The CHA2DS2-VASc (congestive heart failure [or left ventric- ular systolic dysfunction], hypertension, age ,75 years; diabetes mellitus, prior stroke or transient ischemic attack, vascular disease, age 65 to 74 years, female sex) score is a new risk scheme that combines the CHADS2 score with additional moderate risk fac- tors, which were also included in the 2006 American College of Cardiology/American Heart Association/European Society of Cardiology and National Institute for Health and Clinical Excel- lence AF practice guidelines.29,50 Speci cally, the CHA2DS2-VASc score assigns points as in the original CHADS2 score (Table 2) with the exception of age 75 years, which is assigned two points. It also assigns a single point for each of the following additional treatment on nonfatal stroke by assuming a case fatality rate of 50% for hemorrhagic stroke and 25% for ischemic stroke based on population-based stroke registry data and the case fatality rates observed in the RCTs of patients with AF that reported such data.11 For nonfatal major extracranial bleeding, we accepted the de nition of major bleeding from the individual studies, and when the proportion of major extracranial bleeds that were fatal vs nonfatal was not reported, we applied the average case fatality rate for major extracranial bleeding reported across the relevant clinical trials (15%). For the outcome of systemic embolism, we used the total number of events (fatal and nonfatal) because systemic embolism was an infrequent event and typically not reported as fatal vs nonfatal. 1.4 Deriving Baseline Risk of Stroke in Patients With AF The risk of stroke varies considerably across different groups of patients with AF.12 Simple validated tools for the assessment of stroke risk in patients with AF help in identifying those who are more likely to bene t than be harmed from antithrombotic therapy. 