From the Guidelines
CK-MB (Creatine Kinase-Myocardial Band) is a specific enzyme found primarily in heart muscle cells, used as a biomarker to diagnose and monitor heart attacks (myocardial infarction), with elevated levels indicating recent heart muscle injury. When heart muscle is damaged, CK-MB is released into the bloodstream, with levels typically rising 3-6 hours after a heart attack, peaking at 12-24 hours, and returning to normal within 2-3 days 1. In clinical practice, CK-MB is often measured alongside other cardiac markers like troponin for a more comprehensive assessment of heart damage, although troponin is generally more sensitive and specific for heart muscle injury 2. CK-MB can still be useful in certain scenarios, such as detecting a second heart attack soon after the first one, or in the diagnosis of early infarct extension (reinfarction) and periprocedural MI 2. Some key points to consider when using CK-MB include:
- The normal range for CK-MB is generally 0-3.8 ng/mL, but exact reference ranges may vary slightly between laboratories
- Values above this range, especially when accompanied by clinical symptoms, suggest possible heart muscle damage and require further investigation
- CK-MB is not exclusively found in the heart; small amounts can also be present in skeletal muscle, so interpretation should always consider the clinical context and other diagnostic information 1, 2. It's also important to note that the use of CK-MB should be guided by the most recent and highest quality evidence, with a preference for mass immunoassays over other methods previously used 2.
From the Research
Definition of Creatine Kinase (CK) MB fraction
- Creatine Kinase (CK) MB fraction, also known as CK-MB, is a subtype of creatine kinase isoenzyme that is mainly present in myocardial tissue 3, 4, 5, 6.
- CK-MB is released into the blood when myocardial tissue damage occurs, and its serum level significantly increases, making it an important indicator for diagnosing acute myocardial infarction 3, 4, 5, 6.
Clinical Significance of CK-MB
- The CK-MB index can be used to discriminate between myocardial infarction and skeletal muscle damage, with a maximal CK-MB index exceeding 5.0 being diagnostic of myocardial infarction 3.
- The content of CK-MB relative to total CK in myocardial cells is variable, and it is low in normal myocardium and increased several-fold in hypoxic myocardium 5.
- CK-MB levels can be influenced by preinfarctional medication, such as beta-blockers, and the extent of coronary disease 5.
Measurement and Interpretation of CK-MB
- CK-MB can be measured using enzyme immunoassay or mass immunoassay, and the results can be affected by interference 7.
- A pseudo-elevation of CK-MB can occur without myocardial infarction, and laboratory personnel should be aware of the shortcomings of the measurement method and use alternative methods to eliminate interference 7.
- The timing of blood sampling for CK-MB estimation is important, with most patients achieving a CK-MB activity of at least 15 U/l between 6 and 30 h following the onset of symptoms 6.