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Atrial fibrillation (AF) confers increased risk of stroke and other thromboembolic events, and oral anticoagulation therefore is the essential part of AF management to reduce the risk of these complications. Until recently, the vitamin K antagonists (VKAs, e.g., warfarin) were the only oral anticoagulants available, acting by decreased synthesis of vitamin K-dependent coagulation factors (II, VI, IX, and X). The VKAs had many limitations: delayed onset and prolonged offset of action, variability of anticoagulant effect among patients, multiple food and drug interactions affecting pharmacological properties of warfarin, narrow therapeutic window, and obligatory regular laboratory control, which all made warfarin "inconvenient" both for patients and clinicians. The limitations of VKAs led to development of a new class of drugs collectively defined as non-VKA oral anticoagulants (NOACs), which included direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban). The NOACs avoid many of the VKA drawbacks. In this review, we will focus on the current evidence justifying the use of NOACs in non-valvular AF. [ABSTRACT FROM AUTHOR]

Background Current clinical guidelines recommend that risk stratification for ischaemic stroke in patients with nonvalvular AF (NVAF) should be performed using the CHA2DS2-VASc score (Congestive heart failure, Hypertension, Age ≥ 75 years [double], Diabetes mellitus, previous thromboembolism [double], Vascular disease, Age 65-74 years, and female gender) to aid decision making for antithrombotic treatment, with a preference for Non-Vitamin K Oral Anticoagulants (NOACs) in those with CHA2DS2-VASc score ≥ 1. However, CHA2DS2-VASc score is not recommended in the 2014 Japanese Circulation Society (JCS) guidelines for patients with NVAF. Methods To assess the impact of the JCS approach to stroke prevention in AF, and model the impact of using a CHA2DS2-VASc based 2-step decision making strategy, we calculated the incidence of ischaemic stroke in NVAF patients without OAC on basis of the CHADS2 and CHA2DS2-VASc scores using published Japanese data, and estimated the preventable number of stroke events. Results Using a CHA2DS2-VASc-based approach, the potential annual stroke events based on the estimated total number of NVAF patients in Japan was 889,000, as follows: 4369 for dabigatran 150 mg, 6049 for dabigatran 110 mg, 5918 for rivaroxaban (intention-to-treat; ITT), 5302 for apixaban, 5843 for edoxaban 60 mg (ITT), and 7598 for edoxaban 30 mg (ITT), respectively. Using a CHADS2 score-based approach, the number of potential stroke events was much greater for each agent. Conclusion Our modelling analysis has shown that when considering antithrombotic treatment for Japanese NVAF patients, using a CHA2DS2-VASc-based approach would allow greater opportunities for stroke prevention. [ABSTRACT FROM AUTHOR]

Background Both the CHADS2 and CHA2DS2-VASc scores are well-validated in Western populations for predicting risk of stroke among patients with atrial fibrillation (AF). There is some uncertainty as to which risk score is best to guide optimal anticoagulant therapy among Asian populations with AF. Methods A systemic literature search of Cochrane library, Scopus, and PubMed databases was conducted using search terms: atrial fibrillation, CHADS2 and CHA2DS2-VASc. Stroke/thromboembolism (TE) outcome events at low, moderate, and high risk groups were compared in relation to both scores. Statistical analyses were performed using Revman 5.3 software. Results 493 records were retrieved, of which 6 cohort studies focusing on patients from Asian regions were finally appraised and included. Absolute event rates were usually lower when patients were categorized as CHA2DS2-VASc of 0-1, rather than CHADS2 of 0-1, respectively. Meta-analysis revealed that when compared with the CHA2DS2-VASc score, there was a 1.71-fold elevated risk of stroke when patients were stratified as 'low risk' using a CHADS2 score = 0, or a 1.40-fold increase with a CHADS2 score = 1. A 1.19-fold elevated event rate was observed among CHADS2 score ≥ 2 compared to CHA2DS2-VASc, but the total stroke/TE events were numerically higher in patients categorized as CHA2DS2-VASc ≥ 2. Conclusion The CHA2DS2-VASc score is superior to the CHADS2 score in identifying 'low risk' East Asian AF patients. Rather than a categorical approach, Asian guidelines should adopt a 2 step approach, by initially identifying the truly low risk patients, following which effective stroke prevention can be offered to those with ≥ 1 additional stroke risk factors. [ABSTRACT FROM AUTHOR]