood pressure (18.5% vs. 26%) or were fatal at presentation (1.1% vs. 4%). Fewer than 10% of the bleeds required life-saving intervention such as surgery (9.8% in the apixaban group and 8% in the aspirin group).
  • There were no differences noted for the most severe bleeds between the aspirin-treated participants and the apixaban-treated participants, such as fatal bleeds, bleeds requiring surgery or bleeds requiring blood transfusion.
  • In this trial, the rate of major bleeds was 1.69% per year in the apixaban group, which is similar or lower than anticipated, based on earlier major studies of these medications to treat Fib, according to Healey.

“Currently, there is no consistent guidance on how to treat subclinical atrial fibrillation in people with implanted heart devices. I think the results of ARTESIA are strong enough to change the way we practice and lead to changes in management guidelines so that we recommend that many of these individuals who have subclinical AFib receive an anticoagulant,” Healy said. “The study’s findings will also help to address ongoing questions about the potential value of population-based screening for AFib.”

Future studies by these researchers and others will look further into tailoring therapy by determining if there are subgroups of people who are at higher or lower risk for stroke, blood clots and/or bleeding.

Of particular note, this study did not directly address the question of whether the millions of people with consumer technologies, including smart watches, smart rings and smart phones that can detect short-lasting episodes of atrial fibrillation, should be treated with an anti-clotting medication.

Among the study’s limitations are that only people with implanted heart devices were enrolled in the trial, and the approach to aspirin therapy changed somewhat during the years of the trial. Aspirin used to be a recommended therapy for stroke prevention in people with AFib, particularly those with lower risk, Healy explained. After the ARTESIA study was designed, this recommendation fell out of favor. As well, over the last 10 years, there has been a sharp decline in the combined use of aspirin on top of oral anticoagulants, as other studies have demonstrated no incremental benefit to aspirin, but a doubling in the rate of major bleeding.

Study details:

  • The trial included 4,012 adults (average age of 77 years; about 36% were women and 64% were men).
  • People in the study had a single subclinical atrial fibrillation lasting six minutes to 24 hours, which was detected by their implanted cardiac devices.
  • Researchers enrolled participants from May 2015 to July 2021. They completed the last follow-up in August 2023. Average patient participation was 4 years.

Co-authors, disclosures and funding sources are listed in the abstract.

Statements and conclusions of studies that are presented at the American Heart Association’s scientific meetings are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. Abstracts presented at the Association’s scientific meetings are not peer-reviewed, rather, they are curated by independent review panels and are considered based on the potential to add to the diversity of scientific issues and views discussed at the meeting. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.

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