Cardiac troponin I and troponin T: Recent players in the field of myocardial markers

The troponin (Tn) complex consists of three subunits referred to as TnT, Tn l and TnC. Myocardium contains TnT and Tnl isoforms which are not present i n skeletal muscles and which can be separated from the muscular isoforms by immunological techniques. Using commercially available immunoassays, clini cal laboratories are able to determine cardiac TnT and Tnl (cTnT and cTnl) quickly and reliably as classical cardiac markers. After acute myocardial i nfarction, cTnT and cTnl concentrations start to increase in serum in a rat her similar way than CK-MB, but return to normal after longer periods of ti me (approximately one week). Because of their excellent cardiac specificity , Tn subunits appear ideally suited for the differential diagnosis of myoca rdial and muscular damage, for example in noncardiac surgery patients, in p atients with muscular trauma or with chronic muscular diseases, or after in tense physical exercise. cTnT and cTnl may also be used for detecting evide nce of minor myocardial damage: therefore they have found new clinical appl ications, in particular risk stratification in patients with unstable angin a. In spite of the possible reexpression of cTnT in human skeletal muscles, and of the lack of standardization of cTnl assays, Tn subunits are not far to meet the criteria of ideal markers for acute myocardial injury. Only an insufficient sensitivity in the first hours following the acute coronary s yndroms requiries to maintain an early myocardial marker in the cardiac pan el for routine laboratory testing.