Patients With Heart Disease: Which Dose of Aspirin Are You Taking?


Aspirin helps prevent clots from developing in the blood, but it can also increase potential risk for internal bleeding.

If you have heart disease, which puts you at higher risk for a heart attack or stroke, you may be taking a daily aspirin to help prevent those events. But do you know if you’re taking too much or too little, and are you aware of your dosage’s effects?

It may seem odd, but right now there’s not a consensus even among cardiologists about how much aspirin one should take. Some recommend a dose for high-risk patients as low as 81 milligrams per day (a “baby aspirin”) while others recommend 325 milligrams per day.

A new clinical trial called ADAPTABLE, The Aspirin Study is designed to set the record straight on which of those two commonly used doses is more effective. The trial is comparing the benefits and risks of side effects of the two doses among people with heart disease.

One might justifiably think that by now we’d already have a standard regarding these issues, but we don’t. We have guidelines from the American College of Cardiology and the U.S. Preventive Task Force recommending the lower dose in certain situations, but that doesn’t change the fact that many cardiologists are still recommending the higher dose to some of their patients. In fact, 60 percent of patients take a 325-milligram dose each day after a heart attack, and 36 percent take 81 milligrams.

What Does Aspirin Do?

While aspirin may seem harmless when you’re taking it for a headache, it impedes the “stickiness” of your platelets, preventing them from initiating clots. This can help prevent heart attacks, but as you might expect, it also has the potential to increase internal bleeding risk.

That’s why doctors use aspirin differently. We have to weigh the potential benefits with the potential risks for each patient. As of right now, there hasn’t been enough research for a clear-cut recommendation for every situation, particularly for patients who have a high heart attack risk but a low bleeding risk – it’s not clear what dose is the right one. In general, physician recommendations reflect each physician’s personal preference.

The dosage question is a little clearer for patients who have a high risk of both heart attack and bleeding, including patients with a personal bleeding history or those who use blood thinners. Most doctors will prescribe a lower-dose aspirin to these patients unless they’ve recently had bypass surgery (in which case, higher-dose aspirin may help keep vein grafts open in the initial year after surgery).

If you have heart disease and you’re concerned about whether you should take aspirin – and, if so, at what dose – talk to your doctor. Discuss your risk of heart attack and your risk of bleeding so you’ll better understand the risks and benefits of aspirin at different doses.

If this situation seems confusing, I completely agree, and it’s why the ADAPTABLE trial is so important. Results from this trial will provide the data we need to inform future treatment decisions for our patients.

A Novel Approach

Having those results will be exciting and interesting in and of itself, but the ADAPTABLE trial has some other qualities that make it truly novel. In contrast to the typical clinical trial, which can involve extra visits and tests, ADAPTABLE is a “pragmatic” trial designed to simply follow how patients get care from their own doctors. The trial was funded by PCORI, the Patient-Centered Outcomes Research Institute, and patients were heavily involved in the protocol design. Enrollment is managed via the web, and data are collected by central coordinating centers in collaboration with the local sites. The burden on the patient is much less than in a traditional trial format.

If this works well, it has tremendous implications for further trials that are patient-centered and much less expensive to enroll in and run than traditional randomized clinical trials.

So not only will we have better information about using aspirin to prevent heart attacks in heart disease patients, but this particular trial has the potential to be a real game-changer in how we design future clinical trials.