Risk reduction for stroke afforded by warfarin treatment in atrial fibrillation (AF) is impressive: Clinical trials consistently show approximately two-thirds reduction in risk of stroke compared to placebo. Additionally, overall mortality is reduced by more than 25%. Because efficacy is closely linked to time in the therapeutic range, and toxicity is equally closely linked to time outside the therapeutic range, it is valuable to see if we can identify clinical characteristics that predict which patients are most likely to maintain adequate anticoagulation.

With data from the Atrial Fibrillation Follow-up Investigation of Rhythm Management trial, Apostolakis et al derived the acronym “SAMe-T2TR2” using the metrics of female sex, age < 60, minority ethnicity, > 2 comorbidities, medication regimen (beta-blocker, verapamil, or amiodarone), and tobacco use. The SAMe-T2TR2 score would stratify patients into low risk for suboptimal control (score 0-1) vs at risk for suboptimal control (score > 2).

Newer antithrombotic agents (apixaban, dabigatran, rivaroxaban) offer little efficacy advantage over warfarin for patients who can maintain anticoagulation within the therapeutic range more than 70% of the time. Stratification tools that are comprised of readily identified clinical elements may help us suggest the most appropriate therapeutic choices.

Source: Apostolakis S, et al. Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: The SAMe-TT2R2 Score. Chest 2013;144:1555-1563.