Submaximal cardiopulmonary exercise testing predicts 90-day survival after liver transplantation

Abstract

Liver transplantation has a significant early postoperative mortality rate. An accurate preoperative assessment is essential for minimizing mortality and optimizing limited donor organ resources. This study assessed the feasibility of preoperative submaximal cardiopulmonary exercise testing (CPET) for determining the cardiopulmonary reserve in patients being assessed for liver transplantation and its potential for predicting 90-day posttransplant survival. One hundred eighty-two patients underwent CPET as part of their preoperative assessment for elective liver transplantation. The 90-day mortality rate, critical care length of stay, and hospital length of stay were determined during the prospective posttransplant follow-up. One hundred sixty-five of the 182 patients (91%) successfully completed CPET; this was defined as the ability to determine a submaximal exercise parameter: the anaerobic threshold (AT). Sixty of the 182 patients (33%) underwent liver transplantation, and the mortality rate was 10.0% (6/60). The mean AT value was significantly higher for survivors versus nonsurvivors (12.0 ± 2.4 versus 8.4 ± 1.3 mL/minute/kg, P < 0.001). Logistic regression revealed that AT, donor age, blood transfusions, and fresh frozen plasma transfusions were significant univariate predictors of outcomes. In a multivariate analysis, only AT was retained as a significant predictor of mortality. A receiver operating characteristic curve analysis demonstrated sensitivity and specificity of 90.7% and 83.3%, respectively, with good model accuracy (area under the receiver operating characteristic curve = 0.92, 95% confidence interval = 0.82-0.97, P = 0.001). The optimal AT level for survival was defined to be >9.0 mL/minute/kg. The predictive value was improved when the ideal weight was substituted for the actual body weight of a patient with refractory ascites, even after a correction for the donor's age. In conclusion, the preoperative cardiorespiratory reserve (as defined by CPET) is a sensitive and specific predictor of early survival after liver transplantation. The predictive value of CPET requires further evaluation.