Long-term outcomeS of cavotrIcuspid isthMus-dePendent fLuttEr Ablation: Single vs Double Catheter Procedure

Single venous femoral access will be obtained and the ablation will be performed similar to Group A. After the ablation line is over, we will confirm CTI block using the PRI. During atrial pacing (10 V, 1.5 ms) at a stable cycle length (range 500-700ms) from the tip of the ablation catheter with a sweep speed of 300mm/s, the ablation catheter will be placed first at 5 o'clock (medial to CTI line), then at 7 o'clock (lateral to CTI line), and finally at 9 o'clock position, and the corresponding PRIs will be measured for each pacing site. CTI block is assumed when: (i) the PRI at 7 o'clock is \>80ms longer than that at pacing sites of 5, and (ii) the PRI at 9 o'clock is shorter than the PRI at 7 o'clock.

Double venous femoral access will be obtained. A duodecapolar catheter will be positioned in the right atrium around the tricuspid valve annulus (TVA) to record activation sequence around the tricuspid annulus. An ablation catheter will be positioned using fluoroscopic guidance in the central CTI, 6 o'clock in a left anterior oblique view. The distal ablation electrode position will then be adjusted toward or away from the TVA, based on the ratio of atrial and ventricular electrogram amplitudes with an optimal ratio of 1:2 or 1:4 at the TVA. After the ablation catheter is positioned, it will be very slowly withdrawn during ablation toward the inferior vena cava while radiofrequency energy is applied continuously. CTI block will be evaluated after ablation by determining the right atrial activation sequence during pacing from the low lateral right atrium and coronary sinus ostium.