Ingenuous interpretation of elevated blood levels of macromolecular markers of myocardial injury: A recipe for confusion

Several assumptions about elevations of macromolecular markers of myocardia l injury in blood require critical consideration. The dichotomy of modest, persistent elevations of troponins I and T as prognostic factors in patient s with unstable angina and absent elevations of isoenzymes of creatine kina se is presently unexplained. Factors influencing the appearance of macromol ecular markers of myocardial injury in blood are considered, including the need to estimate baseline values, to consider elevations as deviations from baseline rather than simply points within a distribution of baseline value s in normal subjects, to recognize operative biochemical and physiologic de terminants of marker release from injured myocytes and washout and to take into account the influence of apoptosis. Elucidation and consideration of m echanisms underlying the appearance of specific macromolecular markers in b lood appear likely to improve diagnosis and explain the prognostic power of the troponins in patients with unstable angina. Detection of proteolytic b reakdown products of troponins in blood is Likely to explain the modest, pe rsistent elevations seen in some patients with unstable angina and their pr ognostic implications. (J Am Coll Cardiol 2000;35:1355-8) (C) 2000 by the A merican College of Cardiology.