The CPK-MB test (creatine phosphokinase-MB), also known as CK-MB test, is a
cardiac marker used to assist diagnoses of an
acute myocardial infarction,
myocardial ischemia, or
myocarditis
Myocarditis is inflammation of the cardiac muscle. Myocarditis can progress to inflammatory cardiomyopathy when there is associated ventricular remodeling and cardiac dysfunction due to chronic inflammation. Symptoms can include shortness of bre ...
. It measures the blood level of CK-MB (creatine kinase myocardial band), the bound combination of two variants (isoenzymes
CKM and
CKB) of the enzyme
phosphocreatine kinase.
In some locations, the test has been superseded by the
troponin test. However, recently, there have been improvements to the test that involve measuring the ratio of the CK-MB1 and CK-MB2 isoforms.
The newer test detects different
isoforms of the B subunit specific to the myocardium whereas the older test detected the presence of cardiac-related
isoenzyme
In biochemistry, isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. Isozymes usually have different kinetic parameters (e.g. di ...
dimers.
Many cases of CK-MB levels exceeding the blood level of total CK have been reported, especially in newborns with cardiac malformations, especially ventricular septal defects. This reversal of ratios is in favor of pulmonary emboli or vasculitis. An autoimmune reaction creating a complex molecule of CK and IgG should be taken into consideration.
See also
*
Troponin
Troponin, or the troponin complex, is a complex of three regulatory proteins (troponin C, troponin I, and troponin T) that are integral to muscle contraction in skeletal muscle and cardiac muscle, but not smooth muscle. Measurements of cardiac-spe ...
References
{{Blood tests
Blood tests
Cardiology