Harvard Heart Letter

Heart Beat: Aspirin gets a backup against atrial fibrillation

Heart Beat

Aspirin gets a backup against atrial fibrillation

Stroke is the most worrisome complication of atrial fibrillation. When the heart's upper chambers (the atria) don't contract efficiently, blood can pool in them. Slow-flowing blood has a tendency to clot. If a blood clot gets into circulation, it can cause a stroke by lodging in an artery feeding the brain. A blood thinner like warfarin (Coumadin, Jantoven, generic) is the best defense against clot formation. But many people can't take warfarin because of bleeding problems or interactions with other medications. For them, aspirin is the mainstay. It fights stroke, but not quite as well as warfarin. Adding clopidogrel (Plavix) may help.

In a large international trial called ACTIVE, the combination of aspirin plus Plavix was better than aspirin alone at preventing stroke in people with atrial fibrillation who couldn't take warfarin. Over the four-year trial, 7.8% of those taking both aspirin and Plavix had a stroke compared with 10.8% in the aspirin-only group. The downside to the combination was more bleeding problems (The New England Journal of Medicine, May 14, 2009).

If you have atrial fibrillation and can't, or won't, take warfarin, aspirin is the next best thing. Adding Plavix to aspirin may be even better. But the combination isn't for everyone, especially those prone to bleeding problems. It's yet another one of those situations in which you and your doctor need to carefully weigh the benefits and risks.

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