Underuse of Antithrombotic Therapy Caused High Incidence of Ischemic Stroke in Patients with Atrial Fibrillation

BACKGROUND: Atrial fibrillation is one of the most important causes of ischemic stroke. The purposes of this study were to recognize the incidence of ischemic stroke, the use of antithrombotic agents, the predictors of ischemic stroke, and prescription of warfarin during the three-years after atrial fibrillation was diagnosed. METHODS: This was a descriptive design and chart review study, comprised of 1211 subjects at two hospitals in Northern Taiwan who were aged ≥ 60 at their first diagnosis of atrial fibrillation. Chi-square and logistic regression were used for data analysis. RESULTS: The incidence of ischemic stroke was 46.2% during the three-years after atrial fibrillation was diagnosed, with 86.3% of those occurring in the first year. The prescription rate was 53.3% in antithrombotic therapy, which included 42.5% antiplatelet agents and 10.8% warfarin. The positive predictors of ischemic stroke were age ≥ 75 (odds ratio = 1.48) and a history of ischemic stroke (odds ratio = 3.19); the negative predictors were continued use of warfarin (odds ratio = 0.01), transient use of warfarin (odds ratio = 0.25), alternating use of warfarin and antiplatelet agents (odds ratio = 0.04), and use of antiplatelet agents alone (odds ratio = 0.13). The positive predictors of prescribing warfarin were a history of ischemic stroke (odds ratio = 2.32), thromboembolism (odds ratio = 31.06), mitral stenosis (odds ratio = 10.02), and mechanical valve replacement (odds ratio = 136.02). The negative predictor of prescribing warfarin was age ≥ 75 (odds ratio = 0.62). CONCLUSIONS: It is important in prevention of ischemic stroke to give antithrombotic therapy to newly diagnosed atrial fibrillation patients. Underuse of antithrombotic therapy and warfarin were more severe in our study than in Western countries.