Validation of the Zwolle Risk Score in STEMI Patients Undergoing Primary PCI: Insights from the ISCAS-STEMI COVID-19 Registry

Background: Several scores have been developed to facilitate risk stratification and early discharge following primary angioplasty, particularly the Zwolle Risk Score (ZRS). However, validation in large-sized studies is still lacking. Therefore, the aim of the current study was to validate the use of the ZRS in a contemporary global population, including patients who were treated during the SARS-CoV-2 pandemic and enrolled in a large intercontinental observational study. Methods: The ISACS-STEMI COVID-19 is a large-scale retrospective multicenter registry involving primary PCI centers from Europe, Latin America, South-East Asia, and NorthAfrica, including patients treated from March 1^st until June 30^th, in 2019 and 2020]. ZRS was calculated for each patient. The patients were additionally categorized according to the following values of the ZRS [≤3; 4-6; 7-9; ≥10]. Our study outcomes were in-hospital and 30-day mortality. The discriminatory capacity of the ZRS was assessed by the area under the ROC curve [c statistic] as an index of model performance. Results: Our population is represented by 16084 STEMI patients undergoing mechanical reperfusion enrolled in 109 centers. The score showed a very good performance in the predicting mortality both in-hospital [AUC=0.83 [0.82-0.85], p<0.0001] and at 30-day follow-up [AUC=0.82 [0.81-0.84, p<0.0001]. The results were confirmed when the ZRS was separately applied to patients treated in 2019 and 2020, with good stability across time. ZRS was able to identify a large cohort [n=10672, 66.3%] of low-risk patients [score ≤3] with a very low mortality rate at 2 days [1%] and between 3 and 10 days [0.7%], with a very good negative predictive value for in-hospital [98.3%] and 30-day mortality [97.7%], with similar results in 2019 and 2020. Conclusion: This study is the first to demonstrate the good prognostic performance of the ZRS in a large-scale contemporary global multicenter validation set. Similar results were obtained both in the pre-pandemic and the COVID-19 era. ZRS ≤3 identified a very low-risk population that could be discharged early, even during the COVID-19 pandemic, with expected advantages in the availability of hospital beds and nursing staff, costs of medical care, and in-hospital risk of contagion.