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)
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
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)