PVR and pulmonary arterial hypertension: In parallel, a PCA was performed using four clinical parameters including mPAP, mRAP, PVR and NT-proBNP, resulting in significant separation of IPAH versus CTD-PAH and CTEPH, and a significant clustering of survival subgroups in Dim1, which was dominated by mPAP and PVR (p = 0.00014; Fig. 5b, d; Additional file 1: Fig. 4B).