Initiative Lowers Unnecessary Aspirin Use in Warfarin Users

It’s possible to reduce excess aspirin use among patients taking warfarin for atrial fibrillation (AF) and/or venous thromboembolism (VTE) with a dedicated quality-improvement initiative, and doing so will improve clinical outcomes, researchers report.

Though aspirin use was already on the decline in these patient groups, the initiative—implemented at anticoagulation clinics in Michigan—accelerated the trend, according to Jordan Schaefer, MD (University of Michigan, Ann Arbor), and colleagues.

That was associated with lower rates of major bleeding without an uptick in thrombotic events, they report in a study published online this week in JAMA Network Open.

Prior work from the group revealed that among warfarin-treated patients who did not have a clear indication for taking aspirin, use of the antiplatelet was associated with higher rates of bleeding, as well as more emergency department (ED) visits and admissions related to bleeding, senior author Geoffrey Barnes, MD (University of Michigan, Ann Arbor), pointed out to TCTMD. That got the researchers thinking about whether they could reduce unnecessary aspirin use and in turn prevent those bleeding complications.

We were really able to be effective in our goal of getting patients off of aspirin, doing it in a systematic way, and then helping patients avoid those bleeding complications. Geoffrey Barnes

The Michigan Anticoagulation Quality Improvement Initiative (MAQI²), encompassing six outpatient anticoagulation clinics across the state, provided the infrastructure to test that idea. For the initiative, investigators screened for potentially unnecessary aspirin use in patients taking warfarin for AF and/or VTE, after which the primary care physicians managing those patients were contacted and asked whether there was an indication for ongoing aspirin therapy. If there wasn’t, aspirin was stopped with the approval of the managing clinician.

For the current study, Shaefer, Barnes, and colleagues examined data on 6,738 adults (mean age 63 years; 47% men) treated with warfarin—mostly for VTE—before and after implementation of the aspirin-reduction intervention.

Aspirin use was already sliding a few years before the intervention, declining from a mean of 29.4% in the 2 to 8 years before implementation (historical period) to 27.1% in the 2 years before the intervention (preintervention phase), “probably reflecting the fact there have been a number of studies showing aspirin for primary prevention is not as helpful as we once thought, and so doctors were less enthusiastic about it,” Barnes said.

But that trend accelerated after the intervention, with aspirin use averaging 15.7% in the 2 years after the intervention.

That change was associated with a lower monthly risk of major bleeding (0.21% postintervention vs 0.31% preintervention), translating into one major bleed prevented for every 1,000 patients who stopped aspirin. The risk of thrombotic events did not change.

Because aspirin use was already falling in the 2 years before the initiative, the researchers also compared outcomes between the historical period and a combined preintervention/postintervention period. That analysis showed lower rates of any bleeding, major bleeding, and ED visits for bleeding, without a change in thrombotic risks, in the latter period.

“When we put our system in place, we were able to accelerate the deprescribing of aspirin quite significantly,” Barnes said. “We were really able to be effective in our goal of getting patients off of aspirin, doing it in a systematic way, and then helping patients avoid those bleeding complications.”

He acknowledged that there are some obstacles to broader implementation of this type of effort. In Michigan, there was an infrastructure already set up with dedicated anticoagulation clinics and nurses that could be trained to carry it out. “If your health system doesn’t have a dedicated team of nurses or pharmacists or somebody who is able to look this over and make it a systematic approach, then that’s going to be a challenge,” Barnes said.

In addition, patients take aspirin for a wide variety of reasons and clinicians need to be prepared to address all of them when contemplating a deprescribing effort, he said.

Finally, there has been a shift in recent years away from warfarin and toward direct oral anticoagulants (DOACs), which don’t require the same level of oversight in anticoagulation clinics. Barnes said his group is currently testing a couple of different models for what they’re calling “anticoagulation stewardship” programs that can bring this type of initiative to patients irrespective of the type of anticoagulant they’re taking.

But even though there’s a need for more research, Barnes said he would “absolutely recommend” that parts of the country with the necessary infrastructure start to explore similar initiatives “and then monitor their own patients to see how effective they are at deprescribing aspirin and whether that’s leading to safer outcomes for their patients.”