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Posts Tagged ‘rv inflow vs outflow’

The right ventricle  is considered as a docile cardiac chamber with passive filling and  emptying  properties .

This belief  was reinforced when Fontan  in early 1970s suggested a principle in the management of  cyanotic heart disease  when  the right side of the heart is underdeveloped. He  proved  RV can be by-passed safely , with  great veins  (IVC/SVC)  by  themselves  take care of filling the pulmonary circulation  without the need of RV pumping function.

While it is true for few complex cyanotic heart disease, largely this a misleading  concept. In clinical cardiology practice  ,sudden or non sudden  RV deaths happen every day in the form of . . .

  • RV Infarction
  • Acute RV dysfunction in massive pulmonary embolism
  • COPD with RV dysfunction
  • Most cases dilated cardiomypathy  the terminal event is due to RV  failure.

So , RV function can never be dispensable in day to day cardiac hemodynamics.

RV has some unique properties in terms of shape , size and  hemodynamics . We are getting more insights from  modern blood pool imaging by MRI , about  how the RV handles the blood volume .

We know RV has a unique shape  triangular ( partially  pyramidal ) . It can be inferred the RV cavity is formed by fusion of  many  eccentric spacial planes. We have always believed  RV handles the blood it receives from right atrium in a unique way .Now we are beginning to understand it .It is now documented the RV segregates the blood it receives into 4 components.

 

right ventricle physiology anatomy hemodynamics

It is curious  to know  RV inflow is connected to the outflow by an invisible   physiologic Bridge . About 44% of  blood traverse the RV in this fashion.

 

RVOT blood flow right ventricle

Note : RV blood flow preferentially enters the RVOT with out transiting RV body and apex.Image courtesy http://ajpheart.physiology.org/

 

Which is the most important part in RV ? (Among Inflow, Body, Apex, Out flow)

After reading this article it seems to me , the mechanical  function of RVOT could be most  vital. If it fails to handle the first increment  which  comes directly from  RV inflow, stasis  is likely in RV body and apex , elevating RVEDP and later promoting stasis leading to clinical events.

Clinical implication of this study

  • Differential dilatation RV chambers to pressure or volume  overload is observed .
  • We need to analyse why RV dilates in some   but   goes for hypertrophy in others when confronted with pressure overload (VPS vs PAH)
  • RV apical clot in restrictive cardiomyopathy  is a direct consequence of stasis  of blood  in RV apical zone .
  • RVOT pacing  may have a hemodynamic advantage  over RV apical pacing  . However , for anatomical reasons RV apical pacing  is  far safer than RVOT pacing where the lead  is subjected to constant life long strain due to this busy RV inflow to outflow express  high way !

Final message

Traditionally we have labeled  RV  as a  passive venous chamber .It is clearly a misnomer.It  has to handle both the venous and pumping function beat to beat with precision  without  back log .Obviously ,  RV has to think and work  more than it’s  big brother !

Reference

I wonder , if  there is  any other site other than APS . . . to  find crucial  answers in cardiac physiology  !

 

Right ventricle physiology blood flow  3d 4d analysisAfter thought

  • There is huge gap between physiologists  who work in research labs and the physicians at bed side .
  • I appeal all young cardiologists  to visit  APS  once in a while ,between your busy cath lab schedule and help narrow this gap.
  • Without understanding the physiology properly how are we going to intervene the pathology ?

 

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It sounds  to be a  simple question . But, cardiology literature is sparse  on the subject.

RV mimics a three dimensional triangular chamber .The inflow, body and outflow align themselves in complex planes .This makes measurement difficult.

What  are the measurements to be made  ?

  • RV inflow tract (RVIT)
  • RV body
  • RV outflow tract (RVOT)
  • RV Free wall thickness

How to measure RV size ?

  • Inflow diameter is assessed in inflow view ( Para sternal long axis,probe  tilted down towards lower  sternal edge (cool . . .That is were tricuspid valve is located !)
  • RV body can be assessed in long axis or 4 chamber view
  • RVOT in short axis view.

What is the normal range ?

RV Body

< 3 cm in parasternal long axis view

<8 cm Long axis ( RV apex to mid point of TV )

RV inflow(RVOT)

<  3- 4cm

RV outflow (RVOT)

1.8 to 3 cm

Note :

  • All measurements are taken in end diastole .
  • The largest diameter of RV is at its inflow(it is roughly equivalent to tricuspid annulus)
  • RVOT size can vary  , generally tapers as it reaches near the pulmonary valve .

How common is the  differential RV enlargement*?

The complex shape and architecture of RV  make  the  direction , sequence  and magnitude of  RV enlargement less predictable .

  • Diastolic loading of RV generally have more uniform enlargement of RV .(Inflow, body, outflow )
  • In dilated cardiomyopathy RV enlargement  common in short axis > long axis
  • Pressure over  loading may not result in uniform enlargement as the pressure points on RV surface is not homogeneous.
  • In congenital heart disease , RV shape and size  depend more on the morphology(location of VSD, infundibular  anatomy, muscle bundles, extent of trabeculations etc)
  • In arrhythmogenic  RV dysplasia (ARVD) outflow  tract enlargement is more dominant.

* The fact that ,  RV can enlarge  in focal and localised manner make it mandatory to measure RV dimension in multiple views and in all possible diameters.

At what  pressure RV begins to enlarge ?

RV is believed to enlarge at > 60mmhg .Hypertrophy is usually precedes dilatation  .

At what volume overload RV begins to enlarge ?

Our experience with ASD indicate when the pulmonary  blood flow  is twice that of systemic blood flow RV is distinctly enlarged. May be it begins to enlarge at>  1.5: 1 shunt

RV begins to enlarge horizontally or longitudinally ?

this aspect is not studied much.  Generally volume overload causes more uniform enlargement.

How does acute RV enlargement differ from chronic RV enlargement ?

Dilatation is more conspicuous in acute RVE ( Pulmonary embolism, RV infarct ) associated wall motion defects and thinning favors acute RVE.

Normal or increased thickness is expected in chronic RV enlargement

Here is a  five-star rated  article on RV dimension

Published in 1986 , still considered a  land mark paper  . . .

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