Mimickers of chronic thromboembolic pulmonary hypertension on imaging tests: a review

Abstract

Chronic thromboembolic pulmonary hypertension (CTEPH) is caused by mechanical obstruction of large pulmonary arteries secondary to one or more episodes of pulmonary embolism. Ventilation perfusion scan is the recommended initial screening test for this condition and typically shows multiple large mismatched perfusion defects. However, not all patients with an abnormal ventilation perfusion scan have CTEPH since there are other conditions that be associated with a positive ventilation perfusion scan. These conditions include in situ thrombosis, pulmonary artery sarcoma, fibrosing mediastinitis, pulmonary vasculitis and sarcoidosis, among others. Although these conditions cannot be distinguished from CTEPH using a ventilation perfusion scan, they have certain characteristic radiological features that can be demonstrated on other imaging techniques such as computed tomography scan and can help in differentiation of these conditions. In this review, we have summarized some key clinical and radiological features that can help differentiate CTEPH from the CTEPH mimics.

Beyond the clot: perfusion imaging of the pulmonary vasculature after COVID-19

“…It is worth being mindful, when using any perfusion technique, that classical segmental ventilation-perfusion mismatches (figure 5B) could occur with non-thrombotic conditions of the vascular tree, such as vasculitis and sarcoidosis. 49 In the context of COVID-19 follow-up, some…”

“…It is worth being mindful, when using any perfusion technique, that classical segmental ventilation–perfusion mismatches ( figure 5B ) could occur with non-thrombotic conditions of the vascular tree, such as vasculitis and sarcoidosis. 49 In the context of COVID-19 follow-up, some patterns of interstitial morphology, particularly those with large cystic air spaces, might show a relative ventilation–perfusion mismatch, with perfusion affected more than ventilation, 50 , 51 although this is easily resolved with modern SPECT-CT imaging with a CT template to corroborate lung morphology.…”

Optimizing the diagnosis and assessment of chronic thromboembolic pulmonary hypertension with advancing imaging modalities

“…6, including large-and mediumvessel pulmonary arteritis, pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis, pulmonary artery sarcoma, external compression due to bronchogenic carcinoma, sarcoidosis or fibrosing mediastinitis, and congenital pulmonary vascular abnormalities. 5,[26][27][28][29][30] INSERT FIGURE 6 HERE Several disadvantages can be associated with CT as unlike V/Q scintigraphy, CTPA alone cannot exclude CTEPH. 3 Also some of the practicalities of the technique can be limiting, such as the use of iodinated contrast which can be problematic for some patients as noted above, and which requires good intravenous access, ideally using the antecubital vein with an 18-or -20 gauge catheter.…”

Chronic Thromboembolic Pulmonary Hypertension: the Bedside

“…A positive V/Q scan is insufficient for diagnosis or estimation of the disease burden. Due to recanalization or remodeling of occluded vessels allowing for the penetration of radioisotope into the periphery with distal perfusion, the V/Q scan can underestimate the extent of disease [43]. Thus, a single segmental mismatch should raise suspicion for possible CTEPH.…”