Relationship between time in therapeutic range and comparative treatment effect of rivaroxaban and warfarin: results from the ROCKET AF trial.

BACKGROUND: Time in therapeutic range (TTR) is a standard quality measure of the use of warfarin. We assessed the relative effects of rivaroxaban versus warfarin at the level of trial center TTR (cTTR) since such analysis preserves randomized comparisons. METHODS AND RESULTS: TTR was calculated using the Rosendaal method, without exclusion of international normalized ratio (INR) values performed during warfarin initiation. Measurements during warfarin interruptions >7 days were excluded. INRs were performed via standardized finger-stick point-of-care devices at least every 4 weeks. The primary efficacy endpoint (stroke or non-central nervous system embolism) was examined by quartiles of cTTR and by cTTR as a continuous function. Centers with the highest cTTRs by quartile had lower-risk patients as reflected by lower CHADS2 scores (P<0.0001) and a lower prevalence of prior stroke or transient ischemic attack (P<0.0001). Sites with higher cTTR were predominantly from North America and Western Europe. The treatment effect of rivaroxaban versus warfarin on the primary endpoint was consistent across a wide range of cTTRs (P value for interaction=0.71). The hazard of major and non-major clinically relevant bleeding increased with cTTR (P for interaction=0.001), however, the estimated reduction by rivaroxaban compared with warfarin in the hazard of intracranial hemorrhage was preserved across a wide range of threshold cTTR values. CONCLUSIONS: The treatment effect of rivaroxaban compared with warfarin for the prevention of stroke and systemic embolism is consistent regardless of cTTR.

Comparison of eicosapentaenoic acid concentrations in plasma between patients with ischemic stroke and control subjects.

OBJECTIVE: ω-3 fatty acids, including eicosapentaenoic acid (EPA), prevent ischemic stroke. However, the clinical importance of EPA for ischemic stroke and its subtype has not been fully elucidated. METHODS: In a cross-sectional study, we determined whether ω-3 fatty acids were predictive factors for ischemic stroke. We compared common clinical parameters among 65 patients with ischemic stroke and 65 control subjects. The parameters included blood chemistry data; concentrations of EPA, docosahexaenoic acid, and arachidonic acid (AA); EPA/AA ratio; smoking; alcohol intake; fish consumption more than four times per week; and the incidence of underlying diseases. The comparisons were performed using the Mann-Whitney U test, and multiple logistic regression analysis was applied to the significant factors in the non-parametric test. We also applied the same approach to the ischemic stroke subtypes, cardioembolism and large-artery atherosclerosis. RESULTS: In the multiple logistic regression analysis after the Mann-Whitney U test, a lower EPA concentration was one of the significant risk factors for ischemic stroke, as were a lower body mass index, lower high-density lipoprotein cholesterol, and smoking (sensitivity 0.846, specificity 0.831, positive predictive value 0.833). In the analysis of subtypes, a lower EPA/AA ratio and a lower body mass index were the significant risk factors for cardioembolism (sensitivity 0.800, specificity 0.733, positive predictive value 0.750). However, large-artery atherosclerosis was not related to the EPA concentration or the EPA/AA ratio. CONCLUSIONS: In this study, the plasma EPA concentration and the EPA/AA ratio were potential predictive risk factors for ischemic stroke, especially for cardioembolism. Further prospective studies are necessary.

An update on antithrombotic therapy in atrial fibrillation: the role of newer and emergent drugs.

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with potentially dreadful cardioembolic complications such as stroke. The risk of stroke is stratified based on the patient's comorbid conditions using several scoring systems. Patients are treated with oral anticoagulation using warfarin or aspirin based on their cardioembolic stroke risk. Although warfarin has been the only effective therapy, it is underutilized clinically due to concern for multiple drug-to-drug and drug-to-food interactions and hemorrhagic complications. Dual antiplatelet therapy with aspirin and clopidogrel has been studied as a potential alternative anticoagulant for AF patients; however, the combination of aspirin and clopidogrel was noted to be inferior to warfarin in preventing strokes, with an increased risk of bleeding. As a result, newer anticoagulant agents, including direct thrombin inhibitors, direct and indirect factor Xa inhibitors, and vitamin K antagonists, have been developed and evaluated in AF patients. Results from a recent study demonstrated that high-dose dabigatran, a direct thrombin inhibitor, was superior to warfarin in preventing stroke and systemic embolism with similar bleeding risk. It ultimately received approval by the US Food and Drug Administration for stroke prophylaxis for nonvalvular AF patients. There are several other direct factor Xa inhibitors currently under study. Dabigatran may be considered in AF patients who are intolerant to warfarin or unwilling or unable to follow-up with frequent laboratory monitoring. Other newer anticoagulant agents also provide us with possible suitable alternatives to warfarin, and their clinical use will depend on the results from ongoing studies.