Creatine phosphokinase (CPK) is an enzyme in your body found mainly in the heart, brain & muscle. When your muscle is damaged, CPK leaks into the blood & the level rises. This test maybe used to diagnose heart attack, evaluate cause of chest pain, determine extent of muscle damage, diagnose diseases like Polymyositis & detect brain injury or stroke. CPK is of 3 types: CPK-BB found in your brain & lungs, CPK-MB found in your heart & CPK-MM found in your muscles. This test helps to identify the specific type of CPK which is raised in the blood.