Mild left atrial enlargement in children, i.e., mild enlargement of the left atrium, is a physiological phenomenon caused by individual differences and a pathological phenomenon caused by congenital heart disease, etc., which can be treated with general therapy and nutritive cardiac therapy such as phosphocreatine. 1. Physiological phenomenon: mild left atrial enlargement, partly caused by individual differences, only need to regularly review the heart ultrasound, observation and follow-up. 2. Congenital heart disease: some congenital heart disease can cause mild left atrial enlargement, which needs to be evaluated by a surgeon after completing the cardiac ultrasound to see if surgical operation is needed. It is generally recognized that there is no clinical manifestation, and most of them can be treated with observation and follow-up. Children with mildly enlarged left atrium may have other causes such as dilated cardiomyopathy, so it is recommended to further improve the examination and treat the cause of the problem, and the medication should be in accordance with the doctor’s instructions.