Biomedical Engineering Reference
In-Depth Information
Over 7.6 million MPI tests were performed in the USA in 2008 and ~3.5 million of
these tests required the use of a pharmacological agent to generate maximum coro-
nary blood flow in lieu of exercise. With increasing aging population, there is a rise
in the number of patients unable to perform exercise during diagnostic procedures,
and emerging imaging modalities that require the use of a vasodilator as a
biomarker.
Applications of Biomarkers of Cardiovascular Disease
Novel biomarkers have improved diagnosis and prediction of outcome in AMI, but
only troponin has been used to direct therapeutic intervention and none of the new
prognostic biomarkers have been tested and proven to alter outcome of therapeutic
intervention. Randomized trials are urgently needed to address this translational gap
before the use of novel biomarkers becomes common practice to facilitate personal-
ized management following an acute coronary event (
Chan and Ng 2010
).
Biomarkers for Ischemic Heart Disease
and Myocardial Infarction
Evaluation of patients who present to the hospital with a complaint of chest pain or
other signs or symptoms suggestive of acute coronary syndrome is time consuming,
expensive, and problematic. Recent investigations have indicated that increases in
biomarkers upstream from biomarkers of necrosis (cardiac troponins I and T), such
as inflammatory cytokines, cellular adhesion molecules, acute-phase reactants,
plaque destabilization and rupture biomarkers, biomarkers of ischemia, and bio-
markers of myocardial stretch may provide earlier assessment of overall patient risk
and aid in identifying patients with higher risk of an adverse event. Only two cat-
egories of the biomarkers are approved - troponins and natriuretic peptide.
Specifications that have been addressed for these biomarkers will need to be
addressed with the same scrutiny for the newer biomarkers under investigation.
These include validating analytical imprecision and detection limits, calibrator
characterization, assay specificity and standardization, pre-analytical issues, and
appropriate reference interval studies. Crossing boundaries from research to clini-
cal application will require replication in multiple settings and experimental evi-
dence supporting a pathophysiologic role and, ideally, interventional trials
demonstrating that monitoring single or multiple biomarkers improve outcomes.
Troponin
The contractile unit (or sarcomere) of striated muscle fiber is composed of thick and
thin filaments. The thick filament is composed mainly of myosin. Actin, tropomyosin,
and troponin comprise the thin filament. Muscle contraction occurs when the thick and
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