How is tricuspid regurgitant (TR) max level used to determine pulmonary hypertension (PHTN)?

From the Guidelines

In echocardiography, tricuspid regurgitation (TR) maximum velocity is used to estimate pulmonary artery systolic pressure (PASP) and diagnose pulmonary hypertension, with a TR max velocity greater than 2.8-3.0 m/s suggesting elevated pulmonary pressures, as stated in the 2015 ESC/ERS guidelines 1.

Echocardiographic Assessment of Pulmonary Hypertension

The TR max velocity is measured using continuous wave Doppler across the tricuspid valve during systole. Using the modified Bernoulli equation (4V²), the pressure gradient between the right ventricle and right atrium is calculated. By adding an estimated right atrial pressure (typically 3-15 mmHg based on IVC size and collapsibility), the PASP can be determined.

Determining the Probability of Pulmonary Hypertension

The probability of pulmonary hypertension is determined based on the peak tricuspid regurgitation velocity and the presence of other echocardiographic signs suggestive of PH, as outlined in the 2022 ACR Appropriateness Criteria 1.

• Low probability for PH is a peak tricuspid regurgitation velocity ≤2.8 m/s and no suggestive echocardiographic signs.
• Intermediate probability for PH is a peak tricuspid regurgitation velocity ≤2.8 m/s and presence of 2 categories of echocardiographic signs suggestive of PH or peak tricuspid regurgitation velocity 2.9 to 3.4 m/s without additional echocardiographic signs of PH.
• High probability for PH is a peak tricuspid regurgitation velocity of 2.9 to 3.4 m/s with two categories of echocardiographic signs of PH or >3.4 m/s without additional echocardiographic signs of PH.

Clinical Implications

Individuals who fall into intermediate or high probability for PH should have further evaluation with right heart catheterization (RHC) to confirm PH before initiation of therapy, as recommended by current guidelines 1. The accuracy of this measurement depends on obtaining good Doppler alignment with the TR jet and properly estimating right atrial pressure. Some key echocardiographic signs suggestive of PH include:

• Right ventricular findings: right ventricle/left ventricle basal diameter ratio >1.0, flattening of the interventricular septum (left ventricular eccentricity index >1.1 in systole and/or diastole) 1
• Pulmonary artery findings: right ventricular acceleration time <105 msec and/or midsystolic notching, early diastolic pulmonary regurgitation velocity >2.2 m/sec, PA diameter >25 mm 1
• Inferior vena cava and right atrium findings: inferior cava diameter >21 mm with decreased inspiratory collapse (<50 % with a sniff or <20 % with quiet inspiration), right atrial area (end-systole) >18 cm2 1

From the Research

Determining Pulmonary Hypertension using TR Max Level in Echo

• The TR max level, which refers to the maximum velocity of tricuspid regurgitation, is a parameter used in echocardiography to estimate pulmonary artery pressure and diagnose pulmonary hypertension (PH) 2.
• A study published in the Journal of Cardiovascular Medicine found that a multiple logistic regression model using echocardiographic parameters, including tricuspid regurgitation Vmax, can predict the presence of pulmonary hypertension at right heart catheterization (RHC) with a high degree of accuracy 2.
• The model, which also included right atrium and ventricular diastolic area, tricuspid regurgitation severity degree, and left ventricular ejection fraction, had an area under the curve of 0.786, indicating good predictive value 2.
• A score value of more than 57 was associated with a 93% sensitivity and 67% specificity for predicting pulmonary hypertension at RHC, suggesting that this model can be useful in selecting patients who should undergo RHC 2.
• While echocardiography is a useful non-invasive tool for estimating pulmonary artery pressure and diagnosing PH, right heart catheterization remains the gold standard for diagnosis and classification of PH 3, 4.

Echocardiographic Parameters and PH Diagnosis

• Echocardiographic parameters, including TR max level, can provide valuable information for diagnosing PH and estimating disease severity 2, 5.
• However, the diagnosis of PH should be confirmed by RHC, which provides direct measurements of pulmonary artery pressure and other hemodynamic parameters 3, 4.
• The use of echocardiographic parameters, including TR max level, can help identify patients who are likely to have PH and require further evaluation with RHC 2.