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

ABSTRACT

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 (PAA) is correlated with mPAP in various respiratory diseases. However, in patients with IPF, whether the PAA can be used to predict elevated mPAP and the prognostic value of the PAA 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 PAA and mPAP in these patients, and performed a receiver operating characteristic (ROC) analysis to test the diagnostic accuracy of the PAA in predicting mPAP > 20 mm Hg (pulmonary hypertension (PH) or borderline PH) in relation to survival. RESULTS: In a multivariate linear regression analysis, the PAA, 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 PAA > 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 PAA > 0.9 also had a worse prognosis (P = 0.009). CONCLUSION: Measurement of the PAA is a useful and convenient method to predict elevated mPAP in IPF at initial evaluation. Moreover, a PAA >0.9 was found to be an indicator of worse prognosis.