Severe pulmonary hypertension in lung disease: phenotypes and response to treatment.

Pulmonary hypertension (PH) due to lung disease (World Health Organization (WHO) group 3) is common, but severe PH, arbitrarily defined as mean pulmonary artery pressure ≥35 mmHg is reported in only a small proportion. Whether these should be treated as patients in WHO group 1 (i.e. pulmonary arterial hypertension) with PH-targeted therapies is unknown. We compared the phenotypic characteristics and outcomes of 118 incident patients with severe PH and lung disease with 74 idiopathic pulmonary arterial hypertension (IPAH) patients, all treated with pulmonary vasodilators. Lung disease patients were older, more hypoxaemic, and had lower gas transfer, worse New York Heart Association functional class and lower 6-min walking distance (6MWD) than IPAH patients. Poorer survival in those with lung disease was driven by the interstitial lung disease (ILD) cohort. In contrast to IPAH, where significant improvements in 6MWD and N-terminal pro-brain natruiretic peptide (NT-proBNP) occurred, PH therapy in severe PH lung disease did not lead to improvement in 6MWD or functional class, but neither was deterioration seen. NT-proBNP decreased from 2200 to 1596 pg·mL(-1) (p=0.015). Response varied by lung disease phenotype, with poorer outcomes in patients with ILD and emphysema with preserved forced expiratory volume in 1 s. Further study is required to investigate whether vasodilator therapy may delay disease progression in severe PH with lung disease.