Vascular pruning or loss of small, distal pulmonary arteries is associated with evolution of bronchiectasis to a more severe stage, suggests a study published in the Respiratory Medicine Journal.^1,2

In this study, researchers from the Brigham and Womens Hospital in Boston, Colorado School of Public Health, University of Colorado and University of California, San Diego evaluated 185 patients with COPD and 201 patients without COPD for bronchiectasis on CT at baseline and at 5 years. All the 386 participants, aged 64 years (mean), had ≥10 pack-years smoking history. Women formed 41% of the study group.

Researchers measured the blood vessel volume in arteries that were < 5 mm2 in cross-sectional area (BV5a) and the total arterial blood vessel volume (BVTa) on baseline CT scans and their ratio (BV5a:BVTa) was calculated to measure the vascular pruning or loss of small pulmonary arteries. Bronchiectasis was visually scored with higher scores suggesting more severe disease.

Arterial pruning was found to be more prevalent among the non-Hispanic Black women participants (36%) compared to those with less arterial pruning (18%). The FEV1 was lower (1.73 L) among patients with more arterial pruning versus 2.24 L among subjects with less arterial pruning. They also had lower 6-minute walk distance (1,268 ft vs 1,447 ft) and resting oxygen saturation (96% vs 97%) and higher baseline 10 mm inner perimeter airway (2.43 mm vs. 1.89 mm).

Overall, 34.5% of the study subjects fulfilled the criteria of progression of CT-derived bronchiectasis; the mean change at 5 years an increase of 5.7 points. Increase in pulmonary segments with bronchiectasis was the major factor responsible for this. Other contributory factors were the severity of extent of airway wall thickness and airway dilation. At 5 years follow up, lower BV5a:BVTa values at baseline, indicative of more vascular pruning, were associated with progressing CT-derived bronchiectasis among smokers for every 5% lower BV5a:BVTa with odds ratio of 1.28. Smokers with COPD showed similar results with OR of 1.45.

Bronchiectasis is characterized by abnormal dilatation and thickening of the airways with dilated and tortuous bronchial arteries. Pulmonary hypertension is a known complication of severe bronchiectasis. These patients are at high risk of cardiovascular diseases.

This study sheds light on the intraparenchymal pulmonary circulation and implicates vascular pruning or loss of small distal pulmonary arteries in the structural progression of bronchiectasis in accordance with evidence that have also shown a link between pulmonary vascular pruning and chronic airway diseases such as COPD, asthma.

References

1. Wojciech R. Dolliver, et al. Pulmonary arterial pruning is associated with CT-derived bronchiectasis progression in smokers. Respiratory Medicine Journal. 2022 Aug. 29. DOI:https://doi.org/10.1016/j.rmed.2022.106971.
2. https://www.healio.com/news/pulmonology/20220902/loss-of-small-distal-pulmonary-arteries-associated-with-bronchiectasis-progression, Sept. 2, 2022.