In patients with cyanotic precordial disease, which is the right-to-left shunt type, because the blood of the right heart system is non-oxygenated blood with little oxygen carried by red blood cells and the blood of the left heart system is oxygenated blood with mainly oxygen carried by red blood cells, when the blood of the left heart flows to the whole body, it sends oxygen to the whole body for tissue utilization. As soon as there is a right-to-left shunt, the oxygen content of the blood will drop and it will not be able to meet the needs of the whole body. Often, the surrounding tissues will be deprived of oxygen and the function of the organs will be affected. When the brain tissue is deprived of oxygen, the intelligence of the child will be affected.