The effect of diffuse pulmonary fibrosis on the reliability of CT signs of pulmonary hypertension.

PURPOSE: To determine whether pulmonary artery (PA) dilatation is a reliable indicator of pulmonary hypertension (PH) in patients with pulmonary fibrosis.

MATERIALS AND METHODS: This study had institutional review board approval. Patient consent was not required. Seventy-seven patients (39 men, 38 women) who underwent right heart catheterization were studied. The study population was divided into 30 patients with pulmonary fibrosis (group A), and 47 without (group B). The main PA diameter (dPA) and ascending aorta diameter (dAA) were measured by using computed tomography (CT), and the extent of fibrosis was recorded in group A. The dPA and the dPA/dAA ratio were correlated (Spearman rank) with mean PA pressure (mPAP) and pulmonary vascular resistance index (PVRi). The relationship between dPA and pulmonary fibrosis extent and total lung capacity (TLC) was examined by using multivariate linear regression.

RESULTS: There were strong correlations between dPA and both mPAP (r = 0.67, P < .0001) and PVRi (r = 0.78, P < .0001) in group B. In contrast, there were no significant correlations in group A (r = 0.23, P = .22 for mPAP and r = 0.23, P = .28 for PVRi). The dPA/dAA ratio had similar relationships to dPA alone in group B (r = 0.72, P < .0001 for mPAP and r = 0.71, P < .0001 for PVRi), but significantly strengthened the correlations in group A (r = 0.54, P < .005 for mPAP and r = 0.48, P = .04 for PVRi). PA dilatation occurred in group A in the absence of significant PH, and was unrelated to CT fibrosis score or TLC.

CONCLUSION: PA dilatation occurs in the absence of PH in patients with pulmonary fibrosis and is therefore an unreliable sign of PH in these patients.