Pulmonary Artery Enlargement Is Associated With Cardiac Injury During Severe Exacerbations of COPD

Abstract

Background: Relative pulmonary arterial enlargement, defined by a pulmonary artery to aorta (PA/A) ratio > 1 on CT scanning, predicts hospitalization for acute exacerbations of COPD (AECOPD). However, it is unclear how AECOPD affect the PA/A ratio. We hypothesized that the PA/A ratio would increase at the time of AECOPD and that a ratio > 1 would be associated with worse clinical outcomes.

Methods: Patients discharged with an International Classification of Diseases, Ninth Revision, diagnosis of AECOPD from a single center over a 5-year period were identified. Patients were included who had a CT scan performed during the stable period prior to the index AECOPD episode as well as a CT scan at the time of hospitalization. A subset of patients also underwent postexacerbation CT scans. The pulmonary arterial diameter, ascending aortic diameter, and the PA/A ratio were measured on CT scans. Demographic data, comorbidities, troponin level, and hospital outcome data were analyzed.

Results: A total of 134 patients were included in the study. They had a mean age of 65 ± 10 years, 47% were male, and 69% were white; overall, patients had a mean FEV1 of 47% ± 19%. The PA/A ratio increased from baseline at the time of exacerbation (0.97 ± 0.15 from 0.91 ± 0.17; P < .001). Younger age and known pulmonary hypertension were independently associated with an exacerbation PA/A ratio > 1. Patients with PA/A ratio > 1 had higher troponin values. Those with a PA/A ratio > 1 and troponin levels > 0.01 ng/mL had increased acute respiratory failure, ICU admission, or inpatient mortality compared with those without both factors (P = .0028). The PA/A ratio returned to baseline values following AECOPD.

Conclusions: The PA/A ratio increased at the time of severe AECOPD and a ratio > 1 predicted cardiac injury and a more severe hospital course.

Keywords: COPD; CT scan; acute exacerbation of COPD; enzymes (cardiology); pulmonary circulation.

Figure 1

Patient flow diagram. AECOPD = acute exacerbations of COPD; ICD-9 = International Classification of Diseases, Ninth Revision.

Figure 2

Pulmonary artery enlargement measured on CT scans. The pulmonary arterial diameter (A) and perpendicular measurements of the ascending aortic diameter (B and C) are measured on the same axial CT image to calculate the pulmonary artery to aorta ratio.

Figure 3

Enlargement in pulmonary arterial diameter is associated with increased cardiac injury during AECOPD. A, Serum troponin levels are increased at hospital admission in patients with a PA/A ratio > 1. B, There are no differences between admission serum BNP levels in patients with and without enlargement in pulmonary arterial diameter. ^aP < .05 according to Student t test.BNP = brain natriuretic peptide; PA/A = pulmonary artery to aorta ratio. See Figure 1 legend for expansion of other abbreviation.

Figure 4

Association between enlargement of pulmonary arterial diameter and severity outcomes during AECOPD. Patients with a PA/A ratio > 1 and a Tn level > 0.01 ng/mL at the time of AECOPD had a higher rate of respiratory failure, ICU admission, or in-hospital mortality (59%) vs those with either a PA/A ratio > 1 or Tn level > 0.01 ng/mL (39%) and vs those with a PA/A ratio < 1 and a Tn level > 0.01 ng/mL (19%; P = .0008 for linear trend between groups, P = .0029 by one-way analysis of variance). ^aP = .001 between the PA/A ratio < 1 and Tn level < 0.01 ng/mL group and the PA/A ratio > 1 and Tn level > 0.01 ng/mL group by one-way analysis of variance with a Tukey post hoc analysis. Tn = troponin. See Figure 1, Figure 3 legends for other abbreviations.