In case of hypoxia, the child should be placed in the knee-chest position, and if oxygen is needed, the child should be placed in the flat position. The knee-chest position is beneficial to the blood flow of the heart and reduces the load on the heart, and the flat position is beneficial to oxygen absorption. The main clinical manifestations are hypoxia, progressive cyanosis and dyspnea. The child is easily fatigued and will rest in the squatting position after exertion, and severe hypoxia will lead to syncope. If no surgical treatment is given in childhood, the prognosis of this disease is not good, and the child will die of cardiac insufficiency or cerebrovascular accident before the age of 12.