[Serum markers for ischemic myocardial damage].
Assays of serum enzymes, such as aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK) and isoenzyme MB, are widely performed in the early phase of suspected ischemic myocardial injury. However, these enzymes are not restricted to cardiac muscle tissue and increases in their serum concentrations have been observed in non-cardiac conditions. The levels of CK, and especially those of the myocardial specific isoform (CK-MB), have served as essential components for clinical decision in emergency rooms for over 25 years. This standard diagnostic test is far from perfect in specificity and the time delay necessary for the detection of a rise in levels. The clinician needs specific and sensitive biological parameters that can be rapidly measured in serum immediately after ischemic damage. In the last years, several new serum markers of myocardial damage have been developed. Currently, an important place is reserved for some non-enzyme muscle constituents, such as myoglobin and troponin sub-units, which have better specificity and allow an earlier detection of myocardial damage. The immunoassay of human cardiac troponin is a specific and sensitive diagnostic method for acute and sub-acute myocardial damage. It is ideal for the detection of myocardial necrosis in complex clinical situations when the usual enzymatic markers may be ineffective. An important prognostic value of troponin levels, especially troponin T, is currently under investigation. Myoglobin is a protein with low molecular weight that is abnormally high in serum two hours after myocardial infarction. Despite their high sensitivity, the use of serum measurements in the emergency room is controversial because of their low specificity, requiring the exclusion of skeletal muscle damage. Sensitivity could be lost in patients with renal function damage. The measurement of CK-MB protein weight (CK-MBmass) is another marker that has been confirmed as more accurate than CK-MB activity assays, especially in patients presented within four hours after the onset of chest pain, but could be inaccurate in several circumstances. In this research article, the authors describe the most important parameters of enzymatic and non-enzymatic markers, the kinetics of serum release, the clinical applications and the problems.
Fontes
J P
JP
Serviço de Cardiologia, Centro Hospitalar de Gaia.
Gonçalves
M
M
Ribeiro
V G
VG
D001219:Aspartate Aminotransferases / Q000097:blood; D015415:Biomarkers / Q000097:blood; D003402:Creatine Kinase / Q000097:blood; D003404:Creatinine / Q000097:blood; D006801:Humans; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000097:blood; D017202:Myocardial Ischemia / Q000097:blood*; D009211:Myoglobin / Q000097:blood; D012680:Sensitivity and Specificity; D014336:Troponin / Q000097:blood
D015415:Biomarkers; D007527:Isoenzymes; D009211:Myoglobin; D014336:Troponin; D003404:Creatinine; D007770:L-Lactate Dehydrogenase; D001219:Aspartate Aminotransferases; D003402:Creatine Kinase