Why get tested?
To determine whether muscle, particularly heart muscle, has been injured
When to get tested?
Every 2-3 hours for the first several hours after experiencing chest pain that is suspected to be a Heart Attack; rarely ordered alone these days as a cardiac biomarker but ordered with Troponin instead to help rule out a heart attack
A blood sample drawn from a vein in the arm
What is being tested?
Blood is being tested for the presence of Myoglobin, which is a small protein found in heart and other muscles. While hemoglobin brings oxygen to most of the body, myoglobin traps oxygen in muscle to allow muscle cells to work properly. When heart or other skeletal muscle is injured, Myoglobin is released into the blood. It is one of the first Cardiac Biomarkers to rise in the blood after a Heart Attack.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.
How is it used?
As a cardiac biomarker, Myoglobin is used in conjunction with Troponin and other tests to help rule out a heart attack. Myoglobin levels start to rise within 2-3 hours of a heart attack or other muscle injury, reach their highest levels by about 8-12 hours, and generally fall back to normal by about one day after injury occurred. Consequently, myoglobin testing is used to help rule out a heart attack in emergency room situations.
When is it ordered?
Because of the high confidence in the Troponin Test, many physicians do not order myoglobin. When it is ordered, it is ordered with Troponin to assess persons with chest pain who are suspected of having a heart attack. Myoglobin levels are often used every 2-3 hours for the first several hours after a patient who has chest pain comes to the emergency room.
What does the test result mean?
NOTE: A standard reference range is not available for this test. Because reference values are dependent on many factors, including patient age, gender, sample population, and test method, numeric test results have different meanings in different labs. Your lab report should include the specific reference range for your test. Health.am strongly recommends that you discuss your test results with your doctor.
When myoglobin rises, this means that there has been very recent injury to the heart or other muscle tissue. If myoglobin does not increase after about 5 hours, a heart attack is very unlikely, unless the chest pain started more than a day before.
Because myoglobin is also found in other muscles, high levels usually require using other tests (such as CK-MB or Troponin) to tell whether the damage was to heart or to other skeletal muscle. High levels can occur in accidents, seizures, surgery, or any muscle disease, such as Muscular Dystrophy.
Is there anything else I should know?
Increased myoglobin levels can occur after muscle injections or strenuous exercise. Because the kidneys remove myoglobin from the blood, myoglobin levels may be high in persons whose kidneys are failing. Rarely, heavy alcohol abuse and certain drugs can cause muscle injury and increase myoglobin.
What are the other heart attack tests?
Doctors often use more than one test to determine if a person who has chest pain is having a heart attack. Troponin is generally considered the most accurate test, and CK-MB (the heart isoenzyme of CK) is also highly accurate in detecting damage to the heart, even when there is no other evidence of a heart attack. Myoglobin and creatine kinase almost always rise in patients with a heart attack, but they are less specific - other conditions can also produce an increase in these two tests.
Also Check Myoglobin - serum
Revision date: June 11, 2011
Last revised: by Jorge P. Ribeiro, MD