Heart Enzyme (CK-MB) Test - Creatine Kinase-MB (CK-MB) Test

The serum creatine kinase MB isomerase (CK-MB) test measures the level of the MB subtype of the creatine kinase (CK) enzyme. While CK enzyme is found in skeletal muscle, the heart, and the brain, CK-MB isomerase is found primarily in cardiac muscle cells (to a lesser extent in skeletal muscle). Its blood level rises when there is damage to cardiac muscle cells, such as in acute myocardial infarction (heart attack), making it a useful cardiac marker.