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Heart Attack Tests - Myoglobin

What is myoglobin?

Myoglobin is a protein found in heart muscle and other muscles in the body. When the muscle is injured, myoglobin is released into the blood. Myoglobin levels rise about one to four hours after heart attack symptoms begin and reach their highest level eight to 12 hours later. Because myoglobin is released into the blood more rapidly than CKMB or troponin, it is useful for diagnosing a heart attack in the very early stages. Myoglobin levels fall off after about 24 hours.

Who might have the test?

Myoglobin tests help diagnose or rule out heart attack. The test is usually ordered in patients with chest pain who may be having a heart attack; levels will be checked every two to three hours from the time they enter the emergency room.

What does the test entail?

A blood sample is taken from a vein in your arm. In some hospitals, a bedside or point-of-care test is available that requires only a finger prick and a few drops of blood. The blood is placed on a strip and positive results are available almost immediately if myoglobin is present in an elevated amount. It takes about 15 minutes to ensure a negative result. The test takes less than a minute.

What do the results mean?

A high level of myoglobin, or an increase in the level between the first and subsequent tests, indicates that there has been very recent injury to the heart or other muscle tissue.

What are the limitations of this test?

High myoglobin levels indicate muscle damage but they can’t tell whether the heart specifically is affected. Other tests (CKMB or troponin) are needed to confirm that the heart is affected. Myoglobin levels can rise after muscle injections or strenuous exercise. Patients with kidney failure may also have higher myoglobin levels without having a heart attack. In rare cases, alcohol abuse and certain drugs can increase myoglobin levels.


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