What is CK-MB (Creatine Kinase MB)?
CK-MB is an isoenzyme fraction of the enzyme creatine kinase (CK). Creatine kinase is found in several tissues in the body, particularly in skeletal muscle, heart muscle, and the brain. CK-MB is present in higher concentrations in the heart muscle and has therefore historically been used as a marker of heart muscle damage, for example in suspected myocardial infarction. Today, CK-MB has largely been replaced by troponin, which is more heart-specific and more sensitive. However, CK-MB may still be used in certain clinical situations.
What is the difference between CK and CK-MB?
CK (total CK) measures the total amount of creatine kinase in the blood, regardless of origin (skeletal muscle, heart, brain).
CK-MB measures the fraction of CK that is more closely associated with the heart muscle.
Elevated total CK may be seen after intense exercise, muscle injury, or inflammation in skeletal muscle, whereas elevated CK-MB more strongly raises suspicion of heart muscle involvement.
Why is CK-MB measured?
CK-MB is primarily analyzed when heart muscle damage is suspected. Typical clinical situations include:
Chest pain where myocardial infarction needs to be ruled out or confirmed
Follow-up after a confirmed myocardial infarction
Assessment of cardiac involvement in other serious illnesses
In acute myocardial infarction, CK-MB usually rises within a few hours, peaks within about 24 hours, and then gradually declines. This time pattern has previously been used to assess whether a new infarction has occurred.
What can cause elevated CK-MB?
The most common and important cause is heart muscle injury, such as:
Acute myocardial infarction
Myocarditis (inflammation of the heart muscle)
Cardiac surgery or other medical interventions affecting the heart
However, it is important to note that CK-MB can also increase in cases of:
Severe skeletal muscle injury
Major trauma
Intense physical exertion
Therefore, the value is always interpreted together with clinical symptoms, ECG findings, and often troponin levels.
Symptoms that may prompt testing
Pressing or persistent chest pain
Shortness of breath
Cold sweats, nausea
Sudden weakness or discomfort in the upper body
In case of acute symptoms, medical care should always be sought immediately.
Sampling and interpretation
CK-MB is measured through a standard blood test. Since levels change over time in cases of heart injury, repeated samples are often taken a few hours apart to assess the dynamics (rising or falling values).