An older adult with chronic heart failure and atrial fibrillation asks why warfarin has been prescribed to continue at home. What is the best response?

• A. The medication prevents blood clots from forming in your heart.
• B. The medication dissolves clots that develop in your coronary arteries.
• C. The medication reduces clotting by decreasing serum potassium levels.
• D. The medication increases your heart rate so that clots do not form in your heart.

Answer: (A)

In atrial fibrillation, the irregular and often slowed blood flow in the atria can lead to clot formation. The goal of continuing warfarin at home is to prevent these clots from forming and, by doing so, reduce the risk that a clot will travel to the brain and cause a stroke. Warfarin works as an anticoagulant by inhibiting vitamin K–dependent clotting factors, lowering the blood’s ability to clot. It does not dissolve clots that have already formed, it does not affect potassium levels, and it does not directly change heart rate. Because this is long-term prevention, ongoing home management with regular monitoring (INR) helps keep the risk of stroke in check while balancing bleeding risk.