Pulmonary Arterial Hypertension Diagnostics

Last updated: 17 March 2026
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Laboratory Tests and Ancillaries

Non-Invasive Diagnostic Tests for Pulmonary Hypertension Detection  

Electrocardiogram (ECG)  

An electrocardiogram may raise suspicion of pulmonary hypertension, provide prognostic information and detect arrhythmias and signs of left heart disease. ECG should be performed in patients with a suspicion of PAH to screen for cardiac anatomic problems and arrhythmias. This does not serve as an effective screening tool because of its low sensitivity but can assist in determining prognosis.  

The typical ECG abnormalities in patients with pulmonary hypertension include:

  • P pulmonale (P >0.25 mV in lead II)
  • Prolonged QTc interval (non-specific)
  • Right bundle branch block (RBBB) - complete or incomplete (qR or rSR patterns in V1)
  • Right or sagittal axis deviation (QRS axis >900 or indeterminable)
  • RV hypertrophy
  • RV strain pattern (ST depression or T-wave inversion in the right precordial V1-4 and inferior II, III, aVF leads)

Pulmonary Function Test (PFT) and Arterial Blood Gas (ABG)  

Initial work-up in patients suspected with pulmonary hypertension may include forced spirometry, body plethysmography, lung diffusion capacity for carbon monoxide (DLCO) and ABG. These help to distinguish between pulmonary hypertension groups and determine disease severity, assess comorbidities and the necessity for oxygen (O2) supplementation. These may be helpful in diagnosis based on evidence of irreversible airflow obstruction with increased residual volume and decreased diffusion capacity for carbon monoxide (40-80% of predicted value) and normal or increased CO2 tension. These can identify the presence of underlying airway or parenchymal lung disease.  

Blood Tests and Immunology  

Routine biochemistry, hematology and thyroid function tests are required in all patients. Liver function tests (LFTs) may be abnormal because of high hepatic venous pressure, liver disease and/or endothelin receptor antagonist (ERA) therapy. Hepatitis serology should be performed if clinical abnormalities are suspected. Thyroid disease is common in PAH and may develop during the course of the disease. Serological testing is required to detect underlying CTD, hepatitis and HIV. Patients with CTEPH should undergo thrombophilia screening, including antiphospholipid antibodies, anticardiolipin antibodies and lupus anticoagulant.

Biomarkers  

Examples of biomarkers are brain natriuretic peptide (BNP), N-terminal proBNP (NT-proBNP).  

Biomarkers may be considered if echocardiography cannot be performed. The presence of BNP and NT-proBNP correlates with the presence of PAH. Other biomarkers under investigation include atrial natriuretic peptide, endothelin-1, uric acid, troponin T, nitric oxide (NO), asymmetric dimethylarginine, cyclic guanosine monophosphate, D-dimer, and serotonin.  

Cardiopulmonary Exercise Testing 

Cardiopulmonary exercise testing helps to assess the underlying pathophysiologic mechanisms leading to exercise intolerance. Several parameters such as reduced peak oxygen uptake, an increased CO2 equivalent and lower end-tidal CO2 tension may suggest pulmonary hypertension. Cardiopulmonary exercise testing can also aid in diagnosing CTEPH even in patients with a low echocardiographic probability of pulmonary hypertension and it has also been proposed as a screening tool for pulmonary hypertension in patients with systemic sclerosis. 

Genetic Counseling  

Patients with sporadic or familial PAH or PVOD/pulmonary capillary hemangiomatosis (PCH) should be advised about the availability of genetic testing and counseling because of the strong possibility having a disease-causing mutation.

Imaging

Non-Invasive Diagnostic Tests for Pulmonary Hypertension Detection

Chest X-Ray  

A chest x-ray may also show evidence of underlying lung disease. Radiographic signs suggestive of PAH are enlarged main and hilar PA shadows with concomitant attenuation of peripheral pulmonary vascular marking (pruning). The extent of radiographic abnormalities is not representative of the severity of pulmonary hypertension.  

Transthoracic Doppler Echocardiography (TTE)  

Transthoracic Doppler echocardiography is the recommended first-line, non-invasive diagnostic tool in patients suspected with pulmonary hypertension. Echocardiography is the most useful imaging modality for detecting pulmonary hypertension and excluding cardiac disease. It is the most important non-invasive modality for obtaining comprehensive information on LV and RV anatomy and function, valvular abnormalities, and pulmonary circulation. It can estimate the PAP and provide information regarding the cause and consequences of PAH. This should be performed in asymptomatic patients to detect elevated PAP. An echocardiographic probability of pulmonary hypertension is based on an abnormal tricuspid regurgitation velocity (TRV) and the presence of other echocardiographic signs suggestive of pulmonary hypertension. A TRV of >2.8 m/s is the recommended threshold for echocardiographic probability of pulmonary hypertension. A TRV of >3.4 m/s indicates a high probability of pulmonary hypertension, regardless of any additional echocardiographic signs of pulmonary hypertension. TRV values between 2.9 and 3.4 m/s indicate an intermediate probability of pulmonary hypertension; however, if additional echocardiographic signs of pulmonary hypertension are present, the probability is considered high. A TRV of ≤2.8 m/s is associated with low probability of pulmonary hypertension; however, additional echocardiographic signs of pulmonary hypertension may increase the probability to intermediate.

Additional echocardiographic signs suggestive of pulmonary hypertension include:

  • Ventricles:
  • RV/LV basal diameter/area ratio of >1.0
  • Flattening of interventricular septum (LV eccentricity index [LVEI] >1.1 in systole and/or diastole)
  • Tricuspid annular plane systolic excursion (TAPSE)/systolic PAP (sPAP) ratio <0.55 mm/mmHg
  • PA
  • RV outflow tract (RVOT) acceleration time <105 milliseconds and/or mid-systolic notching
  • Early diastolic pulmonary regurgitation velocity >2.2 m/s
  • PA diameter > aortic root diameter; PA diameter >25 mm
  • Inferior vena cava (IVC) and right atrium (RA)
  • IVC diameter >21 mm with decreased inspiratory collapse
  • RA area (end-systole) >18 cm2

TTE assists in differential diagnosis of possible causes, in pulmonary hypertension class identification and in PAH evaluation.



Pulmonary Arterial Hypertension_DiagnosticsPulmonary Arterial Hypertension_Diagnostics




Ventilation/Perfusion Ratio  

The ventilation/perfusion ratio is a recommended screening method of choice in patients with unexplained pulmonary hypertension to look for CTEPH.  

High-resolution Computed Tomography (CT) Scan, Contrast-enhanced CT and Pulmonary Angiography  

High-resolution computed tomography (CT) scans, contrast-enhanced CT scans and pulmonary angiography provide important details on vascular, cardiac, parenchymal and mediastinal abnormalities, as well as prognostic information. High-resolution CT provides detailed views of the lung parenchyma. These facilitate the diagnosis of ILD, emphysema and PVOD. It must be noted that chest CT is preferred over chest radiography in patients with pulmonary hypertension because it provides more detailed information on pulmonary hypertension and can help identify underlying lung disease or specific associated conditions. The CT signs that are suggestive of pulmonary hypertension include an enlarged PA diameter, a PA-to-aorta ratio of >0.9, and enlarged right heart chambers. The CT signs that are highly predictive of pulmonary hypertension include a combination of PA diameter ≥30 mm, RVOT wall thickness ≥6 mm, and septal deviation ≥1400 or RV:LV ratio ≥1. These are the screening methods of choice for CTEPH. 

CT pulmonary angiography (CTPA) is recommended in the work-up of patients suspected with CTEPH to detect direct or indirect signs of CTEPH (eg filling defects, webs or bands in the PA, PA retraction or dilatation, mosaic perfusion, and enlarged bronchial arteries). Digital subtraction angiography (DSA) is used to confirm the diagnosis of CTEPH and to assess treatment options. High-resolution CT is recommended for current or former cigarette smokers who have a markedly reduced DLCO (below 45% of predicted). 

Cardiac Magnetic Resonance Imaging (cMRI) 

cMRI is the gold standard for the non-invasive assessment of RV function. It also provides accuracy in the assessment of RV size, morphology and function. It allows non-invasive assessment of blood flow, including stroke volume, CO, PA distensibility, and RV mass. This provides useful prognostic information in patients with PAH both at baseline and follow-up.

Abdominal Ultrasound  

Abdominal ultrasound may be useful for the identification of the clinical entities associated with PAH. It is recommended to screen for portal hypertension. Portal hypertension can be confirmed or excluded by measuring the gradient between the free and occluded (wedge) hepatic vein pressure at the time of RHC.  

Invasive Diagnostic Test for Pulmonary Hypertension Detection  

Right Heart Catheterization (RHC)  

Right heart catheterization is the gold standard to confirm the diagnosis and evaluate the severity of PAH and the gold standard to assess cardiopulmonary hemodynamics during exercise and to define exercise pulmonary hypertension. It is required to confirm the diagnosis of PAH and CTEPH, assess the severity of hemodynamic impairment, and undertake vasoreactivity testing of the pulmonary circulation. Prior to initiation of therapy, RHC should be ordered in all patients that are still suspected of PAH after non-invasive evaluation. It is useful in diagnosing occult shunts, CHD, and distal PA stenosis. This should be performed for confirmation of efficacy of PAH-specific drug therapy and to monitor response to therapy. Exercise RHC is used in the assessment of patients with unexplained dyspnea and normal testing hemodynamics to detect early pulmonary vascular disease (PVD) or left heart dysfunction.  

Diagnostic Tests for Pulmonary Hypertension Clinical Classification  

Two or more pathologies may co-exist, and any one may be contributory to or be the predominant cause of pulmonary hypertension; thus, an abnormality in one test does not preclude abnormality in another.

The following will help clarify the etiology of pulmonary hypertension:  

Ventilation and Perfusion (V/Q) Lung Scan  

Ventilation and perfusion lung scans may be able to differentiate CTEPH from IPAH. This is the screening method of choice for CTEPH because of its high sensitivity and specificity. A normal or low probability scan effectively excludes a diagnosis of CTEPH.  

Echocardiography  

Echocardiography is recommended in patients with liver disease or portal hypertension with signs and symptoms suspicious of pulmonary hypertension. This is used for screening of patients for liver transplant evaluation or transjugular portosystemic shunt.  

High-Resolution CT (HRCT) Scan of the Lung  

High-resolution CT scan of the lung assists in the diagnosis of ILD and emphysema. PVOD may be seen along with lymphadenopathy and pleural shadows and effusions. PCH may also become apparent.  

Pulmonary Angiography  

Pulmonary angiography is important in managing patients with CTEPH. This confirms the diagnosis and helps assess operability.  

Diagnostic Tests to Determine Associated Causes of PAH

  • Complete blood count (CBC), prothrombin time (PT), partial thromboplastin time (PTT), thyroid function
  • Thrombophilia screen including antiphospholipid antibodies (lupus anticoagulant, anticardiolipin antibodies)
  • Autoimmune screen consists of antinuclear antibodies (ANA), anti-centromere antibody, anti-SCL-70 and RNP. Patients with elevated ANA may need further serological assessment and rheumatology consultation
  • HIV test
  • LFTs, hepatitis serology
  • Abdominal ultrasound (to detect liver cirrhosis and/or portal hypertension)
  • Exercise capacity with the 6-minute walk test (6MWT)
  • Assess hemodynamics with RHC if it has not been done already
  • Clinical and hemodynamic assessments are important in the prognosis and consequent management