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Archive for the ‘pulmonary hypertension’ Category

The right ventricle  is considered as a docile cardiac chamber with passive filling and  emptying  properties .

This belief  was reinforced when Fontan  in early 1970s suggested a principle in the management of  cyanotic heart disease  when  the right side of the heart is underdeveloped. He  proved  RV can be by-passed safely , with  great veins  (IVC/SVC)  by  themselves  take care of filling the pulmonary circulation  without the need of RV pumping function.

While it is true for few complex cyanotic heart disease, largely this a misleading  concept. In clinical cardiology practice  ,sudden or non sudden  RV deaths happen every day in the form of . . .

  • RV Infarction
  • Acute RV dysfunction in massive pulmonary embolism
  • COPD with RV dysfunction
  • Most cases dilated cardiomypathy  the terminal event is due to RV  failure.

So , RV function can never be dispensable in day to day cardiac hemodynamics.

RV has some unique properties in terms of shape , size and  hemodynamics . We are getting more insights from  modern blood pool imaging by MRI , about  how the RV handles the blood volume .

We know RV has a unique shape  triangular ( partially  pyramidal ) . It can be inferred the RV cavity is formed by fusion of  many  eccentric spacial planes. We have always believed  RV handles the blood it receives from right atrium in a unique way .Now we are beginning to understand it .It is now documented the RV segregates the blood it receives into 4 components.

 

right ventricle physiology anatomy hemodynamics

It is curious  to know  RV inflow is connected to the outflow by an invisible   physiologic Bridge . About 44% of  blood traverse the RV in this fashion.

 

RVOT blood flow right ventricle

Note : RV blood flow preferentially enters the RVOT with out transiting RV body and apex.Image courtesy http://ajpheart.physiology.org/

 

Which is the most important part in RV ? (Among Inflow, Body, Apex, Out flow)

After reading this article it seems to me , the mechanical  function of RVOT could be most  vital. If it fails to handle the first increment  which  comes directly from  RV inflow, stasis  is likely in RV body and apex , elevating RVEDP and later promoting stasis leading to clinical events.

Clinical implication of this study

  • Differential dilatation RV chambers to pressure or volume  overload is observed .
  • We need to analyse why RV dilates in some   but   goes for hypertrophy in others when confronted with pressure overload (VPS vs PAH)
  • RV apical clot in restrictive cardiomyopathy  is a direct consequence of stasis  of blood  in RV apical zone .
  • RVOT pacing  may have a hemodynamic advantage  over RV apical pacing  . However , for anatomical reasons RV apical pacing  is  far safer than RVOT pacing where the lead  is subjected to constant life long strain due to this busy RV inflow to outflow express  high way !

Final message

Traditionally we have labeled  RV  as a  passive venous chamber .It is clearly a misnomer.It  has to handle both the venous and pumping function beat to beat with precision  without  back log .Obviously ,  RV has to think and work  more than it’s  big brother !

Reference

I wonder , if  there is  any other site other than APS . . . to  find crucial  answers in cardiac physiology  !

 

Right ventricle physiology blood flow  3d 4d analysisAfter thought

  • There is huge gap between physiologists  who work in research labs and the physicians at bed side .
  • I appeal all young cardiologists  to visit  APS  once in a while ,between your busy cath lab schedule and help narrow this gap.
  • Without understanding the physiology properly how are we going to intervene the pathology ?

 

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Many decades ago Potts  shunt  (Central Aortic -PA shunt)was used to increase pulmonary blood flow for severe RVOT obstruction mostly for TOF  and tricuspid atresia .With the advent of  ICR and  Fontan role for central aorti shunts waned.

Now, read this

Chronic ,refractory pulmonary hypertension of any cause has dismal  outcome.In  patients with severe PAH  many patients  reach supra-systemic pressures . RV   a volume handling chamber faces a uphill task of overcoming huge RV after load. As cardiac physicians , we  struggle  to  perfuse the lungs in such situations.

The only option  seems to be  lung transplantation !

How to perfuse the lungs if the RV is failing ?

Is there any other alternative ?

Why not,use LV contractility  to perfuse lungs .

Great Idea isn’t ? After all , how can we allow left ventricle known for it’s  robust bumping function  sit idle and relax  when it’s counterpart is struggling with heavy load ?

How to use LV for increasing pulmonary blood flow ?

Create a central Aortic -Pulmonary shunt.

That’s resurgence of Potts shunt.

Dr Julie Blanc from France suggested this approach in in NEJM as a letter  (Potts Shunt in Patients with Pulmonary Hypertension N Engl J Med 2004; 350:623) .  It  was a great Idea.

Since then lots of patients  have a benefited from this vintage surgery.

potts shunt in severe pulmonary hypertension

Final message

A surgery blamed for early onset of pulmonary vascular damage due to potential Eisenmenger reaction is back .Indication for refractory Eisenmenger syndrome to perfuse lungs  at very high pressure Nothing is obsolete in medical science .Nothing is ironical as well !

Another Innovation : Now Transcatheter Potts Surgery

potts shunt for eisenmenger and severe pulmonary arterial  pht pah

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The primary determinant of pulmonary artery systolic pressure is . . . ?

  1. Pulmonary arterial tone
  2. Pulmonary venous pressure
  3. RV contractility
  4. Pulmonary blood flow

Answer : All of the above

But what is the relative contribution of each ?

I am  100 %  sure  ,  no  one can answer this question  correctly !

It is  true  , in some  pathological situations  one can  be  fairly certain about  cause of   elevated pulmonary arterial pressure .

When we confront a patient  with left heart disease  it is the transmission of  mean venous pressure .

Whatever be  our understanding ( Pre/Post capillary pulmonary hyper tension and the related stuff !  ), the one parameter that makes mystery contribution  to PA pressure is RV contractility !

In physiology  RV   generates  about 30mmhg systolic pressure that becomes the  pulmonary systolic  pressure .The  diastolic pressure  will be around 15 and mean around 20 . During exercise  contractility of both RV and LV increase .There has been documented PASP up to 50 mmhg in normal healthy adults during   exertion .

Here one can assume RV contractility is causing  a entity called transient Isolated  systolic  pulmonary arterial  hypertension.(ISPAH)

Consider a entirely different situation

A patient with COPD  with raised  PASP .  The right ventricle pressure has to equilibrate with PASP  during systole .For this to happen   it has to generate the 60mmhg .  If the RV fails  to augment it’s contractility for some reason ,  will the  ineffective RV contraction will  lower the  PASP  ? This is the perplexing question !

While the popular understanding is ,  RV dysfunction will under- estimate the severity of   pulmonary hypertension   . . . still  . . .  we are not sure whether RV dysfunction will  reduce the PASP   per-se  ( and  subsequently PA  diastolic pressure as well )

We often see a  good example  . A patient who develops tricuspid valve disease and RV  dysfunction get symptomatic relief  from  lung congestion .

Final message

The relationship between RV function and pulmonary artery pressure is a real enigma. Though hyper functioning  RV is expected to elevate PASP  and hypo functioning  RV would pull  it down  , the relationship  is not that simple. If only we decode this  mysteries   we can try  specific  RV negative inotropic  agents  as a  modality to treat pulmonary hypertension .

After thought

Total artificial hearts  are going to come in a big way in the coming decades .It  will specifically address this issue  ,  as RV and LV contractility  need to  be individually tuned to avoid pulmonary congestion.

Coming soon

While  RV function is critical for human survival  ,  Fontan  principle  simply says entire RV is dispensable . How ?

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Here is an X-ray of classical rheumatic mitral stenois with a mitral orifice of  .8 square cm.

Why the left heart border is straight in mitral stenosis ?

It is due to 4 factors.

  1. Hypoplastic aorta
  2. LAA
  3. PA
  4. Under filled LV

Note :

  • This straightening occurs   only  in  isolated , severe forms of mitral stenosis  as it requires under filling of left  ventricle   and Aorta.
  • Significant mitral regurgitation will lift the lower end of straight line .
  • In associated aortic valve lesions especially in aortic regurgitation the straightening can not occur as LV and  Aorta continues  to be conspicuous.
  • If mitral stenosis  causes severe PAH and tricuspid regurgitation , RV  can  become  huge  and form the left heart border and distort the straight line.

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Echocardiogram in pulmonary HT has many aims .

  •  Identify the etiology
  • Assess the effects of PAH  on the right heart
  •  Estimate the severity of PAH.
  • Possibly prognosticate

Echo helps us to confirm the valvular, myocardial or congenital heart diseases in the evaluation of PAH. Apart from these etiological diagnosis of PAH predominantly lies in a systematic medical work up .(Read Dana Point classification )

2-D features

  • RA RV dilates
  • RVH*may occur (Dilation is more common )
  • IVS assumes  a D shape  ( RV pressure is close  to or   even > than  LV pressure )
  • Tricuspid annulus dilates

* For some reason RVH  does not occur commonly in pulmonary hypertension ,  while LV hypertrophies promptly in systemic hypertension .

Doppler

  • Tricuspid valve begins to leak  and RV ejects   with giant “cv”  waves into RA/JVP

Other Echo  findings

  • MPA may dilate
  • Pulmonary regurgitation

At what pressure RV begins to dilate  in PAH ?

It is  not known .It is highly variable . But most will dilate their RV at a systolic pressure > 50mmg.

It is also possible the onset of TR and the magnitude of  TR has a major say in the  timing  of RV enlargement .

We know RV is more sensitive to volume overload than pressure overload .

Paradoxically , it is often observed   acute elevation in RV pressure  dilate the RV faster than chronic ones.

Right atrium and right ventricle are significantly

The tricuspid annulus is dilated .Note the severe TR with twin jet morphology.

Estimating Pulmonary artery pressure

PA systolic pressure  :  TR jet + 10 mmhg

PA diastolic pressure : PR end diastolic jet + 10

PA mean pressure  :  Peak PR gradient

Other complex methods to arrive ar PAP in the absence of TR or PR

The Dabestani -Mahan  ‘s equation*   – The  mean PA pressure = 90 – (0.62 X acceleration time).

It is popular   for  calculating PAP by measuring pulmonary artery Doppler  acceleration  time  .

Many   believe  it is  neither  sensitive  nor practical  in real  clinical setting.

*Even though Dabestani is the first author of this paper   Mahan  got the full credits for the simple reason his name is easily remembered   !

Note the peak TR jet is around 50mmhg and predicted RVSP would be 60mmhg.One would have expected still higher RV pressure but since the RV is dysfunctional the true PAP may be underestimated.

The classical D shaped IVS during systole . D shape indicates RV pressure during systole is almost equal or even higher than LV. ( Please recall D shape occurs in Volume overload also but the timing is in diastole !)

Pulmonary valve  M-Mode

According to Wyeman  the following M mode signs are useful in diagnosing PAH.

  1. Presence or  absence and the amplitude of the “a” wave
  2. magnitude of the e-f slope
  3. presence of mid-systolic closure or notching
  4. fluttering of the posterior pulmonic leaflet

Currently ,  one may consider M-Mode echo to be  an obsolete  ,  but still the foundations help us understand the hemo-dynamics.

The most important principle in  the motion of  pulmonary valve ,   is  the relationship between pulmonary “a” wave and right atrial “a” wave

Normally atrial contraction produce an inward movement* on the closing pulmonary leaflet . This  happens because the MPA  end diastolic  pressure is usually lower than  right atrial a wave    .In severe PAH  the elevated pulmonary diastolic pressure  does not  allow  the atrial contraction to   intend the pulmonary leaflet in pre-systolic atrial contraction .Hence pulmonary valve  a wave in m -mode  is  diminished or even absent .

In PAH even   premature closure of pulmonary valve may occur resulting in mid systolic notch   .This  is referred to as flying “W” -Mid systolic notch.   (See below)

* The motion  we see in  short axis M-Mode is that of   left pulmonary cusp that moves  posteriorly.

Image source : Karmarkar SG. Pulmonary valve echocardiography. J Postgrad Med 1979;25:219-23

Absence of a dip is a hemo-dyanmicaly important sign pf PAH  but with one important caveat  .This absence of a dip is valid  only until RV failure occur.In th presence of elevated RVEDP a begin to appear again

Reference

1 Karmarkar SG. Pulmonary valve echocardiography. J Postgrad Med 1979;25:219-23

2.http://circ.ahajournals.org/content/50/5/905.full.pdf

4.Kitabatake A, Inoue M, Asao M, Masuyama T, Tanouchi J, Morita T. et al. Noninvasive evaluation of pulmonary
hypertension by a pulsed Doppler technique. Circulation. 1983; 68(2): 302-9.

5.Stevenson JG. et al, Comparison of several noninvasive methods for estimation of pulmonary artery pressure. J Am
Soc Echocardiogr. 1989; 2: 157-71.

 6.Yock PG, Popp RL. Noninvasive estimation of right ventricular systolic pressure by Doppler ultrasound in patient  with tricuspid  regurgitation. Circulation 1984; 70:657-62.

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Pulmonary hypertension (PH)is a very common clinical problem in cardiology.The classification of PH  has been little complex. Now we have a fairly clear scheme formulated in 2008 in a small beach side county of  California called Dana point .

I have tried to simplify it without affecting the core

Click on the image if  slide is not displaying

Category 1 is again divided into 5 categories

1.1 /1.2/1.3/1.4/1.5

Other categories( Category 2 to 5)

* Note there is a special category called 1 ‘ for pulmonary veno-occlusive disease .This should be distinguished from CTEPH

Summary

Remember  99 %  all  pulmonary hypertension will be constituted by the following  seven entities .

Idiopathic PAH  1.1

Familial PAH       1.2

Connective tissue disease 1.4.1

Congenital heart disease  1.4.4

Left sided valvular /Myocardial heart disease 2.3.3

Secondary to  COPD  3.1

CTEPH   4

In India  (probably worldwide ) the commonest  cause for  PH is  2.3.3

The updated pulmonary hypertension  classification is available here

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Uric acid is a  metabolite of purine metabolism.Purine is dynamically present in  every  active multiplying cell .Uric acid is formed when Xanthine oxidase  acts on   Xanthine and hypoxanthine  which are products of purine . The estimation of serum uric acid level can give us a rough estimate of cell metabolism and turn over. We need to  understand there is a dietary source for purines as well.

UA is mainly  excreted in urine . Normal levels of UA is   3-6mg in women and can be 1 mg higher  in men

Biological actions of uric acid

UA is a physiological molecule . It is more of an byproduct  and  devoid of any unique  action. Hence , most physicians still   believe it to be an unwanted  dangerous toxic molecule. What we fail to realise is ,  uric acid is a strong natural reducing agent .Hence it acts as an antioxidant .(Comparable to Ascorbic acid Vit C !)

Some believe excess uric acid is  a natural metabolic weapon against cellular degeneration . In fact , hypo- urecemia has a well known  association with multiple sclerosis and augmenting UA  is known to improve multiple sclerosis.

However, the problem with this  physiological molecule  is ,  we do not know yet,  when the  levels become pathological .We know uric acid in excess can lead to  urate stones  in kidney and Gout in joint . Does these crystals have any effect on coronary and cerebral circulation ?

Is uric acid a marker of inflammation and cell turn over ?

Yes it is.  What ESR  means to  inflammation , uric acid means for cell turnover . Since Inflammation induces white cell turnover  uric acid  level  becomes   a marker of inflammation as well .

Uric acid in  excess  is a  marker of vascular  damage as  atherosclerosis  is an inflammatory process  , especially  with  pulmonary endothelial damage. So , in patients  with primary pulmonary  vascular diseases  like PPH , uric acid levels   may indicate  the progression or regression of PAH.

Some studies have correlated right atrial pressure with uric acid levels.

Uric acid and hypoxic states

Uric acid formation is more in hypoxic states as hypoxia depletes ATP and adenine metabolism is promoted and more inosine and  Xanthines  are produced . Uric acid can be a simple  marker  of increased oxidation stress of human biological system.

No surprise  to note   pulmonary hypertension  an important hypoxic state  increase uric acid levels .

Why uric acid is rarely considered as a useful diagnostic marker in cardiology  ?

  • The major  reason is it is an old molecule and has  lost its  flavor .
  • The name is not exotic (Like BNP, Di dimer etc)
  • Finally it is  a  cheap investigation and hence  lacks the required glamor.

Technical limitations

  • Uric acid levels are non specific (Like any other  modern  molecules  Tropinin , CRP etc! ) No one  would like  to compare uric acid vs hs CRP one to one as a marker of inflammation in vascular  disease.
  • UA  levels depend on kidney function .
  • Dietary influence can be significant (Especially meat, Liver Beans, Cauliflower etc)

Knowing the  basal level of uric acid  in a given patient ,   help us  monitor the net cell turnover during medical   management of chronic illness.

UA’s Clinical utility in cardiology practice

Importance of UA in PAH   is well recognised now  . Most studies on PAH  use it as a marker  or even  to define a therapeutic endpoint  But , please remember  elevated uric acid is a  simple  index of elevated  cell turnover and oxidative stress and it mainly represent  the effect of  pathology rather than a pathology itself.

So , attempting to reduce uric acid levels   with drugs like  Allopurinol may not  improve the  vascular function as one would wish ! The only indication for  reducing uric acid level   is  when the levels   become  too much and it starts depositing   in body.

Final message

Uric acid is a useful bio marker for  vascular function. It can indicate  the  quantum of  inflammatory , metabolic  and cell turnover of any progressive vascular  disease. With serial measurements  it definitely helps us in monitoring   cardiovascular disease  especially pulmonary hypertension  as  lung tissue is major source of this molecule . Now , uric acid  is used  for prognosticating  cardiac failure also.

Reference

http://qjmed.oxfordjournals.org/content/93/11/707.full.pdf+html

 

 

 

 

http://ajrccm.atsjournals.org/cgi/reprint/160/2/487?ijkey=dc24281a22fcf54ed27ac4466393abd691047408

http://cel.webofknowledge.com

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