Although the prevalence of AF worldwide is increasing steadily, large variation can be seen between studies and countries. Further epidemiological studies should be undertaken globally, especially in Asian and African countries so that a better and more accurate picture of the incidence and prevalence of AF can be captured, to enable stroke prevention strategies to be appropriately implemented to prevent or reduce the risk of stroke, the most severe consequence of AF.

Patients receiving oral anticoagulant (OAC) therapy for stroke prevention in atrial fibrillation (AF) and prevention of venous thromboembolism (VTE) face an increased risk of bleeding with OAC treatment. Clinicians need to weigh the benefits of OAC treatment against the risk of bleeding. To help formalize bleeding risk assessment, various bleeding risk scores have been developed to help predict the risk of bleeding in AF and VTE patients receiving OAC therapy. This review summarizes the literature involving original studies deriving bleeding risk scores and validation studies of these scores for stroke prevention in AF and treatment/prevention of VTE. To date, there are 10 bleeding risk scores, 6 for use in AF populations, 3 in VTE cohorts, and 1 for mixed indications; they differ markedly in the number of, and risk factors for, bleeding and complexity. In conclusion, many clinical prediction tools to assess bleeding risk prior to starting OAC treatment for either stroke prevention in AF or treatment of VTE are available and should be used in clinical practice to identify and manage modifiable risk factors.

Identifying patients who are likely to achieve and maintain a therapeutic international normalized ratio when prescribed a vitamin K antagonist for stroke prevention in atrial fibrillation (AF) and venous thromboembolism (VTE) is challenging. The SAMe-TTR score was developed on the basis of common clinical factors that can highlight patients who may be unable to achieve and maintain good anticoagulation control and for whom a "trial of warfarin" would be inadvisable. This review summarizes the main published prospective and retrospective studies that have validated the SAMe-TTR score in patients with AF and VTE treated with a vitamin K antagonist and how the SAMe-TTR score could aid clinical decision making; 19 studies were included. Taken together, validation studies suggest that the SAMe-TTR score is able to predict good or poor anticoagulation control in patients with AF and VTE, although data on patients with VTE are limited (3 studies). The available evidence suggests that the SAMe-TTR score may be a useful tool to aid clinical decision making for oral anticoagulants in patients with AF and VTE.

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