Abstract
A prolonged myocardial ischemia, which results from a total deprivation of blood supply
to an area of cardiac muscle for an appreciable period of time, is the leading mechanism
responsible for acute myocardial infarction (AMI). The irreversible injury of myocardiocytes
and the subsequent release of a variety of intracellular components into blood is
the cornerstone of the diagnosis of AMI. Cardiac troponins are advocated as the biochemical
gold standards among the various biomarkers of plaque instability, plaque rupture,
ischemia, reversible cellular injury, and early and late necrosis (i.e., irreversible
injury). The assessment of cardiac troponins in the diagnostic approach of patients
with chest pain presents, however, some specific challenges due to the complex mechanisms
of release from the injured myocardium, as well as to the enzymatic degradation by
cardiac and extracardiac proteases (i.e., calpains, caspases, cathepsin L, and gelatinase
A) that might alter the immunoreactivity (and thus laboratory detection) of the molecules.
These two aspects will be discussed in this article, with specific focus on cardiac
troponin I, as a variety of immunoassays based on antibodies which recognize different
epitopes on the molecule is available for the measurement of this important cardiac
biomarker.
Keywords
troponin - proteolysis - degradation - interference - preanalytical variability
