Biomarkers of Cardiovascular Disorders - Applications of Biotechnology in Cardiovascular Therapeutics - page 99

Roche Troponin I, and Siemens' Troponin I Ultra) as well as a standard assay
(Roche Troponin T) that were performed on blood samples obtained in the emer-
gency department from patients who presented with symptoms suggestive of acute
MI (Reichlin et al. 2009 ). The diagnostic performance of sensitive cardiac troponin
assays was excellent, and these assays can substantially improve the early diagnosis
of acute MI, particularly in patients with a recent onset of chest pain. Another mul-
ticenter study determined levels of troponin I as assessed by High-Sensitive
Troponin T and traditional biomarkers of myocardial necrosis in patients with sus-
pected acute MI, on admission and 3 and 6 h after admission (Keller et al. 2009 ).
It concluded that the use of a sensitive assay for troponin I improves early diagnosis
of acute MI and risk stratification, regardless of the time of onset of chest-pain.
In most patients with stable coronary artery disease, plasma cardiac troponin T
levels are below the limit of detection for the conventional assay. A study with
follow-up period of >5 years used a new, high-sensitivity assay to determine the
concentration of cardiac troponin T in plasma samples from patients with stable
coronary artery disease and analyzed the results of the assay in relation to the inci-
dence of cardiovascular events (Omland et al. 2009 ). After adjustment for other
independent prognostic indicators, cardiac troponin T concentrations as measured
with a highly sensitive assay were significantly associated with the incidence of
cardiovascular death and heart failure but not with MI in patients with stable coro-
nary artery disease.

Natriuretic Peptide

Several terms relevant to natriuretic peptide (NP) are defined as follows:

• B-Type Natriuretic Peptide (BNP) is a biologically active hormone, which cor-

responds to the C terminal fragment of proBNP (amino acids 77-108) and is
present in both myocardium and plasma.
Pre-proBNP is the cellular precursor synthesized in the myocardial cell. It con-

•

tains 134 amino acids, including a signal peptide of 26 amino acids and is pres-
ent only in myocardial tissue.
ProBNP contains 108 amino acids (1-108) and is produced from pre-proBNP by •

cleavage of the signal peptide, when appropriate signals for hormone release are
given. It is present in both myocardium and plasma.
NT-proBNP, the entire N-terminal fragment of proBNP (amino acids 1-76),

•

lacks hormonal activity and is present in both myocardium and plasma. Further
degradation products of this molecule are sometimes identified with the same
abbreviation, for example, NTproBNP (amino acids 1-21), but little metabolic
and pathophysiologic information is available for these molecules.

The NP system is primarily an endocrine system that maintains fluid and pressure
homeostasis by modulating cardiac and renal function. The physiologic functions
of the NP system in healthy humans and in patients with cardiovascular disease are