The CPK-MB test is a cardiac marker used to assist diagnoses of an acute myocardial infarction.
The CPK-MB test measures the blood levels of two variants, isoenzymes CKM and CKB, of the enzyme phosphocreatine kinase.
The newer CPK-MB tests detect different isoforms of the B subunit specific to the myocardium whereas the older tests detect the presence of cardiac-related isoenzyme dimers.
Many cases of CK-MB levels exceeding the blood level of total CK have been reported in newborns with cardiac malformations, ventricular septal defect, pulmonary emboli or vasculitis.