Brain Natriuretic Peptide (BNP) Test for heart failure
Brain Natriuretic Peptide (BNP) Test for heart failure
Brain Natriuretic Peptide is elevated in the patients with heart failure which acts as one of the marker for cardiac dysfunction. But sometimes, it may be also elevated in other conditions such as hypoxia and pulmonary embolism.
Content
0.4 -> Hi everyone, today in this video we are
going to discuss about BNP test. What is BNP?
9.68 -> BNP is the brain natriuretic peptide. Since
this peptide is extracted from porcine brain,
17.2 -> it is called as brain natriuretic peptide
20.32 -> and here the letter B can also be designated as B
type, so this is the B type natriuretic peptide.
27.92 -> This hormone is natriuretic that means it increase
the natriuresis, excretion of sodium and it is a
35.36 -> peptide in nature, which is locally released so
it is a paracrine peptide. It is having 32 amino
42.4 -> acid, generally it is released as a pro hormone
which is then converted into active hormone form,
49.92 -> resulting in the increased natriuresis. These
natriuretic peptides are of three types. First one
56.56 -> is ANP, second one is BNP and third one is CNP.
ANP is also called as atrial natriuretic peptide.
66.24 -> This peptide is mainly released from the
atria, that's why it's called as ANP and
71.92 -> BNP is the brain natriuretic peptide, which is
also called as B-type natriuretic peptide. This
77.84 -> peptide is released mainly from the ventricles
but also from atria as well as the brain,
83.6 -> but it is mainly released from the ventricles
due to any overstretch of ventricular walls,
89.76 -> particularly associated with congestive heart
failure. Similarly, the third one is the CNP,
95.6 -> which is also called as c-type natriuretic
peptide. This peptide is released from the
100.56 -> brain as well as chondrocytes, that's why it is
responsible for long growth of bones, as well as
107.52 -> it is also released from endothelium. In this way,
three natriuretic peptides are present within the
112.8 -> body and all these peptides are mainly responsible
for natriuresis, increased excretion of sodium
119.28 -> along with vasodilation. So today in this
video, we are going to discuss about this BNP,
125.2 -> the brain natriuretic peptide and how the
levels of BNP are useful as a diagnostic test
132.72 -> and what is the role of this BNP, what
are the normal values and abnormal values,
137.28 -> all these things we will discuss in this video.
So brain natriuretic peptide, which is also
142.4 -> designated as BNP, this BNP is mainly elevated in
the conditions such as heart failure. In the heart
149.36 -> failure, the heart is unable to pump so that a
small amount of the blood is going to be ejected,
154.56 -> so that the cardiac output is going to be reduced,
in such conditions the heart can release one
160.16 -> of the mediator brain natriuretic peptide, BNP.
This BNP is secreted into the circulatory system,
167.68 -> where it can be transported to renal
system to increase the natriuresis.
172.08 -> In this way, in heart failure, BNP is
released and secreted into the bloodstream
177.68 -> resulting in the increased levels of BNP which
indicates a possible heart failure in the
182.96 -> patients. When this test is required? Just we have
seen that BNP levels are elevated in the patients
189.36 -> with heart failure, so the patients with symptoms
of heart failure along with other risk factors,
196.72 -> in such conditions BNP tests can be done in
order to assess any progression of heart failure
201.92 -> within the patients. So few of the symptoms
such as dyspnea, difficulty in breathing,
207.2 -> abnormal heartbeat, some irregular
heartbeat can be observed
211.6 -> and unexpected weakness in the patients because
of decreased cardiac output, sudden increase the
218.32 -> weight gain as well as edema because of decreased
circulation and persistent coughing, chest pain,
227.12 -> all these symptoms may indicate a possible risk
of heart failure. So in such conditions, the BNP
233.44 -> test may be done in order to assess the function
of cardiac system. Now let us see what is the role
239.44 -> of this BNP. BNP is having the two important
targets. One is the vascular smooth muscle
245.28 -> and second is the renal system. This BNP can act
on the vascular smooth muscle, where it produces
251.68 -> the vasodilation and it can also act on the renal
system, where it can increase the excretion of
258.48 -> sodium so that sodium is more excreted. So both
vasodilation as well as increased sodium excretion
265.92 -> can reduce the cardiac work by reducing
the body volume as well as blood pressure,
272.24 -> which improves the symptoms of heart
failure. Similarly, BNP can also act on the
277.36 -> ventricular walls. So cardiac hypertrophy can
also be reduced by BNP. So this BNP can act on
285.04 -> the receptors located on ventricular walls so that
it can reduce the thickness of ventricular wall
291.36 -> and increase the blood flow. By all of these
actions, BNP can reduce the heart failure but
299.2 -> in the uncontrolled heart failure, the BNP levels
are elevated which indicates the progressive heart
305.68 -> failure within the patients. So within the
cardiac cells, NPR-A receptors are present.
311.36 -> These are the natriuretic peptide receptor
type A on which ANP as well as BNP can act.
319.76 -> Now the BNP, brain nitrite peptide can bind to
this NPR-A receptors which activates the guanyl
326.72 -> cyclase system. Now this GC can convert the GTP
into secondary messenger cyclic GMP. This cyclic
334.16 -> GMP then can stimulate the protein kinase-G,
which is going to inhibit the inward going L-type
341.36 -> calcium channels. So calcium cannot enter so that
the cardiac contraction is going to be reduced
348.32 -> which reduce the cardiac work and improves
the symptoms of heart failure. Similarly,
354 -> the cyclic GMP can also inhibit MLCK
activity within the vascular smooth muscle
359.44 -> which produce relaxation. In this way, BNP
can reduce the cardiac contractility as well
367.44 -> as it can reduce the cardiac work, at the same
time it can produce vasodilation by relaxation
373.84 -> of the vascular smooth muscle. Similarly BNP
can act on the renal system. Just we have seen
380.16 -> that it can produce a vasodilation, so BNP can
increase the afferent arteriolar vasodilation
386.64 -> which increase the rate of filtration resulting in
the increased glomerular filtration rate. So this
392.16 -> improves the excretion of minerals such as sodium.
BNP can also reduce the renin release so that
398.4 -> renin angiotensin system is somewhat inhibited and
it can also inhibit the Angiotensin II secretion
405.04 -> and finally BNP can also inhibit the
activity of ADH, antidiuretic hormone,
409.52 -> thereby it also promotes excretion of water
which reduce the body volume and cardiac work.
415.2 -> In this way, BNP can reduce the cardiac work in
the patients with heart failure but when it is
420.96 -> untreated, the BNP levels are elevated which can
be used as a diagnostic tool to assess the heart
429.2 -> failure within the patients. Now at the collecting
tubules, on the apical membrane, sodium channels
434.88 -> are present. These sodium channels are responsible
for absorption of sodium at the apical membrane.
441.52 -> Now sodium can enter into the renal tubules
which is going to be absorbed into the systemic
446 -> circulation by another pump sodium potassium
ATPase pump. This pump is responsible for
451.84 -> exchange of sodium for potassium. So sodium can
enter into the systemic circulation and potassium
457.12 -> can enter into the renal tubules. Similarly V2
channels are responsible for absorption of water
462.72 -> which are stimulated by antidiuretic hormone.
Now BNP can inhibit activity of many of these
468.96 -> ion channels. It can inhibit the sodium channel
activity so that sodium cannot be absorbed
474.96 -> and it is excreted resulting in the increased
natriuresis. It can also inhibit the V2 channels
482.48 -> so that water is not reabsorbed and it can also
block the sodium potassium ATPase pump, so that
488.56 -> the sodium exchange is also not possible at the
basolateral membrane and it can also inhibit the
494.88 -> renin secretion. By all of these actions, BNP
can increase the natriuresis finally resulting
502.24 -> in the increased excretion of sodium and decreased
body volume in the patients with heart failure.
508.72 -> In this way, BNP plays an important role in the
patients with heart failure. That's why it is
514 -> going to be elevated in such patients which can be
detected to identify the heart failure within the
519.28 -> patients. BNP and it's prohormone. We have seen
that BNP is a hormone which is locally released
526.16 -> but it is going to be released from its
pro hormone during the any stretch of
530.96 -> ventricular walls. So the proBNP can be cleaved
to produce active form of peptide, that is BNP.
538.72 -> Otherwise it can be cleaved into N-terminal
proBNP, which is the inactive form. So in the
544.56 -> patients with heart failure, both BNP as well
as N-terminal pro BNP, which is also called as
550.88 -> NT- proBNP, both of these peptides are elevated
and both can be used as markers for heart failure.
560.08 -> What are the normal values? The normal value of
BNP is less than 100 picogram per ml. Similarly
567.76 -> we can identify the NT proBNP which is the
inactive form, so the normal NT pro BNP levels
573.76 -> are less than 125 picogram per ml. But these
values are variable with the age of the patient
580.16 -> as well as gender of the patient. For example,
if the patients with age greater than 75 years,
586.4 -> the normal value of NT pro BNP is modified so that
the normal value is less than 450 picogram per ml.
595.6 -> Abnormal value of NT proBNP can be considered when
its levels are greater than 450 picogram per ml,
603.52 -> in the patients with age is less than 50 years.
607.68 -> But in the elder patients with age above 50
years, again this cutoff value is not valid.
613.6 -> In such patients, the NT pro BNP, if it is greater
than 900 picogram per ml, then it is considered as
620.72 -> abnormal value. So these factors plays an
important role in considering the abnormal value
626.96 -> but when this BNP levels are less than 100
picogram per ml and NT pro BNP levels are less
632.32 -> than 125 picogram per ml, it can be considered
as normal values without any significant risk of
639.04 -> heart failure within the patients. Other factors
that can elevate BNP. Not only the heart failure,
646 -> in other few conditions again BNP levels
are elevated within the blood. For example,
651.84 -> in the patients with any pulmonary
embolism , where there is a block of
655.52 -> circulation within the lungs, similarly in the
pulmonary hypertension or conditions like renal
662 -> failure, where the natriuresis is reduced
or in the patients with any chronic hypoxia,
669.04 -> in all these conditions BNP may be more
secreted and it is elevated within the blood.
674.64 -> So when this BNP levels are elevated
along with any cardiac symptoms,
680.08 -> it may be related with heart failure within
the patient. So that's about this BNP test.
686.32 -> The BNP acts as an important tool to diagnose the
heart failure and when these levels are elevated
693.12 -> along with any other risk factors within the
patient, a possible heart failure may be suspected
700.4 -> which can be confirmed by other cardiac
diagnostic tests. So that's about this test BNP,
707.04 -> hope you have enjoyed this video, if you like this
video please subscribe to our channel, share this
711.12 -> video with your friends, post your comments in the
comment box, thank you for watching this video.
Source: https://www.youtube.com/watch?v=LFLEcaHoLM8