Aspirin and OAC in AF: Beware

Samuel Z. Goldhaber, MD


February 19, 2014

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Hello. This is Dr. Sam Goldhaber for the Clot Blog at, speaking to you from Brigham and Women's Hospital and Harvard Medical School on the topic of using caution when prescribing aspirin to patients with atrial fibrillation (AF) on oral anticoagulation. This is based on new data from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF), done in 176 US practices, so this is a real-world type of registry.[1]

There are about 10,000 AF patients in the registry, and over 7000 have received anticoagulation to prevent stroke. The question was, how many of these patients were also receiving aspirin? It turns out that about one third of the patients with AF were receiving aspirin plus anticoagulation. But what is concerning is that one third of the patients who were prescribed aspirin had no evidence whatsoever of any vascular disease.

Now, this is important because the bleeding complication rate was about 50% higher in the patients who were taking aspirin plus anticoagulation vs anticoagulation alone. Additionally, the rate of hospitalization to treat bleeding complications was about 50% higher in patients taking aspirin plus anticoagulation compared with anticoagulation alone.

Maybe this would be a justified risk (in terms of more bleeding and more hospitalization) if the stroke rate were much lower in the aspirin-plus-anticoagulation group or if the myocardial infarction rate was much lower. But in fact, in the ORBIT-AF registry, the cardiovascular event rates were very low in both groups.

I think the take-home message here is that there will be some situations in which aspirin is absolutely necessary and is the right thing to prescribe to patients who are also taking anticoagulation to prevent stroke with AF. But for a patient without any evidence of vascular disease who is taking an anticoagulant for stroke prevention and AF, I would think once, twice, and even 3 times before prescribing aspirin as well.

This is Dr. Sam Goldhaber, signing off for the Clot Blog.


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