Creatine Kinase MB (Blood)
Does this test have other names?
What is this test?
This test measures the amount of an isoenzyme of creatine kinase (CK) in your blood. It is called CK-MB.
Your body makes 3 forms of CK, including 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 more directly to heart damage.
Each year millions of Americans visit the emergency room with chest pain, but only a fraction of those people are actually having a heart attack or another serious, sudden heart problem. This test helps your doctor figure out whether you're having a heart attack.
Measuring CK-MB used to be a common tool for diagnosing heart attacks, but doctors use it less often today. Cardiac troponin is now the test of choice for finding a heart attack. This is because cardiac troponin is more specific and more sensitive than CK-MB.
Why do I need this test?
You may have this test if your doctor thinks you are having a heart attack. Symptoms of a heart attack often include:
Pain or discomfort in the chest, such as a squeezing sensation or feeling of fullness
Pain in the neck, back, left arm, or jaw
Shortness of breath
Lightheadedness or dizziness
Nausea or vomiting
What other tests might I have along with this test?
Your doctor may also order a test to measure cardiac troponin, or CTn. This test is more commonly used than CK-MB because it more specifically shows heart damage.
Your doctor may also order an electrocardiogram, or ECG, to measure electrical activity in your heart and help diagnose a heart attack.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.
Levels of CK-MB do not rise in your blood within the first 4 to 6 hours after a heart attack. You may need to have repeated tests to see if you've had a heart attack.
Higher levels of CK-MB may mean that you have had a heart attack or have other heart problems. These include:
Myocarditis, an infection and inflammation of the heart muscle
Pericarditis, an infection and inflammation of the thin sac that surrounds the heart
Cardiac defibrillation, when an electric shock is used to fix the heart rhythm
Higher levels of CK-MB may also mean more of the heart was damaged in the attack.
Higher levels may also be caused by muscle damage elsewhere in your body, by diseases that affect your muscles, and by trauma to your chest.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Timing is important. If you have the test too soon after a heart attack, your may have a false-negative result.
Strenuous exercise and cocaine use can also affect your results.
How do I get ready for this test?
You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.