PASP Calculation on Echocardiography: ASE 2025 Guide

 

PASP Calculation on Echocardiography: ASE 2025 Guide, Interpretation, Pitfalls, and Clinical Significance

Pulmonary artery systolic pressure (PASP) is one of the most frequently reported measurements on transthoracic echocardiography (TTE). It provides a non-invasive estimate of pulmonary artery pressure and serves as an important screening tool for pulmonary hypertension (PH). However, PASP should never be interpreted in isolation. The latest American Society of Echocardiography (ASE) guidelines emphasize a multiparametric, probability-based approach rather than relying solely on a numerical PASP value.

This article reviews the latest ASE recommendations, explains how PASP is calculated, discusses common pitfalls, and highlights how to interpret PASP accurately in daily clinical practice.

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What is PASP?

Pulmonary artery systolic pressure (PASP) represents the peak systolic pressure within the pulmonary artery. In the absence of pulmonic valve stenosis or right ventricular outflow tract obstruction, PASP is considered equal to the right ventricular systolic pressure (RVSP).

Because the right ventricle ejects directly into the pulmonary artery, RV systolic pressure closely reflects pulmonary artery systolic pressure under normal circumstances.

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Why is PASP Important?

PASP estimation helps clinicians:

• Screen patients for pulmonary hypertension

• Evaluate unexplained dyspnea

• Assess right ventricular pressure overload

• Monitor disease progression

• Evaluate response to pulmonary hypertension therapy

• Risk stratify patients with heart failure, congenital heart disease, valvular heart disease, and chronic lung disease

Although echocardiography is an excellent screening modality, right heart catheterization remains the gold standard for diagnosing pulmonary hypertension.

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ASE 2025 Formula for PASP Calculation

The calculation remains straightforward.

PASP = 4 × (TR Peak Velocity)² + Right Atrial Pressure (RAP)

Where:

TR Peak Velocity = Peak velocity of tricuspid regurgitation jet (m/s)

RAP = Estimated right atrial pressure derived from inferior vena cava (IVC) size and respiratory collapse.

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Step 1: Measure Peak TR Velocity

Continuous-wave Doppler is used to record the highest measurable tricuspid regurgitation jet.

Important recommendations:

• Use multiple acoustic windows

• Apical four-chamber view

• RV inflow view

• Parasternal short-axis

• Subcostal view (when required)

Always use the highest measurable TR velocity.

Incorrect alignment with the jet results in underestimation of PASP.

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Step 2: Calculate TR Pressure Gradient

Apply the modified Bernoulli equation:

Pressure Gradient = 4 × (TR Velocity)²

Examples:

TR velocity = 2.8 m/s

Gradient = 31 mmHg

TR velocity = 3.5 m/s

Gradient = 49 mmHg

TR velocity = 4.0 m/s

Gradient = 64 mmHg

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Step 3: Estimate Right Atrial Pressure (RAP)

ASE recommends estimating RAP using IVC diameter and inspiratory collapse.

IVC ≤2.1 cm with >50% collapse

RAP = 3 mmHg

IVC >2.1 cm with <50% collapse

RAP = 15 mmHg

Intermediate findings

RAP = 8 mmHg

When IVC assessment is unreliable, RAP estimation should be interpreted cautiously.

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Step 4: Calculate PASP

Example:

TR velocity = 3.4 m/s

Pressure gradient

= 4 × (3.4²)

= 46 mmHg

Estimated RAP = 8 mmHg

PASP = 46 + 8

= 54 mmHg

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Normal PASP

Normal PASP is generally considered:

≤35 mmHg

Values above this should prompt careful clinical assessment.

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PASP Severity

Although many echocardiography reports still categorize PASP as mild, moderate, or severe, ASE no longer recommends making clinical decisions based solely on these cutoffs.

Traditional echocardiographic ranges are:

Normal

≤35 mmHg

Mild elevation

36–50 mmHg

Moderate elevation

51–70 mmHg

Severe elevation

«70 mmHg»

Older literature often used:

Severe PASP

«60 mmHg»

However, this threshold is not part of current ASE or ESC/ERS guideline recommendations.

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ASE 2025: Probability-Based Interpretation

The major shift in recent ASE recommendations is moving away from severity labels based solely on PASP.

Instead, clinicians should estimate the probability of pulmonary hypertension.

TR Velocity ≤2.8 m/s

Low probability

TR Velocity 2.9–3.4 m/s

Intermediate probability

TR Velocity >3.4 m/s

High probability

This assessment must always be integrated with additional echocardiographic findings.

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Additional Echocardiographic Findings That Increase the Likelihood of Pulmonary Hypertension

Right ventricular enlargement

Reduced RV systolic function

Right atrial enlargement

Interventricular septal flattening

Pulmonary artery dilatation

Dilated IVC with poor inspiratory collapse

Short pulmonary acceleration time

Abnormal RV outflow Doppler profile

Presence of pericardial effusion

The more abnormal findings that are present, the greater the likelihood of clinically significant pulmonary hypertension.

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Common Causes of Elevated PASP

Left-sided heart disease

Heart failure

Mitral valve disease

Aortic valve disease

Pulmonary arterial hypertension

Chronic thromboembolic pulmonary hypertension

Chronic lung disease

Obstructive sleep apnea

Congenital heart disease

Pulmonary embolism

High cardiac output states

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Causes of Incorrect PASP Estimation

Several factors may lead to inaccurate PASP estimation.

Poor TR Doppler signal

Suboptimal Doppler alignment

Very severe tricuspid regurgitation

Absent measurable TR jet

Incorrect RAP estimation

Mechanical ventilation

RV outflow tract obstruction

Pulmonic stenosis

These limitations explain why PASP should never be interpreted without considering the overall clinical picture.

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When Should PASP Not Be Reported?

ASE advises caution when:

No measurable TR jet is present.

TR Doppler envelope is incomplete.

Signal quality is poor.

Severe Dopacardiographic artifacts prevent reliable measurement.

Reporting an inaccurate PASP can be more misleading than not reporting it.

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When is Right Heart Catheterization Needed?

Echocardiography estimates the probability of pulmonary hypertension.

Right heart catheterization is recommended when:

Diagnosis remains uncertain

Pulmonary hypertension-specific therapy is being considered

Advanced pulmonary hypertension is suspected

Pre-operative assessment requires confirmation

Clinical findings disagree with echocardiography

Right heart catheterization remains the definitive diagnostic test.

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Key Clinical Pearls

• PASP equals RVSP unless pulmonic stenosis or RVOT obstruction is present.

• Always use the highest measurable TR velocity.

• Estimate RAP using IVC diameter and respiratory collapse.

• PASP is an estimate, not a definitive diagnosis.

• Avoid interpreting PASP without assessing right ventricular size and function.

• TR velocity is often more useful than PASP alone.

• Current ASE guidelines recommend a probability-based approach rather than strict PASP severity categories.

• Confirmation with right heart catheterization is essential whenever clinically indicated.

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Take-Home Message

PASP estimation remains one of the most valuable components of echocardiography for screening pulmonary hypertension. The latest ASE recommendations reinforce that PASP should be interpreted as part of a comprehensive right heart assessment rather than as an isolated number. A high-quality TR Doppler signal, accurate estimation of right atrial pressure, and integration with other echocardiographic findings provide the most reliable assessment. When pulmonary hypertension is suspected or treatment decisions depend on the diagnosis, right heart catheterization remains the gold standard.

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