Clinical significance of serum enzyme alterations associated with myocardial infarction

Abstract

Acute myocardial infarction is associated with alterations in the activity of serum glutamic-oxaloacetic transaminase (SGO-T) and serum lactic dehydrogenase (SLD). These serum enzymes can be measured readily by simple techniques. From 6 to 12 hours following the onset of myocardial infarction there is a rise of 2 to 8 or 10 times the activity of the serum enzymes, with a maximum elevation within 24 to 48 hours. The peak rise in the serum enzymes is proportional to the extent of myocardial tissue necrosis, and the serum enzyme changes are thought to be due to the loss of cardiac muscle enzyme from necrotic tissue into the circulation. In the presence of equivocal electrocardiographic changes or tracings in which classical patterns of myocardial infarction are obscured, the rise in SGO-T and SLD activity in a clinical setting suggestive of infarction is an especially helpful diagnostic tool. The serum enzymes are altered in several other specific clinical settings but the serial and quantitative serum enzyme changes are usually different from those observed in association with myocardial infarction.