Fig. 3.

Study population and data flowchart. A total of 235 paired 12-lead and 6-lead ECGs were obtained from 130 patients, including 115 pairs in the supine position and 120 pairs in the sitting position. None of the patients underwent multiple recordings in the same position. For exploratory analysis, 12-lead ECGs acquired in the supine position were matched post hoc with 6-lead ECGs acquired in the sitting position to evaluate the postural effects. An “ungradable ECG” was defined as a recording in which rhythm interpretation was not possible. In contrast, “noisy recordings” refer to ECGs in which reliable beat-level annotation (e.g., identification of fiducial points) was not feasible, and these were excluded only from the numerical agreement analysis. ECG, electrocardiogram