How do you diagnose pulmonary hypertension?

Diagnosis of Pulmonary Hypertension

Pulmonary hypertension is definitively diagnosed by right heart catheterization (RHC) showing mean pulmonary arterial pressure (mPAP) >20 mmHg, with further classification based on pulmonary arterial wedge pressure (PAWP) and pulmonary vascular resistance (PVR). 1

Hemodynamic Diagnostic Criteria

The gold standard requires RHC with specific thresholds 1:

• Pre-capillary PH: mPAP >20 mmHg, PAWP ≤15 mmHg, and PVR >2 Wood Units
• Isolated post-capillary PH: mPAP >20 mmHg, PAWP >15 mmHg, and PVR ≤2 WU
• Combined post- and pre-capillary PH: mPAP >20 mmHg, PAWP >15 mmHg, and PVR >2 WU

Stepwise Diagnostic Algorithm

Step 1: Clinical Suspicion and Initial Screening

Begin with transthoracic echocardiography when PH is suspected based on symptoms (dyspnea, exercise intolerance, syncope, chest pain) or physical findings suggesting right heart dysfunction 2, 3. Echocardiography estimates the probability of PH and is the most widely used non-invasive diagnostic tool 4, 5.

Key clinical red flags requiring evaluation 4:

• Exertional dyspnea disproportionate to underlying disease
• Episodes of syncope
• Signs of right heart failure
• Progressive limitation of exercise capacity

Step 2: Risk-Stratified Echocardiographic Interpretation

The European Respiratory Society provides clear guidance on next steps based on echo findings 5:

"PH unlikely" on echo:

• No symptoms, no risk factors → No additional workup needed
• Symptoms AND risk factors for PAH → Echocardiographic follow-up
• Symptoms but NO risk factors → Evaluate other causes for symptoms

"PH possible" on echo:

• No symptoms, no risk factors → Echocardiographic follow-up
• Symptoms AND risk factors → Consider RHC
• Symptoms but no risk factors → Alternative diagnosis evaluation and echo follow-up; if symptoms are at least moderate, consider RHC

"PH likely" on echo:

• With symptoms (regardless of risk factors) → RHC recommended
• Without symptoms (regardless of risk factors) → Consider RHC

Step 3: Mandatory Screening Tests Before RHC

All patients with suspected or confirmed PH must have 2, 5:

• Ventilation-perfusion (V/Q) lung scan to exclude chronic thromboembolic PH (CTEPH) - this is mandatory in all patients with unexplained PH 5
• Contrast CT angiography if CTEPH is suspected 5

Additional baseline diagnostic workup 5, 3:

• Laboratory testing: routine biochemistry, hematology, immunology, thyroid function tests
• Electrocardiogram (ECG)
• Chest radiography
• Pulmonary function tests
• Abdominal ultrasound for screening of portal hypertension
• Consider high-resolution CT in all PH patients

Step 4: Right Heart Catheterization

RHC is essential for accurate diagnosis and classification 2. It should be performed at baseline in all patients being evaluated for PAH 6.

Critical pitfall to avoid: Never perform open or thoracoscopic lung biopsy in patients with PAH, as it carries substantial morbidity/mortality risk and rarely alters management 4, 5.

Assessment of Disease Severity at Diagnosis

Once PH is confirmed, comprehensive baseline assessment is required 6:

• WHO Functional Class (I-IV)
• 6-minute walk test (6MWT) with Borg dyspnea score
• Cardiopulmonary exercise testing (CPET)
• BNP/NT-proBNP levels
• Echocardiography with specific attention to:
  • Pericardial effusion presence
  • TAPSE (tricuspid annular plane systolic excursion)
  • Right ventricular function
• Hemodynamic parameters: cardiac index, right atrial pressure

When to Refer to Specialist Centers

Immediate referral to a PH specialist center is required for 4:

• Severe PH and/or severe right ventricular dysfunction on echocardiography
• Mild underlying lung disease but severe PH (to determine if concurrent PAH exists)
• PH due to left heart disease with severe pre-capillary component (high diastolic pressure gradient and/or high PVR)
• Suspected PAH or CTEPH after excluding left heart disease and lung disease
• All confirmed PAH or CTEPH patients 2

Important caveat: Primary care physicians should NOT initiate PAH-approved therapies in patients with PH due to left heart disease or lung disease outside of specialist centers 4. Optimize underlying conditions (heart failure, COPD, sleep apnea) first 4.

Distinguishing PH-Left Heart Disease

When evaluating for PH-LHD, multiple features raise suspicion 6:

• Age >65 years
• Features of metabolic syndrome
• History of heart disease or persistent atrial fibrillation
• Echocardiographic findings: left atrial enlargement (>4.2 cm), LV dysfunction, concentric LV hypertrophy, increased E/e' ratio
• ECG showing LVH, atrial fibrillation/flutter, LBBB, or Q waves
• Imaging showing Kerley B lines, pleural effusion, or pulmonary edema

The combination of diastolic pressure gradient (DPG) and PVR is recommended to define isolated versus combined post-capillary PH 6.