CT measured pulmonary artery to aorta ratio as a predictor of pulmonary hypertension in COPD

Abstract

Background

Pulmonary hypertension (PH) in COPD is associated with morbidity and mortality.

Previous studies showed that pulmonary artery to aorta ratio (PA:A ratio) is associated with PH in patients with severe COPD who was evaluated for lung transplantation. However, it remains unknown in patients with COPD without resting hypoxemia.

Method

A retrospective observational study of COPD patients without resting hypoxemia at Tosei General Hospital between 2007 and 2013 was conducted to evaluate the relationships between PA:A ratio and pulmonary hemodynamics. Clinical characteristics, pulmonary function, blood gas analysis, 6-min walk distance (6MWD) and SpO₂ at the end of the 6-min walk test (6MWT), CT scans and right heart catheterizations were reviewed. The PA diameter at the bifurcation and aorta diameter from the same CT image were measured. Correlation analysis and stepwise regression analysis were performed to determine the predictor of mean pulmonary artery pressure (mPAP).

Result

68 consecutive patients with a mean predicted FEV₁ of 49±22% were evaluated. In univariate analysis, mPAP presented a positive correlation with CT-measured PA:A ratio (r=0.65, p<0.001), as well as negative correlations with predicted FEV1 (r=-0.37,p<0.01), FEV1/FVC (r=-0.31,p<0.01), predicted DL_CO (r=-0.44,p<0.01), 6MWD (r=-0.40, p<0.01) and SpO₂ at the end of 6MWT (r=-0.68, p<0.001). In stepwise regression analysis, PA:A ratio, 6MWD and SpO₂ at the end of 6MWT remained as independent predictors of mPAP (R²=0.63).

Conclusion

In addition to 6MWD and SpO₂ at the end of 6MWT, CT-measured PA:A ratio predicts PH in patients with COPD without resting hypoxemia.