Creatine kinase and myoglobin determination in myocardial infarction (determination of infant size).

In order to evaluate the diagnostic and prognostic importance of serum myoglobin (Mb) determination during acute myocardial infarction (AMI) we determined the time of first rise of both CK and Mb, that is the time in hours between the onset of pain and the last normal myoglobin and enzyme determination (TFR for Mb = 2.2 +/- 1.5 h; TFR for CK = 4.0 +/- 2.5 h). We also attempted to evaluate infarct size by mathematical analysis of the serum concentrations of Mb. The average percentage difference between the infarct size calculated from the CK concentrations and Mb concentrations was 35.8 +/- 35.2%. The results show that the determination of serum myoglobin is a useful and sensitive test for the early diagnosis of AML. On the other hand, the serum myoglobin cannot be utilized to evaluate infarct size. The main limitation in the determination of infarct size from the serum Mb concentrations lies in the extreme variability of the disappearance rate (Kd), mainly resulting from the renal elimination of the substance.