Aspartate aminotransferase is mainly found in the myocardium, followed by tissues such as liver, skeletal muscle and kidney. Normal serum levels of aspartate aminotransferase are relatively low, but when the corresponding cells are damaged, the cell membrane permeability of the damaged cells increases, and the aspartate aminotransferase in the cytoplasm is released into the blood, which can lead to an increase in serum concentrations, and is generally used as an auxiliary test for infarcts and myocarditis as well as hepatitis. The normal value of AAT is 0-40U/L. When AAT is significantly elevated and the ratio of AAT to ALT is greater than 1, it suggests that there is extensive damage to the liver. Commonly, increased AAT can be seen in acute viral hepatitis, cirrhosis, hepatocellular carcinoma, biliary tract obstruction, myocardial infarction, myocarditis, extrusion syndrome and other diseases.