When both systolic pulmonary artery pressure (SPAP) and right ventricular systolic pressure (RVSP) are measured on a 2D echo, which value should be used to assess for pulmonary arterial hypertension (PAH)?

Using RVSP for Assessing Pulmonary Arterial Hypertension on 2D Echo

When both systolic pulmonary artery pressure (SPAP) and right ventricular systolic pressure (RVSP) are measured on a 2D echo, RVSP should be used to assess for pulmonary arterial hypertension (PAH) in the absence of pulmonic valve stenosis or right ventricular outflow tract obstruction. 1

Relationship Between RVSP and SPAP

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

Diagnostic Approach Using RVSP

• RVSP < 35 mmHg is considered normal 2
• RVSP 35-40 mmHg is considered borderline elevated 2
• The European Society of Cardiology (ESC) and European Respiratory Society (ERS) recommend using peak tricuspid regurgitation velocity (TRV) rather than the estimated SPAP as the main variable for assigning echocardiographic probability of PH 3
• The ESC/ERS guidelines provide a table for echocardiographic probability of PH based on TRV and other echo signs:
  • TRV ≤ 2.8 m/s (or not measurable) without other echo signs: low probability 3
  • TRV ≤ 2.8 m/s with other echo signs: intermediate probability 3
  • TRV 2.9-3.4 m/s without other echo signs: intermediate probability 3
  • TRV 2.9-3.4 m/s with other echo signs or TRV > 3.4 m/s: high probability 3

Technical Considerations for Accurate Measurement

• The Doppler beam should be aligned parallel to the TR jet 1
• Multiple transducer positions should be used to record the highest velocity to reduce underestimation 1
• TR jets are analyzable in only 39% to 86% of patients, highlighting the importance of obtaining adequate imaging 1
• When TR is inadequate, agitated saline contrast can be used to enhance the Doppler signal 1

Limitations and Pitfalls

• Echocardiography may underestimate SPAP by a mean of 11 mmHg, with underestimation of 20 mmHg in up to 31% of patients 1
• In severe tricuspid regurgitation, TRV may be significantly underestimated and cannot be used to exclude PH 3, 1
• The discordance between estimated and true pulmonary artery pressure is greatest when SPAP exceeds 100 mmHg 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
• Real-time 3D echocardiography evaluates RV volumes and ejection fraction more accurately than conventional 2D echocardiography 3, 1

Confirmation of PAH Diagnosis

• Echocardiography alone is not sufficient to confirm a diagnosis of PAH and initiate treatment 3
• Right heart catheterization is necessary for confirmation of PH in patients with intermediate or high echocardiographic probability of PH before treatment initiation 3
• PAH is hemodynamically defined by right heart catheterization demonstrating a mean pulmonary artery pressure greater than 20 mmHg, a pulmonary artery wedge pressure of 15 mmHg or lower, and a pulmonary vascular resistance of 3 Wood units or greater 4, 5

In conclusion, RVSP derived from tricuspid regurgitation velocity should be used for echocardiographic assessment of PAH when both SPAP and RVSP are available on a 2D echo, as they are physiologically equivalent in the absence of pulmonic stenosis or RVOT obstruction. However, it's important to remember that echocardiography provides only an estimate and right heart catheterization remains the gold standard for definitive diagnosis.