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 )
- 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 .
- 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.
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 !
Pulmonary valve M-Mode
According to Wyeman the following M mode signs are useful in diagnosing PAH.
- Presence or absence and the amplitude of the “a” wave
- magnitude of the e-f slope
- presence of mid-systolic closure or notching
- 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.
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