Intra-arterial Thrombolysis For Acute Ischemic Stroke With Medium Vessel Occlusion

Inclusion Criteria:

* Age 18 to 80 years.
* Time from symptom onset or last known well to randomization within 24 hours.
* Clinical diagnosis of acute ischemic stroke confirmed by CTA or MRA as being caused by isolated acute medium vessel occlusion, including distal M2/M3/M4 segments of the middle cerebral artery, A2/A3/A4 segments of the anterior cerebral artery, or P2/P3 segments of the posterior cerebral artery. Isolated occlusion is defined as a single symptomatic vessel occlusion; patients with multiple vessel occlusions or uncertain culprit vessel are excluded.
* Baseline NIHSS score ≥ 6, and NIHSS score ≤ 25 at the time of randomization.
* For patients presenting beyond 6 hours from symptom onset: perfusion imaging criteria require a Tmax \> 6 s volume ≥ 10 mL and a core infarct volume (defined as rCBF \< 30%) \< 50% of the Tmax \> 6 s volume.
* Patient or legally authorized representative is able to understand and voluntarily sign the informed consent form.

Exclusion Criteria:

* Clinical Exclusion Criteria:
* Pre-stroke modified Rankin Scale (mRS) score \> 2.
* Presence of contraindications to intravenous thrombolysis.
* Known allergy to heparin, contrast media, anesthetics, or other definite contraindications to endovascular treatment.
* Comorbid severe diseases that may affect outcome assessment, including but not limited to malignancy, severe heart failure, or renal failure, with expected life expectancy \< 6 months.
* Uncontrolled hypertension refractory to medical therapy (systolic blood pressure \> 220 mmHg or diastolic blood pressure \> 120 mmHg).
* Baseline blood glucose \< 2.8 mmol/L (50 mg/dL) or \> 22.2 mmol/L (400 mg/dL).
* Known bleeding diathesis, including but not limited to: platelet count \< 100 × 10⁹/L; heparin treatment within 48 hours with APTT ≥ 35 seconds; oral warfarin with INR \> 3. Note: Patients without a history or suspicion of coagulation disorders do not require laboratory testing for coagulation parameters prior to enrollment.
* Stroke onset with seizure or seizure occurring during the course of stroke, precluding accurate determination of baseline NIHSS score.
* Female patients who are pregnant, lactating, or have a positive pregnancy test at hospital admission.
* Currently participating in another investigational drug or device study that may interfere with the results of this study.
* Other conditions judged by the investigator to be unsuitable for participation or posing significant risk to the patient.
* Imaging Exclusion Criteria:
* Intracranial hemorrhage confirmed by baseline head CT or MRI, including parenchymal hemorrhage, intraventricular hemorrhage, subarachnoid hemorrhage, or subdural/epidural hemorrhage.
* Presence of midline shift or cerebral herniation, or other ventricular mass effect with midline shift.
* Anticipated inability to complete endovascular treatment due to vascular tortuosity, severe vessel wall calcification, or other anatomical challenges.
* Aortic dissection.
* Multiple vessel occlusions confirmed by CTA or MRA with inability to identify the symptomatic culprit vessel, such as bilateral middle cerebral artery occlusion or concurrent middle cerebral artery and basilar artery occlusion.
* Suspected or confirmed non-acute occlusion of the symptomatic culprit vessel.