Abstract WP045: Antithrombotic Management and Recurrent Stroke in EVT-Treated ESUS Patients With Intracranial Occlusions

Background: Patients with embolic stroke of undetermined source (ESUS) represent a heterogeneous population in whom optimal secondary prevention remains an open question. Prior antithrombotic trials largely enrolled patients with mild strokes. In this study, we reviewed cases of ESUS patients who underwent endovascular thrombectomy (EVT) to characterize post-EVT secondary stroke prevention treatment patterns and recurrence risk. Methods: We analyzed a prospectively maintained database to identify consecutive cases with planned EVT for intracranial occlusions at a single institution between 2019 - 2023. Patients were included if initial workup supported an ESUS diagnosis, excluding those with high risk causes including atrial fibrillation (AF), left ventricular (LV) thrombus, or >50% intra- or extracranial stenosis. Patients with lower risk causes were enrolled, including those with heart failure and EF ≤35% without LV thrombus, possible hypercoagulability of malignancy, and/or deep venous thrombosis (DVT). Demographics, discharge antithrombotic regimen, and incidence of recurrent stroke/TIA were recorded. Results: Among the thirty-nine patients meeting entry criteria, age was 64.8 ±16.3, 61.5% were women, and median pre-EVT NIHSS was 14 (IQR, 7-20). Occlusion sites included M1 (41.0%), M2 (25.6%), M3 (5.1%) terminal ICA (17.9%), and single cases of basilar, cervical ICA, PCA, and VA (2.6% each). Patent foramen ovale (PFO) was present in 8 patients (20.5%). Follow-up information was available in 21 (53.8%) patients (median 17 months). Sixteen (76.2%) were discharged on antiplatelets and 5 (23.8%) on anticoagulation, of whom two had known DVTs (one without right-to-left shunt). Recurrent ischemic stroke (4) or TIA (2) occurred in 28.6% (6/21) of patients at a median of 14 months after the index event ( Table 1 ). Among the four recurrent ischemic strokes, 3 were large vessel occlusions. All recurrences occurred on antiplatelet. Mechanisms included AF in three patients, unclosed PFO in one, dissection in one, and LV thrombus (EF 19% at index event) in one. Conclusions: In this consecutive patient cohort, ESUS patients treated with EVT had a high rate of recurrent ischemic events, all occurring on antiplatelet therapy. Interpretation is limited by incomplete follow-up and potential ascertainment bias. Prospective studies of secondary prevention in ESUS should include patients with LVO to better understand optimal secondary stroke prevention in this ESUS subtype.