A left atrium of 45mm is generally abnormal. The normal size of the left atrium, for example, in adults, is generally within 30~35mm; so the left atrium 45mm, which belongs to mild enlargement, is generally abnormal. Clinically, obese patients may have a mild enlargement of the left atrium, which is a physiological change, and generally does not have clinical symptoms and has no major impact. Some patients with hypertension and atrial fibrillation, generally mild enlargement of the left atrium will not affect the hemodynamics of the body, and active treatment of the primary disease, mild enlargement of the left atrium may be reversed. However, many cases are caused by pathological factors, such as long-term pulmonary heart disease, dilated cardiomyopathy, coronary artery disease and other conditions, will appear in the left atrium of mild enlargement. Therefore, it is recommended that the patient undergo further examination and be given targeted treatment after the cause is clarified by the doctor.