What diagnostic test is used to diagnose pulmonary hypertension?

Right Heart Catheterization is the Gold Standard for Diagnosing Pulmonary Hypertension

Right heart catheterization (RHC) is the definitive diagnostic test required to confirm pulmonary hypertension, as it directly measures mean pulmonary artery pressure (mPAP) and distinguishes between different PH subtypes based on hemodynamic parameters. 1, 2

Diagnostic Algorithm

Initial Screening

While RHC is mandatory for diagnosis, the pathway typically begins with:

• Echocardiography serves as the initial non-invasive screening tool when PH is suspected clinically 2, 3
  • However, echocardiography has significant limitations with only 83% sensitivity and 72% specificity 3
  • The correlation between echo-estimated and catheter-measured pulmonary pressures is moderate (r=0.70) 3
  • Echocardiography alone is insufficient for diagnosis or monitoring - it can only raise suspicion 3

Definitive Diagnosis: Right Heart Catheterization

RHC must be performed in all patients before confirming PH diagnosis or initiating PH-specific therapy 1, 2, 4. The procedure provides:

Essential Hemodynamic Measurements:

• mPAP >20 mmHg defines PH (updated from the older threshold of ≥25 mmHg) 2
• Pulmonary artery wedge pressure (PAWP) distinguishes:
  • Pre-capillary PH: PAWP ≤15 mmHg with PVR >2 Wood Units 2
  • Isolated post-capillary PH: PAWP >15 mmHg with PVR ≤2 WU 2
  • Combined pre- and post-capillary PH: PAWP >15 mmHg with PVR >2 WU 2

Critical Technical Requirements 1:

• Pressure transducer must be zeroed at the midthoracic line (level of left atrium) 4
• Accurate PAWP measurement is essential - errors here lead to misclassification and potentially harmful treatment decisions 1
• The standard catheter is 110 cm long, 6-8 French diameter, with a 1.5 mL balloon 1

Common Diagnostic Pitfall

The most frequent error is distinguishing pulmonary arterial hypertension (PAH) from PH due to heart failure with preserved ejection fraction (HFpEF) 4. A normal resting PAWP does not exclude HFpEF 4. When uncertainty exists, volume or exercise challenge during RHC may unmask left heart disease, though these techniques require further standardization before routine use 4.

When to Refer for RHC

Fast-track referral to a PH center for RHC is indicated when there is high probability of severe pulmonary vascular disease, especially with signs of right heart failure 2. This should occur at any point during workup when clinical suspicion is high 2.

Adjunctive Testing

Before RHC, complete the diagnostic workup with:

• Ventilation-perfusion scan - mandatory to exclude chronic thromboembolic disease 5
• Assessment for left-to-right shunting 5
• CT pulmonary angiography can provide supportive data but cannot replace RHC 6