Initial Evaluation for CTEPH
Any patient with unexplained pulmonary hypertension should undergo ventilation/perfusion (V/Q) lung scanning as the primary screening test to exclude CTEPH, as a normal V/Q scan effectively rules out the diagnosis with 90-100% sensitivity. 1, 2
Algorithmic Approach to Initial Evaluation
Step 1: Clinical Screening
Evaluate patients in two key scenarios:
- Post-PE patients: Those with persistent or new dyspnea, exercise intolerance, or signs of right heart failure 3-6 months after acute pulmonary embolism 2, 3
- Unexplained PH patients: Any patient presenting with pulmonary hypertension of unclear etiology 1, 2
High-risk features warranting evaluation include: history of recurrent PE, prior splenectomy, ventriculoatrial shunts, myeloproliferative disorders, chronic inflammatory bowel disease, or permanent intravenous catheters 4
Step 2: Echocardiographic Assessment
Perform transthoracic echocardiography to:
- Screen for presence and severity of pulmonary hypertension using peak tricuspid regurgitation velocity (TRV)
- Assess right ventricular function and dysfunction
- Important caveat: Echocardiography alone is insufficient for diagnosis—it serves only as a screening tool 4
Step 3: V/Q Lung Scanning (Critical Screening Test)
This is the mandatory next step for any patient with suspected CTEPH:
- A normal V/Q scan rules out CTEPH with near 100% negative predictive value 1, 2, 5
- Segmental or larger perfusion defects warrant further investigation
- V/Q scanning is superior to CT pulmonary angiography for screening, as CT can appear relatively normal despite significant V/Q abnormalities 4
Step 4: CT Pulmonary Angiography
Indicated when V/Q scan shows perfusion defects or is indeterminate:
- Look for chronic thromboembolic changes: webs, bands, intraluminal filling defects, complete vessel occlusion, mosaic perfusion pattern
- Critical limitation: Even modern multirow CT cannot exclude operable CTEPH if normal 1, 2
Step 5: Referral to Expert Center
Once V/Q and/or CT show findings compatible with CTEPH, immediate referral to a specialized CTEPH center is mandatory before proceeding with invasive testing 1, 2. This prevents:
- Unnecessary repeated procedures
- Suboptimal risk assessment
- Delays in definitive treatment planning
Step 6: Confirmatory Testing at Expert Center
Right heart catheterization (required for diagnosis):
- Confirms pre-capillary pulmonary hypertension:
Conventional pulmonary angiography:
- Gold standard for defining vascular anatomy and surgical accessibility
- Shows characteristic findings: pouches, webs, bands, vessel cutoffs, irregular vessel contours 4
- Essential for operative planning
Additional workup at expert center:
- Coronary angiography if surgical candidate with coronary risk factors 1, 2
- Pulmonary function testing and arterial blood gases 4
- Exclude other causes of PH (left heart disease, parenchymal lung disease)
Common Pitfalls to Avoid
Do not rely on CT alone for screening—V/Q scanning remains superior for detection 4
Do not perform invasive testing at referring hospitals—RHC and pulmonary angiography should be done at the expert center to minimize risks and avoid repeated procedures 1, 2
Do not assume absence of PE history excludes CTEPH—many patients develop CTEPH without clinically apparent prior pulmonary embolism 1, 2
Do not use echocardiography alone to diagnose or exclude CTEPH—hemodynamic confirmation by RHC is mandatory 4
Diagnostic Criteria Summary
Final CTEPH diagnosis requires ALL three elements: