Normal ARPHT Echo and Pulmonary Hypertension
A normal or "low probability" echocardiogram does NOT rule out pulmonary hypertension, and echocardiography alone is never sufficient to make treatment decisions—right heart catheterization remains the only definitive diagnostic test. 1
Why Echocardiography Cannot Exclude PH
Echocardiography has significant limitations in both sensitivity and specificity for detecting pulmonary hypertension:
- Tricuspid regurgitation velocity (TRV) is not measurable in 46-61% of patients, making RVSP estimation impossible in a large proportion of cases 2, 3
- In patients with severe tricuspid regurgitation, TRV may be significantly underestimated and cannot be used to exclude PH 1
- Doppler-derived pressure estimation may be inaccurate in individual patients, with echocardiography underestimating systolic PAP by a mean of 11 mmHg, and underestimating by ≥20 mmHg in up to 31% of patients 4
- In patients with lung disease (especially COPD), RVSP values are notoriously inaccurate due to suboptimal acoustic imaging windows 2
Clinical Management Based on Echocardiographic Probability
The ESC/ERS guidelines provide a risk-stratified approach based on clinical context:
For Symptomatic Patients WITHOUT Risk Factors:
- Low probability echo: Consider alternative diagnoses 1, 5
- Intermediate probability echo: Further investigation of PH may be considered 1
- High probability echo: Further investigation including right heart catheterization is recommended 1
For Symptomatic Patients WITH Risk Factors or Associated Conditions:
- Low probability echo: Echocardiographic follow-up should be considered (Class IIa) 5
- Intermediate probability echo: Further assessment including RHC should be considered 1, 5
- High probability echo: Further investigation including RHC is recommended 1
Risk factors and associated conditions include: connective tissue diseases, congenital heart disease, portal hypertension/liver disease, HIV infection, history of stimulant use, and thromboembolic disease history 5
When to Pursue Further Workup Despite Normal Echo
If clinical suspicion remains high based on symptoms and risk factors, initiate comprehensive PH workup including:
- Complete blood count, metabolic panel, thyroid function, NT-proBNP 5
- Autoimmune serologies 5
- Pulmonary function tests 5
- High-resolution CT chest or CT angiography 5
- Ventilation/perfusion scan (essential to exclude chronic thromboembolic PH, which has 90-100% sensitivity with V/Q scanning) 1, 5
- Six-minute walk test 5
- Sleep study evaluation 5
Critical Pitfalls to Avoid
Do not rely solely on TRV or estimated PASP for diagnosis—consider the full clinical context and additional echocardiographic variables including RV/LV basal diameter ratio >1.0, interventricular septal flattening, RV outflow tract acceleration time <105 msec, early diastolic pulmonary regurgitation velocity >2.2 m/sec, main PA diameter >25 mm, IVC diameter >21 mm with decreased inspiratory collapse, and right atrial area >18 cm² 5, 4
Exercise Doppler echocardiography is NOT recommended for screening of PH (Class III recommendation) 5
In one study of COPD patients being evaluated for bronchoscopic lung volume reduction, 88% of patients with suspected PH based on echocardiography (RVSP >45 mmHg) did NOT have significant PH on right heart catheterization 2
Definitive Diagnosis
Right heart catheterization is the only definitive method to diagnose or exclude pulmonary hypertension and should be performed when high probability echocardiogram is present in symptomatic patients, or when intermediate probability echocardiogram with risk factors/associated conditions is present 5, 6
When treatment of PH itself is being considered, echocardiography alone is not sufficient to support a treatment decision and cardiac catheterization is required 1