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Posts Tagged ‘unifocalisation single vs multiple staging pulmonary atresia’

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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