The human body makes three (3) forms of an isoenzyme of creatine kinase (CK). One of these three isoenzymes is called CK-MB. CK is found in the heart, muscles, and other organs. These include the small intestine, brain, and uterus. If you have a heart attack, injured heart muscle cells release CK-MB into your blood. Because many tissues contain CK, high levels of CK can be a sign of a variety of problems. Higher CK-MB may point most directly to heart damage.