Novel Oral Anticoagulants for Stroke Prevention in Patients with Non-valvular Atrial Fibrillation

Atrial fibrillation (AF) is the cause of ischemic stroke in approximately 20 % of patients with stroke [1]. As compared with other etiologies stroke in patients with AF is associated with higher mortality, severe disability and high recurrence rate. Antithrombotic therapy is effective to prevent stroke in AF patients. Vitamin K Antagonists (VKA) are much more effective than aspirin and, in the absence of contraindication, are highly recommended for the majority of these patients [1, 2]. However, warfarin (a VKA) have numerous limitations (narrow therapeutic range, multiple interactions with diet and other medications, complex individualized dosing, delayed onset of action, etc.), which complicate its use [1, 2]. Target International Normalized Ratio (INR) is determined by the balance between the risk of thrombotic events and that of the catastrophic intracranial bleed. Stable therapeutic anticoagulation requires multiple blood tests and is very often hard to achieve, leading to suboptimal balance between thrombosis and bleeding. Novel Oral Anticoagulants (NOACs) were developed to overcome these limitations [3, 4]. The NOACs are divided into two classes: the oral direct thrombin inhibitors (e.g. dabigatran) and oral direct factor Xa inhibitors (e.g. rivaroxaban, apixaban and edoxaban). These agents inhibit a single step in coagulation, at major variance from warfarin, which block the formation of multiple vitamin K-dependent coagulation factors (II, VII, IX, and X).