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Posts Tagged ‘pulmonary hypertension’

A short systolic murmur over pulmonary area (ie Left second inter coastal space ) is listed among 6 other auscultatory  feature  of pulmonary arterial hypertension.Though it is an accepted sign  many would question  the existence of such a murmur or its relevance in PHT.

Why does it occur  ?

Acoustics  principle  tells us whenever  velocity of blood  flow exceeds a critical point(Raynolds number*) in a specific anatomical territory , a  turbulent zone is created  and  a murmur could be generated .This is why many physiological situations like pregnancy, anemia, and some benign outflow murmurs occur.

 

In pulmonary hypertension , three things are thought to contribute for the murmur generation

  1. Dilated pulmonary artery  promotes Raynauld turbulence
  2. Increased flow velocity (This is correlated with pulmonary artery acceleration time in Doppler)
  3. RV contractility  (A normally functioning   RV is required to generate the murmur .Once RV dysfunction sets the  murmur of pulmonary hypertension usually disappear , of course a TR murmur may appear and confuse the picture )

Reference

* Reynolds number is a way to predict under ideal conditions when turbulence will occur. The equation for Reynolds number is:

Reynolds number(Where v = mean velocity, D = vessel diameter, ρ = blood density, and η = blood viscosity )

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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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Pulmonary  arterial hypertension (PAH ) is  an uncommon manifestation of dilated cardiomyopathy .While pulmonary venous hypertension of some degree is expected in most patients with DCM,  it is rare for these patients to go for severe arterial hypertension.

The reason for this may be the  natural history of DCM do not allow these patients to live that longer to manifest severe PAH.  Still ,  we encounter this problem  atleast in tertiary hospitals. Presence of moderate to severe PAH (> 50mm peak PAP) is a sinister sign in  DCM. They not only do badly , they also make  the transplant outcome dismal .

What causes this severe   PAH in DCM ?  The following observations are made in our institute .

Now we know , isolated  systolic dysfunction is  rarely associated with PAH  .It is the presence of  LV diastolic dysfunction (Often restrictive )  that raises the pulmonary pressures.  PAH of DCM is rarely progressive.

One important suggestion is the DCMs  which are associated with  severe  PAH may indeed represent  late stages of RCM , when the LV begin to dilate.

Associated mitral regurgitation   contributes  to PAH

Atrial fibrillation has a significant impact on elevating  pulmonary  venous and arterial  pressures in DCM.

Hypoxic PAH can occur in any medical situation  in susceptible population . DCM is no exception

For some reason  idiopathic DCM is more often result in PAH than ischemic DCM . (Is that possibel , some form of  idiopathic   PAH and DCM are etiologically  related ?)

Further , the positive inotropic agents when liberally used will worsen the diastolic  properties of LV.

Finally involvement of  right ventricle  in the cardiomyopathy  process can have an ameliorating effect on PAH.  A good RV function is essential to lift the PA systolic pressure. If RV failure is causing a low PAP , do not be happy .It simply means RV is going to  say  good bye  . . .  for the final  time !

How to manage PAH in DCM ?

There is no specific management strategy .

We do not know yet  whether Sildenafil ,  Bosentan, and Epoprostenol  have any role in this  form of  PAH. These are all basically vasodilators. It’s use in DCM is vested with a risk of  catastrophic hypotension . Of course ,  we do have a role for balanced vasodilators in cardiac failure .(As most of these patients would be already on adequate ACEI )

Presence of PAH should be considered as an independent indication for anticoagulants as in situ  pulmonary thrombus is common.

The effect of  cardiac resynchronisation therapy in reducing the PAH of DCM is not convincing.

Final message

PAH  in DCM is an unwelcome development. It makes the situation  tough .  The mechanisms are diverse  .Understanding the mechanism would help us deal  this problem better .  Conventional anti failure treatment may help  ,but  it is wiser to try  reserve drugs.

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 Excercise physiology has been studied most extensively in the last century.The hemodynamic impact of excercise in various disorders of heart has been well established.
Dyspnea on exertion is the commonest symptom in clinical cardiology practice. It is well-known pulmonary stretch receptors located in pulmonary vasculature is one of the  major mechanism of dyspnea.

Excercise increases the cardiac output manyfold.Transporting  up to 10-12 litres of blood every minute across the lungs with a narrow pressure  head (about 10 mmhg ) is not an easy job . It needs lot of lung discipline .

It is surprising to note, there is little data on excercise induced pulmonary hypertension in the evaluation of patients with unexplained dyspnea.

We know, excercise increases the systemic blood pressure ,we  presume it should not raise the PAP (however severe the exertion is 1 )as pulmonary circulation  is a  high compliant low pressure system. 

Is our presumption correct ?

Exercise induced PAH can occur in both   health and disease 

In patients with preexisting disease

  • Stress induced LV dysfunction and resultant raise in LVEDP-PCWP-PAP .This is the most common mechanism in valvular and myocardial  disease.

Apparently healthy population

  • Excercise  induced PAH as a  marker for silent CAD .
  • Transient Hyperkinetic PAH* (Note :Here PCWP is usually normal )

This is similar  to hypertensive response to EST in systemic circulation.Existence  of this entity , is controversial, But this may reflect  reduced pulmonary vascular reserve  or reduced pulmonary nitric oxide secretion.

*The main difference here is the PAH is more often an  isolated systolic PAH. While LV dysfunction induced PAH is  a combined diastolic and systolic PAH .
How to assess excercise induced  PAH ?
It is not an easy job. Invasive catheter derived pressure measurements have been done ,but it is not practical .

The simplest way is to look for the TR /PR jet in echo in both pre and post excercise phase.

Final message

Excercise induced PAH is an inadequately studied entity in cardiology , in spite  it’s great significance .
This phenomenon is observed  in both diseased and normal heart.

The quantum of excercise induced PAH  is  widely variable depending upon the cardiac  status especially  LV function and the  functional integrity of pulmonary microvasculature .

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PAH  is  the major determinant of surgical outcome of left to right shunts. In this  modern era of cardiac care  allowing a child  with   left to right shunt   to progress to a  stage of   Eisenmenger syndrome  is  considered  as a  huge medical failure . But  , this is still rampant in many of the developing countries .

Cardiologists are divided over the issue of  operability of Eisenmenger syndrome .The confusion is largely due to the conflicting data of outcome in these patients. While  there is strong   data  when  PVR exceeds  SVR  ,  the death is imminent in the post operative period .

What has complicated the issue is   there are  many case reports  where severe PAH patients have been successfully operated. Most would think it is a statistical exception and one can  not alter the traditional criteria based on few case reports.

But ,it remains an irony as on 2009 ,  we do not have a proper methodology to assess reversibility of PAH in Eisenmenger syndrome . Further ,  there is a  significant number of  patients with high PVR  , who continue to experience  an  unabated left to right shunting .  We do not have an answer  for either the mechanism of such shunts and  how to manage these patients.

Click over the slide  to view full  PPT  presentation in PDF format .

This short paper was presented in the Annual scientific sessions of cardiological society of India 2009 regarding the usefulness of a new parameter to assess reversibility of PAH. This may not be called as  a study rather a report of  our experience  in  five  patients  with eisenmenger syndrome

Download the full PPT presentation in PDF  format.

pulmonary artery pulse pressure

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                                  Even as cardiology community is preoccupied with systemic hypertension & CAD  ,  pulmonary arterial hypertension(PAH) is a much neglected , still  an important clinical cardiac problem encountered . The irony is self evident , there are half a dozen methods to grade systemic hypertension not even a single stadardised grading available for pulmonary arterial hypertension. The WHO  working group defined pulmonary hypertension  few decades ago and was not clinically graded .The only grading available is based on  the pulmonary vascular biopsy changes (Heath Edwards) 

                                   Currently PAH management has gone through revolutionary changes. There is an urgent  need for grading  this entity .This will facilitate to  diagnose , manage and assess the efficacy of the currently available treatment.

                                Developing countries like ours have a great number of PAH due to rampant rheumatic heart disease.  A simple study was done in  100 patients with PAH .Bulk of the study population had RHD .Few had primary pulmonary  hypertension .Systolic , diastolic, and mean pressure was assessed by doppler echocardiographic analysis of tricuspid regurgitation (TR) and pulmonary regurgitaion(PR) jets. TR jet provided the systolic PA pressure , PR jet provided mean as well as diastolic PA pressure .TR jet was available in all patients. PR jet was available only in 60 patients .Hence the diastolic andmean PA pressure data has been extrapolated in some  and  was plotted in a scatter diagram. Five equal quintiles were divided. Patients in first  and 2nd quintiles were graded 1   and third  and 4th  quintile were  graded 2 ,  5 th  was graded 3 respectively. From this cut off points for  various grades of PAH were identified .The top 3% of patients  with highest PAP were graded as grade 4 and all of them had supra systemic PAH. 

The following grading is suggested for PAH* 

 *This is a preliminary  attempt to grade PAH. This could be applicable mainly in rheumatic heart disese and primary pulmonary hypertension .Further refining of methodology is  required.PAH grading may be little different in congenital left to right shunts.

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Atherosclerosis is  the number one killer of mankind  .It involves all medium and large sized blood vessels.Any intima and media can be invaded by the disese process.Most common to involve are  cerebral, carotid, coronary, aortic  and it’s branches, renal, and peripheral arteries. But how pulmonary artery is missing in this list ? Is it really true (or) are we missing it ? One logical explanation is pulmonary circulation is a low pressure circulation and the maximum presssure is less than  30mmhg . This pressure may be insufficient to induce endothelial injury that predispose lipid mediated injury.

Other explanation could be a structural difference in the media and intima compared to aorta .But in patients  with primary or secondary pulmonary hypertension where,   inspite of PA pressure being high ,  still atherosclerotic changes is very uncommon . or Is it the Heath Edwards pulmonary vascular sclerosis  grading  reflects nothing but pulmonary atherosclero-thrombosis !

If this is true there could be a major role for HMG Coa reductase inhibitors in altering the natural course of pulmonary obstructive vascular  disese . Statins might be tried in PPH  a disese with no specific  treatment !

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