Abstract Number: Esoc2026a1713 Diagnostic Value of Implantable Loop Recorders in Patients With Embolic Stroke of Undetermined Source: Real-World Detection of Atrial Fibrillation and Stroke Recurrence

Abstract Background and aims In patients with embolic stroke of undetermined source (ESUS), identification of atrial fibrillation (AF) is essential for secondary prevention. Although implantable loop recorders (ILRs) improve AF detection, real-world data regarding subsequent treatment decisions and stroke recurrence remain limited. Methods We retrospectively analyzed patients diagnosed with ESUS who underwent ILR implantation at a single comprehensive stroke center between 2016 and 2024 and were followed for at least 1 year. We evaluated AF detection rate and time to detection, antithrombotic therapy at implantation, treatment modifications after AF detection, and characteristics of recurrent ischemic stroke during follow-up Results A total of 190 patients were included (median age 72 years; 36.8% female). AF was detected in 59 patients (31.1%), with a median time to detection of 104 days. At the time of ILR implantation, 144 patients (76.8%) were receiving antiplatelet therapy and 41 (21.4%) anticoagulation. After AF detection, anticoagulation was initiated in all patients (direct oral anticoagulants in 98.3%), and catheter ablation was performed in 8 patients (13.6%). During follow-up, 13 patients (6.8%) experienced recurrent ischemic stroke (median NIHSS score at recurrence, 4); AF had not been detected in 11 of these cases. 2 patients without AF presented with large vessel occlusion. Anticoagulation, mainly warfarin, was newly initiated in 6 patients at recurrence. Conclusions ILR-guided monitoring contributed to AF identification and therapeutic decision-making in patients with ESUS. However, recurrent stroke often occurred in the absence of detected AF, highlighting the need for continuous etiological reassessment beyond AF surveillance alone. Conflict of interest Takafusa Ando: nothing to disclose. Naruhiko Kamogawa: nothing to disclose. Junpei Koge: nothing to disclose. Masayuki Shiozawa: nothing to disclose. Sohei Yoshimura: nothing to disclose. Eriko Yamaguchi: nothing to disclose. Masafumi Ihara: nothing to disclose. Kazunori Toyoda reports honoraria from Janssen Pharmaceuticals and Daiichi Sankyo. Masatoshi Koga reports honoraria from Daiichi Sankyo and research funding from Boston Scientific and Daiichi Sankyo.