Model for End-Stage Liver Disease Score Independently Predicts Mortality in Cardiac Surgery

Although liver disease increases surgical risk, it is not considered in The Society for Thoracic Surgeons (STS) risk calculator. This study assessed the impact of Model for End-Stage Liver Disease (MELD) on outcomes after cardiac surgical procedures and the additional predictive value of MELD in the STS risk model.

Deidentified records of 21,272 patients were extracted from a regional STS database. Inclusion criteria were any cardiac operation with a risk score available (2011-2016). Exclusion criteria included missing MELD (n = 2,895) or preoperative anticoagulation (n = 144). Patients were stratified into three categories, MELD < 9 (low), MELD 9 to 15 (moderate), and MELD > 15 (high). Univariate and multivariate logistic regression assessed risk-adjusted associations between MELD and operative outcomes.

Increasing MELD scores were associated with greater comorbid disease, mitral operation, prior cardiac operation, and higher STS-predicted risk of mortality (1.1%, 2.3%, and 6.0% by MELD category; p < 0.0001). The operative mortality rate increased with increasing MELD score (1.6%, 3.9%, and 8.4%; p < 0.0001). By logistic regression MELD score was an independent predictor of operative mortality (odds ratio, 1.03 per MELD score point; p < 0.0001) as were the components total bilirubin (odds ratio, 1.22 per mg/dL; p = 0.002) and international normalized ratio (odds ratio, 1.40 per unit; p < 0.0001). Finally, MELD score was independently associated with STS major morbidity and the component complications renal failure and stroke.

Increasing MELD score, international normalized ratio, and bilirubin all independently increase risk of operative mortality. Because high rates of missing data currently limit utilization of MELD, efforts to simplify and improve data collection would help improve future risk models.