Severe pulmonary hypertension (PH) is not common even in patients with severe chronic lung disease (CLD) but data on hemodynamic characteristics among patients with severe CLD is scarce. All adult patients who had right heart catheterization for lung transplant assessment for severe CLD in the only lung transplant service and for PAH management in the only tertiary pulmonary hypertension service in Hong Kong from 2010 to 2020 were included and classified into CLD group and PAH group. Patient characteristics and hemodynamic parameters were analyzed. There were 153 patients included with 106 patients in the CLD group and 47 in the PAH group. There were only 19.8% of the patients in the CLD group had severe pulmonary hypertension. Patients in the CLD group had significantly lower systolic pulmonary arterial pressure (PAPs), lower mean pulmonary arterial pressure (PAPm), higher cardiac index, and lower PVR when compared with the PAH group ( p < 0.001). The area under curve (AUC) of PAPs, PAPm, and PVR were excellent, 0.973, 0.970, and 0.938, respectively for discrimination between CLD and PAH on receiver operator characteristics curve analysis. Optimal cutoff values were 55.5 mmHg, 35.5 mmHg, and 6.1 Wood Units for PAPs, PAPm, and PVR with Youden Index 0.85, 0.80, and 0.82, respectively. There were distinct hemodynamic characteristics between the CLD group and the PAH group. Systolic pulmonary arterial pressure, mean pulmonary arterial pressure, and pulmonary vascular resistance are useful to discriminate between the phenotype of severe CLD and PAH.

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