ABSTRACT NUMBER: ESOC2026A1003 SUBTYPE SPECIFIC PATTERNS OF RECURRENCE AFTER ISCHAEMIC STROKE

Abstract Background and aims Ischaemic stroke is divided into aetiological subtypes to guide secondary prevention. A substantial portion of ischaemic stroke cases are classified as cryptogenic, where the cause and optimal strategy of secondary prevention are unknown. We aimed to determine the subtypes of recurrent stroke in patients with cryptogenic index stroke to further understand the underlying cause of cryptogenic stroke. We also investigate recurrence patterns of other subtypes. Methods We used data from the Sahlgrenska Academy Study on Ischaemic Stroke (SAHLSIS), a prospective, observational study of adult patients with acute ischaemic stroke under 70 years of age who were included 1998-2013 (n=1,335) and followed through December 31st 2022 (median 8.0 years, IQR 6.8). Recurrent strokes were identified using national registers and verified by review of medical records. Stroke subtype was adjudicated using the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. Results During follow-up, 324 (24.3%) patients had a recurrent ischaemic stroke. Cryptogenic stroke survivors most often (30%) had a cryptogenic recurrent stroke and a smaller fraction (20%) of their recurrent events was classified as cardioembolic. Other subtypes also displayed concordance between index and recurrent subtype, except for small artery occlusion where cardioembolism was the predominant cause of recurrent stroke. Conclusions Recurrent ischaemic stroke patterns after cryptogenic stroke show substantial concordance between recurrent and index stroke subtype, suggesting that cryptogenic stroke may arise from distinct underlying mechanisms rather than being driven solely by unrecognised cardioembolic sources. Further research is needed to elucidate the underlying pathophysiology and the best secondary prevention strategies for cryptogenic stroke. Conflict of interest All authors: Nothing to disclose