With contemporary troponin assays, creatine kinase myocardial isoenzyme (CK-MB) and myoglobin are not useful for diagnosis of ACS.158 164 (Level of Evidence: A) 3.4.2. Biomarkers: Prognosis Class I 1. The presence and magnitude of troponin elevations are useful for short- and long-term prognosis.71,73,165,166 (Level of Evidence: B) Class IIb 1. It may be reasonable to remeasure troponin once on day 3 or day 4 in patients with MI as an index of infarct size and dynamics of necrosis.164,165 (Level of Evidence: B) 2. Use of selected newer biomarkers, especially B-type natriuretic peptide, may be reasonable to provide additional prognostic information.87,88,167 171 (Level of Evidence: B) Cardiac troponins are the mainstay for diagnosis of ACS and for risk stratification in patients with ACS. The primary diagnostic biomarkers of myocardial necrosis are cardiac troponin I and cardiac troponin T. Features that favor troponins for detection of ACS include high concentrations of troponins in the myo- cardium; virtual absence of troponins in nonmyocardial tissue; high-release ratio into the systemic circulation (amount found in blood relative to amount depleted from myocardium); rapid release into the blood in proportion to the extent of myocardial injury; and the ability to quantify values with reproducible, inexpensive, rapid, and easily applied assays. 