How is mean pulmonary artery pressure measured and by whom?

How Mean Pulmonary Artery Pressure is Measured and Who Performs It

Mean pulmonary artery pressure (mPAP) is definitively measured by right-heart catheterization, which is performed by interventional cardiologists, pulmonologists with advanced training in pulmonary hypertension, or specialized cardiac catheterization teams. 1

Gold Standard Measurement: Right-Heart Catheterization

Right-heart catheterization remains the gold standard for measuring mean pulmonary artery pressure and is required to confirm the presence of pulmonary hypertension, establish specific diagnosis, and determine disease severity. 1

What Right-Heart Catheterization Provides:

• Direct and accurate measurements of mean pulmonary artery pressure, right atrial pressure, pulmonary capillary wedge pressure (pulmonary venous pressure), pulmonary blood flow, and mixed venous oxygen saturation 1
• Calculation of pulmonary vascular resistance, which is essential for distinguishing pulmonary arterial hypertension from other forms 1
• Exclusion of other etiologies such as intracardiac or extracardiac shunts and left-heart disease 1
• Assessment of right-heart dysfunction through measurement of right atrial pressure and cardiac output 1

Who Performs the Procedure:

Consultation with a cardiologist, pulmonologist, or pulmonary hypertension expert is good practice when referring patients for right-heart catheterization, interpreting results, and considering therapeutic options. 1

Important Limitations to Recognize:

• Measurements are typically obtained only under resting conditions in the supine position, which may not represent hemodynamic responses to upright posture, activity, or sleep 1
• Spontaneous variability exists: Studies show wide intraindividual variability in pulmonary arterial pressure (up to 20 mm Hg in some patients, with a mean coefficient of variability of 8%) 1
• Risk of complications: In sickle cell disease patients, vaso-occlusive crisis occurred in 3% of patients shortly after catheterization, though without permanent sequelae 1

Non-Invasive Estimation: Echocardiography

While Doppler echocardiography can provide a proxy measurement of pulmonary hemodynamics by estimating right ventricular pressure, it is not a substitute for the more accurate values obtained by right-heart catheterization. 1

Echocardiographic Methods:

• Estimated pulmonary artery systolic pressure (ePASP) is calculated by measuring the velocity of the tricuspid regurgitation jet using the modified Bernoulli equation (TR gradient = 4 × [TR velocity]²) and adding estimated right atrial pressure based on inferior vena cava size and collapsibility 1
• Mean PAP can be estimated using the mean gradient method, Chemla equation (0.61 × systolic PAP + 2 mm Hg), or Syyed equation (0.65 × systolic PAP + 0.55 mm Hg) 2, 3
• Accuracy varies: Echocardiographic methods show correlation coefficients ranging from r = 0.57 to r = 0.95 with catheterization measurements, with mean differences of 3 to 38 mm Hg 1, 2

Critical Pitfall:

Absence of a measurable tricuspid regurgitation jet does not rule out elevated pulmonary artery pressure. 1 In these cases, look for alternative echocardiographic signs including short pulmonary acceleration time, notching in the Doppler flow recording in the right ventricular outflow tract, and presence of right ventricular hypertrophy, dilation, or dysfunction 1

Clinical Decision-Making for When to Catheterize

Right-heart catheterization is required in patients with suspected pulmonary hypertension to confirm diagnosis and guide therapy. 1

Specific Indications:

• Elevated estimated PASP > 30 mm Hg on echocardiography warrants consideration for catheterization, as this correlates with mPAP ≥ 20 mm Hg 1, 4
• In sickle cell disease patients with peak tricuspid regurgitation jet velocity ≥ 2.5 m/s, decisions should be based on echocardiograms obtained at steady state (not during acute illness), with additional consideration of NT-BNP (≥160 pg/mL) and 6-minute walk distance (<333 m) 1
• Symptomatic patients with dyspnea, fatigue, chest pain, syncope, or signs of right heart failure require catheterization regardless of echocardiographic findings 1

Diagnostic Thresholds

Pulmonary hypertension is defined hemodynamically by right-heart catheterization as mean pulmonary artery pressure > 20 mm Hg (recently reduced from > 25 mm Hg), with additional criteria for pulmonary arterial hypertension including pulmonary artery wedge pressure ≤ 15 mm Hg and pulmonary vascular resistance ≥ 3 Wood units 1, 4