Atrial septal defects are divided into primary foramen ovale and secondary foramen ovale from the point of view of their occurrence. Primary foramen ovale septal defect is usually included in the scope of endocardial cushion defect, so the clinical term of atrial septal defect refers to secondary foramen ovale septal defect. Secondary foramen type atrial septal defect is divided into: central type (foramen ovale type), inferior chamber type, superior chamber type, and mixed type. Xiao Shiliang, Department of Cardiac Surgery, Wuhan Union Hospital 1. The etiology, like other precordial diseases, is currently considered to be the result of the interaction of complex relationships such as genetic and environmental factors, and the following factors may affect the fetal development and produce congenital malformations. (1). Environmental factors of fetal development: Infections, viral or bacterial infections in the first trimester, especially rubella virus and, to a lesser extent, coxsackievirus, have a higher incidence of congenital heart disease in infants born with these infections. Other: such as lesions of the amniotic membrane, fetal compression, preterm abortion in early pregnancy, maternal malnutrition, diabetes mellitus, phenylketonuria, hypercalcemia, the application of radiation and cytotoxic drugs in early pregnancy, and the mother’s excessive age have the potential to cause congenital heart disease in the fetus. (2). Genetic factors: Most congenital heart disease is formed by the interaction of multiple genes and environmental factors. (3). Others: Some congenital heart diseases are more frequent in highland areas, and some congenital heart diseases have significant differences in incidence between the sexes, suggesting that altitude and sex at birth are also associated with the occurrence of the disease. In patients with congenital heart disease, the cause of the disease can be identified is very few, but it is of positive significance to prevent congenital heart disease by strengthening health care for pregnant women, especially actively preventing rubella, influenza and other rubella viral diseases in early pregnancy and avoiding all factors related to the onset of the disease. 2. pathophysiology Atrial septal defect can lead to enlargement of the right atrium and right ventricle, thickening of the ventricular wall, different degrees of pulmonary artery dilatation, increased blood volume in the pulmonary circulation and increased pulmonary artery pressure. 3. Classification Atrial septal defect can be divided into small, medium and large defects. In young children, the defect less than 0.5 cm is small, 0.5-1.0 cm is medium, and 1.0 cm or more is large. In adults, small defects are usually less than 1.0 cm, 1.0-2.0 cm are medium-sized and small defects, and 2.0-3.0 cm are large defects. The overall rate of natural closure of atrial septal secondary foramen defects is 87%. Atrial septal defects with defects <3 mm diagnosed before 3 months of life can approach almost 100% spontaneous closure within 1.5 years of age; many atrial septal defects with defects between 3 and 8 mm can close spontaneously within 1.5 years of age; few defects above 8 mm close spontaneously. It has been statistically reported that 20 of 91 ASDs healed spontaneously, with a self-healing rate of 21.98%. 69.23% of ASDs with a diameter of 0.5-0.7 cm healed spontaneously, 27.27% with a diameter of 0.8-10 cm, and 2.27% with a diameter of >1.0 cm. The self-healing rate of central ASD was 23.26%, and the vena cava sinus type ASD did not heal spontaneously. the age of spontaneous healing of ASD ranged from 7 months to 6 years, with a median of 1.6 years. The self-healing rate of ASD with enlarged right ventricle was 9.46%, and the self-healing rate of ASD with normal right ventricle was 63.64%. It is concluded that ASDs with ASD diameter ≤1.0 cm, central ASD, normal right ventricle and age <6 years especially up to 2 years have a higher chance of natural healing. ASDs with ASD diameter >1.0 cm, cavernous sinus ASD, enlarged right ventricle and ASDs older than 6 years have a low chance of natural healing. Infective endocarditis does not occur in simple atrial septal defects, so prophylactic treatment is not necessary if there are no other co-morbidities. Small atrial defects in infants and children have the potential to close on their own and generally do not require treatment. Traditionally, it was thought that small atrial defects smaller than 10 mm without heart enlargement and symptoms could be treated without surgery, but nowadays, considering that small atrial defects may have two rare complications, namely paradoxical thrombosis and cerebral abscess, which occur in adult patients with secondary foramen ovale, especially after the age of 60, interventional treatment is advocated for small atrial defects in adults. Most clinicians still believe that a small atrial defect “less than 5 mm” can be treated without treatment. Clinical manifestations and complications When atrial septal defect exists, blood flows from left to right, right heart blood volume increases, right atrium and right ventricle enlarge, ventricular wall thickens, pulmonary artery dilates to different degrees, pulmonary circulation blood volume increases, and pulmonary artery pressure rises. With the development of the disease, intimal hyperplasia, thickening of the middle layer and narrowing of the lumen occur in the wall of small pulmonary arteries, thus the pulmonary vascular resistance increases, pulmonary hypertension changes from dynamic to resistance, the right atrial and right ventricular pressure increases, the right atrial pressure exceeds the left atrial in the late stage of the disease, a right-to-left shunt occurs, and clinical purple crucible and heart failure appear. Rare and serious complications of atrial septal defects can also occur, namely brain abscess and paradoxical thrombosis, causing embolism of organ arteries.5. Effective therapeutic measures for the treatment of atrial septal defects are surgical repair and surgical occlusion. The technique of atrial septal defect sealing is well established, and any atrial septal defect with indications for sealing treatment should be firstly selected for sealing treatment. The ideal age stage for surgery is 2 – 6 years. For huge atrial septal defect, early surgery should be performed regardless of age, such as large defect, large fractional flow, severe pulmonary congestion, often accompanied by heart failure, pneumonia and other complications. Very young age is not a contraindication to surgery. The surgical methods include conventional intracardiac repair with extracorporeal circulation, non-stop cardiac repair with extracorporeal circulation and closed repair with non-extracorporeal circulation. Secondary foramen ovale septal defects can be divided into: central, superior, inferior, and mixed types. The central type secondary foramen ovale septal defect is the most suitable for interventional treatment. Main indications: (1) Patients with surgical indication for secondary foramen ovale atrial defect who meet the following conditions: adult secondary foramen ovale defect diameter less than 30 mm, balloon maximum elongation diameter less than 36 mm, pediatric patients should be evaluated for interventional septal defect diameter according to age and heart size. The secondary foramen ovale type of atrial defect is central, with the margins of the upper and lower septum greater than 5 mm.(2), secondary foramen ovale <10 mm in diameter, without cardiac enlargement and symptoms, may be treated without surgical intervention, but may have two rare complications, namely paradoxical thrombosis and brain abscess, which occur in adult patients with secondary foramen ovale, especially after 60 years of age, so intervention is advocated for small atrial defects in adults.(3), oval (3), foramen ovale is not closed, especially those who have ever combined with cerebral embolism, suitable for interventional treatment. (4), post-surgical residual shunt atrial septal defect, mainly referring to those with left-to-right shunt. (5) In patients with significant left-to-right shunts at the atrial level after balloon mitral valvuloplasty and radiofrequency ablation. (6), those with atrial septal defects aged 2 years or older, because the age of natural closure of atrial septal defects is within 1.5 years. The main postoperative complications are; cardiac rhythm disturbances, coronary and cerebral artery air embolism, acute left heart insufficiency and residual leak.13, The septal defect sealing treatment may have (1). Residual bypass. (2). Dislodgement of the blocker (3). Embolization. (4). Improper blocker position. (5). Infective endocarditis. (6). Cardiac arrhythmia. (7). Hemolysis. (8). Pericardial tamponade. The surgical outcome of simple secondary foramen ovale septal defects is good, and the mortality rate of in-hospital surgery has been close to zero. Approximately 2% of patients require reoperation for recurrence of the septal defect. At rest, a pulmonary/body circulation flow ratio of less than 1.5, a pulmonary/body circulation systolic pressure ratio of >0.75, a right-to-left shunt on cardiac ultrasound, elevated pulmonary vascular resistance of 8–12 U/m2 at rest that cannot be reduced to less than 7 U/m2 with pulmonary vasodilators, and clinical manifestations of purple crucible and hemoptysis (Eisenmenger’s syndrome) are considered contraindications to surgery. Contraindications for atrial septal defect sealing treatment: (1) Primary foramen ovale type atrial septal defect. (2) Venous sinus type atrial septal defect. (3) Partial or complete ectopic pulmonary venous drainage. (4 ) Left atrial septum or hypoplasia. (5 ) Intracardiac, inferior vena cava, or intrapelvic thrombosis. (6 ) With other congenital heart defects or large vessel anomalies requiring surgical treatment. (7 ) Eisenmenger’s syndrome. Relative contraindications:(1). Infants and children aged less than 2 years. (2). Recent severe infection or foci of infection in the body. The current cost of surgical treatment in China ranges from RMB 8,000 – 15,000, which varies considerably. It may be related to the fast or slow economic development. The price of blocking treatment is about 1 – 2 times of the price of surgical operation.6. Ovular foramen is not closed During the development of fetal atrium, the primary septum and the continuing septum separate the right and left atrium when they are fully developed, and the living valve-like orifice remains between the two septum, namely the oval foramen. After birth, the fetus is separated from the placenta and the fetal blood circulation is terminated. The blood pressure in the left atrium is higher than that in the right atrium, forcing the first interatrial septum to close structurally to the foramen ovale. If the foramen ovale is still not closed in children older than 3 years of age, it is called an unclosed foramen ovale. About 25% of the normal population has an unclosed foramen ovale. The difference between patent foramen ovale and small atrial defect is that there is no continuous interruption of the septum on transthoracic ultrasound (TTE) or transesophageal ultrasound (TEE), and there is usually no left-to-right blood shunt. Ovarian foramen ovale is usually not treated, but interventional occlusion should be considered if the patient is older than 40 years old and has no other causative factors such as recurrent cerebral embolism.