ECG assessment
For each patient, ECG with baseline preexcitation and/or ECG with full preexcitation were analysed (per availability). Full preexcitation ECG pattern was obtained during electrophysiological study via incremental atrial pacing, programmed atrial pacing or adenosine administration. QRS polarity/type was coded as one of the six following categories: completely positive (monophasic R) without notches, completely positive (R) with notches (notch/plateau at the top of monophasic R wave), predominantly positive (Rs, Rsr’, qR etc.), equiphasic (RS, QRS, RSR’, etc.), predominantly negative (Qr, rS, rSr’, etc.) or completely negative (QS) - depending on the dominant polarity. Examples of QRS categories are presented in Figure 2 and inside the application next to each question. Most representative full preexcitation patterns for the 19 regions are illustrated in Figure 3 and Supplementary Figures 1-2 .