Background: The efficacy and safety of anticoagulation with use of vitamin K antagonists (VKAs) is highly dependent on the quality of anticoagulation control as reflected by the average time in a therapeutic range of 2.0 to 3.0. A clinical dilemma is trying to predict which anticoagulation-naive patients with atrial fibrillation (AF) would do well on a VKA (with a time in therapeutic range > 70%) and which are less likely to do well on a VKA but could be managed with novel oral anticoagulants.
Methods: The cohort comprised 8,120 patients, among whom 4,637 patients were receiving VKA. We investigated whether the SAMe-TT₂R₂ (sex female, age < 60 years, medical history [more than two comorbidities], treatment [interacting drugs, eg, amiodarone for rhythm control], tobacco use [doubled], race [doubled]) score could discriminate among patients with AF who were likely to have a labile international normalized ratio (INR) during follow-up as well as stroke/thromboembolism (TE), clinically relevant bleeding (defined as severe bleeding and as Bleeding Academic Research Consortium [BARC]-defined major bleeding), and death while being treated with a VKA.
Results: During a mean follow-up of 1,016 ± 1,108 days, there was a significant increase in risk of severe bleeding events (risk ratio [RR], 1.38; 95% CI, 1.12-2.68; P = .002) and a significant increase in risk of major BARC bleeding (RR, 1.77; 95% CI, 1.29-2.44; P = .0005) in patients with AF with a high SAMe-TT₂R₂ score (> 2). Increasing SAMe-TT₂R₂ score was associated with an increasing risk of labile INR (P = .004), stroke/TE (P = .007), severe bleeding (P < .0001), major BARC bleeding (P < .0001), and death (P = .002) at follow-up. Among the patients taking VKAs, the SAMe-TT₂R₂ score was predictive of labile INR (C statistic approximately 0.58) as well as of stroke/TE, severe bleeding, major BARC bleeding, and death (C statistic, 0.54-0.57 for events), reflecting the suboptimal time in therapeutic range in such patients. This was not the case for patients who were not taking VKAs.
Conclusions: We demonstrate that the SAMe-TT₂R₂ score was predictive for an increasing risk of stroke/TE, severe bleeding, major BARC bleeding, and death, reflecting poor anticoagulation control (and labile INRs) among patients with AF given VKAs.