CT-determined pulmonary artery to aorta ratio as a predictor of elevated pulmonary artery pressure and survival in idiopathic pulmonary fibrosis.

BACKGROUND AND OBJECTIVE: Elevated mean pulmonary artery pressure (mPAP) is a significant prognostic indicator in idiopathic pulmonary fibrosis (IPF). It has been reported that the computed tomography-determined ratio of the diameter of the pulmonary artery to the aorta (PA:A) is correlated with mPAP in various respiratory diseases. However, in patients with IPF, whether the PA:A can be used to predict elevated mPAP and the prognostic value of the PA:A has not been fully evaluated.

METHODS: We conducted a single-centre, observational study of 177 consecutive IPF patients who underwent right heart catheterization. We examined the association between the PA:A and mPAP in these patients, and performed a receiver operating characteristic (ROC) analysis to test the diagnostic accuracy of the PA:A in predicting mPAP > 20 mm Hg (pulmonary hypertension (PH) or borderline PH) in relation to survival.

RESULTS: In a multivariate linear regression analysis, the PA:A, 6-min walk distance and diffusion capacity for carbon monoxide (DLCO ) % predicted were independent explanatory variables of elevated mPAP (P < 0.0001, P = 0.009 and P = 0.002, respectively). ROC analysis revealed a PA:A > 0.9 to be optimal for predicting mPAP > 20 mmHg (area under the curve (AUC) = 0.75; 95% CI: 0.65-0.84). Patients with a PA:A > 0.9 also had a worse prognosis (P = 0.009).

CONCLUSION: Measurement of the PA:A is a useful and convenient method to predict elevated mPAP in IPF at initial evaluation. Moreover, a PA:A >0.9 was found to be an indicator of worse prognosis.