Apixaban Lowers Stroke Risk, but Increases Major Bleeding Risk in Subclinical AFib


Results of the ARTESIA trial suggest apixaban lowered stroke risk by 37% in subclinical atrial fibrillation versus aspirin, but increased major bleeding risk.

Jeff Healy, MD | Credit: McMaster University

Jeff Healy, MD
Credit: McMaster University

Data from the phase 4 ARTESIA trial suggests patients with subclinical atrial fibrillation receiving apixaban were 37% less likely to have a stroke or systemic embolism than those receiving aspirin.

Presented at the American Heart Association Scientific Sessions 2023, results of the study provide insight into a statistically significant decrease in risk of stroke relative to aspirin, but investigators also highlight this was accompanied by a statistically significant increase in risk of major bleeding events among the study’s on-treatment population.

“Currently, there is no consistent guidance on how to treat subclinical atrial fibrillation in people with implanted heart devices,” said Jeff Healey, MD, MS, cardiology division director and professor of medicine at McMaster University. “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.”

Citing previous research suggesting the magnitude of stroke risk associated with short duration, asymptomatic, subclinical atrial fibrillation was less than with longer-lasting symptomatic atrial fibrillation, investigators launched the Apixaban for the Reduction of Thrombo-Embolism in Patients with Device-Detected Subclinical Atrial Fibrillation (ARTESIA) trial to examine the stroke risk with apixaban relative to aspirin, with an acceptably low risk of major bleeding, among patients with risk factors for stroke factors who also had subclinical atrial fibrillation detected by a pacemaker, defibrillator, or implantable cardiac monitor (ICM).

The trial used a double-blind, double-dummy design and randomized patients to apixaban at a dose of 5 mg twice daily or aspirin at a dose of 81 mg daily. Per trial protocol, medication was discontinued and anticoagulation started if subclinical atrial fibrillation lasting more than 24 hours or clinical atrial fibrillation developed.

The trial’s primary efficacy outcome, which was a composite of stroke or systemic embolism, was assessed in the intention-to-treat population. The trial’s primary safety outcome, which was major bleeding, was assessed in the on-treatment population.

Overall, 4012 patients from 247 clinical sites in 16 European and North American countries were identified for inclusion. This cohort had a mean age of 76.8 (Standard Deviation [SD], 7.6) years, 36.1% were women, and had a mean CHA2DS2-VASc score of 3.9 (SD, 1.1). OF the 4012 who underwent randomization, 2015 were randomized to apixaban and 1997 were randomized to the aspirin group.

Upon analysis, results of the trial, which included a mean follow-up of 3.5 (SD, 1.8) years, suggested stroke or systemic embolism occurred in 55 patients in the apixaban group (0.78% per patient-year) and 86 patients in the aspirin group (1.24% per patient-year) (Hazard Ratio [HR], 0.63; 95% confidence interval [CI], 0.45 to 0.88; P=.007). Analysis of the trial’s safety outcome indicated a rate of major bleeding of 1.71% per patient-year in the apixaban group and 0.94% per patient-year in the aspirin group (HR, 1.80; 95% CI, 1.26 to 2.57; P=.001). However, investigators pointed out fatal bleeding events occurred among 5 patients in the apixaban group and 8 patients in the aspirin group.

“The study’s findings will also help to address ongoing questions about the potential value of population-based screening for AFib,” Healy added.


  1. Healy JS, Lopes RD, Granger CB, et al. Apixaban for the Prevention of Stroke in Patients With Subclinical Atrial Fibrillation. Paper presented at: American Heart Association Scientific Sessions 2023; November 10 - 13; Philadelphia, PA. Accessed November 12, 2023.
  2. Anti-clotting pill reduced stroke risk in adults with symptomless, Irregular Heart rhythm. American Heart Association. November 12, 2023. Accessed November 12, 2023. https://newsroom.heart.org/news/anti-clotting-pill-reduced-stroke-risk-in-adults-with-symptomless-irregular-heart-rhythm?preview=dd10.
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