Compared with individuals with chronic obstructive pulmonary disease (COPD) with moderate pulmonary hypertension (PH) or without PH, those with acute PH-COPD have lower capillary density and significantly greater pulmonary microvessel muscularization, according to a study recently published in CHEST.

This study included 30 participants with COPD who underwent lung transplant, 10 of whom had acute PH-COPD, 10 of whom had moderate PH-COPD (mean pulmonary pressure, 25-34 mm Hg without low cardiac index), and 10 with no PH (mean pulmonary pressure <25 mm Hg). The 3 groups were compared retrospectively in terms of muscular pulmonary arterial wall thickness, microvascular muscularization, and pulmonary capillary density. Dunn’s post-test, chi-squared test, and the Kruskal-Wallis test were used to perform univariate analyses, while a Spearman test was used to estimate correlation coefficients.

Compared with individuals with moderate pulmonary hypertension, the acute PH-COPD group had significantly greater microvessel remodeling scores (1.284 vs 0.867; P =.0045) and lower capillary density (0.00235 per μm² vs 0.00526 per μm²; P =.0049). Medium-size arterial alterations were less discriminating. Low levels of ERG staining in participants with acute PH appears to be associated with capillary network loss.

Limitations to this study included a retrospective design, a low number of participants with PH-COPD, a slightly older definition of acute PH-COPD, and the exclusive examination of lungs with end-stage lung disease.

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The researchers of the study concluded that “the morphological correlate or hallmark of severe PH-COPD, when compared with moderate PH-COPD, lies in the substantially increased muscularization of pulmonary microvessels (arterioles and/or venules), as well as in the lower capillary density. Importantly, no significant differences were observed in the muscular-type pulmonary arteries, which are relevant in PAH (group 1) and no typical PAH lesions, such as plexiform lesions or onion-skin lesions (concentric laminar intimal fibrosis) were detected, stressing at least the different morphological phenotype of severe PH-COPD and [pulmonary arterial hypertension].”

Reference

Bunel V, Guyard A, Dauriat G, et al. Pulmonary arterial histological lesions in COPD patients with severe pulmonary hypertension [published online March 11, 2019]. CHEST. doi:10.1016/j.chest.2019.02.333