Diagnosis:
Cardiac biomarkers
• After an acute myocardial infarction, CK-MB2 (the cardiac form of CK-MB) is released into the circulation and the C-terminal lysine residue is removed from the M subunit of CK-MB2 by the enzyme carboxypeptidase to form CK-MB1.
• In an acute myocardial infarction, the ratio of CK-MB2 to CK-MB1 in serum exceeds 1.5 within 6 hours after the onset of symptoms.
• The advantage of measuring CK- MB isoforms is that an acute myocardial infarction can be detected earlier by this approach, compared with measuring CK-MB alone.
• The disadvantage of measuring CK-MB isoforms to diagnose an acute myocardial infarction is that they have the same specificity as CK-MB and can be elevated in skeletal muscle disease.
• CK-MB isoforms are measured by a high-resolution electrophoresis procedure. This method is labor intensive and may not be able to detect small changes in CK-MB isoform concentrations. It also requires careful interpretation of the CK-MB isoform pattern.
• An immunochemical procedure for measuring CK-MB isoforms was developed, but there was cross-reactivity with CK-MM.
