Echocardiography Nomogram for Predicting Survival among Chronic Lung Disease Patients with Severe Pulmonary Hypertension

Abstract

Severe pulmonary hypertension in chronic lung diseases (severe CLD-PH) differs significantly from other types of PH in physiology and prognosis. We aimed to assess whether echocardiography helps predict long-term survival in patients with severe CLD-PH. This single-centre, observational cohort study enrolled 100 patients with severe CLD-PH (mean pulmonary arterial pressure ≥35 mm Hg or ≥25 mm Hg with cardiac index <2.0 L/min/m2 or pulmonary vascular resistance ≥6 Wood units) between 2009 and 2014. The population was randomly divided into a derivation and validation cohort in a 2:1 ratio. To construct a nomogram, a multivariable logistic regression model was applied, and scores were assigned based on the hazard ratio of independent echocardiographic predictors. Multivariate Cox hazards analysis identified the strongest predictors of mortality as pulmonary arterial systolic pressure (PASP), tricuspid annular plane systolic excursion, and right ventricular end-diastolic transverse dimension. The three independent predictors were entered into the nomogram. Compared with PASP alone, the nomogram resulted in an integrated discrimination improvement of 15.5% (95% confidence interval, 5.52−25.5%, p = 0.002) with a net improvement in model discrimination (C-statistic from 0.591 to 0.746). Using echocardiographic parameters, we established and validated a novel nomogram to predict all-cause death for patients with severe CLD-PH.

Keywords: chronic lung diseases; echocardiography; haemodynamics; pulmonary hypertension; right heart catheterization; survival.

Figure 1

Flow diagram of patient enrolment and study design. CLD: chronic lung diseases; DE: Doppler echocardiography; RHC: right heart catheterization.

Figure 2

Kaplan–Meier survival for all-cause mortality of severe CLD-PH: (A) in the derivation cohort population; (B) in subgroups with scores of −1, 0, 1, 2 and 3; (C) in subgroups with scores < 0 vs. scores ≥ 0; (D) in the validation cohort according to the mean value of the total points calculated by each patient’s nomogram.

Figure 3

Cut-off values for echocardiographic parameters calculated using the X-tile program. X-tile analyses of TAPSE (A), PASP (B) and RVEDTD (C) levels in the cohort population with severe CLD-PH. X-tile plots for the cohort patients are shown in the left panels; black circles highlight the cut-off values, which are also shown in histograms (middle panels). Kaplan–Meier plots are presented in the right panels. RVEDTD: right ventricular end-diastolic transverse dimension; PASP: pulmonary arterial systolic pressure; TAPSE: tricuspid annular plane systolic excursion.

Figure 4

Comparisons of ROC curves of PASP alone and the composite scores in predicting all-cause mortality in patients with severe CLD-PH. AUC: area under the curve; PASP: pulmonary arterial systolic pressure; CLD: chronic lung diseases; PH: pulmonary hypertension; ROC: receiver operating characteristic.

Figure 5

Nomogram for predicting all-cause mortality in severe CLD-PH. PASP: pulmonary arterial systolic pressure; RVEDTD: right ventricular end-diastolic transverse dimension; TAPSE: tricuspid annular plane systolic excursion.

Figure 6

Cox univariate regression analyses for all-cause mortality among COPD patients. COPD: chronic obstructive pulmonary diseases; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; DLco: diffusing capacity for carbon monoxide; RVEDTD: right ventricular end-diastolic transverse dimension; PASP: pulmonary arterial systolic pressure; ENDSEI: end-systolic stage eccentricity index; TAPSE: tricuspid annular plane systolic excursion.