Congenital heart disease refers to a disease in which the heart and large blood vessels develop abnormally during the fetal period, and the lesion is already present at birth. This disease is the most common of all neonatal defects, and the current statistical incidence accounts for 0.6-1.4% of all live births. This series of lectures is launched to give you a better understanding of congenital heart disease because of its high incidence and impact on families. This time we will be talking about one of the most common types of congenital heart disease – atrial septal defect. Atrial septal defect is the most common type of congenital heart disease in adults. If the defect is small, the disease affects less hemodynamics and has a long natural life span, so statistically there are more cases in adults, and most people will be found by chance after adult checkups. There are three types of the disease: primary foramen type, secondary foramen type, and venous sinus type. The primary foramen type is more severe, anatomically a partial endocardial cushion defect, often combined with mitral and tricuspid valve dysplasia; the secondary foramen type defect is a more simple condition, referring to the central type; the venous sinus type is divided into the inferior and superior chamber types. In patients with atrial septal defect, the left atrial pressure is higher than that of the right atrium, and the pulsatile blood flow produces a left-to-right shunt due to the pressure difference; the hemodynamic impact of this disease depends mainly on the amount of shunt flow caused by the defect; the larger the defect, the greater the impact on cardiac function. If the disease is not treated for a long time, the right heart load will increase due to the long-term left-to-right shunt, and the right heart will eject more blood to the lungs, which will lead to right heart failure and pulmonary hypertension in the later stage. Note: Pictures are from the Internet. Clinical manifestations of this disease are usually no clinical symptoms in the early stage if the defect is small, mainly found by physical examination, and patients may have symptoms of decreased activity tolerance and frequent colds in childhood. Most of them start to have symptoms in adulthood, mainly arrhythmia (atrial flutter and atrial fibrillation are common), exertional dyspnea, and lower limb edema. The main findings of the disease are systolic murmurs audible in the pulmonary valve area on examination and hyperactive and fixed splitting of the second heart sound in the pulmonary valve area. The main auxiliary examination is the choice of cardiac ultrasound, which can clearly see the atrial septal defect, left-to-right shunt, right heart enlargement, and in severe cases, pulmonary hypertension and right-to-left shunt. Electrocardiogram may reveal right-sided electrical axis, right bundle branch block, etc. Chest X-ray may reveal right heart enlargement, increased pulmonary blood, etc. Treatment is mainly based on age, symptoms, type of disease, etc. Patients with primary foramen ovale defects, venous sinus defects, other cardiac malformations, right-to-left shunts, pulmonary hypertension, and hemodynamic instability generally require surgical intervention. Secondary foramen ovale defects have the probability of closing on their own, and the overall closing rate is currently about 87%. Almost all defects under 3 mm in infants before 3 months of age can be closed spontaneously within 1.5 years of age; defects 3-8 mm have more than 80% probability of closing spontaneously within 1.5 years of age; defects larger than 8 mm are less likely to close spontaneously. It is recommended that patients with secondary foramen ovale defects be treated promptly. Statistics show that the survival rate of this type of defect does not differ from that of normal subjects when closure is performed before the age of 24. Secondary foramen ovale defects can be treated by minimally invasive interventional occlusion. If the defect is found to be greater than 5 mm and less than 36 mm on cardiac ultrasound, there is no right-to-left shunt, load other indications for interventional occlusion treatment, and the general age is around 3 years, minimally invasive occlusion can be chosen.