Fig. 1: Flowchart of the study design showing the sample sizes for different experimental splits.

We divided the entire ECG dataset, allocating 60% for model development (including fivefold internal cross-validation for training and fine-tuning) and setting aside 40% as a holdout set for final validation. For evaluation, we assessed our models using two approaches: first, exclusively on the first ECGs from each episode captured during an ED visit or hospitalization, reflecting the intended point-of-care deployment; second, on all ECGs from the holdout set. Additionally, we evaluated our models’ performance within specific patient subgroups categorized by sex and the presence of cardiac pacing or ventricular assist devices.