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Posts Tagged ‘cyanotic heart disease’

I stumbled upon this presentation which deals  how to approach to a problem of  congenital heart disease. In a newborn or an infant . It is clearly a master piece .  A life time experience  of a pediatrician  condensed in  130 slides . It is from Kerala .India.

Link to the  presentation

To  quote an  example  from this presentation.

When you want to rule out  urgently a congenial cyanotic heart disease in the bed side *  What will you do ?

What is  hyperoxia test  ?

Axminster 100 % O2 . Measure satutration.If the  PO2 crosses  200 ,  virtually any cyanotic heart disease is ruled out.

If it is less than 150 , it  is very much  likely the baby has  a CHD !

(* Echocardigram may not be available everywhere . Even if it is there it needs a certain expertise to do it  new-born  )

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                                         .It is a well known fact  squatting  is a simple compensatory posture adapted by children with cyanotic heart disease  during exertion to get relief from breathlessness. The children with tetrology of fallot and related  conditions  have baseline hypoxia due to right to left shunting .This gets aggarvatged during exertion. Squatting promptly relieves  this exercise  induced worsening of dyspnea. The oxygen saturation improves immediately after assumption of squatting posture. The exact mechanism by which squatting relives the dyspnea is not clear.

 Hemodyanmics of squatting has two phases

  • Immediately ( First 15 seconds) after squatting  there is sudden drop in venous return.
  • Sustained  squatting for 1-2 minutes result in steady increase in venous return, raised systemic vascular resistance.

                                    Both these effects help the children with TOF.The initial trapping of highly desaturated blood in the lower extremity gives a quick relief as soon as the child assumes this posture.In the next 15 seconds  or so the systemic vascular  resistance increases and bring the  the aortic after load sufficiently  high to divert the blood  into the pulmonary artery.

The net effect of squatting is there is a   transient or sustained (as long as child squats) increase  in  pulmonary blood flow  and this is made possible by the relative reduction of right to left shunt as the aortic and systemic  resistance is raised  by this  posture.

What is the clinical inference from squatting in cyanotic heart disease?

Squatting implies there  should be a large VSD,  associated with a  delicate  right to left shunting very much dependent on the degree  of pulmonary stenosis  or ( any RVOT obstruction) and the systemic vascular   resistance.

How common is squatting history in pulmonary atresia with VSD ?

It can occur with collaterals are sparse.The mechanism of relief is slightly different.

The likely mechanism of relief with  squatting in pulmonary Atresia, VSD is two fold.

1.The Initial relief is due to trapping of deoxygenated venous blood in squat posture , which is similar to TOF

2.Sustained benefit is due to raised systemic vascular resistance which favors more flow across MAPCAs from Aorta.

The second one has no authentic reference , but its a hemodynamic plausiblity as there is zero RVOT flow in PA with VSD.

 

What are the other cyanotic heart diseases in which squatting is reported ?

Tricuspid atresia

Double outlet right ventricle with pulmonary stenosis

Any combination of large VSD and RVOT obstruction

Very rarely in eisenmenger syndrome

Reference

 1.Paul R. Lurie ,Postural effects in tetralogy of Fallot The American Journal of Medicine Volume 15, Issue 3, September 1953, Pages 297-306

2. Warren G. Guntheroth.  M.D.Beverly C. Mortan. m.Venous return with knee-chest position and squatting in tetralogy of Fallot American Heart Journal  Volume Volume 75, Issue 3, March 1968, Pages 313-318

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