The SPAF (Stroke Prevention in Atrial Fibrillation) trial¹ found a 42% reduction in overall risk of stroke with daily aspirin (325 mg). However, critics note that no benefit was observed among patients > 75 y or those with severe stroke.

7 other studies on the topic failed to confirm reduction in the risk of stroke at a range of aspirin doses (25mg bid-1,300mg qd) ². These studies reported that aspirin is associated with a 19% reduction in stroke incidence (similar to patients with vascular disease), with a 95% CI that crosses zero (-1% to 35%), raising doubts about its actual benefit in AF³. For secondary prevention, aspirin was associated with a 2.5% reduction in the annual risk of stroke. However, these results were influenced by the only trial with a favorable outcome, SPAF-1⁴.

In short, even at higher doses, aspirin may not be the answer for stroke prevention in patients with AF.

 References

1. Stroke Prevention in Atrial Fibrillation Study. Final results. Circulation 1991;84, 527–39.
2. January CT, Wann LS, Alpert  JS, et al. 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. Circulation  2014;130, e199–e267.
3. European Heart Rhythm Association et al. Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC). Europace  2010; 12, 1360–420.
4. Sabir IN, Matthews GDK,  Huang, CL-H. Antithrombotic therapy in atrial fibrillation: aspirin is rarely the right choice. Postgrad Med J 2013; 89, 346–51.

Contributed by Jacqueline Boehme, M.D., Medical Resident, Mass General Hospital