Predictors of mortality in interstitial lung disease patients without pulmonary hypertension

BACKGROUND: There is a paucity of information regarding prognostic factors associated with reduced survival in interstitial lung disease (ILD) patients without pulmonary hypertension (PH). AIMS: The aim of this study was to determine physiological and hemodynamic parameters that impact survival among ILD patients without PH based on right heart catheterization (RHC). METHODS: Consecutive ILD patients who underwent RHC (n = 169) at one center were included. The information analyzed included demographics and physiological and hemodynamic parameters. Cox regression models were used to identify independent predictors of survival. RESULTS: The mean age was 55.0 years, and 49.7% of the patients were females. Thirty-three patients died, and two underwent transplantation. Patients with predicted diffusion capacity of the lung for carbon monoxide <35%, walking distance <300 m, and 6-min walk test (6MWT) final oxygen saturation measured by pulse oximetry (SpO2) <85% were significantly associated with an increased mortality risk (P = 0.022, P < 0.0001, and P = 0.049, respectively; all by log-rank analysis). Advanced age, idiopathic pulmonary fibrosis diagnosis, reduced forced vital capacity, and low cardiac index were independent predictors of increased mortality in the ILD cohort. CONCLUSIONS: Our study demonstrates that parameters obtained from baseline pulmonary function tests and 6MWTs are important determinants of survival in ILD patients without PH. Importantly, cardiac index was the only hemodynamic variable independently associated with survival. Thus, in the absence of PH, when ILD patients perform poorly during the 6MWT manifested as reduced walking distance and desaturation at the end of the test, cardiovascular impairment must be ruled out.