title: CT scan-measured pulmonary artery to aorta ratio and echocardiography for detecting pulmonary hypertension in severe COPD.
abstract: BACKGROUND
  COPD is associated with significant morbidity primarily driven by acute exacerbations. Relative pulmonary artery (PA) enlargement, defined as a PA to ascending aorta (A) diameter ratio greater than one (PA:A>1) identifies patients at increased risk for exacerbations. However, little is known about the correlation between PA:A, echocardiography, and invasive hemodynamics in COPD.
  
  
  METHODS
  A retrospective observational study of patients with severe COPD being evaluated for lung transplantation at a single center between 2007 and 2011 was conducted. Clinical characteristics, CT scans, echocardiograms, and right-sided heart catheterizations were reviewed. The PA diameter at the bifurcation and A diameter from the same CT image were measured. Linear and logistic regression were used to examine the relationships between PA:A ratio by CT scan and PA systolic pressure (PASP) by echocardiogram with invasive hemodynamics. Receiver operating characteristic analysis assessed the usefulness of the PA:A ratio and PASP in predicting resting pulmonary hypertension (PH) (mean pulmonary artery pressure [mPAP]>25 mm Hg).
  
  
  RESULTS
  Sixty patients with a mean predicted FEV1 of 27%±12% were evaluated. CT scan-measured PA:A correlated linearly with mPAP after adjustment for multiple covariates (r=0.30, P=.03), a finding not observed with PASP. In a multivariate logistic model, mPAP was independently associated with PA:A>1 (OR, 1.44; 95% CI, 1.02-2.04; P=.04). PA:A>1 was 73% sensitive and 84% specific for identifying patients with resting PH (area under the curve, 0.83; 95% CI, 0.72-0.93; P<.001), whereas PASP was not useful.
  
  
  CONCLUSIONS
  A PA:A ratio>1 on CT scan outperforms echocardiography for diagnosing resting PH in patients with severe COPD.
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham.
authors.forename: Anand S
authors.initials: AS
authors.lastname: Iyer
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham; Division of Pulmonary, Allergy, and Critical Care, Department of Medicine and University of Alabama at Birmingham Lung Health Center, University of Alabama at Birmingham; Birmingham Veterans Affairs Medical Center, Birmingham, AL. Electronic address: jmwells@uab.edu.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Wells
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham; Division of Pulmonary, Allergy, and Critical Care, Department of Medicine and University of Alabama at Birmingham Lung Health Center, University of Alabama at Birmingham.
authors.forename: Sonia
authors.initials: S
authors.lastname: Vishin
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham.
authors.forename: Surya P
authors.initials: SP
authors.lastname: Bhatt
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham; Division of Pulmonary, Allergy, and Critical Care, Department of Medicine and University of Alabama at Birmingham Lung Health Center, University of Alabama at Birmingham.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Wille
authors.affiliation: Department of Internal Medicine, University of Alabama at Birmingham; Division of Pulmonary, Allergy, and Critical Care, Department of Medicine and University of Alabama at Birmingham Lung Health Center, University of Alabama at Birmingham; Birmingham Veterans Affairs Medical Center, Birmingham, AL.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Dransfield
mesh_terms: D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D004452:Echocardiography; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed