Predictors of Waitlist Mortality in Portopulmonary Hypertension

Abstract

Background: The current Organ Procurement Transplantation Network policy grants Model for End-Stage Liver Disease (MELD) exception points to patients with portopulmonary hypertension (POPH), but potentially important factors, such as severity of liver disease and pulmonary hypertension, are not included in the exception score, and may affect survival. The purpose of this study was to identify significant predictors of waitlist mortality in patients with POPH.

Methods: We performed a retrospective cohort study of patients in the Organ Procurement and Transplantation Network database with hemodynamics consistent with POPH (defined as mean pulmonary arterial pressure >25 mm Hg and pulmonary vascular resistance [PVR] ≥240 dynes·s·cm) who were approved for a POPH MELD exception between 2006 and 2014. Using a Cox proportional hazards model, we identified predictors of waitlist mortality (or removal for clinical deterioration).

Results: One hundred ninety adults were included. Age (hazard ratio [HR], 1.04; 95% confidence interval [CI], 1.00-1.08; P = 0.0499), initial native MELD score (HR, 1.11; 95% CI, 1.05-1.17; P < 0.001), and initial PVR (HR, 1.12 per 100 dynes·s·cm; 95% CI, 1.02-1.23; P = 0.02) were the only significant univariate predictors of waitlist mortality and remained significant predictors in a multivariate model, which had a c-statistic of 0.71. PVR and mean pulmonary arterial pressure were not significant predictors of posttransplant mortality.

Conclusions: Both the severity of liver disease and POPH (as assessed by MELD and PVR, respectively) were significantly associated with waitlist, but not posttransplant, mortality in patients with approved MELD exceptions for POPH. Both factors should potentially be included in the POPH MELD exception score to more accurately reflect waitlist mortality risk.

Figure 1

Flow diagram of patients included and excluded in the final analysis

Figure 2

Kaplan-Meier survival curves for the composite outcome of waitlist mortality or removal from the waitlist due to clinical deterioration in four groups of patients stratified by the median MELD and PVR for the cohort [MELD≦12 and PVR≦450 dynes•s•cm⁻⁵ (n=41), MELD≦12 and PVR >450 dynes•s•cm⁻⁵ (n=59), MELD>12 and PVR≦450 dynes•s•cm⁻⁵ (n=51), and MELD>12 and PVR>450 dynes•s•cm⁻⁵ (n=35)]. The groups had significantly different waitlist mortality rates (log-rank P=0.006).