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THE GENERATION DIAGNOSTIC SYSTEM
Myoglobin is an iron- and oxygen-binding protein found in both skeletal and myocardial muscles. It acts as a transport protein and is involved in diffusion of oxygen in the muscle tissue. Myoglobin is a single-chain globular protein of 154 amino acids. It is composed of a central iron-containing ‘Heme’ which is enclosed in a compact bundle-like or prism-like arrangement formed by the eight right-alpha-helices[1,2]. Being a cytoplasmic protein having low molecular weight (of 17,699 daltons), myoglobin is released into the serum more rapidly as compared to other cardiac markers upon damage to the myocardial cells. Serum concentration of myoglobin increases above the normal range as early as 1 hour after acute myocardial infarction (AMI), attains peak level in approximately 4 to 8 hours after the onset and normalize rapidly afterwards. Thus myoglobin is better suited as a cardiac marker for early diagnosis of AMI. However, the elevated myoglobin is not specific to AMI owing to its large quantities in skeletal muscles as well. Despite its low clinical specificity and weak predictive value towards AMI, myoglobin is still a promising cardiac marker when other markers such as Creatin Kinase Isoenzyme-MB (CK-MB) and Cardiac Troponin-I (cTn-I) as well as other indicators like clinical signs and ECG are taken into account for diagnosis/confirmation of AMI.[3-8]
- 1. Kent Lewandrowski, Ahchean Chen and James Januzzi, Cardiac markers for myocardial infarction, Am J Clin Pathol 2002; 118 (Suppl 1):S93-S99
- 2.Cox, MM, Nelson, DL. Lehninger: Principles of Biochemistry, 3rd edition. W.H. Freeman and Company, New York, 2000, 206.
- 3.Ordway GA, Garry DJ. Myoglobin: An essential hemoprotein in striated muscle. J Exp Biol.. 2004; 207(Pt 20):3441-6.
- 4.Lewandrowski K, Chen A, Januzzi J. Cardiac markers for myocardial infarction. A brief review. Am J Clin Pathol. 2002:118:S93-9.
- 5. Vaidya HC. Myoglobin: an early biochemical marker for the diagnosis of acute myocardial infarction. J Clin Immunoassay. 1994; 17:35-39.
- 6.Gibler WB, Gibler CD, Weinshenker C, et al. Myoglobin as an early indicator of acute myocardial infarction. Ann Emerg Med. 1987; 16:851-856.
- 7.Adams JE, Abendschein DR, Jaffe AS. Biochemical markers of myocardial injury: is MB creatine kinase the choice for the 1990s? Circulation. 1993; 88:750-763.
- 8. Mair J, Morandell D, Genser N, et al. Equivalent early sensitivities of myoglobin, creatine kinase–MB mass, creatine kinase isoforms ratios, and cardiac troponins I and T for acute myocardial infarction. Clin Chem. 1995; 41:1266-1272