New Anticoagulants in Atrial Fibrillation

Atrial fibrillation (AF) requires anticoagulation for prevention of arterial embolism, especially in the presence of defined risk factors summarized in the CHADS(2) score (congestive heart disease, hypertension, age >75 years, diabetes, history of ischemic stroke or transient cerebral ischemia). Vitamin K antagonists as drugs of choice have several limitations. International normalized ratio (INR) adjustment to 2.0 to 3.0 may be difficult to maintain, and doses vary widely between patients. Inherited variations of the vitamin K epoxide reductase C1 enzyme and of the cytochrome P450 2C9 system influence the dosage as well as exogenous factors such as food and drug intake or intercurrent diseases. Increasing age and risk of falling are the main factors behind the underuse of anticoagulation in AF. Anticoagulants with a lack of all or most of these characteristics and without need of regular monitoring for dose adjustment may improve the adherence to the indication for anticoagulation. Indirect systemic and oral direct factor Xa and oral direct thrombin inhibitors are currently being developed for the prevention of embolism in patients with AF.