The symptoms of patients with atrial septal defect in infancy and early childhood are related to the size of the defect. In mild cases, the clinical manifestations may not be obvious, and the diagnosis is often confirmed by the detection of heart murmurs during physical examination; in large cases, the fractional flow is large and the lung is obviously congested, making them susceptible to bronchopneumonia and affecting growth and development due to insufficient blood flow in the circulation. In cases of severe crying, breath-holding, pneumonia or heart failure, the right atrial pressure may exceed the left atrium, and a temporary right-to-left shunt may appear, resulting in cyanosis. As the patient ages, patients with atrial septal defect may exhibit growth retardation, decreased activity tolerance, recurrent respiratory infections, excessive sweating, and an enlarged heart, increased pulmonary circulation pressure and resistance, heart failure, and atrial arrhythmias. Because most atrial septal defects have mild symptoms, most patients are not detected until adolescence or adulthood, and some patients have lost the opportunity for treatment at the time of diagnosis or have failed to return to normal cardiac and pulmonary circulation function, which seriously affects the patient’s activity tolerance, quality of life, life expectancy, social competitiveness, and psychological well-being. In small defects, the patient’s development may be unaffected; in large defects, there may be growth retardation, wasting, weakness, excessive sweating, and shortness of breath after activity. On examination of the heart, there is an elevated precordial region, enlarged heart borders, and elevated pulsations on palpation. A grade II-III systolic jet murmur can be heard in the pulmonary valve region due to the relative stenosis of the pulmonary valve. With high left-to-right shunt flow, a diastolic rumbling murmur produced by relative stenosis of the tricuspid valve can be heard below the left sternal border. In cases of marked pulmonary artery dilatation or concomitant pulmonary hypertension, early systolic karate sounds may be heard in the pulmonary valve region.