Validation of CTI with the single ablation catheter
In SR, the ablation catheter was positioned on the septal part (at the CS ostium) of the CTI line and PR interval was measured on surface ECG from the atrial CS spike to the peak QRS measured on lead II (septal delay, Figure 1). We used this definition to better define the end of PR interval, because the beginning of the QRS can be harder to precisely identify as compared to the peak of the QRS. This measurement was performed during pacing at 800 ms or 10 bpm faster than the baseline patient heart rate. Then, pacing at the same cycle length was performed on the lateral side of the CTI line (lateral delay). PR measurement were recorded before and after the CTI block was confirmed with the standard method. Delta PR interval was obtained by subtracting the septal delay from the lateral delay. Figure 2 shows examples of PR measurement before and after CTI block achievement.