Mortality prediction in Indian cardiac surgery patients: Validation of European System for Cardiac Operative Risk Evaluation II

BACKGROUND AND AIMS: Risk Stratification has an important place in cardiac surgery to identify high-risk cases and optimally allocate resources. Hence various risk scoring systems have been tried to predict mortality. The aim of the present study was to validate the European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) in Indian cardiac surgical patients. METHODS: After obtaining ethics committee clearance, data on EuroSCORE II variables were collected for all patients >18 years undergoing on-pump coronary artery bypass graft (CABG), valve surgery and mixed (CABG + valve) procedures between January 2011 and December 2012. Mortality prediction was done using the online calculator from the site www.euroscore.org. The calibration of the EuroSCORE II model was analysed using the Hosmer–Lemeshow test and discrimination was analysed by plotting receiver operating characteristic curves (ROC) and calculating area under the curve (AUC). The analysis was done in the total sample, CABG, valve surgery and in mixed procedures. RESULTS: The overall observed mortality was 5.7% in the total sample, 6.6% in CABG, 4.2% in valve surgeries and 10.2% in mixed procedures whereas the predicted mortality was 2.9%, 3.1%, 2.4%, 5.1% in total sample, CABG, valve surgery and mixed procedure, respectively. The significance (P value) of Hosmer–Lemeshow test was 0.292, 0.45, 0.56 and 1 for the total sample, CABG, valve surgery and mixed procedure, respectively, indicating good calibration. The AUC of ROC was 0.76, 0.70, 0.83 and 0.78 for total sample, CABG, valve surgery and mixed procedure, respectively. CONCLUSION: Mortality of the sample was under-predicted by EuroSCORE II. Calibration of the EuroSCORE II model was good for total sample as well as for all surgical subcategories. Discrimination was good in the total sample and in the mixed procedure population, acceptable in CABG patients and excellent in valve surgeries.