Relationship between different enzymatic estimations of the infarct size

In 592 patients with an acute myocardial infarction different enzymatic estimations of the infarct size were compared. Heat stable lactate dehydrogenase (LD) was analysed every 12 hours for 48-108 hours. Aspartate amino transferase (ASAT) was analysed once daily for 3 days. In a subgroup creatine kinase (CK) and creatine kinase subunit B (CK B) were analysed every 6 hours for 48 hours. A strong positive correlation was observed between the peak activity of the different enzymes (r-values varying between 0.81 and 0.85). The peak activity of heat stable LD, CK and CK B were strongly related to the area under the enzyme curve (r-values varying between 0.94 and 0.98). A substantial decrease in estimated infarct size was observed in a large number of patients when intervals between sampling increased, most often found for CK B. It is concluded that the calculated peak activity of heat stable LD, ASAT, CK and CK B seems to give a similar information about the infarct size in the majority of patients with acute myocardial infarction. Analyses of the area under the enzyme curve do not deviate from calculated peak enzyme activity.