Abstract
Severe diffusion impairment in pulmonary arterial hypertension (PAH), particularly in idiopathic PAH (IPAH), has garnered considerable attention. However, comprehensive data on low diffusion capacity of the lungs for carbon monoxide (DLCO) with preserved lung function remain limited in broader pulmonary hypertension (PH) cohorts. We analyzed patients with PH, preserved lung function, low DLCO, and available computed tomography (CT) scans. The analysis included 117 patients, with 34% cases of combined pulmonary fibrosis and emphysema (CPFE), 22% IPAH, 15% interstitial lung disease (ILD), 9% pulmonary veno-occlusive disease (PVOD), and 8% connective tissue disease (CTD). Based on hemodynamic and CT imaging features, the overall population could be broadly categorized into two phenotypic patterns. "Parenchymal Type" (n = 81; 69%), predominantly consisted of CPFE and ILD, with an average age of 69 ± 9 years, 89% male. The median mean pulmonary arterial pressure (mPAP) was 39 mmHg, and lung abnormalities observed included emphysema, interstitial fibrosis, and diffuse ground-glass opacities (GGO). "Vascular Type" (n = 36; 31%), mainly composed of PVOD and CTD cases. with average age of 52 ± 19 years, 64% female, median mPAP of 53 mmHg and centrilobular GGO (78%). IPAH patients were distributed across both phenotypic categories, exhibiting mixed characteristics of the "Parenchymal Type" and "Vascular Type". The 5-year survival rate for the overall patient cohort was 31%. In conclusion, PH patients with low DLCO and preserved lung function represent two distinct phenotypic patterns and are associated with a poor prognosis.