Pulmonary Hypertension

Click here to listen to the learning module on assessment of neonatal pulmonary hypertension by echocardiography

Abnormal PA pressure defined (> 3 months of age):

  • Normal PA pressure usually around sPAP: 15 mmHg and dPAP: 5 mmHg (mean of 10) after 3 months of age

  • Mean PAP ≥ 20 mmHg (measured by cath but can be estimated by echo)

  • Highly suspect if systolic PAP ≥ 40 mmHg, estimated by Echo

  • First 3 months: PVR dropping and PA pressures should be < systemic (if systemic within normal for age).

From: Changes in systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) during gestation. (Lakshminrusimha and Saugstad, 2016).

  • Systemic HTN = abnormal high BP in systemic compartment. Similarly, pulmonary hypertension (PH) = ”Abnormally” High pressure in PA

  • Etiologies of systemic hypertension: idiopathic, renal, cancer, steroids, etc.

    • One must identify the cause to tailor treatment

  • PH is a symptom of underlying process: Congenital heart, BPD, HIV, Pulmonary Embolus, Mitral Regurgitation, PPHN…

    • Similary to systemic HTN, one must identify cause to tailor treatment in a case of PH.


  • Etiologies have different pathophysiology and management:

      • Hypoplastic pulmonary vasculature (TOF-MAPCA, pulmonary hypoplasia)

      • High PVR, such as in acute PH of newborns (ie: PPHN) with disturbed transition to extra-uterine life

      • Pulmonary Embolus, pulmonary thromboembolic diseases

      • Congenital heart defect, such as Large PDA or Aortic to PA window: equalization of pressure during Systole and Diastole between Aorta and PA, pulmonary vasculature is exposed to excessive pressure and volume = PA has pressure similar than Aorta (depending on restrictive of PDA) = PH.

      • Post-Capillary, such as in: obstruction of pulmonary veins, severe mitral regurgitation, LV disease with poor drainage of venous return and backflow in pulmonary circulation


Tricuspid regurgitation jet velocity gradient

During systole, tricuspid valve is closed (prevents backflow in RA)

As RV pressure starts rising and RV dilates, the annulus dilates and coaptation of valve becomes less competent. TR appears: blood flow from high pressure RV to low pressure RA generates a velocity of low.

  • Measuring speed using Doppler allows to estimate the “gradient” (difference) between RV and RA chamber at peak of systole

Simplified Bernoulli equation tells you that :

  • Pressure difference between the 2 cavities = 4 x velocity2

  • True if the opening of jet is a narrow point.

  • Assuming RA pressure – 0-5mmHg (will increase with diastolic RV dysfunction)

  • TR = 5.45 m/s à 119 mmHg at peak of systole à RV-RA gradient of 119 mmHg

  • Assuming RA pressure about 5 mmHg: estimate of systolic PAP = 119+5 = 124 mmHg

Significant RV failure and dilation in the context of severe pulmonary hypertension.

As pressure rises on RV side (or pressure decreases on LV side), it can become iso-systemic (same as pressure on the LV compartment) or supra-systemic (higher pressure than on RV side).

Because there is a shared wall:

Isosystemic (>2/3 systemic) = Flat Interventricular septum at peak of contraction - D-Shape LV

Supra-systemic = Bowing septum into the LV cavity

With persistent increased afterload, RV hypertrophies and dilate

LV end-systolic eccentricity index as a way to quantify septal deformation

Eccentricity index (RV-LV Interaction: D1/D2) (Normal < 1.23)

RV/LV ratio (marker of RV dilation: D3/D2) (Normal < 1.00)


References:

Jone JG, Ivy D, Frontiers in Pediatrics - November 2014 , Volume 2, Article 124

Nagiub M, Echocardiography 2015;32:819–833

The following image is from the above article. The article outlines:

  • Systolic septal flattening recognized at EIs ≥ 1.15.

  • High inter-observer agreement for EIs.

  • Quantitative parameters of RV systolic function were impaired only at EIs ≥ 1.3.

  • Reference: Echocardiography 2016;33:910–915



RV-LV crosstalk

  • Often assessed by septal-curvature (shared wall)

  • At peak of systole, when both contracted, pulmonary and aortic valve are open à RV equalize with pressure in PA; LV equalize with Aorta.

  • Usually LV under higher pressures than RV in systole (contraction)

  • LV round and RV crescentic (surrounds LV) in systole

  • Flattening only assessed at end systole on cross-sectional view (parasternal short axis)

  • Flat in diastole indicative of similar pressure in RV-LV during diastole (ex: volume overload from ASD, severe RV failure with diastolic dysfunction)

Pulmonary insufficiency - CW-Doppler

Same concept as TR

  • Pulmonary valve is closed during diastole

  • If RV/PA dilation à PV annulus dilate, valve becomes less competent à Pulm Ins.

  • Early Insufficiency jet speed gives you estimate of mean PA pressure; end diastolic of diastolic PA pressure


Diastolic pulm pressure (DPAP) estimated from pulm regurgitation jet from velocity of end-diastolic PI velocity

DPAP = 4 (end-diastolic PI velocity)2 + estimated RA pressure*

mPAP = 4 (early diastolic PI velocity)2 + estimated RA pressure*

*estimated RA pressure = RV end-diastolic pressure


PAAT/RVET - Pulmonary artery acceleration time / Right ventricular ejection time

  • PW-Doppler of the RVOT – indicates pulmonary arterial flow velocity profile

  • Usually parabolic smooth acceleration and deceleration

  • With increase afterload – shorter acceleration

  • Adjusted by Ejection time to take into consideration heart rate

  • Pulmonary artery acceleration time on RV ejection time

  • PAAT/RVET (< 0.3 suggestive of PVD)

  • Mid-systolic notch with significant afterload increase due to recoil of pulmonary arterial wall

From: Steven A. Goldstein MD; Echo in Pulmonary HTN, ASE - Georgetown University Medical Center MedStar Heart Institute

PV stenosis suspected if mean gradient ≥ 4 mmHg on echo

Right to left patent ductus arteriosus in the context of supra-systemic pulmonary pressure.

CW-Doppler of the Right to Left PDA - Peak systolic gradient indicates that the PA pressure is 46 mmHg above the aortic pressure.

RV-LV cross-talk - Inter-Atrial shunt:

•LA-RA assessment of PFO/Atrial shunting reflects end-diastolic pressure relationships (influenced by MR-TR)

•With severe PH – RV diastolic dysfunction, increased RV end-diastolic pressures and bidirectional, eventually R to L shunt (and retrograde flow in hepatic veins with diastolic dysfunction).


Ventricular Septal Defect:

  • Relationship between LV and RV

  • Restrictive L to R with peak gradient of 20 means that LV pressure is 20 points > RV pressure when Aortic / Pulmonary valves open. If systolic BP is 60, sPAP is 40 (60 – 20 = 40)

  • If large and unrestrictive – will expose RV and pulmonary circulation (unless pulmonary stenosis) to systemic systolic pressures (and increases Qp:Qs)


  • Relationship between Aorta and PA

  • If large and L à R: expose pulmonary circulation to systemic pressures in systole/diastole

  • If restrictive and bidirectional: isosystemic PA pressures

  • Right to left: Suprasystemic PA pressures

  • When restrictive, may estimate PA pressures with Bernouilli equation (with caveat that PDA tubular)

From: Satyan Lakshminrusimha and Martin Keszler NeoReviews December 2015, 16 (12) e680-e692; DOI: https://doi.org/10.1542/neo.16-12-e680

Acute vasoreactivity testing from PHA (Click here)

"Interpretation/Positive test: The 2009 ACC/AHA and 2015 ESC/ERS guidelines define a positive study based on a reduction in the mean pulmonary artery pressure of at least 10 mmHg to an absolute mean PA pressure of less than 40 mm Hg with a stable or improved cardiac output. Patients should have normal oxygen saturation prior to starting inhaled nitric oxide so that one can assess the true response on pulmonary vascular tone and not response to improved oxygenation."

"Acute vasoreactivity testing in children is undertaken to assess the response of the pulmonary vascular bed to pulmonary specific vasodilators. Similarly, the current practice in children with IPAH or familial PAH (isolated PVHD) is to use AVT to define the likelihood of response to long-term treatment with CCB therapy and for prognosis. There are 2 definitions of responders to AVT in IPAH or isolated PHVD, including 1) a decrease in mPAP of at least 10 mmHg to below 40 mmHg with a normal or increased increase in cardiac output; and 2) a decrease in mean PAP = 20% and increase or no change in CI and decrease or no change in PVR:SVR. AVT in children with PH associated with congenital heart disease (CHD) is undertaken to assess if the PVR will decrease sufficiently for surgical repair to be undertaken in borderline cases. In general, positive AVT for borderline cases with post tricuspid shunts is defined as decreases in PVRI to < 6-8 WUm2 or PVR:SVR <0.3. However, AVT is only one measure used to define operability and the whole clinical picture, the age of the patient and the type of lesion need to be taken into consideration. AVT may be studied with iNO (20–80 ppm), 100% oxygen, inhaled or intravenous PgI2 analogues, intravenous adenosine or sildenafil."

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