Efficacy and Safety of Bailout Intracranial Angioplasty or Stenting After Thrombectomy for Acute Intracranial Atherosclerotic Large Vessel Occlusion (ANGEL-REBOOT 2)

Inclusion Criteria: 1. Age≥18 years. 2. Time interval from symptom onset to puncture ≤24 hours. 3. National Institute of Health Stroke Scale (NIHSS) Score ≥6 before randomisation. 4. Pre-stroke modified Rankin Scale (mRS) of 0-2. 5. Each patient or their legal representative must provide written informed consent before enrolment. Imaging Inclusion Criteria: 1. For patients with anterior circulation stroke, a CT or DWI-based Alberta Stroke Program Early CT Score (ASPECTS) of ≥6 is required. 2. For patients with posterior circulation stroke, CT or DWI-based posterior circulation ASPECTS (pc-ASPECTS) of ≥6 and Pons-Midbrain Index (PMI) of \<3 are required. Angiographic Inclusion Criteria: 1. Acute ischemic stroke (AIS) resulting from large vessel occlusion (LVO) involving the intracranial internal carotid artery, the M1 segment of the middle cerebral artery, the V4 segment of the vertebral artery, or the basilar artery, with high suspicion of intracranial atherosclerotic stenosis-related large-vessel occlusion (ICAS-LVO). 2. Part 1 (RCT): Successful recanalization of the occluded artery (eTICI ≥ 2b) with residual stenosis ≥ 70% after 1-2 thrombectomy attempts. Part 2 (Prospective observational cohort): Failure to achieve successful recanalization (eTICI 0-2a) after at least two thrombectomy attempts. All other inclusion criteria are identical to those for Part 1. 3. Occluded artery amenable to angioplasty (balloon dilation and/or stenting) by the judgement of the treating neurointerventionalist. Exclusion Criteria: 1. Any sign of intracranial hemorrhage (ICH, except microbleeds) on baseline brain imaging. 2. CT or MR imaging evidence of intracranial tumor (except small meningiomas or cerebral aneurysms \< 3mm in diameter). 3. Any indication of intracranial vessel perforation during thrombectomy.. 4. Presence of tandem lesion in the extracranial segment of the internal carotid artery or vertebral artery, or intracranial arterial stenosis with distal vessel occlusion.. 5. Stenosis caused by non-atherosclerotic intracranial arteriopathies (e.g., autoimmune vasculitis, vasospasm, cerebral artery dissection). 6. Evidence of cardioembolism (e.g., atrial fibrillation, prosthetic heart valve, infective endocarditis, mitral stenosis, atrial myxoma, intracardiac thrombus/vegetation, left ventricular aneurysm, etc.). 7. Contraindication for antiplatelet treatment. 8. Excessive vascular tortuosity or anatomical variants that may preclude successful delivery or positioning of interventional devices. 9. History of contraindication to the use of contrast medium. 10. Refractory hypertension (defined as systolic blood pressure\>185 mmHg or diastolic blood pressure\>110 mmHg) that cannot be controlled by drug treatment. 11. Known hereditary or acquired bleeding tendency, lack of coagulation factors, or oral anticoagulants with INR\>1.5. 12. Blood glucose\<2.8 or\>22.2 mmol/L; Platelet count\<100\*109/L, serum creatinine\>2.0 g/L (177 μ mol/L), or glomerular filtration rate\<30 ml/(min\*1.73 m2). 13. Concurrent participation in another drug or device trial, or expected participation within the following 3 months. 14. Patients whose life expectancy is less than 1 year (such as patients with malignant tumor, advanced cardiopulmonary disease, etc.). 15. Known pregnancy or lactation, or positive pregnancy test before randomization (or before enrollment). 16. Known dementia or psychiatric disorder that precludes completion of neurological assessments and follow-up. 17. Any other condition deemed by the site investigator to make the patient unsuitable for participation.