The normal size of the left atrium is 30-35 mm, so a left atrium of 46 mm is a mild enlargement, which is more serious. The etiology of left atrial enlargement includes increased pressure load in the left atrium, increased volume load and arrhythmia. Its severity is related to the severity of the primary disease, such as hypertension, pulmonary heart disease, dilated cardiomyopathy and coronary heart disease. Enlargement of the left atrium predisposes to symptoms of arrhythmia such as atrial tachycardia, atrial premature beats, atrial flutter and atrial fibrillation, and in severe cases, heart failure. If atrial fibrillation occurs, it often leads to blood clots, which in severe cases can cause embolism of vital organs. An enlarged left atrium requires a low-salt, low-fat diet, regular follow-up cardiac ultrasounds, and symptomatic treatment to identify the cause.