From the Guidelines
The inability to assess pulmonary artery systolic pressure (PASP) due to insufficient tricuspid regurgitation (TR) jet should prompt consideration of alternative methods to evaluate for possible pulmonary hypertension, as the absence of a measurable TR jet does not rule out pulmonary hypertension. When this occurs, alternative methods should be considered to evaluate for possible pulmonary hypertension. These include assessing right ventricular size and function, interventricular septal flattening, right atrial enlargement, and pulmonary artery dilation, as suggested by 1. If clinical suspicion for pulmonary hypertension remains high despite the inability to measure PASP by echocardiography, consider right heart catheterization for direct pressure measurement, which remains the gold standard 1. Other non-invasive imaging modalities such as cardiac MRI or CT pulmonary angiography may provide additional information about right heart structure and pulmonary vasculature. Some key points to consider in this scenario include:
- The average PASP in healthy individuals is around 21 ± 4 mm Hg, with an upper limit around 30 mm Hg, as measured by right heart catheterization 1
- An ePASP of > 30 mm Hg is below the traditional threshold of 40 mm Hg typically cited as concerning for possible PH and actually relates more closely to a mean PA pressure ≥ 20 mm Hg 1
- Mean PA pressure in this range (mPAP 20-24 mm Hg) associates independently with increased mortality, suggesting that ePASP levels < 40 mmHg are informative for identifying at-risk patients as well 1
- Clinical suspicion of elevated ePASP based on short pulmonary acceleration time on echocardiography, notching in the Doppler flow recording in the right ventricular outflow track, and presence of right ventricular hypertrophy, dilation or dysfunction may be helpful in identifying at-risk patients 1.
From the Research
Unable to Assess Pulmonary Artery Systolic Pressure (PASP) due to Insufficient TR Jet
- The absence of a sufficient tricuspid regurgitation (TR) jet can make it challenging to estimate pulmonary artery systolic pressure (PASP) using transthoracic echocardiography (TTE) 2, 3.
- Studies have shown that the lack of a measurable TR velocity does not necessarily signify normal pulmonary artery pressure, and pulmonary hypertension (PH) can still be present in patients without a reported TR velocity 3.
- In patients with pulmonary hypertension, the severity of tricuspid regurgitation (TR) is not solely determined by pulmonary artery systolic pressure (PASP), and other factors such as age, gender, and right atrial and ventricular enlargement can also play a role 4.
Alternative Methods for Estimating PASP
- Pulmonary artery acceleration time (PAAT) has been proposed as an alternative parameter for estimating systolic pulmonary artery pressure (SPAP) in patients without sufficient TR jet 2, 5.
- PAAT has been shown to correlate strongly with SPAP estimated by TR jet and can be used to estimate SPAP in neonates and young infants 5.
- However, the accuracy of PAAT in estimating PASP can be affected by various factors, including severe tricuspid regurgitation, which can lead to overestimation of PASP 6.
Clinical Implications
- Clinicians should exercise caution when interpreting TTE results in patients without a measurable TR velocity, as PH can still be present 3.
- The use of alternative methods such as PAAT can provide valuable information for estimating PASP in patients without sufficient TR jet 2, 5.
- Further studies are needed to verify the accuracy of these alternative methods and to determine their clinical utility in various patient populations 5.