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

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 pre-transplant 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.