Prestroke and Poststroke Antithrombotic Therapy in Patients With Atrial Fibrillation: Results From a Nationwide Cohort

IMPORTANCE: Antithrombotic therapies are effective in both primary and secondary stroke prophylaxis in high-risk patients with atrial fibrillation (AF), but they are often underused in community practice. OBJECTIVE: To examine prestroke and poststroke antithrombotic treatment patterns and long-term outcomes in patients with AF presenting with ischemic stroke. DESIGN, SETTING, AND PARTICIPANTS: A retrospective cohort study of Danish patients with AF, with a prestroke CHA(2)DS(2)-VASc score of 1 or higher for men and 2 or higher for women, and presenting with ischemic stroke was conducted from January 1, 2004, to January 31, 2017. Data on hospital admission, prescription fillings, and vital status were assessed using several Danish nationwide registries. EXPOSURES: Patients who survived 100 days after discharge were divided into 3 groups according to poststroke antithrombotic therapy: oral anticoagulation (OAC) therapy, antiplatelet therapy alone, or no antithrombotic therapy. MAIN OUTCOMES AND MEASURES: Long-term outcomes (thromboembolic events and bleeding complications) were examined using multivariable Cox regression analyses across the 3 groups. RESULTS: Among 30 626 patients with AF admitted with ischemic stroke, 11 139 patients (36.3%) received OAC therapy (44.3% female; median age, 79 years [interquartile range, 73-85 years]), 11 874 (38.8%) received antiplatelet therapy alone (55.0% female; median age, 82 years [interquartile range, 75-88 years]), and 7613 (24.9%) received no antithrombotic therapy before stroke (53.8% female; median age, 80 years [interquartile range, 71-86 years]). Following stroke, 31.3% of those receiving antiplatelet therapy alone and 43.7% of those receiving no antithrombotic therapy before stroke shifted to OAC therapy. Yet, 37.5% of patients with stroke did not receive OAC therapy following stroke. However, OAC treatment rates increased over time. During a maximum of 10 years of follow-up, 17.5%, 21.2%, and 21.5% experienced a new thromboembolic event and 72.7%, 86.4%, and 86.2% died among those treated with OAC therapy, antiplatelet therapy, or no antithrombotic therapy, respectively. Poststroke OAC therapy was associated with lower risk of recurrent thromboembolic events (adjusted hazard ratio, 0.81; 95% CI, 0.73-0.89) and no significant difference in bleeding complications (adjusted hazard ratio, 0.97; 95% CI, 0.86-1.10), compared with no poststroke antithrombotic therapy. In contrast, there were no significant differences for those treated with poststroke antiplatelet therapy and no antithrombotic therapy. CONCLUSIONS AND RELEVANCE: Patients with AF receiving poststroke OAC therapy had lower risk of recurrent thromboembolic events. Our findings suggest a substantial opportunity for improving primary and secondary stroke prophylaxis in high-risk patients with AF.