Type I atrial septal defect, also known as primary foramen ovale atrial septal defect, is a combination of genetic and environmental factors during the development of the atrial septum during embryonic period, resulting in the inability of the endocardial cushion to completely join the first atrial septum, leading to a defect at the junction of the atrial septum and endocardial cushion, forming a left-to-right shunt, the incidence of which is about 15%. Due to the left-to-right shunt at the atrial level, right heart blood flow increases, right atrial right ventricle enlarges, pulmonary circulation blood flow increases, and recurrent respiratory tract infections are prone to occur, and insufficient body circulation leads to growth retardation. Type I atrial septal defects cannot be treated with catheter interventional occlusion because of the low site of occurrence. If the defect is large, heart failure and pulmonary hypertension are likely to occur and repair is recommended in childhood. type I atrial septal defects generally require surgical treatment.