Figure 4.

Bidirectional block was demonstrated by pacing on either side of the ablation line. In Panel (A), the ablation catheter was used to perform pacing with a standard cycle length of 600 ms, while moving it from the medial end of the CTI, to the superior portion of the RA and eventually to the lateral end of the CTI. The catheter in the CS shows a progressive increase in its activation times, suggesting CTI block. The same protocol was performed via pacing from the CS catheter and measure of the activation times of the ablation catheter (B). Panels (C) and (D) display respectively the atrium electrograms during atrial flutter and after the ablation with achievement of SR. CS, coronary sinus; CTI, cavotricuspid rhythm; RA, right atrium; SR, sinus rhythm.