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Archive for the ‘cardiology congenital heart disese’ Category

VSD with Pulmonary atresia is a complex form of cyanotic heart disease .Though it’s  a close  companion of Tetrology of Fallot  physiologically, it is a vastly different entity in embryological and anatomic terms.

TOF is cono truncal anomaly where abnormal anterior displacement of conal septum result in malalignment VSD, RVOT obstruction ,aortic override and RVH.

While ,pulmonary atresia with VSD  is not a primary cono truncal anomaly, the defect occurs much earlier than TOF in fetal life , where the origin of PA fails to materialise,(Fetal arteritis?) and which triggers a series of anatomical disarray in pulmonary arterial circulation.  The PA growth arrests in various levels (Somerveille Types) .It is important to realise while the PA may be patent , pulmonary valve is always atretic and disconnected from RV.

In severe forms there is Zero pulmonary artery content .The lung is perfused in chaotic manner. This situation akin to “TAPVC” in arterial side  and result in  total anomalous pulmonary arterial connection.

pulmonary atresia vsd mapcas major aorto pulmonary collaterlal unifocalisation single multiple stage tapac

Natural History of PA with VSD .

The blood supply of lungs is maintained by  MAPCAS.Since , the  fetus is not dependent on its lung for survival,  life goes on well , till  birth  and face the harsh reality that  it has no independent blood supply for  lungs from RV  and has to depend on collaterals from aorta.

Survival depends upon the  the quantum of collateral .( Size , number, arborisation pattern etc). Life is shortened in most babies and  lost by 1 or two years . Exceptions are always there.Survival has  been reported up to third decade in a few with a balanced pulmonary flow.these are the ones we catch up in young adults some times.

In effect , MAPCAS are the life line of these children  , paradoxically  the  fate of these children  piggyback  on the  behavior of the MAPCAS .

MAPCAS  are not natural vessels that is  meant to receive blood at  systemic pressure. They are fragile and thin and when exposed to high pressure react pathologically.

Following anatomical and physiological effects occur in MAPCAS .

  • Collaterals  fail to grow with child
  • Obstruction to  MAOCAS can develop(Often at ostial)
  • Collateral can be extensive causing pulmonary vascular injury.
  • Regional and segmental pulmonary arterial HT can occur
  • MAPCAS can suddenly rupture and cause fatal hemolysis
  • Collaterals perfusing more than normal resulting in volume overload of LV and failure

Principles of  Surgery

The principle  of surgery is to disconnect the arterial   pulmonary  vascular  blood supply and connect all lung segments with pulmonary  arterial supply and ultimately connected  to right ventricle to restore the physiology.

Single vs Multiple staged surgery

The original  concept was to do multi stage surgery , believing in the principle every stage give us time for pulmonary vessels and lung  to grow .It involves extreme commitment of surgical team in identifying and understanding the pulmonary  vasculature and the systemic collateral arborisation. The factors that is taken into account includes the presence of confluent PA , MAPCAS induced lung segment injury  and its maturity . When pulmonary vessels are inadequate , autologus  pericardial rolls are used as alternatives.

There is no point in vascularising  a zone of lung  with  physiological  low pressure neo pulmonary circuit which is unlikely to  to work because of immaturity of distal veesels  or its  already damaged by the harsh pressure of MAPCAS!

We have realised the  hemodynamci behavior of lung segments supplied by  MAPCAS and the subsequent undoing of it  is so unpredictable. The current concept is to recruit maximum  lung segments  and aim to provide revascularization through  physiological manner.

An early single stage unifocalisation is  suggested as a best option.(Reddy VM, J Thorac Cardiovasc Surg. 1995;109:832–45). Single stage repair is attractive not only in long-term  hemodynamic advantage but also  in the  logistics . In multi stage repair ,only about 20-30% of children ultimately complete the treatment for various reasons.

It is heartening to note one of huge accumulated experience for surgical management of PA with VSD has happened in the  southern Indian cities  of Chennai and  Hyderabad where i live.

Kudos to Dr Murthy and team for the pioneering work .Incidentally ,Dr KM Cherian is the legend in the filed of cardiac  surgery and in my opinion  he should get the title of the Father of pediatric cardiac surgery in India !

And  this seminal paper from his team  shares  one of the largest  experience   who underwent single stage  unifocalisation for PA with VSD in 124 patients.

tof vsd with pulmonary atresia unifocalisation

What is the cardiologist  role in VSD and PA ?

Cardiologist are expected to play  a limited role . They can’t provide any cure as such.A meticulous cath study is all that required from them for the surgeon.

Selective  MAPCAS angiogram  requires special expertise ad through knowledge of anatomy .The MAPCAS are clustered around few specific  zones.Now MRI and CT scan also can delineate the anatomy.

What is the  surgical outcome ?

it is steadily improving globally.But only a hand full centers in the world can undertake such complex procedure(Lucile packard Children’s hospital Stanford is pioneer )

Hemoptysis in PA and VSD

It is a rare but an important issue .This can occur any time in the natural history even post operative. Most are managed conservatively .Interventional approach with embolisation is possible in expert centers.(K.Greaves et all)

Can  the  natural history be better than these complex unifocalisation surgery in these tender children ?

Statistically , it is possible in few cases, but to identify those children you need to get an appointment with God ! If parent’s take such a decision it should be welcomed and cardiologists and surgeons  should not lure them with scientific excess !

Final message

The surgical correction of PA with VSD continues to be complex .Meticulous  recruiting and unifocalisation of PAs and creating confluence , connecting the RV through a conduit may be the key.However, ultimately  what is going to matter is the how the lung responds to these surgery  hemodynamically !

It appears to me the whole process is  more of a vascular surgery of lungs rather than  heart !

Reference

  3. An excellent resource on MAPCAS  from Sao Paulo , Brazil
pulmonary atresia mapcas vsd unifoclisation confluence direct and indirect aorto pulmonary rabinovitch

 

 

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Can we close an  ASD in a  25 year old women  severe  pulmonary hypertension ?
Volumes of literature has been written  on the subject.Dedicated cath studies  have been done with multiple parameters .
Still , there is a lingering doubt !
Here is  a  3 minute  practical solution  based on 5 easily available parameters. (* Also referred to as  unscientific  in medical parlance !)
1.  O2 saturation
2. Pulmonary artery diastolic and pulse pressure
3. RV function,
4 .Systemic pressure
5. Functional class
  • If O2 saturation is > 90 % consistently  there is likely to be significant  left to right shunt  .Closure is to strongly considered
  • If 02  saturation is near 95 % there is absolutely no contraindication at any level of PVR.
  • Systolic pulmonary artery pressure derived by TR jet is least useful index.Pulmonary artery diastolic pressure reflects true vascular  reactivity of the pulmonary  circulation.A wide swinging pulmonary arterial pulse indicates dynamism in circulation and hence operablity.
  • If pulmonary artery  pulse pressure is  wide (>50)  , or PA diastolic BP is < 30 one can safely presume irreversible damage to pulmonary vasculature has not occurred and these patients would  benefit  from surgical closure .
  • RV  function should be assessed carefully in every patient.This is as important as PVR .Significant RV dysfunction is an absolute contraindication.
  • Never close the shunt in patients who is in class 4  symptoms.
  • Never close a shunt if the systemic blood pressure is low( 90mmhg)
  • Some believe  PDA may be closed at any given PVR , while  worst outcomes occur with ASD as supra-systemic pulmonary pressure is possible.
Always monitor these patients meticulously especially  in the initial days following surgery  for deterioration .Most patients will do well if they cross the first 30 days. The RV  learns to adopts with  new  pulmonary hemodynamics !

 

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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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Right ventricle is a passive venous component of the heart .It simply acts a  transit pump for blood to reach the lungs.

It  is true  , RV is dispensable in many complex congenital heart disease as we  can connect the great veins directly into the pulmonary artery  by  Fontan , Glean and it’s clones  bye passing this chamber . Still , by no means the importance of this chamber is to be underestimated.  RV dysfunction and failure  is the key to survival  many  disorders.RV shock is is cause of sudden cardiac death in acute pulmonary embolism and RV infarction .

RV is an unique muscular chamber .It is more of a triangular shape. It has  three different parts connected by three different angle .There is no true  apex  for RV , it is   connected  to Inflow and outflow in peculiar fashion .

In the  following table I have  tired to  describe  of how different parts of RV  behave in various disorders.

what is the morphology of  RV enlargement RV inflow outflow body sinus portion of RV

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TAPVC Total anomalous pulmonary venous connection left vertical vein

An animated version

tapvc total anomalous pulmonary venous conncetion vertical vein

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Is this child with Eisenmenger operable or not ?

The answer to this question is  debated for many decades . The old school of thought was  grown with meticulous cath study (Pioneered by Paul wood and his team ) .Calculating PVR is academically fascinating . With  so  many  variables,  assumptions and too much dynamism in a circulatory system , It has never been proven as a  gold standard .

The presence of following  factors points to  possible advantage for  shunt closure .

  1. Pink Eisenengers ( Complete  lack of   clinical  cyanosis   )
  2. Clinically mild cyanosis  but  Oxygen saturation   nearing 92 %  (We  have seen an occasional  patient  with 98 % )
  3. If Echo shows  a dilated left atrium and left ventricle (VSD,PDA) it indicates a significant L-R shunt.
  4. Lack of septal bulge towards  LV (This Indicates  RV has  still  some  useful life in it ! )
  5. Pulmonary  flow velocity > 1.5m/sec indicates fairly good flow across RVOT (Qp/Qs calculation is  almost impossible in bi-drectional shunt )
  6. Pulmonary artery diastolic pressure  <  3o mmhg
  7. Pulmonary artery pulse pressure > 50mmhg

*Oxygen, Tolazoline test in cath lab has  limited value.

**Temporary balloon occlusion and watching  for reversibility is not useful (As fall in PAP and  PVR is a long term affairs )

Final message

Scientific cardiologists may feel awkward  to read this message .

  • With mortality for shunt closure in   Eisenmenger  reaches  nearly 50 %  ,  it is essentially a 50-50 guess game !
  • We  often depend on our collective  clinical acumen (Also called as  Gut  feeling   . . .”I some how feel  this child will do well ! “
  • Most  importantly  surgeon’s  experience and expertise would  finally prevail  over cardiologist !

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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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