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 after drug treatment) ; * 5\) Subclavian artery stenosis ≥50% or subclavian artery steal syndrome; * 6\) Patients with intracranial hemorrhage (parenchymal hemorrhage, subarachnoid hemorrhage, subdural/epidural hemorrhage) within 90 days before enrollment; * 7\) Intracranial tumor, arteriovenous malformation, or aneurysm; * 8\) Patients with severe hematologic diseases or severe coagulation abnormalities; * 9\) Retinal hemorrhage or visceral hemorrhage within 30 days; * 10\) Those who are expected to undergo major surgery (including femoral artery, cardiac, aortic or carotid artery surgery) within 30 days before enrollment or within 12 months after enrollment; * 11\) Those who have received stent implantation, angioplasty or other related medical devices for the target diseased blood vessels, or those who are expected to undergo the above treatments within 12 months after enrollment; * 12\) Any contraindication for remote ischemic adaptation: the upper limb has serious soft tissue injury, fracture or vascular injury, distal upper limb perivascular lesions, etc. * 13\) Damage and lesions in the cerebral veins; * 14\) Pregnant or lactating women; * 15\) Those who are participating in other clinical trials within 3 months; * 16\) Life expectancy is less than 1 year * 17\) Patients not suitable for this clinical studies considered by researcher