Posts Tagged ‘squatting’

During  clinical examination of cyanotic congenital heart disease(CHD) ,  the major  task is to differentiate conditions with reduced  or increased pulmonary blood flow .

When a child with  CHD  is presented in clinical examinations , students are often asked to arrive at  the diagnosis  from history , physical examination before going in for ECG, X ray  or  echocardiography.

History,  surprisingly can  suggest  the  correct diagnosis in many (Most ?)

Reduced pulmonary blood flow is often associated with

  • Cyanosis   appearing with  /or worsening with   exertion*
  • Hypoxic spells.(Almost always occur in reduced pulmonary  blood flow )
  • History of squatting( Majority in reduced pulmonary flow)

Relief  of dyspnea   by assuming squatting position  convey   important hemodynamic information. It implies  there is significant reduction in pulmonary blood flow in standing posture , that  gets corrected  in the squat position.For squatting to improve pulmonary blood flow there must be a communication between right and left heart .This is most often due to a large VSD, rarely an  ASD .

Related article : How squatting relieves hypoxia in TOF ?

*Note :  Cyanosis  is  not  specific for reduced pulmonary  blood flow. In fact , simple reduction in pulmonary blood flow per se , cannot result in significant cyanosis .There need to be admixture /or right to left to shunt to produce cyanosis .Cyanosis in  pure admixutre states like TGV, Single ventricle , Common AV canal , Common atrium TAPVC,  are less Dependant on the reduction of  pulmonary  flow. In these situations RVOT obstruction if  present  will aggravate the baseline cyanosis.


Apart  from direct evidence for reduced pulmonary blood flow , lack of evidence for increased pulmonary  flow could  often mean ,  we are  actually  dealing  with  reduced pulmonary blood flow.

The following are the clinical clues to suspect  reduced pulmonary blood flow.

  • A quiet precardium*
  • A inconspicuous pulmonary component of S 2
  • Generally if  S 2 is well split  and both components are well heard it is highly likely the  pulmonary  blood flow is not reduced.
  • Lack of  pulmonary  arterial pulsations
  • Absence of mid diastolic  flow murmurs  in AV valves
  • Presence  of continuous murmur in a patient with cyanotic CHD almost always mean   reduced pulmonary flow and the lungs are perfused by alternate arterial collaterals (MAPCA)

* A silent  heart is the hall mark of Tetrology of Fallot which constitutes 80% of all CHD with reduced pulmonary blood flow.

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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


 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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