Pulmonary vascular involvement in patients with interstitial lung disease (ILD): a distinct phenotype

<bold>Background:</bold> Pulmonary hypertension (PH) may occur in a minority of patients with ILD influencing prognosis. Pulmonary vascular dysfunction with high vascular resistance in absence of PH has been observed in patients with ILD and seems to favor development of PH. <bold>Aim:</bold> To characterize ILD patients with or without PH but initial vascular dysfunction at right heart catheterization. <bold>Methods:</bold> ILD patients undergoing lung transplant evaluation between 2015-2023 and categorized based to presence or absence (noPH) of PH, were included. Among NoPH, patients with high(H) pulmonary vascular resistances [PVR,>2 woods unit(WU)] were detected and characterized. <bold>Results:</bold> 142 ILD patients were included. 53/142(37%) presented PH. Among noPH, 73/89(82%) presented HPVR. Compared to noPH, PH presented lower diffusing capacity for lung monoxide [22(15-30)Vs.26%pred.(18-35),p=0.002], higher Wedge pressure (WP) [8(6.5–11) Vs 6mmHg(5-8),p<0.0001] and higher PVR[4.4(3.2–6.6) Vs.2.9WU(2.5 – 3.4),p<0.0001]. At CT scan, PH presented larger diameter in pulmonary artery(PA) trunk [35(32-38)Vs.31mm(28-34),p<0.0001] and higher PA/Aorta ratio [1.07(0.97-1.17) Vs.0.95(0.89-1),p=0.0002] compared to noPH. HPVR presented higher WP [7(5-9) Vs 4.5mmHg(3-6),p=0.001], higher PA mean pressure [16(15-19) Vs.12(10-15),p= 0.003] and lower cardiac index [CI,2.9(2.5–3.3) Vs.3.3l/min/cm2(2.8-4.2),p=0.01] compared to noPH with low PVR. <bold>Conclusions:</bold> A minority of advanced ILD patients showed PH, with the majority displaying increased high PVR without PH. These patients presented a low CI value and higher WP, which are associated with left ventricular dysfunction. Further evaluation regarding vascular remodeling is still needed.