Abstract Number: Esoc2026a1269 How Well Do We Identify Af in Esus? Detection of Atrial Fibrillation in Embolic Stroke of Undetermined Source by Implantable Loop Recorder. A Cross-Sectional Study

Abstract Background and aims Embolic stroke of undetermined source (ESUS) accounts for approximately 17% of ischemic events. Detection of atrial fibrillation (AF) guides secondary stroke prevention. Implantable loop recorders (ILR) have demonstrated superior AF detection compared to conventional cardiac monitoring.This study aims to evaluate the accuracy of ESUS classification, appropriateness of ILR referral and the atrial fibrillation detection rate in those who underwent ILR implantation. Methods Using Irish National Audit of Stroke data a cross-sectional review was conducted on a randomized sample of 73 local ischemic stroke cases from 2024. Stroke aetiology was determined using TOAST and ASCOD criteria. Referral rates of ESUS patients for ILR implantation were reviewed. The primary endpoints were appropriateness of ILR referral and AF detection rates. Results Out of the 73 patients, (mean age 72.5 ± 1.4 years; 59% male) 16 were correctly identified as ESUS (mean age 67 ± 9.3 years). Among these, 7 (44%) were referred for ILR implantation. Of the remaining ESUS patients who were not referred, 4 had documented clinical reasons, while 5 patients had no clear reason identified. ILR monitoring detected AF in 3 of the 7 referred cases (43%). Conclusions Accurate stroke classification combined with stroke led decision making improves appropriate ILR utilization and allows for individualized secondary prevention strategies. However, a substantial proportion of ESUS patients were not referred, indicating an opportunity to improve ILR referral rates. ILR monitoring demonstrated an important diagnostic yield for occult AF in ESUS patients. Conflict of interest Tiago do Amaral: Nothing to disclose; Paul Eoin Cotter: Nothing to disclose; Natalie Maloney: Nothing to disclose.