Incremental Value of 24-Hour Ambulatory Electrocardiogram–Derived Heart Rate Variability in Machine-Learning Prognostic Models for Heart Failure

To determine whether heart rate variability (HRV) indices derived from 24-hour ambulatory electrocardiography provide complementary prognostic information in machine-learning prognostic models using conventional clinical variables in patients with heart failure, particularly with regard to calibration and threshold-based performance.