Endovascular Therapy for Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

Inclusion Criteria: Participants must meet all of the following criteria: 1. Aged 18 to 80 years. 2. SAH confirmed by cranial CT, with an intracranial aneurysm identified by CTA, MRA, or DSA and determined to be the source of bleeding. 3. Prior treatment of the aneurysm by endovascular intervention or surgical clipping. 4. Evidence suggestive of CVS within 14 days after onset, defined by at least one of the following: 1. Clinical deterioration, including a decrease in GCS score of \>2 points and/or a new focal neurological deficit not attributable to another known neurological cause; 2. TCD confirmed vasospasm, defined as mean flow velocity (MFV) \>120 cm/s in the middle cerebral artery (MCA) and Lindegaard ratio \>3, after excluding other causes of increased flow velocity such as anemia or fever; 3. Vasospasm confirmed by DSA or CTA. Exclusion Criteria: 1. Hunt-Hess grade 5 with critical illness and inability to tolerate intervention. 2. Contraindications to milrinone, including milrinone allergy, aortic or pulmonary valve stenosis, obstructive hypertrophic cardiomyopathy, acute coronary syndrome, or malignant arrhythmia. 3. Perioperative procedure-related complications that may interfere with study assessment, such as significant stenosis of the parent artery. 4. Irreversible cerebral infarction involving the entire vascular territory affected by vasospasm. 5. Poor blood pressure control, defined as systolic blood pressure \<100 mmHg. 6. Non-aneurysmal SAH, including hemorrhage due to arteriovenous malformation, vasculitis, tumor bleeding, trauma, or other non-spontaneous causes, or cases without an identified bleeding source. 7. Other severe neurological disorders with substantial pre-existing disability (mRS \>3), such as progressive cognitive impairment or status epilepticus. 8. Severe systemic disease, including significant cardiac, hepatic, renal, or psychiatric disorders. 9. Pregnant or breastfeeding women, or women planning pregnancy during the study period. 10. Any other condition considered by the investigators to make the patient unsuitable for participation or likely to limit compliance with study procedures. 11. Current participation in another interventional clinical study, inability to complete follow-up assessments, or failure to provide informed consent.