Researchers from Europe described a group of patients with a distinct, presumably smoking-related form of pulmonary hypertension accompanied by low diffusion capacity for carbon monoxide that resembles patients with pulmonary hypertension due to lung disease rather than classical idiopathic pulmonary arterial hypertension (PAH).
“These observations have pathogenetic, diagnostic, and therapeutic implications, which require further exploration,” the researchers wrote. A low diffusion capacity for carbon monoxide and smoking history are increasingly associated with a new lung phenotype.
Here, a team of researchers led by Michael Halank, MD, from the Clinic of Respiratory Medicine at Hannover Medical School in Germany analyzed data from 2 European pulmonary hypertension registries to identify patients with idiopathic PAH and a diffusion capacity for carbon monoxide of less than 45% predicted plus smoking history.
The researchers compared the characteristics of these patients in terms of response to therapy and survival to those with classical idiopathic PAH and those with group 3 pulmonary hypertension ie pulmonary hypertension due to lung disease.
The results showed that most patients with idiopathic PAH and a lung phenotype had normal spirometry findings, a severe reduction in diffusion capacity for carbon monoxide, and no or a mild degree of parenchymal lung involvement.
Following treatment, 54% of patients with classical idiopathic PAH showed improvements in the World Health Organization (WHO) functional class. Improvements were observed in less than a third (26%) of patients with idiopathic PAH and a lung phenotype and in 22% of those with group 3 pulmonary hypertension.
Read more about the WHO classification of PAH
Improvements in 6-Minute Walk Distance scores also followed the same trend for these 3 groups of patients with 63 m, 25 m, and 23 m respectively as did the reductions in N-terminal-pro-brain-natriuretic-peptide with 58%, 27%, and 16% respectively for each patient group.
The survival of patients with idiopathic PAH and a lung phenotype and patients with group 3 pulmonary hypertension was worse than the survival of patients with classical idiopathic PAH.
“Our observations support the hypothesis that there is a distinct smoking-related pulmonary vasculopathy, which needs to be further investigated,” the researchers concluded.
Hoeper MM, Dwivedi K, Pausch C, et al. Phenotyping of idiopathic pulmonary arterial hypertension: a registry analysis. Lancet Respir Med. Published online June 28, 2022. doi:10.1016/S2213-2600(22)00097-2