Atrial Fibrillation Diagnosis Timing, Ambulatory ECG Monitoring Utilization, and Risk of Recurrent Stroke.

<bold>Background: </bold>The risk of recurrence after an initial ischemic stroke or transient ischemic attack (TIA) may be impacted by undiagnosed atrial fibrillation (AF). We therefore assessed the impact of AF diagnosis and timing on stroke/TIA recurrence rates in a large real-world sample of patients.<bold>Methods and Results: </bold>Using commercial claims data (Truven Health Analytics MarketScan), we performed a retrospective cohort study of patients with an index stroke or TIA event recorded in years 2008 through 2011. Patients were characterized by baseline oral anticoagulation, CHADS2 and CHA2DS2-VASc scores, AF diagnosis and timing with respect to the index stroke, and presence or absence of post-index ambulatory cardiac monitoring. The primary outcome was the recurrence of an ischemic stroke or TIA. Of 179 160 patients (age 67±16.2 years; 53.7% female), the Kaplan-Meier estimate for stroke/TIA recurrence within 1 year was 10.6%. Not having oral anticoagulation prescribed at baseline and having AF first diagnosed >7 days post-stroke (late AF) was highly associated with recurrent stroke/TIA (hazard ratio, 2.0; 95% confidence interval, 1.9-2.1). Among patients with at least 1 year of follow-up, only 2.6% and 9.7% had ambulatory ECG monitoring in the 7 days and 12 months post-stroke, respectively.<bold>Conclusions: </bold>AF diagnosed after stroke is an important hallmark of recurrent stroke risk. Increasing the low utilization of cardiac monitoring after stroke could identify undiagnosed AF earlier, leading to appropriate oral anticoagulation treatment and a reduction in stroke/TIA recurrence. [ABSTRACT FROM AUTHOR]