Abstract WP519: Ischemic Stroke Despite Oral Anticoagulant Therapy in Patients With AF - What is the Risk of Recurrence and How to Prevent Further Events?

Abstract

Background: It is unknown whether patients with atrial fibrillation (AF) having an ischemic stroke despite preventive oral anticoagulant therapy are at increased risk for further recurrent strokes and how secondary prevention should be managed. Methods: We conducted a pooled individual patient data analysis of 7 prospective cohort studies recruiting patients with AF and an index event (ischemic stroke or TIA). We compared patients taking oral anticoagulants (Vitamin K antagonists [VKA] or direct oral anticoagulants [DOAC]) prior to index event (OAC prior ) with those without prior anticoagulation (OAC naive ). We further compared those who changed the type (i.e. from VKA or DOAC or vice versa) of anticoagulation (OAC changed ) with those who continued the same anticoagulation as secondary prevention (OAC unchanged ). Time-to-endpoint was analysed using multivariate cox proportional hazard regression models with frailty term for study and calculating hazard ratios (HR) with corresponding 95% confidence intervals. Results: We included 5413 patients (median age 78years [IQR 71-84years], 5136 [96.7%] had ischemic stroke as index event, median NIHSS-on-admission 6 [IQR 2-12]). The median CHA 2 DS 2 -Vasc score was 5 (IQR4-6) and not different (p=0.103) between prior OAC (n=1195) and OAC naive (n=4119). During follow-up of 6128 patient years, 289 patients had recurrent ischemic stroke (AIS, 4.7%/year, 95%CI 4.2-5.3%). prior OAC was independently associated with an increased risk of AIS (HR 1.6, 95%CI 1.1-2.1, p=0.006). OAC changed (n=307) was not associated with decreased risk of AIS (HR 1.3, 95%CI 0.8-2.2, p=0.326) compared to OAC unchanged (n=585). Conclusion: Patients with AF who failed oral anticoagulation once are at a higher risk for further ischemic strokes although the CHA 2 DS 2 -Vasc scores did not differ between both groups.