Atrial fibrillation (AF) is associated with a fivefold increase in the risk of 
stroke. The Phase III ROCKET AF (Rivaroxaban Once-Daily Oral Direct Factor Xa 
Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and 
Embolism Trial in Atrial Fibrillation) trial showed that rivaroxaban, an oral, 
direct Factor Xa inhibitor, was noninferior to warfarin for the reduction of 
stroke or systemic embolism in patients with AF. Compared with warfarin, 
rivaroxaban significantly reduced rates of intracranial and fatal hemorrhages, 
although not rates of bleeding overall. XANTUS (Xarelto(®) for Prevention of 
Stroke in Patients with Atrial Fibrillation) is a prospective, international, 
observational, postauthorization, noninterventional study designed to collect 
safety and efficacy data on the use of rivaroxaban for stroke prevention in AF 
in routine clinical practice. The key goal is to determine whether the safety 
profile of rivaroxaban established in ROCKET AF is also observed in routine 
clinical practice. XANTUS is designed as a single-arm cohort study to minimize 
selection bias, and will enroll approximately 6,000 patients (mostly from 
Europe) with nonvalvular AF prescribed rivaroxaban, irrespective of their level 
of stroke risk. Overall duration of follow-up will be 1 year; the first patient 
was enrolled in June 2012. Similar studies (XANTUS-EL [Xarelto(®) for Prevention 
of Stroke in Patients with Nonvalvular Atrial Fibrillation, Eastern Europe, 
Middle East, Africa and Latin America] and XANAP [Xarelto(®) for Prevention of 
Stroke in Patients with Atrial Fibrillation in Asia-Pacific]) are ongoing in 
Latin America and Asia-Pacific. Data from these studies will supplement those 
from ROCKET AF and provide practical information concerning the use of 
rivaroxaban for stroke prevention in AF.