Performance of EuroSCORE II in a large US database: implications for transcatheter aortic valve implantation

Validation studies of European system for cardiac operative risk evaluation II (EuroSCORE II) have been limited to European datasets. Therefore, the aims of this study were to assess the performance of EuroSCORE II in a large multicentre US database, and compare it with the Society of Thoracic Surgeons Predicted Risk of Mortality (STS-PROM). In addition, implications for patient selection for transcatheter aortic valve implantation (TAVI) were explored.

EuroSCORE II and the STS-PROM were calculated for 50 588 patients from a multi-institutional statewide database of all cardiac surgeries performed since 2003. Model performance was assessed using the area under the receiver operator curve (AUC), observed vs expected (O:E) ratios and calibration plots. Analyses were performed for isolated coronary artery bypass grafting (CABG) (n = 40 871), aortic valve replacement (AVR) (n = 4107), AVR + CABG (n = 3480), mitral valve (MV) replacement (n = 1071) and MV repair (n = 1059).

The overall in-hospital mortality rate was 2.1%. EuroSCORE II was outperformed by the STS-PROM in the overall cohort with regard to discrimination (AUC = 0.77 vs 0.81, respectively; P < 0.001) and calibration (O:E = 0.68 vs 0.80, respectively). Discrimination for CABG was worse with EuroSCORE II (AUC = 0.77 vs STS-PROM: 0.81, P < 0.001). For other procedures discrimination was similar: AVR (AUC = 0.71 vs STS-PROM: 0.74, P = 0.40), AVR + CABG (AUC = 0.72 vs STS-PROM: 0.74, P = 0.47), MV repair (AUC = 0.82 vs STS-PROM: 0.86, P = 0.55) and MV replacement (AUC = 0.78 vs STS-PROM: 0.79, P = 0.69). Calibration of EuroSCORE II was worse for CABG (O:E = 0.68 vs STS-PROM: 0.80), similar in AVR + CABG (O:E = 0.76 vs STS-PROM: 0.70) and MV repair (O:E = 0.64 vs STS-PROM: 0.67), while EuroSCORE II may be more accurate in AVR (O:E = 0.96 vs STS-PROM: 0.76). Performance of both models improved when only recent cases (after 1 January 2008) were used. Ongoing TAVI trials aimed at patients with an estimated 4-10% risk of mortality are enrolling patients with mean estimated risks of 6.2% (EuroSCORE II) or 6.0% (STS-PROM), and an actual mortality rate of 4.6% (EuroSCORE II) or 4.8% (STS-PROM).

In a large US multicentre database, the STS-PROM performs better than EuroSCORE II for CABG. However, EuroSCORE II is a reasonable alternative in low-risk CABG patients and in those undergoing other cardiac surgical procedures. Clinical trials and physicians that use these scores recruit and treat patients who are at a lower risk than anticipated. This potentially leads to overtreatment with an investigational device. Decision-making should not solely be based on risk scores, but should comprise multidisciplinary heart team discussions.