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Non-vitamin K antagonist oral anticoagulants (NOACs) have changed the landscape for stroke prevention in atrial fibrillation (AF). Given the huge burden of AF in Asians, more attention to stroke prevention is clearly needed. Aiming to provide an overview and reappraisal of stroke prevention in Asians with AF, we searched MEDLINE for information on NOACs in Asians. In addition, abstracts from national and international cardiovascular meetings were studied to identify unpublished studies. In the 4 recent Phase 3 trials comparing NOACs to warfarin, a consistent pattern is evident. For efficacy endpoints in the comparison of NOACs vs warfarin, a significant reduction in stroke/systemic embolization was seen for dabigatran 150mg [HR 0.45 (0.28-0.72)], with non-significant trends seen for lower stroke/systemic embolization with other NOACs, except edoxaban 30mg. A similar pattern was seen for ischaemic stroke, with a significant reduction for dabigatran 150mg [HR 0.55 (0.32-0.950]. For haemorrhagic stroke, all NOAC regimes, except rivaroxaban 20mg, had significantly lower hazard ratios. No evidence of increased myocardial infarction was found for NOACs. All-cause mortality was significantly lowered amongst Asian patients on edoxaban 60mg compared to warfarin [HR 0.63 (0.40-0.98)] with non-significant trends to lower mortality with dabigatran 150mg, rivaroxaban and edoxaban 30mg. For safety endpoints, all the NOAC regimes, except rivaroxaban 20mg, significantly reduced major bleeding and 'all bleeding' events. Intracranial haemorrhage was consistently lowered by all NOACs. None of NOACs increased gastrointestinal bleeding. These information suggested that NOACs should be preferentially indicated for stroke prevention in Asians with AF.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. In 2050, it is estimated that there will be 72 million AF patients in Asia, accounting for almost 2.9 million patients suffering from AF-associated stroke. Asian AF patients share similar risk factor profiles as non-Asians, except that more Asians have a history of previous stroke. Clinical challenges are evident in the field of stroke prevention in AF, amongst Asians. Existing stroke and bleeding risk scores have not been well-validated in Asians. Asians are prone to bleeding when treated with warfarin, and the optimal international normalised ratio (INR) for warfarin use is yet to be determined in Asians, though Asian physicians tend to keep it in a lower range (e.g. INR 1.6-2.6) for elderly patients despite limited evidence to justify this. In general, warfarin is 'difficult' to use in Asians due to higher risk of bleeding and higher stroke rate in Asians than in non-Asians, as shown in randomised controlled trials. Excess of bleeding was not found in Asians when novel oral anticoagulants (NOACs) were used. Besides, the superiority of NOACs to warfarin in reducing thromboembolism was maintained in Asians. Therefore NOACs are preferentially indicated in Asians in terms of both efficacy and safety. Also, some preliminary data suggest that Asian patients with AF might not be the same. Future prospective randomised trials are needed for the selection of NOACs according to different ethnic background.

For Taiwanese patients 50 to 64 years of age, the annual stroke risk was 1.78%, which may exceed the threshold for OAC use for stroke prevention. The annual risk of ischemic stroke for AF patients <50 years of age was 0.53%, which was truly low-risk, and OACs could be omitted. Whether resetting the age threshold to 50 years could refine current clinical risk stratification for Asian AF patients deserves further study.

Although the incidence of venous thromboembolism (VTE) in Asian populations is lower than in Western countries, the overall burden of VTE in Asia has been considerably underestimated. Factors that may explain the lower prevalence of VTE in Asian populations relative to Western populations include the limited availability of epidemiological data in Asia, ethnic differences in the genetic predisposition to VTE, underdiagnoses, low awareness toward thrombotic disease, and possibly less symptomatic VTE in Asian patients. The clinical assessment, diagnostic testing, and therapeutic considerations for VTE are, in general, the same in Asian populations as they are in Western populations. The management of VTE is based upon balancing the treatment benefits against the risk of bleeding. This is an especially important consideration for Asian populations because of increased risk of intracranial hemorrhage with vitamin K antagonists. Non-vitamin K antagonist oral anticoagulants have shown advantages over current treatment modalities with respect to bleeding outcomes in major phase 3 clinical trials, including in Asian populations. Although anticoagulant therapy has been shown to reduce the risk of postoperative VTE in Western populations, VTE prophylaxis is not administered routinely in Asian countries. Despite advances in the management of VTE, data in Asian populations on the incidence, prevalence, recurrence, risk factors, and management of bleeding complications are limited and there is need for increased awareness. To that end, this review summarizes the available data on the epidemiology, risk stratification, diagnosis, and treatment considerations in the management of VTE in Asia.

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Aims Non-vitamin K antagonist oral anticoagulants (NOACs) require dose reductions according to patient or clinical factors for patients with atrial fibrillation (AF). In this meta-analysis, we aimed to assess outcomes with reduced-dose NOACs when given as pre-specified in pivotal trials. Methods and results Aggregated data abstracted from Phase III trials comparing NOACs with warfarin in patients with AF were assessed by treatment using risk ratios (RRs) and 95% confidence intervals (CIs) stratified by patient eligibility for NOAC dose reduction. Irrespective of treatments, annualized rates of stroke or systemic embolism and major bleeding were higher in patients eligible for reduced-dose NOACs than in those eligible for full-dose NOACs (2.70% vs. 1.60% and 4.35% vs. 2.87%, respectively). Effects of reduced-dose NOACs compared with warfarin in patients eligible for reduced-dose NOACs on stroke or systemic embolism [RR 0.84 (95% CI 0.69–1.03)] and on major bleeding [RR 0.70 (95% CI 0.50–0.97)] were consistent with those of full-dose NOACs relative to warfarin in those eligible for full-dose NOACs [RR 0.86 (95% CI 0.77–0.96) for stroke or systemic embolism and RR 0.87 (95% CI 0.70–1.08) for major bleeding; interaction P, 0.89 and 0.26, respectively]. In addition, NOACs were associated with reduced risks of haemorrhagic stroke, intracranial haemorrhage, fatal bleeding, and death regardless of patient eligibility for NOAC dose reduction (interaction P &gt; 0.05 for each). Conclusions Patients eligible for reduced-dose NOACs were at elevated risk of thromboembolic and haemorrhagic complications when treated with anticoagulants. NOACs, when appropriately dose-adjusted, had an improved benefit-harm profile compared with warfarin. Our findings highlight the importance of prescribing reduced-dose NOACs for indicated patient populations.

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