What resting mean pulmonary artery pressure (mm Hg) is required to diagnose pulmonary arterial hypertension?

Diagnostic Threshold for Pulmonary Arterial Hypertension

A mean pulmonary artery pressure (mPAP) of ≥25 mmHg at rest, measured by right heart catheterization, is required to diagnose pulmonary hypertension, though recent guidelines propose lowering this threshold to >20 mmHg. 1, 2, 3

Established Diagnostic Criteria

The traditional and widely accepted hemodynamic definition requires:

• Mean pulmonary arterial pressure ≥25 mmHg at rest measured via right heart catheterization 1, 4
• This 25 mmHg threshold has been used consistently to select patients for all randomized controlled trials and registries of pulmonary arterial hypertension 1
• Normal mean pulmonary arterial pressure at rest is 14-20 mmHg, with an upper limit of normal at 20 mmHg 1

Evolving Diagnostic Standards

Recent 2024 European guidelines have redefined pulmonary hypertension as mPAP >20 mmHg at rest, representing a shift from the traditional 25 mmHg cutoff 2, 5, 3, 6. However:

• The 25 mmHg threshold remains widely referenced in clinical practice and established guidelines 1, 5
• Mean PAP values between 21-24 mmHg are of uncertain clinical significance and warrant close follow-up rather than immediate diagnosis 1

Distinguishing Pulmonary Arterial Hypertension from Other Forms

For a specific diagnosis of pulmonary arterial hypertension (PAH), additional hemodynamic criteria must be met beyond elevated mPAP:

• Pulmonary artery wedge pressure (PAWP) ≤15 mmHg (confirming pre-capillary disease) 1, 3, 4
• Pulmonary vascular resistance (PVR) >3 Wood units (traditional) or >2 Wood units (newer guidelines) 1, 3, 6
• These additional measurements distinguish PAH from pulmonary hypertension due to left heart disease, which presents with PAWP >15 mmHg 1, 3

Critical Diagnostic Considerations

Right Heart Catheterization is Mandatory

• Right heart catheterization remains the gold standard and is absolutely required to confirm the diagnosis before initiating PAH-specific therapy 1, 5, 4
• The procedure must use standardized technique with the pressure transducer zeroed at the midthoracic line (level of the left atrium) 4
• Measurements should be obtained at rest in the supine position 1

Common Diagnostic Pitfalls

• Exercise-based definitions (mPAP >30 mmHg on exertion) are no longer supported due to insufficient published data and wide variability in healthy individuals 1, 2
• A normal PAWP does not rule out heart failure with preserved ejection fraction (HFpEF), which is a frequent diagnostic challenge 4
• Echocardiography can estimate pulmonary pressures but cannot replace catheterization for definitive diagnosis 1
• Spontaneous variability in pulmonary arterial pressure can reach 20 mmHg in individual patients, with a mean coefficient of variability of 8% 1

Clinical Context

• Pulmonary hypertension affects approximately 1% of the global population 5
• Before disease-specific therapies became available, median survival from diagnosis in idiopathic PAH was only 2.8 years 1, 2
• Early and accurate diagnosis is critical because while potentially lethal, pulmonary arterial hypertension is now treatable 7