Pulmonary Artery and Vein Morphology as an Imaging Biomarker for the Diagnosis of Pulmonary Hypertension

<b>Background/Objectives</b>: To evaluate whether peripheral pulmonary artery and vein morphology improves image-based diagnosis of pulmonary hypertension (PH), in accordance with the recently updated hemodynamic definition. <b>Methods</b>: 229 patients underwent CT pulmonary angiography (CTPA) within 30 days of RHC. Pulmonary vessels ranging between 2 and 10 mm in diameter were extracted and labeled as either arteries or veins by an independently validated fully automated algorithm. Segmentation labels were validated by a radiologist. <b>Results</b>: The segmentation algorithm reached a median accuracy of 90%, aligning with the radiologist's assessments. Vessel density of pulmonary arteries with diameters between 6 and 10 mm was higher in patients with versus those without PH (median [inter-quartile range]: 8.9 [6.1-10.8] 1/L vs. 6.2 [3.1-7.0] 1/L; <i>p</i> = 0.007). Artery-to-vein ratio was higher in PH (1.32 [0.93-2.06] vs. 0.88 [0.48-1.17], <i>p</i> = 0.004). The artery-to-vein ratio for vessels with diameters between 6 and 10 mm identified PH with an AUC of 0.73 (95% CI: 0.60-0.87). Combining this readout with the DMPA resulted in a numerically higher AUC (sole DMPA AUC: 0.79 (95% CI: 0.68-0.90)) vs. DMPA + artery-to-vein ratio for vessels with diameters of 6-10 mm: 0.81 (95% CI: 0.71-0.92); however, this improvement was not statistically significant (<i>p</i> = 0.4). <b>Conclusions</b>: PH is associated with an increased ratio of peripheral pulmonary arteries to veins within the 6-10 mm diameter range. Pulmonary vascular morphology may complement the established morphological criterion of MPA diameter and improve the diagnostic accuracy of PH on CT.