Assessing Pulmonary Hypertension

One of the typical requests for an echocardiogram is assessing for possible pulmonary hypertension. This can be subdivided into two clinical questions:

is there a basis for starting NO

should this child be on sildenafil long term

As with every echo done by a clinician, the echo should supplement the clinical findings. The skilled practitioner should not just attempt to report the TR gradient.

Reasonable Indications

1 Recurrent sudden spells of desaturation or cyanosis unrelated to changes in ventilatory performance.

2 High pressures, poor oxygenation, esp in context of clearish lungs

3 Background of recurrent lung problems esp CLDP

4 Unexpectedly big liver or peripheral oedema

Basics – R heart physiology and haemodynamics

The pumonary systolic BP should be less that 1/3 systemic. There are no signs until its 2/3 – 3/4 systemic.

The RV should be smaller walled than the LV. The RV sits on the side of the LV in health. It is not an equal partner as the heart should be built around the LV. The LV should be round in cross section, the RV more like a 1/3 moon in shape.

Triscuspid regurgitation (TR) is present in 1/3 of normal people, more if there is PHT. It is usually trivial, but can still be measured.

R side pressures are always lower than L (in health) so the PFO should be L to R, PDA the same.

Measuring TR

Optimal view – either SA or apical 4 chamber.

E1_PPHN - TR Doppler

Process – simultaneous view 2D and colour – record this. Now use CW doppler across the jet. Measure and store the vmax. Add 10 mmHg (overestimate of RA pressure) to give the systolic RV pressure.

Always good practise to repeat in the other view.

Measuring PR

Optimal view – SA (maybe also apical 5 chamber +)

e1_pr

Process – simultaneous view 2D and colour – record this. Now use CW doppler across the jet. Measure and store the vmax of the jet towards the probe. Add 10 mmHg (overestimate of RA pressure) to give the diastolic RV pressure.

What to look for – chronic changes

Over time, the RV thickens to take on extra work. The RV begins life the same size as the LV, but becomes noticably smaller by 3 months. This does not happen in pulmonary hypertension (PHT). The RV, though thickened, will function well, and emptying will be good until there is an exacerbation of the PHT. This is best appreciated in the apical 4 chamber view.

e1_RVH_apical

Higher pressures in the RV chronically may be seen as changes in the intraventricular septum (IVS). Instead of bowing into the RV, it may move towards the LV – the LV becomes oval, then D shaped in short axis. (shown in the image, with a normal view on the left)

The raised RV pressures may be measured if there is TR or PR. (see above). The RA may also be distended, as in the image above.

Additional information may be obtained from viewing flow across a PFO (SC 4 chamber). Here the flow my be bidirectional if there is raised RA pressure. Also the PDA if there is one (SA or duct cut), may be R to L in suprasystemic pulmonary hypertension.

What to look for – Acute changes

Here there is right heart decompensation, with distension of the RV (best seen in apical 4 chamber), and usually increasing TR. Inability of the RV to empty also leads to high RA pressures and distension of the IVC, which will be fixed.

e1_SA_acute pulm HTb

TR and PR will be useful measurements and can be tracked as ventilation strategy is changed, NO or sildenafil used.

Other than this the changes in chronic PHT will be also seen – with R to L flow at the PFO and, in severe cases, across a PDA.

Reporting the findings

Key information to describe – IVC, RV size, RV muscle thickness, RV performance, TR amount, TR velocity, PR amount, PR velocity, PFO presence and direction, PDA presence and direction, IVS position.

If possible, also report changes following NO.

 

 

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