Study objectives: The development of pulmonary arterial hypertension (PAH) can complicate many interstitial lung diseases, including idiopathic pulmonary fibrosis (IPF). We sought to characterize the prevalence of PAH and its impact on survival in patients with advanced IPF.
Design: Retrospective analysis of consecutive IPF patients undergoing pretransplantation right heart catheterization.
Setting: Lung transplant and IPF referral center.
Methods: PAH was defined as a mean pulmonary artery pressure (mPAP) of > 25 mm Hg. We compared demographic, spirometric, 6-min walk test (6MWT) results, and survival outcomes between those with PAH and those without PAH.
Measurements and results: Seventy-nine patients were included in the study. PAH was present in 31.6% of patients (mean [+/- SD] mPAP, 29.5 +/- 3.3 vs 19.1 +/- 3.7 mm Hg, respectively). Those patients with PAH had a lower mean diffusing capacity of the lung for carbon monoxide (Dlco) (37.6 +/- 11.3% vs 31.1 +/- 10.1%, respectively; p = 0.04) and were more likely to require supplemental oxygen (66.7% vs 17.6%, respectively; p < 0.0001). Mean distance walked (143.5 +/- 65.5 vs 365.9 +/- 81.8 m, respectively; p < 0.001) and mean pulse oximetric saturation nadir (80.1 +/- 3.7% vs 88.0 +/- 3.5%, respectively; p < 0.001) during the 6MWT were also lower among those with PAH. PAH was associated with a greater risk of death during the study period (mortality rate, 60.0% vs 29.9%, respectively; odds ratio, 2.6; 95% confidence interval [CI], 2.3 to 3.1; p = 0.001). One-year mortality rates were higher in those with PAH (28.0% vs 5.5%, respectively; p = 0.002). As a predictor of mortality, PAH had a sensitivity, specificity, and accuracy of 57.1%, 79.3%, and 73.4%, respectively. There was a linear correlation between mPAP and outcomes with higher pressures associated with a greater risk of mortality (hazard ratio, 1.09; 95% CI, 1.02 to 1.16). FVC and Dlco did not predict outcomes.
Conclusions: PAH is common in advanced cases of IPF and significantly impacts survival. A reduced Dlco, supplemental oxygen requirement, or poor 6-min walk performance should raise suspicion of the presence of underlying PAH. Identifying PAH might be an important adjunct in monitoring disease progression, triaging for transplantation, and guiding therapy.