Congenital heart disease is a condition in which the anatomical structure of the heart and large blood vessels is abnormal due to formation disorders or developmental abnormalities during embryonic development (especially during the first 2-3 months of pregnancy), or in which channels that should close automatically after birth fail to close (which is normal in the fetus). According to the hemodynamic combined with pathophysiological changes, congenital heart disease can be classified as cyanotic or non-cyanotic, and can also be divided into three categories according to the presence or absence of shunts: non-shunted (e.g. pulmonary stenosis, aortic constriction), left-to-right shunted (e.g. atrial septal defect, ventricular septal defect, patent ductus arteriosus) and right-to-left shunted (e.g. tetralogy of Fallot, large vessel misalignment). There are many types of congenital heart disease, and their clinical manifestations depend mainly on the size and complexity of the malformation. Complex and severe malformations can present with serious and even life-threatening symptoms soon after birth. Symptoms of atrial septal defect: Most children are asymptomatic in infancy, and may show shortness of breath after activity, reduced activity tolerance, developmental delay, and susceptibility to respiratory infections in childhood. Heart failure may occur in large fractional flow cases. Symptoms of ventricular septal defect: Small ventricular septal defects are mostly asymptomatic and growth and development are generally unaffected. Medium to large ventricular septal defects can occur in late neonatal period and infancy, such as feeding difficulties, shortness of breath, excessive sweating, lack of 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, activity may be limited, and eventually develop into right heart failure. Symptoms of arteriovenous ductus arteriosus: The arteriovenous ductus arteriosus has a small internal diameter and may be clinically asymptomatic. Those with larger internal diameters have high shunt flow and experience shortness of breath, cough, hoarseness, fatigue, excessive sweating, and palpitations. Pulmonary infections or heart failure may occur repeatedly. Symptoms of pulmonary artery stenosis: early stage may be asymptomatic, and the more severe the stenosis, the more obvious the symptoms. The main symptom is cyanosis. In mild cases, shortness of breath after exertion, weakness and palpitations may occur. In severe cases, edema and fainting may occur. Symptoms of tetralogy of Fallot: Before the ductus arteriosus is closed, the symptoms are often not obvious; after the ductus arteriosus is closed, cyanosis usually appears 3-6 months after birth, but in some cases it does not appear until childhood or adulthood. Cyanosis is generalized, worsens with exercise and crying, and decreases when calm, and its degree varies depending on the degree of pulmonary artery stenosis. The degree of cyanosis varies depending on the degree of pulmonary artery stenosis. As a result of reduced arterial oxygen levels, activity tolerance decreases, dyspnea occurs during activity, and in severe cases, hypoxic seizures, loss of consciousness, or convulsions may occur. The child actively adopts a squatting position whenever he walks a short distance, which increases the resistance of the body circulation and thus reduces the right-to-left shunt, resulting in an improvement in the degree of hypoxia.