Many people, most of whom are over age 65, take warfarin to thin the blood due to a condition
called atrial fibrillation. During atrial fibrillation, the heart’s two small upper
chambers (the atria) quiver instead of beating effectively. If the blood isn’t pumped
completely out of the heart’s upper chambers, it may pool and clot. If a piece of a
blood clot in the atria leaves the heart and becomes lodged in an artery in the brain, a
stroke results. About 15 percent of strokes occur in people with atrial fibrillation.
Maintaining the correct dosage of medication is instrumental to assure patient safety. To be
successful on a Coumadin regimen, it is critical that the patient follow the instructions
and comply with request s for regular blood tests. Monitoring the effectiveness of the
warfarin is done with these blood tests. The International Normalized Ratio (INR), are
measured to determine the extrinsic pathway of coagulation. These test measure dosage, liver
damage, vitamin K status and the clotting tendency of blood.