What parameter on echocardiogram (echo) is used to diagnose pulmonary hypertension?

Echocardiographic Parameters for Pulmonary Hypertension Diagnosis

The primary parameter on echocardiogram to assess for pulmonary hypertension is the peak tricuspid regurgitation velocity (TRV), measured by continuous wave Doppler, which is used to calculate right ventricular systolic pressure (RVSP) and estimate pulmonary artery systolic pressure. 1

Primary Diagnostic Parameter: Tricuspid Regurgitation Velocity

TRV is the single most important echocardiographic measurement for PH assessment, with the following diagnostic thresholds 1:

• TRV ≤2.8 m/s: Low probability of PH (corresponds to PA systolic pressure ≤36 mmHg)
• TRV 2.9-3.4 m/s: Intermediate probability of PH (PA systolic pressure 37-50 mmHg)
• TRV >3.4 m/s: High probability of PH (PA systolic pressure >50 mmHg)

The European Society of Cardiology specifically recommends using the peak TRV measurement itself rather than the calculated RVSP/PASP as the main variable, because this avoids amplification of measurement errors from estimating right atrial pressure 1.

Calculation of RVSP from TRV

RVSP is calculated using the modified Bernoulli equation: RVSP = 4v² + RAP, where v is the TR jet velocity in meters per second 1. This calculation assumes RVSP equals systolic pulmonary artery pressure in the absence of pulmonic stenosis or right ventricular outflow tract obstruction 2, 3.

Right atrial pressure (RAP) estimation is based on inferior vena cava characteristics 1:

• IVC <2.1 cm with >50% collapse on sniff: RAP = 3 mmHg (range 0-5)
• IVC >2.1 cm with <50% collapse on sniff or <20% on quiet inspiration: RAP = 15 mmHg (range 10-20)
• Intermediate scenarios: RAP = 8 mmHg (range 5-10)

Additional Echocardiographic Signs Required for Diagnosis

TRV alone is insufficient—you must identify additional echocardiographic signs from at least two different anatomic categories to increase diagnostic probability 1, 4:

Category A: Ventricular Signs

• Right ventricle/left ventricle basal diameter ratio >1.0 1
• Flattening of interventricular septum (LV eccentricity index >1.1 in systole and/or diastole) 1

Category B: Pulmonary Artery Signs

• Right ventricular outflow tract acceleration time <105 msec and/or midsystolic notching 1
• Early diastolic pulmonary regurgitation velocity >2.2 m/sec 1
• Main pulmonary artery diameter >25 mm 1

Category C: Right Atrium/IVC Signs

• Inferior vena cava diameter >21 mm with decreased inspiratory collapse 1
• Right atrial area (end-systole) >18 cm² 1

Alternative Parameters When TR Jet Is Inadequate

TR jets are analyzable in only 39-86% of patients 1, 3. When TRV cannot be measured adequately:

• Use agitated saline or microbubble contrast to enhance the Doppler signal 1, 2
• Measure right ventricular outflow tract acceleration time (<105 msec suggests PH) 1
• Assess pulmonary diastolic pressure from pulmonary regurgitation velocity (correlates well with invasive measurements, r=0.92) 1
• Calculate pulmonary vascular resistance using the equation: PVR = (TRV/RVOT VTI) × 10 + 0.16, where >2 Wood units suggests PH 5

Critical Technical Considerations

To obtain accurate measurements 1, 3:

• Align the Doppler beam parallel to the TR jet to avoid underestimation
• Use multiple transducer positions (apical, parasternal, subcostal) to record the highest velocity
• Recognize that echocardiography may underestimate systolic PAP by a mean of 11 mmHg, with 20 mmHg underestimation in 31% of patients 1, 3

Common Pitfalls to Avoid

Severe tricuspid regurgitation causes significant TRV underestimation and cannot exclude PH 1, 4. The discordance between estimated and true pulmonary artery pressure is greatest when systolic PAP exceeds 100 mmHg 1, 3.

Never rely on TRV/RVSP alone—always integrate clinical context, symptoms, risk factors, and additional echocardiographic signs 1, 4. A "low probability" echocardiogram does not exclude PH in symptomatic patients with risk factors (connective tissue disease, congenital heart disease, portal hypertension, HIV, prior pulmonary embolism) 4.

Do not use exercise echocardiography for PH screening—this is a Class III recommendation due to lack of validated criteria 4.

When to Proceed to Right Heart Catheterization

Echocardiography alone is insufficient to initiate PH-specific treatment—right heart catheterization is mandatory for confirmation 1, 2. Proceed to RHC when 1, 4:

• High probability echo (TRV >3.4 m/s) in symptomatic patients
• Intermediate probability echo (TRV 2.9-3.4 m/s with additional signs) in patients with risk factors or associated conditions
• RVSP >40-45 mmHg with unexplained dyspnea warrants comprehensive PH workup 2