Importance of infarct topography in determination of stroke mechanism and recurrence risk: a post-hoc analysis of the dabigatran acute treatment of stroke trial

OBJECTIVE: To evaluate the relationship between infarct pattern, inferred stroke mechanism and risk of recurrence in patients with ischaemic stroke. The question is clinically relevant to optimise secondary stroke prevention investigations and treatment. DESIGN: We conducted a retrospective analysis of the dabigatran treatment of acute stroke II (DATAS II) trial (ClinicalTrials.gove NCT NCT02295826), in which patients underwent diffusion-weighted imaging (DWI) at baseline and 30 days after randomisation to one of two antithrombotic therapies. Patients were classified as embolic, isolated small subcortical infarcts or transient ischaemic attack TIA (no infarct) at baseline and day 30. Stroke mechanism was determined by traditional and modified (based on DWI lesion findings) Trial of Org 10 172 in Acute Stroke Treatment (TOAST) criteria (DWI-TOAST). SETTING: Multicentre (6) tertiary acute stroke treatment hospitals. PARTICIPANTS: 305 adults with minor ischaemic stroke (National Institutes of Health Stroke Scale (NIHSS) score≤9). RESULTS: Of 305 patients, 148 had embolic pattern infarcts, 93 were isolated small subcortical infarcts and 64 had no infarct on baseline MRI (TIA). In the absence of DWI, TOAST classification indicated the mechanism was cryptogenic in 147 patients (48.2%), and small-vessel occlusion in 127 (41.6%). Using, DWI-TOAST, the number of cryptogenic strokes decreased to 123 (40.3%), and the number of small-vessel occlusion strokes increased to 151 (49.5%). Recurrent infarcts were seen in 13% of patients with an MRI-defined embolic infarct pattern and cryptogenic mechanism on DWI-TOAST. The relative risk of recurrent infarction in patients with undetermined aetiology was increased compared with other categories (standardised coefficient=1.0 (0.1, 1.9), p=0.029). The topography of recurrent infarcts was most often embolic (60.9%), but in 39.1% an isolated small subcortical infarct was seen. CONCLUSIONS: Definitive identification of infarct topography with DWI has a significant impact on infarct mechanism classification. The variable relationship between baseline infarct patterns, clinical presentation and recurrent infarct distribution is a challenge to both the lacunar and embolic stroke of uncertain source (ESUS) concepts. Irrespective of aetiological classification, patients with MRI-defined cryptogenic embolic pattern infarcts are at high risk for recurrent events. TRIAL REGISTRATION NUMBER: Linked to the DATAS II trial. CLINICALTRIALS: gov ID NCT02295826.