Pulmonary arterial hypertension (PAH) occurs in many interstitial lung diseases and may contribute to mortality. PAH has been reported in idiopathic pulmonary fibrosis (IPF), but the incidence has not been as well defined and its impact on survival is unknown. We hypothesized that PAH is common in patients with IPF and is an independent risk factor for mortality.
Review of consecutive IPF patients undergoing right heart catheterization during evaluation for lung transplantation. We compared demographics, spirometric and cardiac measurements between those with and without PAH [mean pulmonary arterial pressure (mPAP) >25 mmHg]. The primary endpoint was the incidence of PAH. Mortality related to the measured variables. represented the secondary endpoint.
79 patients were included. PAH was present in 31.6% (mPAP 29.5±3.3 mmHg versus 19.1±3.7 mmHg). Demographic, spirometric and cardiac measurements did not predict PAH. Those with PAH had lower DLCO (37.6±11.3% versus 31.1±10.1%, p=0.04) and more required supplemental oxygen (66.7% versus 17.6%, p <0.0001). Individuals with DLCO <40% predicted who required supplemental oxygen were 10.2 times more likely to have PAH. Of the measured variables, only mPAP differentiated survivors from non-survivors (21.6±4.7 mmHg versus 24.7±6.1 mmHg, p=0.03). PAH was more common in non-survivors (52.4% versus 24.1%, p=0.008), was associated with greater mortality (48.0% versus 18.5%, OR 2.6, p=0.007) and shorter survival (883±577 versus 530±266 days p=0.01). Both distance walked (143.5±65.5 versus 365.9±81.8 meters, p<0.001) and SpO2 nadir (80.1±3.7% versus 88.0±3.5%, p <0.001) during six-minute walk test were significantly lower in those with PAH. As a screening tool for mortality, PAH had 57.1% sensitivity, 79.3% specificity and 73.4% accuracy.
The incidence of PAH in IPF is high, portends worse outcomes and was a better prognostic marker than other measured variables. A reduced DLCO, supplemental oxygen requirement or poor performance on six-minute walk should raise suspicion for PAH.
Identifying PAH may provide a valuable tool in monitoring disease progression, triaging for lung transplantation and deciding on potential therapies.
Christopher Lettieri, None.