Enlarged atria are categorized into enlarged left atrium and enlarged right atrium, which are often caused by a number of diseases, such as valvular disease and congenital heart disease. 1. Enlarged left atrium. Mitral stenosis: when the mitral valve stenosis left atrium blood into the left ventricle obstacle, in the long run the left atrium blood increase, pressure increases, resulting in left atrial enlargement. Mitral valve insufficiency: Mitral valve insufficiency causes blood to flow back to the left atrium when the left ventricle contracts, which in turn increases blood flow to the left atrium, resulting in left atrial enlargement; at the same time, the increase in left atrial blood further leads to an increase in left ventricular blood volume when the left ventricle fills up, which leads to left ventricular enlargement. Left atrial mucinous tumor: left atrial mucinous tumor may lead to left atrial enlargement, echocardiography has high diagnostic value. 2. Enlarged right atrium. Atrial septal defect: Atrial septal defect is a common congenital heart disease, which will lead to shunting of blood from the left atrium to the right atrium, and enlargement of the right atrium after the pressure in the right atrium increases. Tricuspid stenosis: The principle is the same as that of mitral stenosis, which leads to enlargement of the right atrium. Tricuspid insufficiency: The principle is the same as that of mitral insufficiency, which leads to enlargement of the right atrium. Right ventricular enlargement. Right atrial mucinous tumor: like left atrial mucinous tumor, right atrial mucinous tumor may also lead to right atrial enlargement. As mentioned above, atrial enlargement is a common pathologic change in many diseases, and can also be seen in hypertension, coronary heart disease and other common diseases. Prompt medical attention is recommended to clarify the diagnosis and to intervene in the treatment as early as possible.