There are many types of congenital heart disease, which are clinically classified into 3 major categories based on the presence or absence of shunts between the left and right sides and large vessels. Left-to-right shunt type (latent cyanotic type), right-to-left shunt type (cyanotic type), and no shunt type (no cyanotic type). (1) Left-to-right shunt type (latent cyanotic type): This type is the most common, such as ventricular septal defect, atrial septal defect and patent ductus arteriosus. (1) Symptoms of ventricular septal defect: small ventricular septal defects have no clinical symptoms and growth and development are generally not affected. Medium to large ventricular septal defects can occur in late neonatal period and infancy, such as feeding difficulties, shortness of breath, excessive sweating, weight gain, recurrent respiratory infections, and in severe cases, congestive heart failure often occurs within six months after birth, which can affect growth and development. In large defects with significant pulmonary hypertension, cyanosis may occur, and activity may be limited, and eventually develop into right heart failure. (2) Symptoms of atrial septal defect: Most children are asymptomatic in infancy, but in childhood they may show shortness of breath after activity, reduced activity tolerance, developmental delay and susceptibility to respiratory tract infections. Heart failure may occur in cases of large fractional flow. (3) Symptoms of patent ductus arteriosus: those with small ductus arteriosus may be clinically asymptomatic. Those with thick catheters may have recurrent respiratory infections, shortness of breath, feeding difficulties and growth retardation, etc. In severe cases, heart failure may occur. In the late stage of severe pulmonary hypertension, the reverse shunt of pulmonary artery blood flow into the aorta may occur, and differential cyanosis may appear (the cyanosis of both lower limbs is more significant, the left upper limb has mild cyanosis, and the right upper limb is normal). 2. Right-to-left shunt type (cyanotic type): common ones are tetralogy of Fallot and transposition of the great arteries. Symptoms of tetralogy of Fallot: cyanosis mostly appears six months to one year after birth and gradually worsens with growth and development. The infant has poor activity tolerance and squatting. Infants sometimes have paroxysmal respiratory distress after feeding or crying, which in severe cases can cause sudden loss of consciousness and convulsions that can last for several minutes or longer and then recover spontaneously. This phenomenon is called hypoxic seizure. It is caused by a spasm of the funnel muscles, which causes a transient pulmonary artery obstruction and worsens cerebral hypoxia. Older children often describe headache and dizziness, which are related to cerebral hypoxia. The child is physically less developed. Pestle-shaped fingers and toes are often present. A rough jet-like systolic murmur, often accompanied by tremor, can be heard in the middle left border of the sternum. In very severe cases of right ventricular outflow tract obstruction or pulmonary artery atresia, there may be no heart murmur. The second heart sound of the pulmonary valve is diminished or has a single sensation. 3.No shunt type (no cyanotic type): such as pulmonary artery stenosis and aortic constriction. Symptoms of pulmonary stenosis: early stage may be asymptomatic, the more severe the stenosis, the more obvious the symptoms. The main symptoms are cyanosis, shortness of breath after exertion, weakness and palpitations in mild cases. In severe cases, edema and fainting may occur.