Study objectives: COPD is a systemic disorder that is associated with increases of inflammatory proteins in systemic circulation. However, no data on the potential role of systemic inflammation in pulmonary hypertension secondary to COPD are available. Therefore, our aim was to investigate the degree of systemic inflammation reflected by circulatory levels of C-reactive protein (CRP), tumor-necrosis factor (TNF)-alpha, and interleukin (IL)-6 in COPD patients with and without pulmonary hypertension.
Design: Cross-sectional study.
Setting: University hospital, tertiary referral setting.
Patients and measurements: In 43 consecutive patients with COPD (mean [+/- SD] age, 65.0 +/- 10.5 years; mean FEV(1), 46.2 +/- 18.1% predicted), lung function was assessed using body plethysmography; pulmonary artery pressure (Ppa) levels were measured by echocardiography. Serum TNF-alpha and IL-6 levels were assessed by enzyme-linked immunosorbent assay, and high-sensitivity serum CRP levels were measured by chemiluminescent immunoassay.
Results: Pulmonary hypertension was present in 19 patients and was absent in 24 patients. In patients with pulmonary hypertension, serum CRP and TNF-alpha levels were significantly higher than in those patients without hypertension (median, 3.6 mg/L [25th to 75th percentile, 1.4 to 13.0 mg/L] vs 1.8 mg/L [25th to 75th percentile, 0.8 to 2.8 mg/L; p = 0.034]; and median, 4.2 pg/mL [25th to 75th percentile, 3.4 to 10.9 pg/mL] vs 3.1 pg/mL [25th to 75th percentile, 2.1 to 4.2 pg/mL]; p = 0.042, respectively). No differences were seen in serum IL-6 (median, 10.4 pg/mL [25th to 75th percentile, 8.8 to 12.2 pg/mL] vs 10.5 pg/mL [25th to 75th percentile, 9.4 to 39.1 pg/mL]; p = 0.651) between the groups. In multiple linear regression analysis, the following two variables were independent predictors of systolic Ppa (R(2) = 0.373): Pao(2) (p = 0.011); and log-transformed serum CRP level (p = 0.044).
Conclusion: We conclude that increases in Ppa in patients with COPD are associated with higher serum levels of CRP and TNF-alpha, raising the possibility of a pathogenetic role for low-grade systemic inflammation in the pathogenesis of pulmonary hypertension in COPD patients.