A point-based prediction model for cardiovascular risk in orthotopic liver transplantation: The CAR-OLT score

Abstract

Cardiovascular disease (CVD) complications are important causes of morbidity and mortality after orthotopic liver transplantation (OLT). There is currently no preoperative risk-assessment tool that allows physicians to estimate the risk for CVD events following OLT. We sought to develop a point-based prediction model (risk score) for CVD complications after OLT, the Cardiovascular Risk in Orthotopic Liver Transplantation risk score, among a cohort of 1,024 consecutive patients aged 18-75 years who underwent first OLT in a tertiary-care teaching hospital (2002-2011). The main outcome measures were major 1-year CVD complications, defined as death from a CVD cause or hospitalization for a major CVD event (myocardial infarction, revascularization, heart failure, atrial fibrillation, cardiac arrest, pulmonary embolism, and/or stroke). The bootstrap method yielded bias-corrected 95% confidence intervals for the regression coefficients of the final model. Among 1,024 first OLT recipients, major CVD complications occurred in 329 (32.1%). Variables selected for inclusion in the model (using model optimization strategies) included preoperative recipient age, sex, race, employment status, education status, history of hepatocellular carcinoma, diabetes, heart failure, atrial fibrillation, pulmonary or systemic hypertension, and respiratory failure. The discriminative performance of the point-based score (C statistic = 0.78, bias-corrected C statistic = 0.77) was superior to other published risk models for postoperative CVD morbidity and mortality, and it had appropriate calibration (Hosmer-Lemeshow P = 0.33).

Conclusion: The point-based risk score can identify patients at risk for CVD complications after OLT surgery (available at www.carolt.us); this score may be useful for identification of candidates for further risk stratification or other management strategies to improve CVD outcomes after OLT. (Hepatology 2017;66:1968-1979).

Figure 1

Distribution of 1-year CVD complications among adult first liver transplant recipients (NMEDW, 2002-2011). There were 498 complications among 329 individuals within 1 year of liver transplantation. Abbreviations: PE, pulmonary embolism; MI, myocardial infarction

Figure 2

Distribution of CAR-OLT scores among liver transplant recipients and their relation to probability of a 1-year post-transplant cardiovascular event.

Figure 3

Calibration of the prediction model by decile of risk. Observed (solid bar) and expected (gray bar) of the probability of a cardiovascular event within 1 year of liver transplant showed good agreement. P-value from the Hosmer and Lemeshow Goodness-of-Fit test was 0.33.