Atrial septal defect: It is any joint obstruction during embryonic development such that the atrial septum is hypoplastic or overabsorbed resulting in the presence of a channel between the two heart chambers. It is one of the common precordial diseases. Our data confirm that it accounts for 21-25% of the rate of precordial disease. Atrial septal defects are divided into secondary and primary foramen defects. The size of the flow is related to the size of the defect and the pressure step difference between the two sides of the atrium. Clinical symptoms: In general, small defects with small fractional flow can have no clinical symptoms, but are detected during physical examination. In large defects, due to the large fractional flow and ischemia of the body circulation, there can be a long and thin body shape, pale face, elongated fingers and toes, and easy to feel fatigue. When the blood flow of pulmonary circulation is increased, it is easy to have respiratory infection and heart failure. ②Surgical indications and methods: The appropriate age for surgery is 4-5 years old. Direct intracardiac repair under hypothermic or normothermic extracorporeal circulation is the most reasonable, effective, precise and safe method for repairing atrial defect. Early surgery should be performed if there is severe heart failure. Ventricular septal defect: It is the most common of the pediatric precardiac diseases, accounting for 30% of the precardiac disease rate, and is caused by the underdevelopment of the ventricular septum during embryonic development. The septal defect is most commonly found at the junction of the aortic valve leaflets and the membrane of the posterior ventricular septum under the supraventricular ridge. The fractional flow of blood is related to the size of the defect, pulmonary vascular resistance, and the pressure step difference between the bilateral ventricles. In large ventricular defects, pulmonary blood flow can exceed the body circulation by more than three times. As the disease progresses, not only the left atrium, left ventricle, and pulmonary artery enlarge. Moreover, due to the continuous increase of pulmonary circulation volume, the small pulmonary arteries produce dynamic hypertension, and over time, the inner wall of small pulmonary arteries becomes hyperplastic and the lumen becomes smaller, or even completely awake to form organic pulmonary hypertension. The left-to-right shunt is significantly reduced, and a bidirectional shunt may occur, eventually leading to a right-to-left shunt, which is known as Eisenmenger’s syndrome. ①Clinical manifestations: small ventricular septal defects may be asymptomatic, while large ventricular defects may present with shortness of breath, excessive sweating, slow growth, respiratory tract infection, pneumonia and heart failure. ②Surgical indications and methods: recurrent heart failure within 6 months of age may be treated with pulmonary artery circumferential ligation. 2 years of age or older, direct intracardiac repair is performed under hypothermic extracorporeal circulation. The pathological anatomy includes ventricular septal defect, which is the most common type of cyanotic preconditioning. The pathologic anatomy includes four malformations: ventricular septal defect, pulmonary stenosis, and right ventricular hypertrophy. Its pathophysiology is mainly due to insufficient blood supply of pulmonary circulation, increased burden on the right heart and shunting of blood from right to left, which reduces arterial oxygen and compensates for the increase of red blood cells and hemoglobin, so the blood viscosity increases greatly, which increases the burden on the heart and also makes it easy to form small vessel embolism. ①Clinical manifestations: cyanosis is the main symptom, dyspnea and poor activity endurance, squatting, pestle finger. ②Surgical indications and methods. 4~10 years old is the best age for surgery. If the pulmonary vessels are well developed, direct intracardiac radical surgery can be done under hypothermic extracorporeal circulation. If the pulmonary vessels are very poorly developed, palliative surgery to increase pulmonary blood is considered, and second-stage radical surgery is done after the pulmonary vessels have thickened.