Myoglobin is a hemoprotein having a molecular weight of approximately 17800 daltons. It transports and reversibly binds oxygen in muscle cells. It is found predominantly in striated muscle tissue (skeletal and cardiac muscle). Myoglobin is liberated from damaged heart muscle cells such as occurs during acute myocardial infarction. An increase in myoglobin concentrations in blood can generally be detected 2 to 4 hours after the onset of pain, which is earlier than other cardiac markers such as CK, CK‑MB or troponin. Depending on the therapeutic reperfusion measures taken, the myoglobin concentration reaches its maximum value after 4 to 12 hours and then decreases relatively rapidly to normal levels due to renal elimination (biological half - life: approx. 15 minutes). A very rapid increase in the concentration of myoglobin occurs when therapeutic intervention is successful. The gradient of the concentration increase can be taken as an indication of the success of thrombolysis.
The myoglobin determination is of particular value in exclusion diagnosis for myocardial infarction: if there is no increase in the myoglobin concentration 6 hours after the onset of pain and after a repeat determination within 4 hours, then acute myocardial damage can essentially be excluded.
Increases in concentration of myoglobin not due to infarction may be a result of muscle trauma, crush syndrome, myopathy, muscle strain/stress, shock, rhabdomyolysis or decreased elimination due to renal failure.