From the Guidelines
Diagnosing pulmonary arterial hypertension (PAH) requires a systematic approach that begins with clinical suspicion based on symptoms like dyspnea, fatigue, and syncope, followed by a series of confirmatory tests, as outlined in the most recent guidelines 1. The diagnostic process starts with non-invasive screening tests including:
- Echocardiography, which estimates pulmonary artery pressure and assesses right heart function
- Pulmonary function tests
- Chest imaging (X-ray and high-resolution CT)
- Ventilation-perfusion scanning to rule out chronic thromboembolic disease
- Blood tests including NT-proBNP, HIV testing, liver function tests, and autoimmune markers If PAH is suspected, the definitive diagnosis requires right heart catheterization, which must demonstrate a mean pulmonary artery pressure ≥25 mmHg at rest, pulmonary capillary wedge pressure ≤15 mmHg, and pulmonary vascular resistance >3 Wood units, as recommended by the American College of Radiology 1. During catheterization, vasoreactivity testing with inhaled nitric oxide, intravenous epoprostenol, or adenosine should be performed to identify patients who might respond to calcium channel blockers 1. After confirming PAH, functional assessment including a 6-minute walk test and cardiopulmonary exercise testing helps determine disease severity and prognosis, as suggested by the American Heart Association and American Thoracic Society 1. This comprehensive diagnostic approach is essential because PAH is often diagnosed late in its course, and early detection allows for timely intervention that can significantly improve outcomes, as emphasized in the updated ACCP evidence-based clinical practice guidelines 1.
From the Research
Diagnostic Steps for Pulmonary Arterial Hypertension (PAH)
The diagnosis of PAH involves a stepwise approach to discern patients who need to be referred to a PH centre and undergo invasive haemodynamic assessment 2. The following are the key diagnostic steps:
- Clinical history and physical examination to identify signs of right heart failure and pulmonary vascular disease
- Noninvasive tests such as electrocardiogram (ECG), chest radiography, transthoracic Doppler echocardiography, pulmonary function tests, arterial blood gases, ventilation and perfusion lung scan, and high-resolution CT of the lung to define the population of patients who may have PAH 3, 4
- Right heart catheterization to establish the diagnosis, distinguish pulmonary arterial from pulmonary venous hypertension, and assess pulmonary hemodynamics 2, 3, 5
- Assessment of acute vasoreactivity during catheterization to determine the appropriate therapy for an individual patient 5
- Evaluation of disease severity using functional class, exercise capacity, pulmonary hemodynamics, acute vasoreactivity, right ventricular function, and biomarkers such as brain natriuretic peptide, endothelin-1, uric acid, and troponin levels 6, 5
Invasive Haemodynamic Assessment
Invasive haemodynamic assessment is required to establish the diagnosis of PAH and distinguish it from other forms of pulmonary hypertension 2, 3. The assessment includes:
- Measurement of mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) to diagnose pre-capillary PH, isolated post-capillary PH, and combined post- and pre-capillary PH 2
- Assessment of pulmonary arterial wedge pressure (PAWP) to distinguish pulmonary arterial from pulmonary venous hypertension 2
Referral to a PH Centre
Patients with a high probability of severe pulmonary vascular disease, especially those with signs of right heart failure, should be referred to a PH centre for further evaluation and management 2. A fast-track referral is recommended at any point during the clinical workup if there is a high suspicion of PAH 2.