Researchers Consider Existence of Pulmonary Vascular Phenotype Among COPD Patients

Chronic obstructive pulmonary disease (COPD) often affects pulmonary vessels and mild pulmonary hypertension (PH) is a common feature of COPD. Researchers reviewed the most updated concepts of the pulmonary vascular changes in COPD and concluded that certain subgroups of COPD patients with pulmonary vascular phenotypes may profit from targeted pulmonary arterial hypertension (PAH) therapy. The findings were published in the American Journal of Respiratory and Critical Care Medicine.

The authors noted that certain mechanisms alone or in combination can alter pulmonary circulation of patients with COPD, including tobacco smoking, endothelial dysfunction, structural and functional lung abnormalities, inflammation, and genetic background. The authors assessed the impact of these mechanisms, as well as defining and classifying pulmonary vascular disease in COPD.

Group 1: PAH

Group 2: PH caused by left heart disease

Group 3: PH caused by lung diseases and/or hypoxia

Group 4: Chronic thromboembolic PH

Group 5: PH with unclear and/or multifactorial mechanisms

The diagnostic classification of PH proposed 5 distinct groups:

“The presence of mild airflow limitation (FEV1, >60%), mild or missing lung parenchymal abnormalities on high resolution chest computed tomography, and a primary cardiovascular limitation found during cardiopulmonary exercise testing favor classification into group 1 (PAH), whereas more severe airflow limitation (FEV1, <60%), significant lung parenchymal abnormalities on high resolution chest computed tomography, and a ventilatory limitation during exercise testing favor group 3 PH,” explained the authors.

The authors also considered whether a pulmonary vascular phenotype COPD exists, finding that the there is a tentative working definition of the pulmonary vascular phenotype of COPD based on the presence of severe PH with moderate airflow limitation and no hypercapnia, very low diffusing capacity of the lungs for carbon monoxide (D_Lco), and circulatory exercise limitation and/or progressive right heart failure, according to the report.

“The pulmonary circulation is often abnormal in patients with COPD. Although their [pulmonary arterial pressure] elevation is generally mild, it is associated with a higher frequency of severe exacerbations and hospitalizations as well as poor survival,” concluded the authors. “However, there is a subgroup of patients with COPD characterized by moderate airflow limitation, severe precapillary PH, relatively low PaCO2 levels, strongly impaired D_Lco, progressive right heart failure, and very poor survival.”

The report called for more clinical attention and directed research regarding pulmonary circulation and COPD in the future in order to address the gaps in knowledge and data.

Reference

Kovacs G, Agusti A, Barberà JA, et al. Pulmonary vascular involvement in chronic obstructive pulmonary disease. Is there a pulmonary vascular phenotype? Am J Respir Crit. 2018;198(8):1000-1011. doi: 10.1164/rccm.201801-0095PP.