Timing of surgery Partial endocardial cushion defects are usually operated on between the ages of 2 and 4 years. Earlier surgery is indicated if there is significant mitral regurgitation or structural dysplasia of the left side of the heart such as aortic constriction, mitral valve malformation, or subaortic stenosis. Complete endocardial cushion defects with severe congestive heart failure at 2 to 4 months of age should be operated on at 3 to 6 months of age. If surgery is delayed until after 1 year of age, there is a risk of irreversible increase in pulmonary vascular resistance. The timing of surgery for excessive endocardial cushion defects depends on the size of the ventricular defect; the larger the defect, the earlier the surgery should be performed. Patients with endocardial cushion defects combined with tetralogy of Fallot and significant right ventricular outflow tract stenosis, previously staged, are now favored for early correction in a single operation. Pulmonary artery hypertension and irreversible pulmonary vascular disease are absolute contraindications to surgery for this disease. Surgical treatment Pulmonary artery annuloplasty was used more in the past when the surgical technique was not mature, but it aggravated mitral regurgitation and failed to achieve the effect of palliative treatment, so it is less used at present, only for small infants within 3 months of age with pneumonia and heart failure, and when medical treatment is ineffective, pulmonary artery annuloplasty can be considered first; after 3-6 months of improvement of heart and general condition, radical surgery will be done. The principle of radical surgery is to close the ventricular septal defect and atrial septal defect, restore the mitral valve without stenosis and regurgitation, and avoid damage to the conduction bundle. The key to successful surgery is the effect of left atrioventricular valvuloplasty and avoidance of left ventricular outflow tract stenosis. Surgical approaches for complete endocardial cushion defects include the single-slice, double-slice, and modified single-slice approaches. The results of the three surgical approaches are approximately equal when evaluated in terms of operative mortality and reoperation rates due to mitral regurgitation, pacemaker implantation, left ventricular outflow tract obstruction, residual ventricular septal defect, or atrial septal defect. In comparison, complete endocardial cushion defects are the most complex and have the highest surgical risk, with a mortality rate of approximately 3 to 5% or more. Overall, the long-term mitral valve reoperation rate in patients with endocardial cushion defects is approximately 10% to 15%.