BACKGROUND: Recent randomized trials demonstrated the beneficial effect of endovascular therapy in patients with low Alberta Stroke Program Early CT Score. Despite large follow-up infarct volumes, a significantly increased rate of good functional outcomes was observed, challenging the role of infarct volume as a predictive imaging marker. This analysis evaluates the extent to which the effects of endovascular thrombectomy on functional outcomes are explained by (1) follow-up infarct volume and (2) early neurological status in patients with stroke with low Alberta Stroke Program Early CT Score. METHODS: TENSION (Efficacy and Safety of Thrombectomy in Stroke With Extended Lesion and Extended Time Window) was a randomized trial conducted from February 2018 to January 2023 across 41 stroke centers. Two hundred fifty-three patients with ischemic stroke due to anterior circulation large vessel occlusion and Alberta Stroke Program Early CT Score of 3 to 5 were randomized to endovascular thrombectomy plus medical treatment or medical treatment alone. All patients with the availability of relevant data points were included in this secondary as-treated analysis. The primary outcome was the 90-day modified Rankin Scale score. Confounder-adjusted mediation analysis was performed to quantify the proportion of the treatment effect on a 90-day modified Rankin Scale score explained by (1) 24-hour follow-up infarct volume and (2) 24-hour National Institutes of Health Stroke Scale scores. RESULTS: One hundred eighty-eight patients were included; thereof, 87 (46%) were female patients. Median age was 72 (interquartile range, 63-79) years. The endovascular thrombectomy cohort had a 20.5 (95% CI, 8.3-33.7) percentage points higher probability of achieving independent ambulation (modified Rankin Scale, 0-3) and a 24.2 (95% CI, 13.4-35.8) percentage points lower mortality at 90 days compared with medical treatment alone. The reduction in 24-hour follow-up infarct volume explained 30% of the treatment effect on functional outcomes, while the 24-hour National Institutes of Health Stroke Scale score explained 61%. CONCLUSIONS: In patients with low Alberta Stroke Program Early CT Score, infarct volume demonstrated limited explanatory power for functional outcomes compared with the early neurological status, which may more effectively reflect factors such as the involvement of specific brain regions, disruption of structural networks, and selective neuronal loss.

Clinic of Neurology Jessenius Faculty of Medicine Comenius University Martin Slovakia

Clinic of Radiology Jessenius Faculty of Medicine Comenius University Martin Slovakia

Department of Clinical Neurosciences Hotchkiss Brain Institute Health Science Centre University of Calgary and Foothills Medical Centre AB Canada

Department of Medical Imaging St Anne's University Hospital Brno and Faculty of Medicine Masaryk University Czech Republic

Department of Neurology Aarhus University Hospital Denmark

Department of Neurology and Stroke Center Hospital La Paz Institute for Health Research La Paz University Hospital Universidad Autonoma de Madrid Spain

Department of Neurology Faculty Hospital Trnava Slovakia

Department of Neurology Hôpital Maison Blanche Université Reims Champagne Ardenne France

Department of Neurology Oslo University Hospital Norway

Department of Neurology Universitätsklinikum Carl Gustav Carus an der Technischen Universität Dresden Germany

Department of Neuroradiology Aarhus University Hospital Denmark

Department of Neuroradiology HELIOS Medical Center Campus of MSH Medical School Hamburg Schwerin Germany

Department of Neuroradiology Hôpital Maison Blanche Université Reims Champagne Ardenne France

Department of Neuroradiology Medical University Innsbruck Austria

Department of Neuroradiology Oslo University Hospital Norway

Department of Radiology Aretaieion University Hospital National and Kapodistrian University of Athens Greece

Department of Radiology Faculty Hospital Trnava Slovakia

Department of Vascular Neurology University Hospital Bonn Germany

Division of Neuroradiology Vascular and Interventional Radiology Department of Radiology Medical University Graz Austria

Dresden Neurovascular Center Universitätsklinikum Carl Gustav Carus an der Technischen Universität Dresden Germany

eppdata GmbH Hamburg Germany

Faculty of Medicine in Hradec Kralove Department of Neurology Charles University Prague Czech Republic

Faculty of Medicine in Hradec Kralove Department of Radiology Charles University Prague Czech Republic

Institut für Diagnostische und Interventionelle Neuroradiologie Universitätsklinikum Würzburg Germany

Institut für Diagnostische und Interventionelle Radiologie und Neuroradiologie DIAKO Krankenhaus gGmbH Flensburg Germany

Institut für Neuroradiologie Universitätsklinikum Frankfurt Frankfurt am Main Germany

Institute of Neuroradiology Universitätsklinikum Carl Gustav Carus an der Technischen Universität Dresden Germany

Klinik für Diagnostische und Interventionelle Neuroradiologie Klinikum Bremen Mitte Bremen Germany

Klinik für Diagnostische und Interventionelle Neuroradiologie Universitätsklinikum Bonn Germany

Klinik für Neurologie Klinikum Bremen Mitte Bremen Germany

Klinik und Poliklinik für Neurologie Universitätsklinikum Hamburg Eppendorf Germany

Klinik und Poliklinik für Neuroradiologische Diagnostik und Intervention Universitätsklinikum Hamburg Eppendorf Germany

Klinikum Dortmund gGmbH Klinikum der Universität Witten Herdecke Dortmund Germany

Laboratoire de Biométrie et Biologie Évolutive Université de Lyon Villeurbanne France

Neurologie Universitätsklinikum Heidelberg and Universität Heidelberg Germany

Neuroradiologie Universitätsklinikum Heidelberg and Universität Heidelberg Germany

Norwegian University of Science and Technology Trondheim Norway

Service de Biostatistique Hospices Civils de Lyon France

Vascular Neurology Research Group German Center for Neurodegenerative Diseases

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