More on idiopathic pulmonary arterial hypertension with a low diffusing capacity

Abstract

Pulmonary arterial hypertension (PAH) is defined by the presence of pre-capillary pulmonary hypertension (PH) in the absence of underlying causes such as lung diseases, chronic thromboembolic pulmonary hypertension (CTEPH) or other rare conditions [1,2]. While the idiopathic form of PAH (IPAH) was originally described as a disease affecting primarily younger women [3,4], it is now increasingly being diagnosed in elderly patients, many of whom present with cardiopulmonary comorbidities, which can make the exact diagnostic classification of such patients difficult [5][6][7][8].In 2013, TRIP et al.[9] described a "new" IPAH phenotype of predominantly elderly men with severe pre-capillary PH and a low diffusing capacity of the lungs for carbon monoxide (DLCO). Most of these patients had a smoking history but relatively well-preserved lung function, and 32% had normal findings on chest computed tomography (CT). The authors discussed the possibility that their patients may have had a variant of combined pulmonary fibrosis and emphysema (CPFE), a disease characterised by a distinct CT pattern of upper-lobe-predominant emphysema and lower-lobe-predominant fibrosis with relatively well-preserved lung function, low DLCO, hypoxaemia and a high prevalence of PH [10,11]. Like the patients described by TRIP et al. [9], patients with CPFE are typically elderly men with a history of heavy smoking. The phenotype of the patients described by TRIP et al. [9] resembled CPFE, but the characteristic CT findings were absent, leading the authors to hypothesise that such patients may have a unique, smoking-related pulmonary vasculopathy. In a more recent paper, our group came to similar conclusions in patients with a low DLCO and combined pre-and post-capillary PH because of heart failure with preserved ejection fraction [12].

Idiopathic pulmonary arterial hypertension phenotypes determined by cluster analysis from the COMPERA registry

“…16, 29 −31 Apparently, this pulmonary vasculopathy can develop in patients with or without clinical and radiological signs of parenchymal lung disease. 29 Patients in Cluster 3 had a particularly poor survival, which is consistent with previous reports on patients with IPAH and low DLCO. 16,29,31 Further studies are needed to delineate the mechanisms underlying the survival differences between the clusters.…”

Mild parenchymal lung disease and/or low diffusion capacity impacts survival and treatment response in patients diagnosed with idiopathic pulmonary arterial hypertension

“…Whilst they included patients who had mild or moderate lung disease, we observed a similar distribution of DLCO %predicted in patients without any lung disease (IPAH no-LD , online supplement figure 2). Olsson et al subsequently described a subgroup of patients with IPAH with no parenchymal lung disease but severely reduced gas transfer (23). In keeping with these two studies, our cohort of IPAH no-LD patients with DLCO <45%predicted (IPAH DLCO<45 ) was older, more likely to have a smoking history and had a lower exercise capacity.…”

Characteristics of Japanese elderly patients with pulmonary arterial hypertension

“…Similarly, Olsson's study suggested that elderly I/H-PAH patients, who had a greater smoking history and more parenchymal lung disease, had a lower %DLco and more hypoxemia. They suggested that smoking damaged the capillaries of the lung, causing lower %DLco and poor oxygenation 3 .…”