In our clinical work, we always explain to patients the complications the day before the surgery. This act is not to disclaim responsibility, but to hope that the patient understands the problems that the procedure may bring and is able to face them together with the surgeon when they arise. Although interventional treatment of carotid stenosis is a minimally invasive procedure, less invasive and safer are two different things, and the problem it poses is not the size of the surgical incision. Although the chance of complications from this procedure is low, some complications may have serious consequences, even fatal. Here, I will give a unified answer to the patient’s concern. 1, ischemic complications This complication rate is the highest, the vast majority of them are caused by thrombus dislodgement and embolism of cerebral arteries, the chance is about 3%. Some patients or family members will ask: you are not using the umbrella? How can thromboembolism occur when you can’t be reimbursed for something so expensive? This is a good question. The umbrella only reduces the chances of embolism by 3-4 percentage points and does not eliminate it completely. There are several links where thrombus dislodgement occurs during surgery. One is that during our delivery of the umbrella, does the umbrella need to pass through the stenotic segment? The second is when the umbrella is placed and the balloon is dilated, this is the most likely time to dislodge the plaque, because the pressure of the balloon on the plaque is very high, which will cause the plaque to fragment and even squeeze out the atheromatous material covered by the plaque. squeeze out. Of course, most of these things will fall off into the umbrella, but if the umbrella is not tight enough in the blood vessel, there may be a “leak”, which will cause cerebral embolism. subacute in-stent thrombosis, which can also cause cerebral embolism. Some patients may ask, “How can this happen when you gave me preoperative aspirin and poliovirus, both of which prevent clotting? Although we use dual antiplatelet drugs, a small percentage of patients may not be sensitive to antiplatelet drugs. In addition, the plaque is loosened by the balloon expansion, which may expose some collagen fibers under the plaque, fat-like material, etc. These things may be a little stronger than the stent to cause thrombosis, or they may even act as emboli themselves. These are the causes of ischemic complications. So what are the consequences of having this complication? In most cases, the emboli flow with the blood into the branches of the middle cerebral artery, causing some foci of infarction in the area supplied by the middle artery. The symptoms that these infarcts produce are related to the diameter of the blocked vessel, the functional area in which it is located, and so on. In general, they may cause symptoms such as hemiparesis, speech impairment, comprehension impairment, and eye and mouth distortion, which we call “stroke”. If you are lucky, the infarcted brain tissue is of little use and may be asymptomatic; if you are unlucky, the embolism is in the main trunk of the middle cerebral artery and may be fatal due to the large area of cerebral infarction. A small percentage of patients also suffer from blindness or visual field problems because the embolus drifts into the ophthalmic artery. 2. Hemorrhagic complications Hemorrhagic complications are not complications at our operation site, but bleeding inside the brain. Some patients ask: Why do we operate the blood vessel in the patient’s neck and cause bleeding in the brain? There are two main reasons for this. The first reason is that long-term carotid artery stenosis causes some changes in the structure of the blood vessels in the brain. In the case of carotid stenosis, the brain tissue is in a state of relative undersupply of blood, and the brain tissue will not sit still, it will indirectly increase its own blood supply by increasing the number of capillaries or increasing the diameter of existing vessels to prevent infarction from occurring, in addition, the decrease of blood pressure in the brain will also cause the laziness of the blood vessels in the brain, its smooth muscle layer will be reduced and become weaker than before. Once we suddenly open the narrowed carotid arteries, these vessels may be “spoiled” and may not be able to withstand the sudden pressure and rupture and bleed. The second reason is that the brain tissue is already infarcted due to carotid stenosis, and the vascular bed of the infarcted brain tissue is more fragile, so once the blood flow increases, the infarct itself may bleed. What is the consequence of hemorrhage? This consequence is often catastrophic. Because the patient is on antiplatelet medication and is also anticoagulated with heparin during surgery to prevent thrombosis, the blood does not love to clot once it is out. In addition, this kind of bleeding is usually not fixed a blood vessel bleeding but diffuse brain tissue oozing blood, open surgery to clear the hematoma are very difficult to save. Therefore, once the hemorrhage occurs, the patient suffers a tremendous blow. They usually die or survive with a very low quality of life. The good thing is that the chances of such a hemorrhage are like hitting the jackpot, 6 per 1,000 in the literature, and probably even lower in our center, where out of our 500 or so carotid patients each year, at most 0-1 hemorrhage occurs. But the odds are small, the catastrophe is huge. And for the same patient, there is no question of odds. It is all or nothing. 3. Carotid sinus stimulation The carotid sinus is a structure that exists in the bifurcation of our carotid artery, which is able to sense the blood pressure of the body, and when our blood pressure is elevated in cases of emotional excitement, strenuous exercise, etc., it can bring it down by some mechanism. The sensitivity of the carotid sinus varies from person to person. The most sensitive people may have their heart stop and fainting occur when they are pinched. Many of our patients experience a drop in blood pressure and heart rate during the procedure because the carotid sinus is stimulated by the balloon or stent, but most of them are temporary. However, some people will have a longer decrease in blood pressure after carotid stenting and even develop clinical symptoms, such as dizziness or even cerebral perfusion deficit such as cerebral infarction. This is especially true if there is a combination of other stenoses in the brain, which is a little more dangerous. In conclusion, although this procedure is routine and uncomplicated, it is not negligible in case of complications due to the importance of the carotid artery and its blood supply area. Our center, as the department that performs the largest number of this procedure in the world, cannot guarantee absolute safety. Therefore, we strictly control the indications for surgery. We will not operate on patients with asymptomatic carotid stenosis with a stenosis rate of less than 70%, and we will definitely not operate on patients with symptomatic carotid stenosis with a stenosis rate of less than 50%. This is also the opinion in the guidelines of carotid stenosis.