The difference in pulse and blood pressure between the upper arms of normal people is very small, the pulse is palpable and of equal strength, and the difference in blood pressure is usually not more than 20 mmhg. If the difference in pulse and blood pressure is too large, there may be a pathological condition on the affected side. A more common disease is stenosis or occlusion of the subclavian artery (or unnamed artery), which can cause ischemic symptoms such as weakness, decreased skin temperature, decreased sensation, soreness and discomfort after exertion, and even pain in the affected limb, and even ipsilateral vertebral artery ischemic symptoms such as vertigo, blackness, blurred vision, and syncope. Why does blood flow to the upper extremity affect the blood supply to the brain? When the opening of the subclavian artery is narrowed or occluded, the blood flow to the ipsilateral limb is reduced and compensated by the surrounding collateral vessels. If the compensatory disorder occurs, the blood flow from the ipsilateral vertebral artery has to flow downward into the subclavian artery to supply the upper limb, especially after the movement of the affected limb, the blood flow from the vertebral artery on the healthy side to supply the brain is stolen by the vertebral artery on the affected side, thus affecting the blood volume of the cerebral circulation, which is medically called “subclavian artery blood theft syndrome. In severe cases, it can also cause necrosis of the affected limb and ischemic infarction of the brain, which should be taken seriously. What causes subclavian artery stenosis? The common causes are atherosclerosis and multiple aortitis. The former is mostly in middle-aged and elderly patients with hypertension, diabetes, and hyperlipidemia, and is caused by cholesterol lipid deposition in the intima forming atheromatous plaque to narrow or occlude the lumen; the latter is mostly in female patients under 40 years old, and is caused by thickening of the entire arterial wall, diffuse fibrosis and calcification, stiffness of the lesion, fever, arthralgia, increased sedimentation, positive antinuclear antibody, rheumatoid factor, etc. Atherosclerosis and multiple aortitis can affect not only the subclavian artery, but also the renal artery, carotid artery and other systemic arteries and cause corresponding symptoms and signs. Since the seemingly normal difference in blood pressure and pulse rate in the upper arm may have so many dangers, how can we find out? The easiest way is to take your own pulse. In the case of subclavian artery stenosis or occlusion, the pulse in the affected upper extremity is significantly weaker or even absent. If this and the above symptoms occur, you should go to the hospital to measure the blood pressure in both upper arms. If the difference in blood pressure in both upper arms is obvious, then perform a non-invasive color Doppler ultrasonography to determine the speed and direction of blood flow in the subclavian artery and vertebral artery, which is slow in the case of subclavian artery stenosis and downward in the affected vertebral artery in the presence of subclavian artery steal syndrome. Of course, the final gold standard for diagnosis of stenosis or occlusion of the subclavian artery is angiography of the affected limb. The angiogram is performed by inserting a tube from the brachial artery in the upper arm or the femoral artery at the root of the thigh into the subclavian artery and then injecting a contrast medium to observe the patency of the vessel and the flow rate under X-ray. What should I do after finding stenosis or occlusion of the subclavian artery? First, the cause of the disease should be identified, and then other arteries should be examined for stenosis or occlusion as well. Subclavian artery stenosis or occlusion is not effectively treated with medication and usually requires surgery. For subclavian artery stenosis caused by arteriosclerosis, balloon dilation and stenting can be performed by puncturing the brachial artery at the elbow or the femoral artery at the root of the thigh under local anesthesia and performing angiography, we usually choose to puncture the brachial artery in the upper arm, which is easy to operate and does not affect the patient’s bedtime activities after the procedure. After the stenosis is identified on angiography, a balloon is introduced along the guidewire from the puncture site to dilate the stenosed artery to a normal level, and then the balloon is withdrawn and a stent is introduced to open the stenotic artery to prevent restenosis. Since aortitis affects the subclavian artery stenosis along with stenosis and occlusion of the carotid artery, stenting usually has a poor long-term rate and requires artificial vessel bypass. After these treatments, the patient’s symptoms can be significantly improved and there is basically no difference in pulse and blood pressure. Small pulse, blood pressure differences inside the original these reasons, in daily life more to their own “pulse”, pay attention to their own health, timely detection, problem solving and improve the quality of life.