Wilson D, Ambler G, Shakeshaft C, et al. – Researchers assessed cross-sectional baseline demographic and clinical data from a prospective observational cohort study in order to determine the proportion of patients with known atrial fibrillation (AF), and identify demographic, clinical, or radiological differences between patients with known AF (and not treated) and patients with newly diagnosed AF. The study sample consisted of 1,470 patients— recruited from 79 hospital stroke centers throughout the United Kingdom and 1 center in the Netherlands—who presented with ischemic stroke or transient ischemic attack (TIA) not previously treated with anticoagulation. A total of 999 patients had newly diagnosed AF and 471 had known AF. In all, 68% of patients with known AF demonstrated a strong indication for anticoagulation, and 89% should have been considered for anticoagulation based upon CHA₂DS₂-VASc score. Patients with known AF demonstrated a greater likelihood of having a prior history of dementia and had higher HAS-BLED scores (median 3 vs 2). CHA₂DS₂-VASc, other risk factors, and demographics were comparable. Overall, the researchers found that approximately one-third of patients who present with stroke and have AF who have not been treated with oral anticoagulation have previously known AF. Of these patients, ≥ 68% were not adequately treated with oral anticoagulation.