Validation of EuroSCORE II in atrial fibrillation heart surgery patients from the KROK Registry

Abstract

The study aimed to validate the European System for Cardiac Operative Risk Evaluation score (EuroSCORE II) in patients with atrial fibrillation (AF). All data were retrieved from the National Registry of Cardiac Surgery Procedures (KROK). EuroSCORE II calibration and discrimination performance was evaluated. The final cohort consisted of 44,172 patients (median age 67, 30.8% female, 13.4% with AF). The in-hospital mortality rate was 4.14% (N = 1830), and 5.21% (N = 2303) for 30-day mortality. EuroSCORE II significantly underestimated mortality in mild- and moderate-risk populations [Observed (O):Expected (E)-1.1, 1.16). In the AF subgroup, it performed well [O:E-0.99), whereas in the very high-risk population overestimated mortality (O:E-0.9). EuroSCORE II showed better discrimination in AF (-) [area under curve (AUC) 0.805, 95% CI 0.793-0.817)] than in AF (+) population (AUC 0.791, 95%CI 0.767-0.816), P < 0.001. The worst discriminative performance for the AF (+) group was for coronary artery bypass grafting (CABG) (AUC 0.746, 95% CI 0.676-0.817) as compared with AF (-) population (AUC 0.798, 95% CI 0.774-0.822), P < 0.001. EuroSCORE II is more accurate for patients with AF. However, it underestimated mortality rates for low-to-moderate-risk patients and had a lower ability to distinguish between high- and low-risk patients with AF, particularly in those undergoing coronary artery bypass grafting.

Figure 1

Flow chart of study design. AF atrial fibrillation.

Figure 2

Kaplan–Meier 30-days (inner graphs—90-days) survival analysis in relation to perioperative risk and atrial fibrillation (AF). Patients are stratified to: (A) total population; (B) low-risk patients; (C) mild risk patients; (D) moderate risk patients; (E) high risk patients. Significant differences between occurrence of AF and survival are evident in all groups in 30-days follow-up (p < 0.001) and in patients with risk ≤ 5% in 90-days follow-up.

Figure 3

Kaplan–Meier 30-days survival analysis in relation to type of surgery and atrial fibrillation. (A) Coronary artery bypass grafting (CABG); (B) single non-CABG, (C) 2-procedures; (D) 3-procedures. Significant differences between occurrence of AF and survival are evident in all groups (p < 0.001).

Figure 4

Calibration plot, comparison between observed mortality and mortality predicted by EuroSCORE II. AF atrial fibrillation.

Figure 5

Receiver operating characteristic curves: (A) AF (+) vs. AF (−); (B) studied population for different in-hospital mortality risks; (C) AF (+) for different in-hospital mortality risks. (D) AF (−) for different in-hospital mortality risks. P for comparison between AF (−) vs. AF (+) in —CABG group (< 0.001), —singe non-CABG (0.16), —2 procedures (0.01), —3 procedures (0.44). AUC area under curve, CI confidence interval.

Figure 6

Receiver operating characteristic curves: (A) studied population for different in-hospital mortality risks; (B) AF (+) population for different in-hospital mortality risks; (C) AF (−) population for different in-hospital mortality risks. P for comparison between AF (−) vs. AF (+) in —low group (< 0.001), —mild (< 0.001), —moderate (< 0.001), —high (< 0.001), —very high (0.01). AUC area under curve, CI confidence interval.