External Validation of the ARCH Score in Patients Undergoing Aortic Arch Reconstruction Under Circulatory Arrest

Background Aortic arch surgery with hypothermic circulatory arrest (HCA) carries a higher risk of morbidity and mortality compared to routine cardiac surgical procedures. The newly developed ARCH score (Arch Reconstruction under Circulatory arrest with Hypothermia) has not been externally validated. We sought to externally validate this score in our local population. Methods All consecutive open aortic arch surgeries with HCA from 2014-2023 were included. Univariable and multivariable analyses were performed. Model discrimination was assessed by C-statistic with 95% confidence intervals as part of the Receiver Operating Characteristic (ROC) analysis. Model performance was visualized by calibration plot and quantified by the Brier score. Results A total of 760 patients were included. The mean age was 61 years (±13.6) with 56.4% of patients over the age of 60 years; 38.3% were females. The procedures were carried out mostly emergently or urgently (59.6%). Total arch replacement was performed in 32.5% of patients while aortic root procedures were carried out in 74.6% of patients. In-hospital death was observed in 64 (8.4%) patients while stroke was present in 5.4%. The C-statistic revealed low discriminatory ability for predicting in-hospital mortality (area under the ROC curve 0.62; 95%CI 0.54-0.69; p=0.002); however, the model calibration was found to be excellent (Brier score of 0.07). Conclusion The ARCH score for in-hospital mortality showed low discriminatory ability in our local population although with excellent ability for prediction of mortality.