Patients with AF, VTE receiving warfarin benefit from reduced aspirin use: JAMA

MICHIGAN: According to a study published in JAMA Network Open, patients receiving warfarin for atrial fibrillation (AF) and/or venous thromboembolism (VTE) were found to significantly reduce their excess aspirin consumption after undergoing an anticoagulation clinic-based aspirin deimplementation intervention. Without an elevation in thrombotic events, the reported decline in aspirin consumption was also correlated with declines in bleeding outcomes, reported the authors.

The study's lead author, Geoffrey D. Barnes, MD, MSc, Division of Cardiovascular Medicine, Department of Internal Medicine, University of Michigan, asserted that these results "emphasize the need for improved aspirin administration among patients on warfarin for anticoagulation."

"Our effective intervention across numerous health systems, with diverse patient populations and clinical structures, could serve as a national paradigm for lowering excess aspirin use," the authors wrote.

A possible therapy benefit of adding aspirin (acetylsalicylic acid) while taking warfarin for some people is an increase in bleeding risk. The use of aspirin less frequently may lead to better clinical results.

In order to evaluate changes in aspirin use, bleeding, and thrombosis event rates among individuals using warfarin, the authors conducted their study.

6738 adults who were taking warfarin for atrial fibrillation and/or venous thromboembolism without an obvious indication for concurrent aspirin participated in this pre-post observational quality improvement study between January 1, 2010, and December 31, 2019, at a 6-center quality improvement collaborative in Michigan. From November 26, 2020 to June 14, 2021, statistical analysis was done. If a continuous regimen of aspirin and warfarin was necessary for patients who took aspirin, primary care physicians were questioned about this. In that case, the supervising clinician gave his or her clearance for the aspirin to be stopped. In both the primary and secondary analyses, outcomes were evaluated prior to and following the intervention (i.e., when rates of aspirin use first started to decline) and prior to and following 24 months prior to the intervention. The rate of aspirin use, hemorrhage, and thrombotic events were among the outcomes. An interrupted time series analysis evaluated the evolution of cumulative monthly event rates.

Conclusive points of the study:

• The pre-intervention period, which was 24 months before the intervention, revealed a marginal decline in aspirin use from the baseline mean use of 29.4% (95% CI, 28.9% - 29.9%) to 27.1% (95% CI, 26.1% - 28.0%).
• At a mean use of 15.7% (95% CI, 14.8% - 16.5%), there was a noticeably faster decline in aspirin use.
• The number of major bleeding events per month declined substantially (0.31% vs 0.21%; P =.03 for difference in slope between before and after intervention). The average patient percentage who experienced a thrombotic event did not alter much (0.21% vs. 0.24%; P =.34 for difference in slope).
• In additional analyses, a fall in aspirin use (24 months prior to intervention) was linked to a drop in the mean proportion of patients experiencing any bleeding incident (2.3% vs 1.5%; P =.02) or significant bleeding event (0.31% vs 0.25%; P =.001).

Given that aspirin is not a prescription drug, the researchers hypothesized that "doctors might not always be aware that patients are taking aspirin, which would be a hurdle to efforts to deprescribe aspirin".

The authors concluded that among patients receiving warfarin for atrial fibrillation and/or venous thromboembolism without a clear justification for aspirin therapy, this quality improvement intervention was linked to an acceleration of a preexisting drop in aspirin use.

REFERENCE

Schaefer JK, Errickson J, Gu X, et al. Assessment of an Intervention to Reduce Aspirin Prescribing for Patients Receiving Warfarin for Anticoagulation. JAMA Netw Open. 2022;5(9):e2231973. doi:10.1001/jamanetworkopen.2022.31973