Chronic thromboembolic pulmonary hypertension: a review of imaging findings on ECG gated pulmonary circulation MDCTA

Clinical History

A 63-year-old female patient presented recurrent and progressive dyspnoea. Clinical examination revealed lower legs swelling. History included prior pulmonary embolism. Echocardiography, combined ventilation perfusion scintigraphy, right cardiac catheterisation and CT angiography were performed.

Imaging Findings

Radiological evaluation by means of chest CT angiography revealed a filling defect in the right pulmonary artery (Fig. 1), smaller partial mural adherent defects in the branches for the left lower lobe and smaller webs in others (Fig. 2). Also, shunt circulation in the posterior basal segments of right lower lobe (Fig. 4) and bronchial shunt circulation in mediastinum were noted (Fig. 6). CT scan showed also enlarged pulmonary artery trunk and central branches. High resolution CT of lung parenchyma revealed the characteristic mosaic perfusion pattern (Fig. 5). Venous triplex examination showed no findings of deep venous thrombosis. Right cardiac catheterisation revealed high pressures in the pulmonary artery and echocardiography findings were right ventricle enlargement, hypertrophy, and moderate systolic dysfunction suggesting the diagnosis of severe pulmonary hypertension. Combined ventilation perfusion scintigraphy showed a mismatch between normal ventilation and non-perfused areas.

Discussion

Chronic thromboembolic pulmonary hypertension (CTEPH) is a treatable form of pulmonary hypertension which requires multimodality imaging for accurate diagnosis. Pulmonary hypertension is defined as elevation of pressure in pulmonary circulation higher than 25mmHg at rest and above 30mmHg during physical activity [1]. Catheterisation of the right side of the heart is the gold standard for the diagnosis. It confirms pulmonary hypertension by direct measurement of pulmonary pressures, resistance and cardiac output. [2] Echocardiography estimates peak velocity of tricuspid valve regurgitation, and detects right atrial and right ventricular dilatation, right ventricular systolic dysfunction and Doppler flow abnormalities in the right ventricular outflow tract. ECG-gated pulmonary circulation CT angiography is of great value for the diagnosis of CTEPH. The trunk of pulmonary artery has a diameter larger than 29mm and ratio pulmonary trunk: ascending aorta > 1:1. CTA reveals also the mural defects (thrombus) being attached to the vessel wall with eccentric position and obtuse angle, in contrast to the centrally located and with acute angle defects seen in acute pulmonary embolism patients [3]. Bronchial shunt circulation is of great importance and a highlight of CTEPH. Also imaging with intravenous contrast media, is mandatory for findings such as the webs due to prior pulmonary embolism [4]. A characteristic finding in lung parenchyma is the mosaic perfusion pattern caused by irregular lung perfusion. Parenchymal fibrosis, cavities, irregular peripheral linear densities and wedge-shaped areas —pulmonary infarction— in the periphery of the lung field are seen [5].

Differential Diagnosis List

Final Diagnosis

Chronic thromboembolic pulmonary hypertension.

URL:	https://eurorad.org/case/15721
DOI:	10.1594/EURORAD/CASE.15721
ISSN:	1563-4086