NSTEMI-CARE: A Calibrated Multilayer Decision-Support Tool for Early Level-of-Care Assignment in Non-ST-Segment Elevation Myocardial Infarction

Background: Patients with non-ST-segment elevation myocardial infarction (NSTEMI) are frequently admitted to intensive care or monitored settings despite heterogeneous risk of ICU-requiring complications. We developed NSTEMI-CARE, a calibrated multilayer decision-support algorithm for early hospital level-of-care assignment. Methods: We conducted a retrospective cohort study of consecutive patients with NSTEMI and angiographically confirmed obstructive coronary artery disease admitted between 1 July 2017 and 31 December 2020 to a cardiovascular referral center in Bogotá, Colombia. The primary outcome was a composite of ICU-requiring complications. Candidate machine-learning models were evaluated for discrimination and calibration. The selected probabilistic model was integrated with predefined clinical triggers and a Gray-Zone decision rule to generate a binary recommendation for general ward versus ICU/monitored care. Results: Among 981 patients, 155 (15.8%) experienced the primary outcome. The isotonic-calibrated HistGradientBoosting model achieved an AUC of 0.821, average precision of 0.618, and Brier score of 0.092 during five-fold out-of-fold internal validation. The final algorithm assigned 464 patients (47.3%) to general ward care and 517 (52.7%) to ICU/monitored care. The observed event rate among ward-assigned patients was 3.9%. Sensitivity was 88.4%, specificity 54.0%, positive predictive value 26.5%, and negative predictive value 96.1%. In secondary comparative analysis, NSTEMI-CARE showed greater discrimination than ACTION-ICU (AUC 0.821 vs. 0.645; p < 0.001). Conclusions: NSTEMI-CARE identified a substantial subgroup potentially suitable for general ward management while maintaining a high negative predictive value. By integrating calibrated risk estimation with explicit clinical decision rules, the algorithm provides a clinically interpretable framework for early level-of-care assignment in NSTEMI. External and prospective validation is required before clinical implementation.