Atrial fibrillation is a kind of irregular heart rhythm.
People with atrial fibrillation sometimes develop blood clots in their hearts. These clots can lead to stroke if the blood clots travel from the heart to the brain. Strokes are the neurologic problems, such as weakness or difficulty with speech, that result when brain tissue does not get enough blood. Antithrombotic medicines like warfarin or aspirin make the blood take longer to clot. These medicines can therefore prevent stroke in many people with atrial fibrillation.