Efficacy and Safety of Apixaban Compared With Warfarin at Different Levels of Predicted International Normalized Ratio Control for Stroke Prevention in Atrial Fibrillation

Abstract

Fibrillation (ARISTOTLE) trial, apixaban compared with warfarin reduced stroke and systemic embolism, major bleeding, and mortality. We evaluated treatment effects in relation to 2 predictions of time in therapeutic range (TTR). Methods and Results-The trial randomized 18 201 patients with atrial fibrillation to apixaban 5 mg twice daily or warfarin for at least 12 months. For each patient, a center average TTR was estimated with the use of a linear mixed model on the basis of the real TTRs in its warfarin-treated patients, with a fixed effect for country and random effect for center. For each patient, an individual TTR was also predicted with the use of a linear mixed effects model including patient characteristics as well. Median center average TTR was 66% (interquartile limits, 61% and 71%). Rates of stroke or systemic embolism, major bleeding, and mortality were consistently lower with apixaban than with warfarin across center average TTR and individual TTR quartiles. In the lowest and highest center average TTR quartiles, hazard ratios for stroke or systemic embolism were 0.73 (95% confidence interval [CI], 0.53-1.00) and 0.88 (95% CI, 0.57-1.35) (P interaction =0.078), for mortality were 0.91 (95% CI, 0.74-1.13) and 0.91 (95% CI, 0.71-1.16) (P interaction =0.34), and for major bleeding were 0.50 (95% CI, 0.36-0.70) and 0.75 (95% CI, 0.58-0.97) (P interaction =0.095), respectively. Similar results were seen for quartiles of individual TTR.© 2013 American Heart Association, Inc.Circulation is available at http://circ.ahajournals.org DOI: 10.1161/CIRCULATIONAHA.112.142158Continuing medical education (CME) credit is available for this article. Go to http://cme.ahajournals.org to take the quiz. W arfarin and other vitamin K antagonists effectively prevent stroke in patients with atrial fibrillation (AF), but they have a narrow therapeutic window with an increased risk of stroke and bleeding when above or below the therapeutic range of the international normalized ratio (INR) of 2.0 to 3.0.1-3 The dose response is influenced by several factors such as age, body weight, genetic variation, food, and comedications. Regular INR-guided dose adjustments are therefore necessary.1-3 However, there are large variations of the time in therapeutic range (TTR) across individuals, sites, and countries, and these variations are related to patient outcomes. [4][5][6][7][8][9] Several trials have shown recently that the quality of warfarin use, as measured with INR control at the center or country level, may interact with the treatment effects of new antithrombotic treatments when compared with warfarin. 10-12 Editorial see p 2163 Clinical Perspective on p 2176Apixaban is a new oral direct factor Xa inhibitor providing stable anticoagulation at a fixed dose twice daily without the need for anticoagulation monitoring. In the prospective, randomized, and double-blind Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARISTOTLE) trial including 18 201 patients with AF and at least 1 additiona...

Drug therapy in anticoagulation: which drug for which patient?

“…5 These findings were shown to be independent of the quality of international normalised ratio (INR) control in patients receiving warfarin. 8 …”

Stroke prevention after stroke in patients with atrial fibrillation: A case-based review

“…Wallentin és mtsai [19] vizsgálata szerint azoknál a betegeknél, akiknél a terápiás tartományban töltött idő 60% alatt volt, a stroke kocká-zata 2,5-szeres volt azokhoz képest, akiknek a terápiás tartományban töltött ideje 70% vagy a feletti volt, miközben a major vérzések aránya csak 2%-kal volt kisebb.…”

Direct oral anticoagulants in atrial fibrillation: can data from randomized clinical trials be safely transferred to the general population? No

“…For instance, the value of TTR recorded in the centres participating in the RE-LY trial is very scattered, ranging from 44 % observed in Taiwan or India to 80 % recorded in the Sweden [2]. This point deserves attention, as the overall benefits of DOAC in terms of efficacy and safety are attenuated or lost at centres and in patients with predicted excellent INR control [13][14][15].…”