1, medical and technical examination 1.1 Electrocardiogram: The typical manifestations include QRS wave in the right precordial lead with rSr or rSR’ or R wave with T wave inversion. The electrical axis is right deviated, and sometimes there may be P-R prolongation. 1.2 X-ray examination: right atrial and right ventricular enlargement, prominent pulmonary artery segment and increased pulmonary vascular shadow can be seen. 1.3 Echocardiography: Widening of the pulmonary artery, enlargement of the right atrium and right ventricle, and the site and size of the atrial septal defect are seen. 1.4 Color Doppler: It can show the direction of shunt and measure the volume of blood discharged from the left and right ventricles. 1.5 Cardiac catheterization: This test is not required in typical cases. When other diseases or combined malformations are suspected and pulmonary vascular resistance needs to be measured to determine surgical treatment and prognosis, right heart catheterization should be performed. 2. Diagnostic basis 2.1 The patient presents with the above symptoms and signs. 2.2 The electrocardiogram shows that the P wave may be increased and the electrocardiographic axis is right deviated; the cardiac vector shows right ventricular hypertrophy. 2.3 Echocardiography and color Doppler flow imaging detected the site of atrial septal defect. 3. Ancillary tests 3.1 Echocardiography is the main diagnostic method. Echocardiography can show interruption of the atrial septum, enlargement of the right atrial and ventricular diameters, widening of the pulmonary artery, and increased activity of the tricuspid valve. Doppler color flow imaging can observe left-to-right septal blood flow in the atria. At the same time, echocardiography can accurately classify the atrial septal defect and provide reference advice for the development of treatment options. 3.2 X-ray Chest X-ray shows congested lung fields, enlarged right atrium and right ventricle, bulging pulmonary artery segment, enlarged hilar shadow, increased pulmonary blood, and small aortic node. The fluoroscopy can show the sign of “dancing lung door”. 3.3 Electrocardiogram The typical electrocardiogram of atrial septal defect shows a right-sided electrical axis, incomplete right bundle branch block, and hypertrophy of the right atrium and right ventricle in some patients. 3.4 Cardiac catheterization For atrial septal defect, the anatomical malformation and pulmonary circulation pressure and other important parameters can be clarified by the above-mentioned noninvasive examination, so cardiac catheterization is generally not required.