What it means
Creatine kinase (CK) is an enzyme in muscles; the MB form is found mostly in the heart. When heart muscle is damaged, CK-MB leaks into the blood, rising about 3 to 6 hours after the injury, peaking within a day and returning to normal in 2 to 3 days. Skeletal muscle injury can raise it too, so troponinTROH-puh-ninA protein found in heart muscle cells; its level in the blood is a lab test for heart muscle damage.Full entry is now the preferred test for heart injury; CK-MB is still used in some places, for example to look for a new injury a few days later.
For the nurse
Note the time of each draw and the time the chest pain started; serial levels are compared, so the timing matters.
At a glance
| Normal range | Usually below about 5 ng/mL [5 mcg/L]; each lab sets its own range. |
|---|---|
| Also written | CK-MB isoenzyme, creatine kinase-MB, creatine kinase MB |
Related terms
myocardial infarction
Death of part of the heart muscle because its blood supply is blocked; a heart attack.
troponin
A protein found in heart muscle cells; its level in the blood is a lab test for heart muscle damage.
creatine kinase
An enzyme found mainly in muscle, measured in the blood to look for muscle damage.