Pulmonary arterial hypertension (PAH) is frequently seen in patients with idiopathic pulmonary fibrosis (IPF). We sought to examine the performance of echocardiography, 6-minute walk test (6MWT) distance, distance-saturation product (DSP) and pulse oximetry (SpO2), in detecting underlying PAH in IPF.
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 (RHC), the presence or absence of pulmonary arterial hypertension (PAH) was recorded. Right ventricle systolic pressure (RVSP), 6MWT distance, DSP and lowest SpO2 during 6MWT were compared in PAH and no-PAH groups. Receiver Operating Characteristic (ROC) curves for each variable to assess prediction of PAH were constructed.
131 patients were transplanted due to IPF. Of these 131 patients, 58 (44%) were eligible. PAH was diagnosed in 25 (43%) of 58 eligible patients. The mean RVSP in patients with PAH was 43 mm Hg and 20 mm Hg in patients with no PAH (p=0.0019). 6MWT distance was 321 meters in the PAH group and 346 meters in the no-PAH one (p= 0.38). DSP in PAH subjects was 272 meters% and 286 meters% in those with no PAH (p=0.57). The lowest SpO2 in the PAH and no-PAH groups were 84% and 82 %, respectively (p=0.38). The diagnostic accuracy of the echocardiography exceeded that of the other variables (AUC= 0.72). An RVSP cut-off point of 26 mm Hg detected PAH with a sensitivity of 72% and a specificity of 66%.
Echocardiography, 6MWT distance, DSP and SpO2 perform poorly in detecting PAH in IPF. Echocardiography remains the most accurate test to predict PAH.
Clinicians should not rely on pulmonary function tests or echocardiography to predict PAH in IPF patients.
Ariel Modrykamien, No Financial Disclosure Information; No Product/Research Disclosure Information