Pulmonary arterial remodeling in chronic obstructive pulmonary disease is lobe dependent

Abstract

Abstract Pulmonary arterial remodeling has been demonstrated in patients with severe chronic obstructive pulmonary disease (COPD), but it is not known whether lobar heterogeneity of remodeling occurs. Furthermore, the relationship between pulmonary hypertension (PH) and pulmonary arterial remodeling in COPD has not been established. Muscular pulmonary arterial remodeling in arteries 0.10-0.25 mm in diameter was assessed in COPD-explanted lungs and autopsy controls. Remodeling was quantified as the percentage wall thickness to vessel diameter (%WT) using digital image analysis. Repeat measures mixed-effects remodeling for %WT was performed according to lobar origin (upper and lower), muscular pulmonary arterial size (small, medium, and large), and echocardiography-based pulmonary arterial pressure (no PH, mild PH, and moderate-to-severe PH). Lobar perfusion and emphysema indices were determined from ventilation-perfusion and computed tomography scans, respectively. Overall, %WT was greater in 42 subjects with COPD than in 5 control subjects ([Formula: see text]). Within the COPD group, %WT was greater in the upper lobes ([Formula: see text]) and in the small muscular pulmonary arteries ([Formula: see text]). Lobar differences were most pronounced in medium and large arteries. Lobar emphysema index was not associated with arterial remodeling. However, there was a significant positive relationship between the lobar perfusion index and pulmonary arterial remodeling ([Formula: see text]). The presence of PH on echocardiography showed only a trend to a small effect on lower lobe remodeling. The pattern of pulmonary arterial remodeling in COPD is complicated and lobe dependent. Differences in regional blood flow partially account for the lobar heterogeneity of pulmonary arterial remodeling in COPD.

Figure 1

The lumen and external elastic lamina circumference were measured from A. This enabled an idealized artery to be drawn (B) on the basis of the radius, which was derived from the circumference measures. The percentage wall thickness (%WT) was then calculated as .

Figure 2

Overall, percentage wall thickness (%WT) is greater in the upper lobe compared with the lower lobe (A) and greater in the small muscular pulmonary arteries compared with the medium and large muscular pulmonary arteries (B). The %WT did not vary significantly among the pulmonary arterial pressure group (C). *, †, ‡. ns, not significant; PH, pulmonary hypertension.

Figure 3

Interaction effects of lobar origin, arterial size, and pulmonary hypertension (PH) group on percentage wall thickness (%WT). The %WT for medium and large pulmonary arteries are less in the lower lobes compared with the upper lobes; however, there is no difference in the small pulmonary arteries across lobar origin (A). The %WT for the no PH group is less in the lower lobes compared with the upper lobes; however, there is no difference for mild and moderate-to-severe PH groups across lobar origin (B). There are no interaction effects between pulmonary arterial size and pulmonary arterial pressure group (C). P values are for comparisons between lower and upper lobe. *, †.