Risk factors for cerebral ischemic events in patients with atrial fibrillation on warfarin for stroke prevention

Abstract

Background and purposes Patients with atrial fibrillation (AF) on treatment with oral anticoagulants may still suffer ischemic cerebrovascular events. The aim of this study was to evaluate the risk factors for cerebral ischemic events in warfarin-treated AF patients with an International Normalized Ratios (INR) above 1.8 on admission. Methods In a case–control study, cases were consecutive patients with AF who were on warfarin and who were admitted to four Italian hospitals after an acute cerebrovascular ischemic event (ischemic stroke or transient ischemic attack) with an INR above 1.8. Controls were selected from a single anticoagulation clinic and were patients with AF on adequate warfarin treatment who did not suffer cerebrovascular events. Results Cases were identified among 4785 consecutive patients with an ischemic cerebral event. 148 cases (3.1%, 21 with transient ischemic events and 127 with ischemic strokes) had AF and were taking warfarin with an INR above 1.8 on admission. On multivariate analysis, diabetes (OR 3.8; 95% CI 1.09–13.82, p = 0.025), hyperlipidemia (OR 4.5; 95% CI 1.11–18.23, p = 0.035) and carotid/vertebral atherosclerosis on ultrasound (OR 3.0; 95% CI 1.13–8.41, p = 0.028) were independent predictors for ischemic cerebral events. The use of statins was inversely correlated with an ischemic event (OR 0.1; 95% CI 0.06–0.47. p = 0.001). Conclusions Carotid/vertebral atherosclerosis, diabetes and hyperlipidemia are associated with an increased risk for ischemic events in patients with AF on adequate warfarin treatment. Statins significantly reduce the risk of ischemic events.