Myoglobin, an oxygen-binding protein that is found in striated (cardiac and skeletal) muscle, releases oxygen at very low tensions. Any injury to skeletal muscle will cause a release of myoglobin into the blood. Myoglobin rise in 2-4 hours after an MI making it an early marker for determining cardiac damage.

Normal Lab Values for Myoglobin

  • Myoglobin: 5–70 ng/mL

Nursing Considerations

  • The level can rise as early as 2 hours after a myocardial infarction, with a rapid decline in the level after 7 hours.
  • Because the myoglobin level is not cardiac specific and rises and falls so rapidly, its use in diagnosing myocardial infarction may be limited.