AST is an intracellular enzyme which is present in many body cells, but its concentration is particularly high in heart cells (cardiomyocytes), and slightly lower in liver tissue. The substance plays the role of a catalyst of complex chemical reactions, but for doctors its function is not so important.

Its amount in the blood is clinically significant. As mentioned above, AST is contained within cells, therefore, an increase in blood levels indicates the destruction of these very cells. And as the AST content is greatest in the heart, the clinical interpretation is aimed specifically at detecting cardiac pathologies, in particular - in myocardial infarction. It is worth noting that AST may increase even before the heart attack is seen on the electrocardiogram (ECG).

The diagnosis of a heart attack should never be made on the basis of an elevated AST only. The analysis is necessary to confirm the diagnosis (in addition to the clinical picture and other methods of examination) and to monitor the course of treatment. If on the third day after a heart attack the AST level does not decrease, the prognosis is unfavorable, it means that the area of the heart muscle lesion may expand, and other organs (e.g., liver) may be affected.

In addition, it is possible to judge subjectively about the extent of heart damage by the activity of AST.

In order to control the treatment, it is necessary to take analyses in one laboratory according to the norms, which are obtained in the same laboratory. The thing is that the same index may be explained differently in different medical organizations.