Effect of Remote Ischemic Preconditioning on Collaterals of Atherosclerosis Stroke

Inclusion Criteria: * 1\. Age over 40 years old; * 2\. Diagnosed with ischemic stroke (including TIA and cerebral infarction), with onset time of more than 1 month; * 3\. Culprit arteries are the large arteries of the anterior circulation with atherosclerotic stenosis (≥50%) or occlusion; * 4\. ASITN/SIR collateral circulation of 0-3 based on DSA evaluation; * 5\. First onset or prior onset with no significant sequelae (mRS ≤ 2); * 6\. Those who are not expected to undergo angioplasty within 12 months (judged by the doctor or decided by patients and/or their representatives); * 7\. The availability of informed consent. Exclusion Criteria: * 1\) Patients with severe infection or serious diseases such as liver, kidney, hematopoietic system, endocrine system, etc.; * 2\) Patients with a history of stroke and severe sequelae (mRS≥3); * 3\) arterial stenosis due to aortic dissection, moyamoya disease; Any known vasculitic disease; herpes zoster, varicella-zoster or other viral infections with vascular lesions; neurosyphilis; other intracranial infections; any intracranial artery stenosis associated with hypercytosis of cerebrospinal fluid; radiation-induced vascular lesions; myofiber dysplasia; sickle cell disease; neurofibromas; benign vascular lesions of the central nervous system; postpartum vascular disease; stenosis of the intracranial arteries due to vasospasm or thrombosm; * 4\) Uncontrolled severe hypertension (systolic pressure≥180mmHg or diastolic pressure≥110 mmHg af…