Pulmonary vascular resistance estimated by Doppler echocardiography predicts mortality in patients with interstitial lung disease.

Background: Pulmonary hypertension (PH) is a strong predictor of mortality in patients with interstitial lung disease (ILD). However, patients with ILD often have poor outcomes even in the absence of PH. Pulmonary vascular resistance (PVR) assessed by right heart catheterization is a predictor of mortality in patients with ILD. However, the clinical utility of PVR assessed by Doppler echocardiography (PVRecho) as a predictor of the outcome in patients with ILD remains unclear. The aim of this study was to examine whether PVRecho independently predicts mortality in patients with ILD.

Methods: Echocardiographic examinations were performed in 133 consecutively enrolled patients with ILD (age, 67±9 years; 53% men). Tricuspid annular plane systolic excursion (TAPSE) was measured, and PVRecho was calculated by the following formula: PVRecho=[TRV×10/time-velocity integral of right ventricular outflow (RVOT-VTI)]+0.16. Data for parameters of pulmonary functional tests and for serum biomarkers, which were measured within 3 months before or after the echocardiographic examinations, were collected.

Results: During a mean follow-up period of 18±7 months, 13 patients died due to respiratory failure (n=10), heart failure (n=1), or unknown causes (n=2). In univariate analysis, body mass index, idiopathic pulmonary fibrosis, use of an antifibrotic drug (AD), RVOT-VTI, PVRecho, percentage of predicted vital capacity (%VC), percentage of predicted forced expiratory volume in 1second, and percentage of predicted diffusion capacity of the lungs for carbon monoxide (%DLco), but not TAPSE or serum biomarkers, were significantly associated with mortality. Cox proportional hazard multivariate analysis indicated that %VC [hazard ratio (HR): 0.92, p=0.001], use of AD (HR: 4.05, p=0.043), and PVRecho (HR: 3.79, p=0.029) independently predict mortality in patients with ILD. Replacement of %VC with %DLco in the multivariate analysis did not change the results: %DLco (HR: 0.90, p=0.001), use of AD (HR: 7.53, p=0.029), and PVRecho (HR: 3.65, p=0.020).

Conclusions: In addition to parameters of pulmonary function tests and use of AD, increased PVRecho is an independent predictor of mortality in patients with ILD who were evaluated for screening of PH by echocardiography.