Warfarin, a coumarin derivative and vitamin K antagonist (VKA), is an oral anticoagulant taken to limit the production of coagulation factors II, VII, IX, and X. It is used for the prevention and treatment of thromboembolic events in patients with previous thromboembolism and atrial fibrillation (AF), following the implantation of artificial heart valves and vascular bypass procedures, as well as due to major orthopedic surgery (10-14). This evidence concerns the gene F2 and atrial fibrillation.