This test is done if a CPK test shows that your total CPK level is elevated. CPK isoenzyme testing can help find the exact source of the damaged tissue.
CPK is made of three slightly different substances:
- CPK-1 (also called CPK-BB) is found mostly in the brain and lungs
- CPK-2 (also called CPK-MB) is found mostly in the heart
- CPK-3 (also called CPK-MM) is found mostly in skeletal muscle
Higher-than-normal CPK-1 levels:
Because CPK-1 is found mostly in the brain and lungs, injury to either of these areas can increase CPK-1 levels. Increased CPK-1 levels may be due to:
- Brain cancer
- Brain injury (due to any type of injury including, stroke, or bleeding in the brain)
- Electroconvulsive therapy
- Pulmonary infarction
Higher-than-normal CPK-2 levels:
CPK-2 levels rise 3 to 6 hours after a heart attack. If there is no further heart muscle damage, the level peaks at 12 to 24 hours and returns to normal 12 to 48 hours after tissue death.
Increased CPK-2 levels may also be due to:
- Electrical injuries
- Heart defibrillation (purposeful shocking of the heart by medical personnel)
- Heart injury (for instance, from a car accident)
- Inflammation of the heart muscle usually due to a virus (myocarditis)
- Open heart surgery
Higher-than-normal CPK-3 levels are most often a sign of muscle injury or muscle stress. They may be due to:
- Crush injuries
- Muscle damage due to drugs or being immobile for a long time (rhabdomyolysis)
- Muscular dystrophy
- Myositis (skeletal muscle inflammation)
- Receiving many intramuscular injections
- Recent nerve and muscle function testing (electromyography)
- Recent seizures
- Recent surgery
- Strenuous exercise
Intense physical exercise, such as running a marathon, within a day or two of the test can lead to higher CK-MB levels.
Skeletal muscle damage, especially blunt trauma to the muscles, and cocaine abuse can also increase your levels of CK-MB. CK-MB is found mostly in the heart.
Drinking too much alcohol can also raise your CK levels. In some cases, people with low thyroid hormone levels, kidney failure, or alcohol abuse may also have higher CK-MB levels.
Drugs that can increase CPK measurements include the following:
- Amphotericin B
- Certain anesthetics
- Fibrate drugs
- Steroids, such as dexamethasone
This list is not all-inclusive