Etiologic subtypes of first and recurrent ischemic stroke in young patients using A-S-C-O and TOAST classification criteria: A retrospective follow-up study.

Introduction: Scarce data exist on the etiology of recurrent ischemic strokes (ISs) among young adults. We analyzed the etiology of first-ever and recurrent events and the differences between them.

Patients and methods: Patients aged 15-49 years with a first-ever IS in 1994-2007 were included in the Helsinki Young Stroke Registry. In this retrospective cohort study, data on recurrent ISs were identified from Care Register for Health Care until the end of 2017 and Causes of Death Register and from patient records until the end of 2020. All first-ever and recurrent ISs were classified using Atherosclerosis-Small vessel disease-Cardioembolism-Other Cause (A-S-C-O) and Trial of Org 10172 in Acute Stroke Treatment (TOAST) classifications.

Results: A total of 970 patients were included (median age at index IS 46 years, interquartile range 43-48, 33% women), of which 155 (16.0%) patients had recurrent IS, with 8 (5.2%) fatal cases and 5 (3.2%) unverifiable cases. The median follow-up was 17.4 (IQR 13.9-21.7) years. Median time from the index event to the first recurrent event was 4.5 (interquartile range [IQR] 1.6-10.2) years. Recurrence was more often due to definite cardioembolism (10.7% vs 18.0%, p = 0.013), while the proportion of other definite A-S-C-O subgroups remained the same. With TOAST classification, the proportion of true cryptogenic ISs decreased (16.7% vs 6.7%, p = 0.003), while those with incomplete evaluation increased (9.3% vs 19.3%, p = 0.015). Other TOAST phenotypes remained the same.

Conclusion: The proportion of definite cardioembolism increased at recurrence using the A-S-C-O classification and the number of cryptogenic ISs decreased using the TOAST classification, while cases with incomplete evaluation increased. Most etiologies remained the same.