Creatine Kinase MB

This test measures the enzyme Creatine Kinase (CK) MB in blood. It is also known as CPK (Creatine phosphokinase) MB test. CK MB is an enzyme which is mainly found in cells of heart muscles. It is also found in skeletal muscles but in a lesser amount.  

CK MB is a form of the enzyme which means it is an isoenzyme of Creatine kinase (CK). Other isoenzymes include CK MM and CK BB. While CK MM is found in skeletal muscles and heart, CK BB is found in the brain and smooth muscles. At the time of muscle damage, the cells of muscles release CK, which can be traced in blood. In normal conditions, CK MM can be detected in blood in small amounts, but CK BB cannot be detected in the blood. CK MB is detected in case there is an injury to the heart. This test is done to determine whether the damage is in the heart or in skeletal muscles. The levels of CK MB rise within  3-6 hours of chest pain during a heart attack. These levels rise to the maximum level in 12-24 hours and then come back to normal after 48-72 hours. In case, a person is going to have a subsequent heart attack, the levels of CK MB remain elevated.

Rise of CK MB levels can also be due to any physical damage to heart muscles from trauma, inflammation, surgery, and ischemia (decreased oxygen). High levels of CK MB can be due to kidney failure as well. Strenuous exercises can also increase CK levels, but the CK-MB remains low in that case. Low thyroid hormone levels, alcohol abuse, and chronic muscle disease can rarely cause an elevation in CK MB levels. There are some other factors such as infections, diseases, and drugs that cause injury or inflammation of the muscles which can result in a release of CK MB into the blood.