Old habits die hard in medicine. For decades, the Skeptical Cardiologist and his cardiology brethren and sistren have prescribed aspirin to prevent stroke in patients with atrial fibrillation.
For those patients with atrial fibrillation (Afib, AF) who were considered low risk, it was felt that aspirin provided some benefit in preventing the clots that fly out of the heart (and land in arteries elsewhere in the body) at an acceptably low risk of bleeding. For higher risk patients, more powerful and effective agents -- oral anticoagulants -- are usually recommended.
The gave a IIB recommendation to aspirin: "For patients with nonvalvular AF and a of 1, no antithrombotic therapy or treatment with an oral anticoagulant (OAC) or aspirin may be considered (Level of Evidence: C)." IIB is not a ringing endorsement, having been as "this is our suggestion, but you may want to think about it."
However, in the last 5 years the have become more widely appreciated.
Thus, in the on the management of AF, the authors state that "the evidence supporting antiplatelet monotherapy [e.g., aspirin or clopidogrel] for stroke prevention in AF is very limited" and the bleeding rate is "similar" to OAC. A said:
"Aspirin and other antiplatelets have no role in stroke prevention (III A). The combination of anticoagulation with antiplatelets increases bleeding risk and is only justified in selected patients for a short period of time; for example, in patients with an acute coronary syndrome or stent, balancing the risk of bleeding, stroke and myocardial ischaemia (IIa B/C)."
The European guidelines strongly recommend anticoagulation for males with a CHA2DS2-VASc score ≥2 and females ≥3. While the recommendation is also to consider anticoagulation in males with scores of 1 and females with scores of 2, no antithrombotic therapy of any kind should be prescribed in patients with scores below that.
The guidelines add: "Antiplatelet therapy increases bleeding risk, especially dual antiplatelet therapy (2.0% vs. 1.3% with antiplatelet monotherapy; P<0.001), with bleeding rates that are similar to those on OAC. Thus, antiplatelet therapy cannot be recommended for stroke prevention in AF patients."
While the said nothing about aspirin monotherapy for AF, it's not just European experts who feel this way. At a , American experts in the field were unanimous in their condemnation of aspirin use for low-risk patients, as reported by MDedge:
"The European guidelines have done away with aspirin for stroke prevention in atrial fibrillation. It barely made it into our current US guidelines. I don't think aspirin should be in there and I don't think it will be there in the next guidelines. The role of aspirin will fall away," said Bernard J. Gersh, MB, ChB, DPhil, Professor of Medicine at the Mayo Clinic in Rochester, Minnesota. "It's not that aspirin is less effective than the oral anticoagulants, it's that there's no role for it. There are no good data to support aspirin in the prevention of stroke in atrial fibrillation."
"The use of aspirin has probably been misguided, based upon a single trial which showed a profound effect and was probably just an anomaly," said N.A. Mark Estes III, MD, Professor of Medicine and Director of the New England Cardiac Arrhythmia Center at Tufts University in Boston, and a past president of the Heart Rhythm Society.
"... I would just take it off of your clinical armamentarium because the best available data indicate that it doesn't prevent strokes. I'm certainly not using it in my patients. Increasingly in my patients with a CHA2DS2-VASc of 1, I'm discussing the risks and benefits of a novel oral anticoagulant," said Dr. Estes.
Those are amazingly definitive statements. But as I've learned, we can't just accept what the "experts" and the guidelines tell us -- we have to look at the original studies informing these decisions.
In 1991, the seminal study proving the benefits of warfarin in preventing stroke, the was published.
It compared warfarin (measured by prothrombin time, or INR ratio) to placebo as well as aspirin (325 mg) to placebo in preventing stroke in AF patients. Warfarin reduced stroke by 67% and aspirin by 42%. The risk of significant bleeding was similar at around 1.5% per year for all three arms.
Based on this and other AF trials (AFASAK, CAFA, SPINAF, EAFT, et al.), my message when I gave talks or taught cardiology fellows in the 1990s (similar to ) emphasized the superior benefits of warfarin compared to aspirin (especially when monitored by INR in a 2.0 to 3.0 range) in higher-risk AF patients. Overall it was felt that aspirin (dosing varying from 100 to 325 mg) reduced stroke/embolism by 20% to 30% compared to placebo and would offer benefit to those patients at low risk or who could not tolerate warfarin.
Based on the 2014 American guidelines (and a that did not address this issue), I had not been actively taking my low-risk patients off baby aspirin.
I was prompted to re-research this question and write this post because a 58 year old woman with paroxysmal AF and hypertension called the office recently asking if I wanted her to take a baby aspirin daily. She has a CHA2DS2-VASc score of 2 (woman and hypertension) and falls into the category where we should have an in-depth conversation about the risks and benefits of anticoagulant therapy.
I have that discussion with her each visit, and thus far we've decided to hold off on starting an anticoagulant drug like apixaban (Eliquis). She has promised to record her ECG daily (using her ) and report any onset of AF. If AF recurs, we will have another discussion about the anticoagulant.
I spent several hours pouring over the original studies and more recent studies, reviews, and meta-analyses and reached the following conclusions:
With the advent of the newer oral anticoagulants (NOACs) in the last decade that offer better stroke reduction and less bleeding than warfarin, patient-physician discussions should be about taking a NOAC or not. Aspirin should not be considered as a lower-risk/effective alternative as its benefits are minimal and bleeding risks similar to NOACs.
I told my patient no on the daily baby aspirin, and from now on I will recommend stopping aspirin (assuming no other reason to be on it) to all my low-risk AF patients.
is a private practice noninvasive cardiologist and medical director of echocardiography at St. Luke's Hospital in St. Louis. He blogs on nutrition, cardiac testing, quackery, and other things worthy of skepticism at , where a version of this post first appeared.