Different Definitions Of Pulmonary Hypertension In Interstitial Lung Disease: A Prognostic Evaluation

Background: Although elevated mean pulmonary artery pressure (MPAP, defined as MPAP≥21 or MPAP≥25 mmHg) is an important prognostic indicator in idiopathic pulmonary fibrosis (IPF), little is known about the prevalence rate and the prognostic impact of those MPAP values in all interstitial lung disease (ILD). Objective: To evaluate two definitions, MPAP≥21 and MPAP≥25 mmHg, for PH as prognostic indicators in ILD. Methods: We retrospectively analyzed the consecutive patients with ILD who underwent RHC at initial evaluation from April 2007 to April 2018 in our hospital. Missing data were handled using multiple imputation. We investigated each of MPAP≥21 and MPAP≥25 as prognostic indicators for mortality rate using Cox hazard model with adjustment for age, gender, FVC, DLco, and IPF diagnosis. Results: 925 cases (66% male, mean age 66 years old, percent predicted FVC 81%, percent predicted DLco 63%) were studied. They included IPF (n=421), connective tissue disease related ILD (n=221), and unclassifiable idiopathic interstitial pneumonia (n=199). The prevalence of elevated MPAP (≥21 and ≥25 mmHg) in non-IPF (21% and 9%) was similar to those in IPF patients (24% and 10%). In ILD, Cox hazard model showed that MPAP≥21 and MPAP≥25 were significant prognostic indicators [adjusted HR (aHR) 1.39, p<0.001, c-index 0.79, and 1.98, p<0.001, 0.79, respectively]. Whereas in non-IPF, MPAP≥25 was also a significant prognostic indicator (aHR 1.72, p=0.04), but MPAP≥21 was not (aHR 1.38, p=0.1). Conclusions: Both MPAP≥25 and MPAP≥21 were predictors of adverse outcomes in all ILD, but MPAP≥21 was not when restricted to non-IPF.