Cardiac markers are biomarkers measured to evaluate heart function. Most of the early markers identified were enzymes, and as a result, the term “cardiac enzymes” is sometimes used. However, not all of the markers currently used are enzymes. For example, in formal usage, troponin would not be listed as a cardiac enzyme. Cardiac markers are used in the diagnosis and risk stratification of patients with chest pain and suspected acute coronary syndrome (ACS). The cardiac troponins, in particular, have become the cardiac markers of choice for patients with ACS.