Table 1.

Comparison of diagnostic tests used in the evaluation for CTEPH

Diagnostic test	Findings in CTEPH	Advantages	Disadvantages/limitations
Imaging
Echocardiogram	• Evidence of PH or RH strain: RV dilation, RV systolic dysfunction, RA dilation, PASP elevation, flattening of interventricular septum	• Non-invasive • No exposure to radiation or contrast dye	• Not specific or sensitive to CTEPH • Misses CTED
VQ	• Mismatched defects in perfusion and ventilation defects • Heterogeneity of perfusion	• Highest sensitivity to rule out CTEPH • Less radiation exposure • No contrast dye exposure	• Limited access as performed in nuclear medicine • Unable to provide alternative diagnosis • Sensitive but not specific for CTEPH
CT PA	• Pulmonary arteries: PA dilation, webs/bands, eccentric filling defects, mural thrombi, luminal narrowing with poststenotic dilation, complete occlusion, pouch defects • Heart: RV dilation, septal flattening • Lungs: mosaic attenuation, large bronchial artery collaterals	• Defining vascular anatomy can aid in surgical assessment • Provides data on screening for concomitant lung disease/alternate diagnosis that can aid in surgical risk assessment	• CTEPH findings can sometimes be subtle and require expertise and attention to diagnose • Exposure to IV contrast • Exposure to radiation • Less sensitive than VQ (neg CT does not exclude CTEPH)
Invasive testing
Pulmonary angiogram	• Ring lesions/ring-like stenosis • Poststenotic dilation • Total occlusion • Vascular webs	• Provides complete hemodynamic assessment and aids in surgical planning	• Invasive
RH catheterization	• mPAP ≥25 mm Hg • Wedge ≤15 mm Hg	• Provides complete hemodynamic assessment and aids in surgical planning	• Invasive
Functional testing
Cardiopulmonary exercise testing	• Increased dead space ventilation with widening A-a gradient, flattened stroke volume in response to exercise	• Can detect limitations in function and cardiopulmonary response to exercise	• Requires specialized testing unit • Requires arterial blood gas measurement
6-minute walk test	• Functional limitations and decreased oxygen saturation with exercise	• Simple to perform, low cost, minimal risk	• Not specific to CTEPH

IV, intravenous; PASP, pulmonary artery systolic pressure; RA, right atrium.