Diagnostic evaluation of chronic thromboembolic pulmonary hypertension (CTEPH)

PE: pulmonary embolus; V/Q: ventilation/perfusion; CTPA: computed tomographic pulmonary angiography; PH: pulmonary hypertension; MRPA: magnetic resonance pulmonary angiography; DSPA: digital subtraction pulmonary angiography.
* CTEPH may be suspected during the investigative work-up of pulmonary hypertension or during a formal evaluation for the etiology after the diagnosis of PH is made on right heart catheterization so that pulmonary hypertension can be classified appropriately. Importantly, the diagnosis of CTEPH cannot be made without a diagnosis of pulmonary hypertension.
¶ A normal or low probability V/Q scan accurately excludes chronic thromboembolic disease. However, V/Q scanning may understate the extent of central pulmonary vascular obstruction and is not specific since other obstructive disorders can cause mismatched defects.
Δ In patients with suspected CTEPH who have a known contrast allergy or renal insufficiency, we make every attempt to perform contrast-enhanced studies, including CTPA since defining the location and extent of the thromboembolic obstruction is a critical step in the diagnostic assessment and evaluation for pulmonary thromboendarterectomy. Common findings of CTEPH on CTPA include thromboembolic material adherent to the vessel wall, disparity in segmental vessel size, bronchial artery collateral flow, parenchymal abnormalities consistent with prior infarcts, and mosaic attenuation of the pulmonary parenchyma. However, the absence of such findings does not exclude CTEPH such that when a CTPA is not consistent with CTEPH but a V/Q scan is consistent with CTEPH, referral to a CTEPH center is still appropriate.
◊ MRPA is not routinely used as a diagnostic tool for CTEPH unless V/Q scan, CTPA, or DSPA cannot be performed or are indeterminate.
§ CTEPH is by far the most common cause of PH due to pulmonary artery obstruction. Other causes are rare.
¥ DSPA is the gold standard for the diagnosis of CTEPH. However, it is best performed in CTEPH centers experienced in performing pulmonary thromboendarterectomy.
‡ The diagnosis of CTEPH cannot be made unless other causes of PH have been excluded and thromboembolic material is the assumed cause of PH.