Lung microvasculopathy in chronic thromboembolic pulmonary hypertension: high-resolution findings with photon-counting detector CT in 29 patients

Abstract Purpose To evaluate CT findings suggestive of lung microvasculopathy in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Materials and methods Twenty-nine patients were scanned with high-spatial resolution on a photon-counting detector (PCD)-CT unit. A maximum of three pairs per patient, each composed of hyper- and hypo-attenuating areas of mosaic perfusion, were selected. Results Comparative analysis of the 86 selected pairs showed: (a) a higher frequency of ill-defined micronodules ( p = 0.008), lobular ground-glass opacities ( p = 0.01) and haziness ( p = 0.003) in hypoattenuated areas; (b) there was no significant difference in the frequency of neovascularity ( p = 0.43). Similar trends were observed in hypoattenuating areas of the 66 pairs studied in the 22 patients with central and peripheral CTEPH; an absence of ill-defined micronodules, lobular ground-glass opacities, and haziness in hyperattenuating areas was noticed in the 20 pairs studied in the 7 patients with peripheral CTEPH. Patients with a mean pulmonary artery pressure ≤ 42 mmHg (i.e., the median value of mean pulmonary artery pressure) had 45 pairs compared, showing a higher frequency of ill-defined micronodules ( p = 0.003) and haziness ( p < 0.001) in hypoattenuated areas, together with a higher frequency of subpleural systemic-to-pulmonary anastomoses ( p = 0.02). There were no statistical differences in the frequency of CT findings between hypo- and hyper-attenuating areas in the 41 pairs of patients with a mean pulmonary artery pressure > 42 mm Hg. Conclusion CT features suggestive of microvasculopathy were more frequent in areas of hypoperfusion, with a trend toward homogenization of CT findings in patients with severe PH. Key Points Question Lung microvascular lesions play a crucial role in the origin of residual pulmonary hypertension after successful thromboendarterectomy, currently beyond the scope of imaging . Findings The expected morphological abnormalities at the level of distal pulmonary circulation in CTEPH were found to be depictable in each zone of mosaic perfusion . Clinical relevance This study suggests that the high-spatial resolution of PCD-CT has the capability of approaching the complex pathophysiology of small-vessel disease in CTEPH, providing important information prior to therapeutic decisions . Graphical Abstract