Pulmonary vascular pruning is associated with radiographic bronchiectasis progression

Background: Smokers with bronchiectasis on CT have a loss of distal pulmonary vessels, but whether this loss is related to structural progression is unknown. We aimed to test whether pulmonary vascular pruning is associated with progression of bronchiectasis. Methods: Bronchiectasis was identified and scored at visit 1 (baseline) and visit 2 (5 years later) CT scans in 255 current and former heavy smokers enrolled into the COPDGene Study. Clinical, lung function, and exacerbation data were also collected. The ratio of blood vessel volume in arteries <5 mm2 in cross-section (BV5a) to total blood vessel volume (TBVa) on baseline CT scans was used as mea­sure of vascular pruning, with lower values indicating more pruning. The association of baseline BV5a/TBVa*100 to bronchiectasis progression was assessed with generalized linear mixed models. Bronchiectasis progression was defined as a score difference of one or greater between visits (i.e., visit 2 minus visit 1 CT score) and used as outcome. Results: Out of 255 smokers, 142 met the definition of bronchiectasis progression, with a mean BV5a/TBVa of 57.6%. After adjusting for age, sex, race, BMI, smoking status, FEV1, percentage of blood neutrophils, CT measures of wall thickness and emphysema at baseline, number of exacerbations during follow-up, changes in FEV1 and six-minute walk distance, vascular pruning at baseline was associated with 5-yr bronchiectasis progression on CT (Odds ratio 1.29, 95% Confidence interval 1.02 -1.64, per 5% lower BV5a/TBVa; P=0.035). Conclusion: In smokers, vascular pruning is associated with bronchiectasis progression on CT, suggesting that a vascular factor might be related to structural changes of this disease.