RVSP / PASP
Definitions
|
Parameter |
Definition |
|
RVSP |
Peak systolic pressure generated by the RV during systole |
|
PASP |
Peak systolic pressure within the pulmonary artery during systole |
|
Normal physiology |
RV systolic pressure ≈ PASP because there is almost no pressure gradient across a normal pulmonary valve |
Therefore,RVSP ≈ PASP (if pulmonary valve is normal).
If pulmonary stenosis or RVOT obstruction exists,RVSP > PASP
Clinical Importance
RVSP/PASP estimation helps diagnose:
- Pulmonary hypertension
- Acute pulmonary embolism
- RV failure
- ARDS
- Chronic lung disease
- Left heart disease causing secondary PH
- Congenital heart disease
- Tricuspid regurgitation severity
- Septic shock with RV dysfunction
- Fluid responsiveness assessment (indirectly)
Physiology
RV Pressure = Pulmonary artery pressure + RVOT resistance
Normally RVOT resistance is negligible.
Therefore RVSP ≈ PASP
Principle Behind Echo Measurement
The pressure gradient across the tricuspid valve during systole is produced because RV pressure exceeds RA pressure.
The velocity of tricuspid regurgitation (TR jet) reflects this pressure gradient.
Using the modified Bernoulli equation:ΔP=4V2
where:
- ΔP = pressure gradient between RV and RA (mmHg)
- V = peak TR velocity (m/s)
Thus,RVSP = 4(TR velocity)² + RAP(Right atrial pressure)
SinceRVSP ≈ PASP Then PASP = 4(TR velocity)² + RAP
Measuring TR Velocity
Use Continuous-wave Doppler (CW),Never PW Doppler.
Best Views
|
View |
Comments |
|
Apical 4 chamber |
Most common |
|
RV inflow |
Excellent alignment |
|
Parasternal RV inflow |
Alternative |
|
Subcostal 4 chamber |
ICU favorite |
Always choose the window with:
- Highest velocity
- Best alignment
- Complete envelope
Doppler Settings
Use Continuous-wave Doppler,Cursor parallel to TR jet
Angle error should be minimal.
Importance of Alignment
- Velocity error dramatically affects pressure because Pressure = 4V²,Small velocity errors produce large pressure errors.
- Example True velocity 4 m/s therefore Pressure gradient 64 mmHg
- If measured as 3.5 m/s therefore Pressure 49 mmHg
- Difference 15 mmHg which is Huge error.
TR Envelope
- Use Dense,Complete,Well-defined Parabolic envelope
- Trace outer edge.
- Never trace inside the envelope.
Estimating RAP
Most common method IVC diameter
ASE Recommendation
|
IVC |
Collapse |
RAP |
|
≤2.1 cm |
>50% |
3 mmHg |
|
>2.1 cm |
<50% |
15 mmHg |
|
Intermediate |
Mixed findings |
8 mmHg |
ICU Problem
- Positive pressure ventilation
- PEEP
- Raised intrathoracic pressure
- Large IVC
- Reduced collapse
Therefore IVC becomes unreliable.
Many intensivists instead assume RAP 8–10 mmHg
or estimate using clinical findings, CVP (if available), RA size, hepatic vein Doppler, or direct invasive measurements.
Absence of a measurable TR jet does not exclude pulmonary hypertension.
Normal Values
|
Parameter |
Normal |
|
TR velocity |
<2.8 m/s |
|
Gradient |
<31 mmHg |
|
PASP |
<35 mmHg |
|
RVSP |
<35 mmHg |
PASP Classification
|
PASP |
Severity |
|
<35 mmHg |
Normal |
|
35–45 |
Mild elevation |
|
46–60 |
Moderate PH |
|
>60 |
Severe PH |
These ranges are practical echocardiographic estimates. Definitive pulmonary hypertension is diagnosed by right-heart catheterization using mean pulmonary artery pressure (mPAP), not PASP alone.
|
RVSP Interpretation |
Clinical Significance |
|
High RVSP |
Suggests elevated pulmonary artery pressure (if no RVOT or pulmonic valve obstruction). Causes:Pulmonary hypertension (Group 1–5), pulmonary embolism, ARDS with hypoxic pulmonary vasoconstriction, left-sided heart disease (HFpEF, HFrEF, mitral stenosis/mitral regurgitation), COPD, interstitial lung disease (ILD), obstructive sleep apnea/obesity hypoventilation syndrome, chronic thromboembolic pulmonary hypertension (CTEPH), congenital heart disease, RVOT or pulmonic valve obstruction (RVSP may be elevated despite normal PASP). |
|
Low RVSP |
Usually reflects normal pulmonary artery pressure. May also occur with hypovolemia, low cardiac output, severe right ventricular failure (RV unable to generate pressure), massive tricuspid regurgitation (pressure equalization causing underestimation of RVSP), poor Doppler signal/inadequate TR jet, or severe TR with low RV-RA gradient despite elevated right-sided pressures. |
Pitfalls
|
Pitfall |
Effect |
|
Poor Doppler alignment |
Underestimates TR velocity and RVSP |
|
Incomplete TR envelope |
Underestimation |
|
Severe TR |
Underestimation due to rapid RV–RA pressure equalization |
|
Incorrect RAP estimation |
Directly alters RVSP |
|
Pulmonary stenosis |
RVSP overestimates PASP if assumed equal |
|
No measurable TR |
Cannot estimate RVSP |
|
Positive-pressure ventilation |
IVC-based RAP is unreliable |
|
Low-output state |
Lower TR velocity despite significant disease |
|
Arrhythmias |
Beat-to-beat variability Average multiple beats (≥5 in atrial fibrillation). |
Guideline-Based Interpretation (ASE/EACVI 2025 & ESC/ERS PH Concepts)
Rather than relying solely on an estimated PASP, current echocardiography guidelines emphasize:
- Peak TR velocity (TRV) as the primary Doppler variable.
- Assessment of additional echocardiographic signs from:
- Right ventricle (size/function)
- Pulmonary artery (e.g., RVOT acceleration time)
- Inferior vena cava/right atrium
- Integration of these findings to estimate the echocardiographic probability of pulmonary hypertension.
A high RVSP/PASP should therefore always be interpreted together with:
- RV size and systolic function (TAPSE, FAC, RV free-wall strain)
- Septal flattening (D-shaped LV)
- Pulmonary artery dimensions
- Clinical context (PE, ARDS, HF, COPD, etc.)