Endovascular Treatment Beyond 24 Hours for Acute Ischemic Stroke Caused by Anterior Circulation Large Vessel Stenosis

This study is a multicenter, prospective, randomized, open-label, blinded end-point (PROBE) trial. Eligible participants will be adults (age >18 years) presenting with acute ischemic stroke (AIS) due to anterior circulation large vessel occlusion (LVO), either with a time window of 24 to 120 hours from symptom onset or last known well or progressive ischemic stroke with a time from symptom onset of 24 hours to 7 days. Participants who meet all inclusion criteria and none of the exclusion criteria will be randomly assigned in a 1:1 ratio to one of two treatment arms. The control group will receive best medical management alone, while the intervention group will receive best medical management in combination with endovascular therapy (EVT). EVT procedures may include mechanical thrombectomy, aspiration thrombectomy, intra-arterial thrombolysis, angioplasty, or stenting, as deemed appropriate by the treating physician.

The primary objective of the study is to evaluate the safety and efficacy of EVT in patients presenting with AIS due to anterior circulation LVO beyond 24 hours from symptom onset. The primary endpoint is functional independence at 90 days, defined as a score of 0-2 on the modified Rankin Scale (mRS).

Inclusion criteria

• Age > 18 years
• Acute ischemic stroke with a time window of 24 to 120 hours from symptom onset or last known well, or progressive ischemic stroke with a time from symptom onset of 24 hours to 7 days (A ≥4-point increase in NIHSS attributable to the culprit vessel territory )
• NIHSS score 5-25
• Occlusion or ≥70% stenosis of the internal carotid artery or the M1/M2 segment of the middle cerebral artery, confirmed by CTA, MRA, or DSA, and deemed to be the culprit vessel responsible for the clinical presentation of acute ischemic stroke
• Meet one of the following imaging criteria:

• MRI-based criteria: the infarct volume on DWI is less than one-third of the MCA territory, with evidence of DWI-FLAIR mismatch or MR perfusion showing a core infarct volume ≤30 ml, a mismatch ratio ≥1.8, and a mismatch volume ≥15 ml;
• CTA-based criteria: good collateral circulation on the affected side defined ascollateral filling >50% of the MCA territory (Tan score ≥2) and an ASPECTS score ≥6);
• CTP-based criteria: ischemic core volume ≤30 ml, mismatch ratio ≥ 1.8, and mismatch volume ≥ 15mL
• Signed informed consent obtained

Exclusion criteria

• Pre-stroke mRS ≥ 2
• Patients unable to undergo vascular imaging
• Patients with known allergies to iodine contrast agents, anesthetics, or any contraindication to endovascular treatment
• Prior endovascular therapy performed after the index stroke event during the current hospitalization
• Intracranial hemorrhage identified on initial imaging
• Platelet count <50×10⁹/L, or presence of a known hemorrhagic diathesis , coagulation factor deficiencies, or use of oral anticoagulation therapy with an International Normalized Ratio (INR) > 3.0
• Refractory hypertension, defined as sustained systolic blood pressure >200 mmHg or diastolic blood pressure >120 mmHg despite optimal medical management
• History of intracranial hemorrhage within the past 3 months, including parenchymal hemorrhage, intraventricular hemorrhage, subarachnoid hemorrhage, epidural hemorrhage, or subdural hemorrhage
• Significant mass effect with midline shift confirmed by CT or MRI
• Suspected cardioembolic stroke or stroke due to non-atherosclerotic etiologies, such as:arterial dissection,Moyamoya disease, Infective endocarditis, or Immune-mediated vasculitis
• Prior intracranial stent placement in the same culprit vessel
• Major surgery performed within the past 30 days
• Pregnant or current breastfeeding
• Presence of severe systemic comorbidities with a life expectancy of less than 3 months
• Deemed unsuitable for participation by the investigator for any reason