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Echo Reference › Pulmonary Haemodynamics

Echo Reference — Diastolic Function & Haemodynamics

Pulmonary Haemodynamics

Echocardiographic assessment of pulmonary pressures and PH probability. TR Vmax and RVOTAcT grading, ePLAR for differentiating pre- vs post-capillary PH, ESC/ERS probability algorithm, haemodynamic definitions, and PASP calculator.

Algorithm Reference Tables PASP Calculator

TR Peak Velocity & Estimated PASP

Pulmonary arterial systolic pressure (PASP) is estimated using the simplified Bernoulli equation applied to the peak tricuspid regurgitation velocity: PASP = 4v² + RAP. TR velocity is the single most important echocardiographic variable for PH screening and is the anchor of the ESC/ERS PH probability algorithm.

TR Vmax — ASE Severity Grading

TR Vmax (m/s) Normal Mildly Abnormal Moderately Abnormal Severely Abnormal
Threshold < 2.8 2.8 – 3.1 3.2 – 3.5 ≥ 3.6

RVSP Severity Grading

RVSP (mmHg) Normal Mildly Abnormal Moderately Abnormal Severely Abnormal
Threshold ≤ 34 35 – 49 50 – 69 ≥ 70

TR Vmax — ESC/ERS PH Probability Classification

The ESC/ERS guidelines use a simplified 3-tier classification of TR velocity for PH probability screening, which forms the basis of their diagnostic algorithm:

TR Peak Velocity (m/s) PH Probability (by TR Vmax alone)
≤ 2.8 Low
2.9 – 3.4 Intermediate
> 3.4 High
TR velocity vs PASP: TR Vmax alone (without RAP) is the preferred screening variable for PH probability because it avoids the additional uncertainty of RAP estimation. PASP is useful for quantification and serial monitoring but is less reliable for probability classification.

RVOT Acceleration Time (RVOTAcT)

RVOT acceleration time is measured from the onset of ejection to the peak velocity of the RVOT PW Doppler envelope. It provides an estimate of mean pulmonary arterial pressure and is useful when TR is absent or inadequate.

RVOTAcT (ms) Interpretation
> 105 Normal — suggests normal pulmonary pressures
80 – 105 Mildly abnormal — mildly elevated mean PAP
61 – 79 Moderately abnormal — moderately elevated mean PAP
≤ 60 Severely abnormal — significantly elevated mean PAP. Mid-systolic notching is an additional sign of elevated pulmonary vascular resistance
Mid-systolic notching: A notch in the RVOT Doppler envelope during mid-systole is a specific sign of elevated pulmonary vascular resistance and is associated with pre-capillary PH. It reflects premature pressure wave reflection from the pulmonary vasculature.

ESC/ERS Echocardiographic PH Probability

The 2022 ESC/ERS guidelines use TR velocity as the primary variable, supplemented by additional echo signs when TR velocity is in the intermediate range (2.9–3.4 m/s).

Additional Echo Signs of PH

Category Sign
Ventricles RV/LV basal diameter ratio > 1.0; flattening of interventricular septum (D-sign in systole and/or diastole)
Pulmonary artery RVOTAcT < 105 ms and/or mid-systolic notching; early diastolic PR velocity > 2.2 m/s; PA diameter > 25 mm
IVC and RA IVC diameter > 2.1 cm with decreased collapse; RA area (end-systole) > 18 cm²

PH Probability Classification

TR Velocity Additional Signs PH Probability
≤ 2.8 m/s or not measurable None Low
≤ 2.8 m/s or not measurable Present (≥ 2 from different categories) Intermediate
2.9 – 3.4 m/s None Intermediate
2.9 – 3.4 m/s Present (≥ 2 from different categories) High
> 3.4 m/s Not required High
Clinical action: Low probability → PH unlikely, no further workup unless strong clinical suspicion. Intermediate probability → consider further investigation if clinical suspicion is present. High probability → PH likely, refer for right heart catheterisation to confirm diagnosis and haemodynamic characterisation.

ePLAR — Echocardiographic Pulmonary to Left Atrial Ratio

ePLAR is a non-invasive ratio that helps differentiate pre-capillary from post-capillary pulmonary hypertension. It is calculated as: ePLAR = TR velocity (m/s) ÷ E/e' ratio.

ePLAR Interpretation
> 0.30 Suggests pre-capillary PH (elevated PVR with normal or mildly elevated PCWP)
≤ 0.20 Suggests post-capillary PH (elevated PCWP — left heart disease)
0.20 – 0.30 Indeterminate — may represent combined pre- and post-capillary PH
Clinical utility: ePLAR is most useful when PH is confirmed and the question is aetiology. A high ePLAR points toward intrinsic pulmonary vascular disease (Group 1 or Group 3 PH), while a low ePLAR points toward left heart disease (Group 2 PH). The ratio should not replace right heart catheterisation but can guide initial workup and referral.

Haemodynamic Definitions of PH

The 2022 ESC/ERS guidelines revised the haemodynamic definition of pulmonary hypertension, lowering the mPAP threshold from > 25 to > 20 mmHg. These definitions require right heart catheterisation and are provided here for reference.

Type mPAP PCWP PVR
Pre-capillary PH > 20 mmHg ≤ 15 mmHg > 2 WU
Isolated post-capillary PH (IpcPH) > 20 mmHg > 15 mmHg ≤ 2 WU
Combined pre- & post-capillary PH (CpcPH) > 20 mmHg > 15 mmHg > 2 WU
Exercise PH: The 2022 guidelines also introduced a definition for exercise PH: mPAP/CO slope > 3 mmHg/L/min during exercise. This is relevant for patients with exertional symptoms and normal resting haemodynamics.

PASP Calculator

Estimated PASP

PASP = 4v² + RAP. Enter the peak TR velocity and select the estimated RAP from the IVC assessment.

TR Gradient (4v²) —
Estimated RAP —
Estimated PASP —
TR Vmax Grading —

Clinical Context

When TR Is Absent or Inadequate

TR is absent or yields an inadequate spectral envelope in approximately 10–30% of patients. In these cases, PASP cannot be directly estimated. Use RVOTAcT and the ESC/ERS additional signs (RV/LV ratio, septal flattening, PA diameter, IVC/RA) to assess PH probability. An RVOTAcT < 105 ms with mid-systolic notching is particularly suggestive of elevated PVR.

Limitations of Echo-Derived PASP

Limitation Impact
Incomplete TR envelope Underestimates peak TR velocity → underestimates PASP. Use contrast if native signal is inadequate.
Non-parallel alignment with TR jet Underestimates velocity (angle-dependent). Use multiple windows and the highest velocity obtained.
RAP estimation error Directly shifts PASP by the same amount. See RAP Estimation for details.
Severe TR with large RV–RA gradient equalisation In massive TR, the RV–RA pressure gradient may be low despite elevated PASP. A low TR velocity does not exclude PH when TR is torrential.
Exercise vs resting pressures Resting PASP may be normal in early PH. Exercise echo can unmask elevated pressures but is not routinely performed.
Accuracy: Echo-derived PASP correlates moderately with invasive measurement (r ≈ 0.7–0.8 in most studies) but can over- or underestimate by ≥ 10 mmHg in individual patients. Echo is a screening and monitoring tool — it should not replace right heart catheterisation for definitive PH diagnosis or haemodynamic classification.

References

  1. Humbert M, et al. 2022 ESC/ERS Guidelines for the Diagnosis and Treatment of Pulmonary Hypertension. Eur Heart J. 2022;43(38):3618–3731.
  2. Mukherjee M, et al. Guidelines for the Echocardiographic Assessment of the Right Heart in Adults and Special Considerations in Pulmonary Hypertension: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2025;38(3):141–186.
  3. Lang RM, et al. Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults. J Am Soc Echocardiogr. 2015;28:1–39.
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