Mildly elevated pulmonary vascular resistance and worsened survival in PH-ILD: an opportunity for earlier diagnosis and intervention?
Pulmonary hypertension (PH) is a feared complication of interstitial lung disease (ILD) owing to increased risk for hospitalisation and mortality among affected patients. The development of PH in ILD is attributed to several pathobiological mechanisms that often converge to remodel pulmonary arterioles including hypoxic pulmonary vasoconstriction, endothelial dysfunction, inflammation, increased oxidant stress and the pathogenic effects of parenchymal fibrosis on the alveolar-capillary interface.1 The classical definition of precapillary PH used a mean pulmonary arterial pressure (mPAP) ≥25 mm Hg and pulmonary vascular resistance (PVR) ≥3 Wood units (WU), but these haemodynamic criteria were based largely on consensus opinion in the absence of normative data or information on the association between cardiopulmonary hemodynamics and outcomes. A retrospective meta-analysis involving data from healthy volunteers suggested that the upper limit of normal mPAP is ~20 mm Hg, which converged w