Echocardiography, 6-minute walk distance, and distance-saturation product as predictors of pulmonary arterial hypertension in idiopathic pulmonary fibrosis

Abstract

BACKGROUND: Pulmonary arterial hypertension (PAH) is frequently seen in patients with idiopathic pulmonary fibrosis (IPF). We sought to examine the performance of echocardiography, 6-min walk test (6MWT) distance, distance-saturation product (DSP), and pulse oximetry (SpO2) in detecting underlying PAH in IPF. METHODS: 626 lung transplanted patients from February 1990 to December 2007 were considered. Subjects with pre-transplant diagnosis of IPF were evaluated. Based on findings in pretransplant right heart catheterization, the presence or absence of PAH was recorded. Right-ventricle systolic pressure, 6MWT distance, DSP, and lowest SpO2 during 6MWT were compared in PAH and non-PAH groups. Receiver operating characteristic curves for each variable to assess prediction of PAH were constructed. RESULTS: 131 patients were transplanted due to IPF. Of these 131 patients, 58 (44%) were eligible. PAH was diagnosed by right heart catheterization in 25 (43%) of 58 eligible patients. The mean pulmonary arterial pressure in PAH patients was 33 mm Hg, and 19 mm Hg in non-PAH patients (P=001). 6MWT distance was 321 m in the PAH group, and 346 m in the non-PAH one (P=38). DSP in PAH subjects was 272 meters% and 286 meters% in those with no PAH (P=57). The lowest SpO2 in the PAH and non-PAH groups were 84% and 82%, respectively (P=38). The diagnostic accuracy of the echocardiography exceeded that of the other variables (area under the curve 0.72). CONCLUSIONS: Right-ventricle systolic pressure measured by echocardiography, by 6MWT distance, by DSP, or by SpO2 performs poorly in detecting PAH in IPF. Measured by right heart catheterization, right-ventricle systolic pressure performs better to predict PAH in IPF. © 2010 Daedalus Enterprises.