What is the appropriate workup for pulmonary arterial hypertension?

Workup for Pulmonary Arterial Hypertension

Begin with transthoracic echocardiography as your first-line diagnostic test when PAH is suspected, followed by a systematic algorithmic approach to exclude common causes, identify the specific PAH subtype, and confirm diagnosis with right heart catheterization. 1

Initial Screening and Risk Assessment

When PAH is suspected based on symptoms (progressive exertional dyspnea, fatigue, syncope, or chest discomfort), echocardiography is the mandatory first step to assess the probability of pulmonary hypertension 1. This is a Class I recommendation from the ESC/ERS guidelines.

Echocardiographic Probability Stratification

The echocardiogram determines your next steps:

• High or intermediate probability: Proceed with full diagnostic workup
• Low probability: Consider alternative diagnoses and follow-up; no further PH workup needed at this time 1

Systematic Exclusion of Common PH Causes

If echocardiography shows high or intermediate probability, immediately obtain:

• Clinical history focusing on risk factors for left heart disease, lung disease, connective tissue disease, HIV, portal hypertension, drug/toxin exposure
• ECG to assess for right ventricular strain patterns
• Chest radiograph
• Pulmonary function tests with DLCO (Class I recommendation) 1
• Arterial blood gases
• High-resolution CT chest (Class IIa recommendation) 1

This step identifies Group 2 (left heart disease) or Group 3 (lung disease) pulmonary hypertension, which are the most common causes and require different management.

Critical Decision Point: V/Q Scan

If left heart and lung diseases are excluded, immediately perform a ventilation/perfusion (V/Q) lung scan (Class I recommendation) 1. This is non-negotiable and distinguishes between:

• Multiple segmental perfusion defects: Suspect chronic thromboembolic pulmonary hypertension (CTEPH, Group 4)

  • Proceed to CT pulmonary angiography and right heart catheterization
  • Consider pulmonary angiography (Class IIa) 1

• Normal or subsegmental patchy defects: Suspect PAH (Group 1) or Group 5 conditions

  • Proceed to PAH-specific workup

Common pitfall: CT pulmonary angiography alone can miss CTEPH diagnosis; V/Q scan is superior for screening 1.

PAH-Specific Laboratory Workup

All patients with suspected PAH require the following tests (Class I recommendations) 1:

• Routine biochemistry and hematology
• Complete blood count
• Liver function tests
• Immunology panel (ANA, anti-Scl-70, anti-centromere, anti-RNP for connective tissue disease screening)
• HIV testing
• Thyroid function tests
• Abdominal ultrasound to screen for portal hypertension
• BNP or NT-proBNP for severity assessment and prognosis 2

These tests identify PAH-associated conditions: connective tissue disease (especially systemic sclerosis), HIV, portal hypertension, congenital heart disease, and drug/toxin exposure.

Definitive Diagnosis: Right Heart Catheterization

Right heart catheterization at a pulmonary hypertension expert center is mandatory for PAH diagnosis (Class I recommendation) 1. This is non-negotiable and cannot be replaced by non-invasive testing.

Hemodynamic Criteria for PAH

PAH is confirmed when RHC demonstrates 3, 4:

• Mean pulmonary artery pressure (mPAP) >20 mmHg
• Pulmonary artery wedge pressure (PAWP) ≤15 mmHg (excludes left heart disease)
• Pulmonary vascular resistance (PVR) >3 Wood units (updated from >2 WU in most recent definitions)

Vasoreactivity Testing

During RHC, acute vasoreactivity testing should be performed in selected patients to identify those who may respond to calcium channel blockers—a critical distinction that changes management entirely 4, 5. Only about 7% of patients meet criteria for calcium channel blocker therapy, and this can only be determined during catheterization.

Referral Timing

Refer to a PH expert center immediately if:

• Echocardiography shows high or intermediate probability of PH
• Signs of severe PH or right ventricular dysfunction are present
• Left heart and lung diseases are excluded
• Any suspicion of PAH after initial workup 1, 6

Fast-track referral is indicated when there are signs of right heart failure or severe pulmonary vascular disease 3.

Tests NOT Recommended

Open or thoracoscopic lung biopsy is contraindicated in PAH workup (Class III recommendation) 1 due to high risk and lack of diagnostic benefit.

Algorithmic Summary

1. Suspect PAH → Echocardiography
2. High/intermediate probability → Clinical assessment + ECG + CXR + PFTs with DLCO + HRCT + ABG
3. Exclude Group 2/3 PH → If excluded, perform V/Q scan
4. V/Q scan interpretation:
   • Segmental defects → CTEPH workup (CT angiography, RHC, pulmonary angiography)
   • Normal/patchy → PAH workup continues
5. PAH-specific labs → CBC, LFTs, immunology, HIV, thyroid, abdominal ultrasound, BNP
6. Refer to PH center → Right heart catheterization for definitive diagnosis
7. RHC confirms PAH → Vasoreactivity testing + risk stratification

This systematic approach, based on the 2015 ESC/ERS guidelines 1, ensures timely diagnosis while avoiding unnecessary invasive procedures and identifying the correct PH subgroup for appropriate treatment.