Subclavian artery steal syndrome is a syndrome in which there is a partial or complete occlusive lesion in the proximal segment of the subclavian artery, cephalobrachial trunk artery, or the beginning of the vertebral artery, causing retrograde blood flow in the affected vertebral artery due to siphoning (steal) into the distal segment of the affected subclavian artery, resulting in ischemic episodes in the vertebrobasilar artery (cerebral ischemia), and ischemic episodes in the affected epiploic artery. Most subclavian artery lesions are caused by atherosclerosis. Other etiologies include congenital malformations of blood vessels, carotid arteritis, fibromuscular dystrophy, trauma, radiation injury, mediastinal tumors, inflammation, and rib malformations. Clinical manifestations and diagnosis】 It is common in men over 50 years of age, and stenosis or occlusion of the left subclavian artery is common, probably due to the large angle formed by the left subclavian artery at the beginning of the aorta, which is susceptible to blood flow impulse and causes atherosclerosis. The syndrome can be characterized by neurological symptoms and ischemic symptoms of the upper extremities due to inadequate supply of blood to the vertebral-base artery. 1. Symptoms of inadequate supply of blood to the vertebral-base artery: the most common symptoms are vertigo, light paralysis of the limbs, sensory abnormalities, bilateral visual impairment, ataxia, diplopia, syncope, and rarely intermittent claudication, dysphonia, dysphagia, tinnitus, convulsions, headache and mental disorders. In a few cases, “dumping syndrome” may occur, which is an episode of sudden loss of muscle strength in the lower limbs without aura and fall, but there may be no impairment of consciousness and rapid recovery. 2. Ischemic symptoms of upper limbs: intermittent dyskinesia, upper limb weakness, pain and abnormal sensation are common, and very few of them cause cyanosis or necrosis of fingers. General signs (1) Blood pressure: The blood pressure of the affected upper extremity is reduced, and the difference in systolic blood pressure between the two upper extremities can be 20-150 mmHg, mostly 20-70 mmHg. (2) Pulse: Most of the radial artery on the affected side is weakened or disappeared, and some of the brachial artery or subclavian artery pulsation is also weakened or disappeared. In addition, the pulse on the affected side is delayed, which is due to the fact that the pulse wave has to travel from the contralateral vertebral artery to the affected vertebral artery and then to the wrist, which is a longer distance. (3) Vascular murmur in the supraclavicular region: most of the systolic murmurs can be heard, and the murmur may be aggravated by movement of the affected limb. (4) Auxiliary examinations (1) Color Doppler ultrasonography: a quick, easy and non-invasive diagnostic method that can reveal subclavian artery plaque or obstruction, slowed blood flow or changes in the blood flow spectrum, etc. (2) CT angiography (CTA) or nuclear magnetic arteriography (MRA): non-invasive diagnostic method with accuracy close to that of arteriography. (3) Subclavian artery and aortic arch arteriogram: It is an invasive test that can clearly show the stenosis or obstruction of the affected subclavian artery or vertebral artery, which not only has a high diagnostic accuracy, but also can be used to fully estimate the stenosis and select the best surgical procedure. Treatment methods] Surgical methods are mostly used for subclavian artery-subclavian artery, axillary artery-axillary artery, carotid artery-subclavian artery bypass surgery, etc., which are suitable for arterial stenosis severe or occlusive lesions. Percutaneous endovascular angioplasty (PTA) is suitable for patients with arterial stenosis of 75% or more and symptoms of ischemia.