When assessing pulmonary arterial hypertension (PAH) using a 2D echo, is systolic pulmonary artery pressure (SPAP) or right ventricular systolic pressure (RVSP) more accurate?

RVSP is More Accurate Than SPAP for Assessing PAH Using 2D Echo

When assessing pulmonary arterial hypertension (PAH) using 2D echocardiography, right ventricular systolic pressure (RVSP) is the more accurate measurement as it directly reflects systolic pulmonary artery pressure (sPAP) in the absence of pulmonary valve stenosis or outflow tract obstruction. 1

Understanding RVSP and SPAP Measurements

• RVSP is considered equal to sPAP in the absence of pulmonic valve stenosis or right ventricular outflow tract obstruction 1
• RVSP is calculated using the modified Bernoulli equation: RVSP = 4v² + RAP, where v is the tricuspid regurgitation (TR) jet velocity in meters per second, and RAP is the estimated right atrial pressure 1
• Multiple studies have shown statistically significant correlations (r = 0.83 to 0.95) between RVSP estimated from TR velocity and invasive hemodynamic measurements from right heart catheterization 1

Evidence Supporting RVSP Measurement

• Nine studies incorporating 500 patients with various forms of PAH demonstrated strong correlations between RVSP estimated by echocardiography and invasive measurements, with correlation coefficients ranging from 0.57 to 0.95 1
• The sensitivity of Doppler echocardiography for detecting PAH using RVSP ranges from 0.79 to 1.0, with specificity ranging from 0.6 to 0.98 1
• In pediatric patients, the TR Doppler signal can be enhanced by the use of agitated saline to improve measurement accuracy when the TR jet is inadequate 1

Technical Considerations for Accurate Measurement

• TR jets are analyzable in 39% to 86% of patients, highlighting the importance of obtaining adequate imaging 1
• The Doppler beam should be aligned parallel to the TR jet, and multiple transducer positions should be used to record the highest velocity to reduce underestimation 1
• When TR signals are interpretable, RVSP has an area under the curve of 0.97 for classifying pulmonary hypertension, which increases to 0.98 when combined with eccentricity index 2
• Quality of the TR spectral Doppler profile is the most important factor in accurate RVSP estimation 2

Common Pitfalls and Limitations

• Echocardiography may underestimate sPAP by a mean of 11 mm Hg, with underestimation of 20 mm Hg in up to 31% of patients 1
• The discordance between estimated and true pulmonary artery pressure is greatest when sPAP exceeds 100 mm Hg 1
• Overestimation in clinical reports is often related to not assigning peak TR velocity at the modal frequency, while underestimation typically results from overreading uninterpretable signals 2
• In cases of severe tricuspid regurgitation, TRV may be significantly underestimated and cannot be used to exclude PH 1

Alternative Approaches When TR Jet Is Inadequate

• When TR and pulmonic valve regurgitation jets are not present or quantifiable, right ventricular outflow patterns and time intervals can be used 1
• Parameters include pre-ejection period, acceleration and deceleration times, relaxation, and contraction times 1
• Six out of seven studies found correlations as high as r = 0.92 using various time intervals including acceleration, right ventricular ejection time, and pre-ejection period 1
• When TR signals are uninterpretable, eccentricity index and right ventricular size are independently associated with pulmonary hypertension (area under the curve, 0.77) 2

Recent Advances in Echo Assessment of PAH

• The TAPSE/TRV ratio (tricuspid annular plane systolic excursion divided by tricuspid regurgitation velocity) and TAPSE/sPAP ratio have emerged as powerful prognostic markers in PAH patients 3
• Real-time 3D echocardiography evaluates RV volumes and ejection fraction more accurately than conventional 2D echocardiography 1
• Pressure gradient-volume diagrams derived from 3D echocardiography data can reliably estimate RV stroke work in patients with PH 1

In conclusion, RVSP is the preferred measurement for assessing PAH using 2D echocardiography due to its direct relationship with sPAP and strong correlation with invasive measurements when properly obtained. However, clinicians should be aware of potential underestimation or overestimation in certain clinical scenarios and consider alternative approaches when TR jets are inadequate.