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5 minutes crash course in cardiology : Echocardiogram in Pulmonary arterial hypertension

Posted Apr 13 2012 11:11am

Echocardiogram in pulmonary HT has many aims .

  •  Identify the etiology
  • Assess the effects of PAH  on the right heart
  •  Estimate the severity of PAH.
  • Possibly prognosticate

Echo helps us to confirm the valvular, myocardial or congenital heart diseases in the evaluation of PAH. Apart from these etiological diagnosis of PAH predominantly lies in a systematic medical work up . (Read Dana Point classification )

2-D features

  • RA RV dilates
  • RVH*may occur (Dilation is more common )
  • IVS assumes  a D shape  ( RV pressure is close  to or   even > than  LV pressure )
  • Tricuspid annulus dilates

* For some reason RVH  does not occur commonly in pulmonary hypertension ,  while LV hypertrophies promptly in systemic hypertension .

Doppler

  • Tricuspid valve begins to leak  and RV ejects   with giant “cv”  waves into RA/JVP

Other Echo  findings

  • MPA may dilate
  • Pulmonary regurgitation

At what pressure RV begins to dilate  in PAH ?

It is  not known .It is highly variable . But most will dilate their RV at a systolic pressure > 50mmg.

It is also possible the onset of TR and the magnitude of  TR has a major say in the  timing  of RV enlargement .

We know RV is more sensitive to volume overload than pressure overload .

Paradoxically , it is often observed   acute elevation in RV pressure  dilate the RV faster than chronic ones.

Right atrium and right ventricle are significantly

The tricuspid annulus is dilated .Note the severe TR with twin jet morphology.

Estimating Pulmonary artery pressure

PA systolic pressure  :  TR jet + 10 mmhg

PA diastolic pressure : PR end diastolic jet + 10

PA mean pressure  :  Peak PR gradient

Other complex methods to arrive ar PAP in the absence of TR or PR

The  Dabestani -Mahan  ‘s equation*   – The  mean PA pressure = 90 – (0.62 X acceleration time).

It is popular   for  calculating PAP by measuring pulmonary artery Doppler  acceleration  time  .

Many   believe  it is  neither  sensitive  nor practical  in real  clinical setting.

*Even though Dabestani is the first author of this paper   Mahan  got the full credits for the simple reason his name is easily remembered   !

Note the peak TR jet is around 50mmhg and predicted RVSP would be 60mmhg.One would have expected still higher RV pressure but since the RV is dysfunctional the true PAP may be underestimated.

The classical D shaped IVS during systole . D shape indicates RV pressure during systole is almost equal or even higher than LV. ( Please recall D shape occurs in Volume overload also but the timing is in diastole !)

Pulmonary valve  M-Mode

According to Wyeman  the following M mode signs are useful in diagnosing PAH.

  1. Presence or  absence and the amplitude of the “a” wave
  2. magnitude of the e-f slope
  3. presence of mid-systolic closure or notching
  4. fluttering of the posterior pulmonic leaflet

Currently ,  one may consider M-Mode echo to be  an obsolete  ,  but still the foundations help us understand the hemo-dynamics.

The most important principle in  the motion of  pulmonary valve ,   is  the relationship between pulmonary “a” wave and right atrial “a” wave

Normally atrial contraction produce an inward movement* on the closing pulmonary leaflet . This  happens because the MPA  end diastolic  pressure is usually lower than  right atrial a wave    .In severe PAH  the elevated pulmonary diastolic pressure  does not  allow  the atrial contraction to   intend the pulmonary leaflet in pre-systolic atrial contraction .Hence pulmonary valve  a wave in m -mode  is  diminished or even absent .

In PAH even   premature closure of pulmonary valve may occur resulting in mid systolic notch   .This  is referred to as flying “W” -Mid systolic notch.   (See below)

* The motion  we see in  short axis M-Mode is that of   left pulmonary cusp that moves  posteriorly.

Image source : Karmarkar SG. Pulmonary valve echocardiography. J Postgrad Med 1979;25:219-23

Absence of a dip is a hemo-dyanmicaly important sign pf PAH  but with one important caveat  .This absence of a dip is valid  only until RV failure occur.In th presence of elevated RVEDP a begin to appear again

Reference

4.Kitabatake A, Inoue M, Asao M, Masuyama T, Tanouchi J, Morita T. et al. Noninvasive evaluation of pulmonary
hypertension by a pulsed Doppler technique. Circulation. 1983; 68(2): 302-9.

5.Stevenson JG. et al, Comparison of several noninvasive methods for estimation of pulmonary artery pressure. J Am
Soc Echocardiogr. 1989; 2: 157-71.

  6.Yock PG, Popp RL. Noninvasive estimation of right ventricular systolic pressure by Doppler ultrasound in patient  with tricuspid  regurgitation. Circulation 1984; 70:657-62.


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