@article {1433727,
	title = {Pulmonary arterial enlargement and acute exacerbations of COPD},
	journal = {N Engl J Med},
	volume = {367},
	number = {10},
	year = {2012},
	month = {2012 Sep 06},
	pages = {913-21},
	abstract = {BACKGROUND: Exacerbations of chronic obstructive pulmonary disease (COPD) are associated with accelerated loss of lung function and death. Identification of patients at risk for these events, particularly those requiring hospitalization, is of major importance. Severe pulmonary hypertension is an important complication of advanced COPD and predicts acute exacerbations, though pulmonary vascular abnormalities also occur early in the course of the disease. We hypothesized that a computed tomographic (CT) metric of pulmonary vascular disease (pulmonary artery enlargement, as determined by a ratio of the diameter of the pulmonary artery to the diameter of the aorta [PA:A ratio] of >1) would be associated with severe COPD exacerbations.

METHODS: We conducted a multicenter, observational trial that enrolled current and former smokers with COPD. We determined the association between a PA:A ratio of more than 1 and a history at enrollment of severe exacerbations requiring hospitalization and then examined the usefulness of the ratio as a predictor of these events in a longitudinal follow-up of this cohort, as well as in an external validation cohort. We used logistic-regression and zero-inflated negative binomial regression analyses and adjusted for known risk factors for exacerbation.

RESULTS: Multivariate logistic-regression analysis showed a significant association between a PA:A ratio of more than 1 and a history of severe exacerbations at the time of enrollment in the trial (odds ratio, 4.78; 95\% confidence interval [CI], 3.43 to 6.65; P,
	keywords = {Acute Disease, Aged, Aorta, Aortography, Female, Humans, Logistic Models, Male, Middle Aged, Observation, Pulmonary Artery, Pulmonary Disease, Chronic Obstructive, Recurrence, Risk Factors, Smoking, Tomography, X-Ray Computed},
	issn = {1533-4406},
	doi = {10.1056/NEJMoa1203830},
	author = {Wells, J Michael and Washko, George R and Han, MeiLan K and Abbas, Naseer and Nath, Hrudaya and Mamary, A James and Regan, Elizabeth and Bailey, William C and Martinez, Fernando J and Westfall, Elizabeth and Beaty, Terri H and Curran-Everett, Douglas and Curtis, Jeffrey L and Hokanson, John E and Lynch, David A and Make, Barry J and Crapo, James D and Silverman, Edwin K and Bowler, Russell P and Dransfield, Mark T}
}