Most people who have atrial fibrillation require treatment with blood thinners, called anticoagulants. Atrial fibrillation can cause blood clots to form in the chambers of the heart. The clot can break off of the wall of the heart chamber, where it is carried through arteries by the bloodstream. As the artery becomes smaller and smaller, eventually the clot becomes stuck in the artery. This completely stops blood from flowing to the tissues supplied by the artery. The most common place that this occurs is in the brain, where the clot causes a stroke. The anticoagulant medications reduce the risk of clot formation.

Anticoagulant medications:

• Aspirin
• Heparin
• Low-molecular weight heparin:
• Dalteparin
• Warfarin (Coumadin)

Warfarin should be avoided in those with:

• Active peptic ulcer disease
• Allergy to warfarin
• Aneurysm
• A-V malformation
• Clotting disorder
• Head trauma
• Subarachnoid hemorrhage

Alternatives to warfarin include:

• Aspirin
• Conversion to sinus rhythm
• Enoxaparin

Monitoring
Regular monitoring of prothrombin times is essential for any patient taking warfarin. Most experts recommend a target INR value between 2 and 3. Initial therapy requires daily prothrombin times until stabilized, then 2-3 times per week for 1-2 weeks. Regular prothrombin times should be obtained every 4-8 weeks thereafter.