J Korean Med Sci.  2021 Jun;36(22):e163. 10.3346/jkms.2021.36.e163.

The Performance of the Current Risk Prediction Scoring Systems in Patients Undergoing Anaortic Off-pump Coronary Artery Bypass Grafting

• Choi JW
• Hwang HY
• Kim KB

• KMID: 2516584
• DOI: http://doi.org/10.3346/jkms.2021.36.e163

Abstract

Background
This study aimed to evaluate the performance of the Society of Thoracic Surgeons (STS) risk model and European System for Cardiac Operative Risk Evaluation (EuroSCORE) II for patients undergoing anaortic off-pump coronary artery bypass grafting (OPCAB).
Methods
From January 2010 to June 2017, 1,048 patients (isolated anaortic OPCAB: 1,043, on-pump conversion:5) undergoing isolated anaortic OPCAB were enrolled. The STS risk score and EuroSCORE II were calculated with dedicated online software. Calibration of the models were performed by the risk-adjusted event ratio that was defined as observed events divided by expected events (O/E ratio) and Hosmer-Lemeshow test. The discrimination powers were evaluated by the area under the receiver operating characteristic curve (AUC).
Results
Operative mortality occurred in 10 patients (0.95%). The predicted mortality rates by the EuroSCORE II and STS risk model were 2.58 ± 4.15% and 1.72 ± 2.92%, respectively. The O/E ratio of the EuroSCORE II was 0.370 with significant overprediction of operative mortality (confidence interval [CI], 0.157–0.652; P = 0.003). The STS score also overpredicted the operative mortality (O/E ratio, 0.556) with marginal significance (CI, 0.266–1.023; P = 0.052). Permanent stroke occurred in 6 patients (0.53%). The predicted permanent stroke occurrence rate was 1.73 ± 1.48%. The O/E ratio was 0.332 with significant overprediction of permanent stroke (CI, 0.121–0.722; P = 0.011). Regarding discrimination power for the STS risk model, the operative mortality was excellent (AUC, 0.876) and permanent stroke was acceptable (AUC, 0.740). The EuroSCORE II showed good discrimination power (AUC, 0.784). There was a significant difference in discrimination power for mortality between STS and EuroSCORE II risk models (P = 0.007).
Conclusion
Preexisting risk predicting scoring systems, STS risk model and EuroSCORE II, overpredict the risk of mortality and stroke rate for anaortic OPCAB. These findings suggest the possibility that anaortic OPCAB can lower the operative mortality and occurrence of postoperative stroke than conventional coronary artery bypass grafting.

Keyword

Risk Prediction Scoring System; Coronary Bypass Graft Grafting; Off-pump; Anaortic

Figure

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  Fig. 1 Summary flow diagram of enrolled patients.CABG = coronary artery bypass grafting.

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  Fig. 2 Calibration plot of the (A) EuroSCORE II, (B) mortality calculated by the STS risk model and (C) permanent stroke calculated by the STS risk model.EuroSCORE = European System for Cardiac Operative Risk Evaluation, STS = Society of Thoracic Surgeons.

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  Fig. 3 ROC curves of (A) EuroSCORE II, (B) mortality and (C) permanent stroke calculated by the STS risk model.ROC = receiver operating characteristic, EuroSCORE = European System for Cardiac Operative Risk Evaluation, STS = Society of Thoracic Surgeons, AUC = area under the receiver operating characteristic curve.

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