One of the cardiac markers, protein substances (enzymes), the serum level of which increases after a heart attack, and therefore suitable as one of the parameters indicating Myocardial Infarction.
CPK is found in many tissues of the body, mainly in skeletal muscles, and therefore its increase does not necessarily mean cardiac damage. In fact, any muscular trauma, even the slightest (for instance after an intramuscular injection) can significantly increase CPK levels.
Therefore, in the examination of CPK when a heart attack is suspected, an iso-enzyme, called CPK-MB, is evaluated. Increasing levels of this iso-enzyme are much more specific for cardiac damage.