• Posted September 21, 2022

Already Taking a Blood Thinner? Adding Aspirin May Do Harm

For many years, doctors have advised taking low-dose aspirin to help prevent first-time heart attacks and stroke. But increasingly, they're doing an about-face.

The latest warnings come from University of Michigan researchers who reported that patients simultaneously taking another blood thinner, warfarin, along with aspirin are more likely to have bleeding problems.

The research team found the risk of a bleeding event dropped by almost one-third when aspirin use was reduced in this group.

Aspirin is not a panacea drug as it was once thought to be, said Dr. Geoffrey Barnes, study co-author and cardiologist at the university's Cardiovascular Center.

"We said, 'Let's see if we can identify the patients who we don't need to be on aspirin because they're already on another blood thinner. Let's stop their aspirin and let's see if we can actually avoid those bleeding events,'"said Barnes.

For the study, nurses reviewed charts of patients in six Michigan anticoagulation clinics, and asked their doctors whether the aspirin was necessary. If not, the aspirin was discontinued.

Over time, the researchers discovered that reducing the excess aspirin use led to better patient outcomes.

The study included more than 6,700 adults taking warfarin for atrial fibrillation or venous thromboembolism between 2010 and 2019. Atrial fibrillation is an irregular heart rhythm. Venous thromboembolism is a blood clot.

Many patients were taking low-dose aspirin without a clear indication to do so, such as a recent heart attack, recent stent placement or having a mechanical heart valve, Barnes said.

In a statistical analysis done between November 2020 and June 2021, the investigators found significantly fewer bleeding problems, minor or major. They did not see an increase in clotting issues, they noted.

Accelerating the pace at which patients who don't need aspirin stop taking it can help prevent serious bleeding complications and be lifesaving, Barnes said.

However, he noted that aspirin is still incredibly important for some patients. Guidelines have also been evolving in recent years.

"One of the most fascinating parts of this study is that already doctors were showing that aspirin was probably not as important as we once thought,"Barnes said. "The percent of patients using aspirin was slowly declining. What we did is we said, 'Let's make this a systematic process.'"

The United States has more than 1,000 anticoagulation clinics, and this could be a great opportunity for nurses and pharmacists in those clinics to improve the safety of their patients by identifying those who could stop using aspirin, Barnes said.

That could move the needle more quickly, he suggested.

"The model that we tested here could be replicated in other health systems,"Barnes said.

Of course, it's also important that patients not decide to quit aspirin on their own, but first consult with their doctor. Some conditions need both therapies, doctors say.

While the U.S. Preventive Services Task Force updated guidelines in April, recommending against starting low-dose aspirin in people 60 and older, those with existing heart problems were not part of that recommendation.

Many patients who have a history of ischemic stroke, heart attack or other cardiovascular disease can benefit from aspirin, according to the study authors.

Although the study focused on concurrent aspirin and warfarin use, the standard of care is now to take a different medication known as a direct-acting oral anticoagulant (DOAC) rather than warfarin for these issues, said Dr. Eugene Yang, chair of the American College of Cardiology Prevention of Cardiovascular Disease Council.

Even so, patients are often told to take both aspirin and a DOAC (such as Eliquis or Pradaxa), which is not necessary in many cases, he said.

"We have trouble even in that population of trying to eliminate the aspirin from the treatment algorithm,"Yang said.

Having nurses systematically check patient records and contact doctors about these dual treatments could be helpful, Yang noted. If that could be automated through electronic health records, it would be even more efficient, he added.

Yang suggested patients should talk to their clinicians about whether they need aspirin in addition to other medications.

"More and more studies are showing that aspirin for primary preventions show no benefit, but I think there's a lag where the physicians and clinical providers are not recognizing that taking this aspirin for primary prevention has no benefit,"Yang said.

The report was published online Sept. 19 in JAMA Network Open.

More information

Here's the U.S. Preventive Services Task Force recommendation on low-dose aspirin.

SOURCES: Geoffrey Barnes, MD, cardiologist, University of Michigan Health Frankel Cardiovascular Center, Ann Arbor, Mich.; Eugene Yang, MD, chair, American College of Cardiology Prevention of Cardiovascular Disease Council and professor of medicine, University of Washington, Bellevue; JAMA Network Open, Sept. 19, 2022, online