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

Inclusion criteria:

• Age > 18 years

• Acute ischemic stroke with a time window of 24 to 120 hours from symptom onset orlast known well, or progressive ischemic stroke with a time from symptom onset of 24hours to 7 days (A ≥4-point increase in NIHSS attributable to the culprit vesselterritory )

• NIHSS score 5-25

• Occlusion or ≥70% stenosis of the internal carotid artery or the M1/M2 segment ofthe middle cerebral artery, confirmed by CTA, MRA, or DSA, and deemed to be theculprit vessel responsible for the clinical presentation of acute ischemic stroke

• Meet one of the following imaging criteria:

1. MRI-based criteria: the infarct volume on DWI is less than one-third of the MCAterritory, with evidence of DWI-FLAIR mismatch or MR perfusion showing a coreinfarct volume ≤30 ml, a mismatch ratio ≥1.8, and a mismatch volume ≥15 ml;

2. CTA-based criteria: good collateral circulation on the affected side definedascollateral filling >50% of the MCA territory (Tan score ≥2) and an ASPECTSscore ≥6);

3. CTP-based criteria: ischemic core volume ≤30 ml, mismatch ratio ≥ 1.8, andmismatch 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 anycontraindication to endovascular treatment

• Prior endovascular therapy performed after the index stroke event during the currenthospitalization

• Intracranial hemorrhage identified on initial imaging

• Platelet count <50×10⁹/L, or presence of a known hemorrhagic diathesis , coagulationfactor deficiencies, or use of oral anticoagulation therapy with an InternationalNormalized Ratio (INR) > 3.0

• Refractory hypertension, defined as sustained systolic blood pressure >200 mmHg ordiastolic blood pressure >120 mmHg despite optimal medical management

• History of intracranial hemorrhage within the past 3 months, including parenchymalhemorrhage, intraventricular hemorrhage, subarachnoid hemorrhage, epiduralhemorrhage, or subdural hemorrhage

• Significant mass effect with midline shift confirmed by CT or MRI

• Suspected cardioembolic stroke or stroke due to non-atherosclerotic etiologies, suchas:arterial dissection,Moyamoya disease, Infective endocarditis, or Immune-mediatedvasculitis

• 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 3months

• Deemed unsuitable for participation by the investigator for any reason