Patients diagnosed with a condition called atrial fibrillation (irregular heart beat) are at an increased risk for developing blood clots. If left untreated, these clots can cause severe reactions within the body such as stroke, heart attack, pulmonary embolism, and deep vein thrombosis. For over 50 years, doctors have treated this condition with a blood thinning medication called warfarin or brand name Coumadin. Patients taking warfarin require monthly blood testing to make sure the thickness of their blood is within a certain therapeutic range. The side effects of warfarin are well known and until recently, there has been no alternative medication to warfarin.