CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 7, August 2013
286
AFRICA
Review Article
Diagnostic and prognostic values of B-type natriuretic
peptides (BNP) and N-terminal fragment brain natriuretic
peptides (NT-pro-BNP)
LORENA MARIES, IOAN MANITIU
Abstract
B-type natriuretic peptide (BNP) is a member of a four-
natriuretic peptide family that shares a common 17-peptide
ring structure. The N-terminal fragment (NT-pro-BNP) is
biologically inert, but both are secreted in the plasma in
equimolar quantities and both have been evaluated for use
in the management of congestive heart failure. BNP and
NT-pro-BNP are frequently used in the diagnosis of conges-
tive heart failure and distinguishing between patients with
dyspnoea of cardiac or pulmonary origin. Values of NT-pro-
BNP are affected by age or the presence of one or several
co-morbidities such as chronic renal failure, type 2 diabetes,
and acute coronary syndrome. ‘Normal’ values of these
peptides also vary depending on the type of test used. The
performance characteristics of these tests vary depending on
the patients on whom they are used and the manufacturer.
For this reason, the determination of reference values for this
peptide represents such a challenge.
Keywords:
natriuretic peptides, prognostic values, NT-pro-BNP
Submitted 6/12/12, accepted 14/8/13
Cardiovasc J Afr
2013;
24
: 286–289
DOI: 10.5830/CVJA-2013-055
BNP was initially discovered in the porcine brain, but the
largest concentrations are found in the heart. It is a peptide with
32 amino acids, synthesised in the ventricles as a response to
stretching of the myocytes and/or pressure overload. It is released
as an active hormone and as an inactive N-terminal fragment
(NT-pro-BNP).
1
Once released in the blood flow, BNP has numerous
physiological actions, their net effect being to reduce pre- and
post-load. Specifically, BNP produces a decreased vascular
tonus by relaxing the smooth muscles, leading to a decrease in
post-load. In addition, it induces a movement of fluid into the
interstitial space, thus leading to a decrease in pre-load.
BNP reduces the proliferation of fibroblasts and smooth
muscle cells, sympathetic nervous activity, water and salt
retention, release of the antidiuresis hormone, and synthesis
of aldosterone and its release from the adrenal glands. In the
kidneys, BNP increases glomerular filtration rate and renal blood
flow by increasing the outgoing arterial tonus and decreasing the
ingoing one. In addition it decreases the release of renin and the
reabsorption of sodium, leading to diuresis and natriuresis.
2
The N-terminal fragment of BNP is derived from proteolysis
of pro-BNP, which is composed of 108 amino acids. It consists of
76 amino acids and has recently caused great interest, due to its
possible role in monitoring heart failure and distinguishing acute
coronary syndromes. Its effects on diuresis and natriuresis in
patients with congestive heart failure represent a compensatory
mechanism for stress on the myocytes, which leads to ventricular
dysfunction.
1
Diagnostic and prognostic value of BNP and
NT-pro-BNP
Serum levels of natriuretic peptides are important, not just as
indicators of numerous cardiovascular deficiencies but also
as markers of their severity.
1
For patients with acute coronary
syndromes, the determination of BNP levels offers predictive
information on the apportioning of risk, in the absence of
elevation in the S-T interval. In addition, BNP and NT-pro-BNP
have prognostic significance for acute pulmonary embolism.
1
The diagnostic value was recently confirmed by Coutance
et
al.
3
Even if high levels of BNP demonstrate a high sensitivity
for detecting patients with risk of sudden death, the specificity
of this neurohormone is decreased. A diverse analysis between
mortality and levels of BNP was recently conducted by Nunez
and his team, which demonstrated a positive linear correlation
between the risk of death and BNP level.
4
With regard to the prognostic value of NT-pro-BNP for chronic
heart failure, the Val-HeFT study (Valsartan Heart Failure Trial)
demonstrated the positive nature of advanced heart failure.
Moreover, BNP concentrations appeared significantly increased
in patients with dilated cardiomyopathy and cardiovascular
disease in NYHA classes III or IV, but it could not predict
mortality or the requirement for a heart transplant.
1
Variability of BNP
Despite the evidence that BNP is secreted in ventricular overload
states, there is an individual and inter-individual variation in
both healthy subjects and those with stable chronic heart failure,
which makes the interpretation of BNP levels difficult. Multiple
Lucian Blaga University, Sibiu, Romania
LORENA MARIES, MD, PhD student,
IOAN MANITIU, MD, PhD
