title: 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 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.
authors.affiliation: Respiratory Institute, A90, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA. modryka@ccf.org
authors.forename: Ariel M
authors.initials: AM
authors.lastname: Modrykamien
authors.forename: Ravindra
authors.initials: R
authors.lastname: Gudavalli
authors.forename: Kevin
authors.initials: K
authors.lastname: McCarthy
authors.forename: Joseph
authors.initials: J
authors.lastname: Parambil
mesh_terms: D006328:Cardiac Catheterization; D004452:Echocardiography / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D054990:Idiopathic Pulmonary Fibrosis / Q000150:complications* / Q000503:physiopathology / Q000601:surgery; D016040:Lung Transplantation; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010101:Oxygen Consumption / Q000502:physiology*; D011237:Predictive Value of Tests; D011669:Pulmonary Wedge Pressure; D012372:ROC Curve; D012189:Retrospective Studies; D016138:Walking / Q000502:physiology*