Intra-arterial Alteplase for Acute Ischemic Stroke After Mechanical Thrombectomy

Inclusion Criteria: 1. Aged 18 years or older. 2. Clinical diagnosis of acute ischemic stroke. 3. Time from symptom onset to randomization within 24 hours, including wake-up stroke or no-witness stroke; the onset time refers to "Last Known Well" (LKW). 4. CTA or MRA confirmed occlusion of the intracranial segment of the internal carotid artery, or M1 or M2 segment of the middle cerebral artery; stable eTICI score of 2b50-3 after mechanical thrombectomy, with or without intravenous thrombolysis. Patients with an eTICI score of 2b50-3 on the diagnostic cerebral angiography before mechanical thrombectomy are also eligible for the study. 5. Baseline NIHSS of 6-25. 6. NCCT/DWI-MRI ASPECTS ≥ 6; 7. Pre-stroke mRS score ≤ 1, or mRS \>1 but not related to neurological disease (e.g., amputation, blindness). 8. Signed informed consent. Exclusion Criteria: 1. Contraindication to rt-PA (except time to therapy). 2. Planned use of dual antiplatelet therapy within the first 24 hours after mechanical thrombectomy. 3. Angiographic evaluation showing dissection, severe stenosis, or complete occlusion of the carotid artery, which requires the use of carotid artery stents during the endovascular procedure. 4. Suspected cerebral vasculitis based on medical history and/or angiographic evaluation. 5. Women who are pregnant or breastfeeding. 6. Participation in other clinical trials. 7. Preoperative intracranial hemorrhage confirmed by cranial CT or MRI. 8. Known genetic or acquired bleeding disposition with anticoagulation factor deficiency. 9. Coagulation disorder with INR \> 1.7 or use of new oral anticoagulants (within 48 hours of symptom onset). 10. Platelet count \<50X10\^9/L. 11. Suspected vascular occlusion as a result of infective endocarditis. 12. Known severe renal insufficiency with glomerular filtration rate \<30 ml/min or blood creatinine \>220 μmol/L (2.5 mg/dl). 13. Severe allergy to contrast (non-mild rash allergy) or absolute contraindication to iodine contrast. 14. Suspected aortic dissection. 15. Previous parenchymal organ surgery or biopsy in the last 1 month; 16. Any active bleeding or recent bleeding (gastrointestinal, urinary tract bleeding, etc.) in the last 1 month; 17. SBP \> 185 mmHg or DBP \> 110 mmHg refractory to treatment. 18. Anticipated life expectancy \< 6 months (e.g., malignancy, severe cardiopulmonary disease, etc.). 19. Any condition that, in the judgment of the investigator, makes the patient unsuitable for this study or where this study may impose a significant risk to the patient (e.g., inability to understand and/or comply with study procedures and/or follow-up due to psychiatric disorders, cognitive or emotional impairment).