Detailed Description:

Background Ablation procedures for CTI-dependent TF have classically been guided by fluoroscopy and intracavitary electrograms from diagnostic catheters placed in the right atrium (RA), the coronary sinus (CS) and the CTI (ablation catheter). Over the last few years, the use of navigators has increased considerably not only for complex procedures, but also for simple procedures, with the aim of reducing and even completely eliminating irradiation to both the patient and the operator (1). The investigators´ group is looking to characterize the high voltage and the low velocity regions in the CTI to minimize the procedure times. This has been addressed in a recent observational study with very good results. Rationale There is increasing evidence of the benefits using 3D-systems not only to diminish fluoroscopy, but also to guide ablation targeting high voltage areas in the CTI (2-5). It is well known also the existence of low speed areas in the CTI, facilitating the presence of reentrant circuits (6,7). Currently, the investigators´ center performs all CTI ablation procedures using a 3D-navigator system, mostly with zero or minimal fluoroscopy. The investigators´ group has carried out a preliminary study with 13 patients to assess the effectiveness of CTI ablation with the use of the Ensite X navigator in magnetic mode with Omnipolar technology and HDGrid catheter. In this observational study the investigators were able to characterize the high voltage and the low velocity regions in the CTI to minimize the RF lesions and procedure times. Acute bidirectional block was achieved in 100% of patients with an average fluoroscopy time of 1 ± 2 min (77% patients with zero fluoroscopy) and an average RF time of 5,7 ± 3,2 min (38% below 3 min). This results were significantly lower than results obtained with classical linear ablation: median fluoroscopy time 19.3 min, IQR 12.9 to 36.4 min, median fluoroscopy dose 3520.7 cGycm(2), IQR 1700.0 to 6709.0 cGycm(2). From the investigators´ point of view this observational study, together with previous evidence justify a randomized study in order to confirm our hypothesis: Hypothesis Omnipolar technology is able to guide the ablation procedure minimizing both the RF time and the fluoroscopy time (compared to linear ablation) by targeting only the critical regions on the CTI. Therefore Omnipolar technology will diminish RF time and fluoroscopy time/exposition compared to classical CTI ablation, and by means of this the investigators expect an inferior complications rate. Importantly acute success rate and 6 months follow-up recurrences rate will remain similar. OBJECTIVES Primary objectives: to optimize procedure times of CTI ablation with 3 different strategies based in voltage and/or conduction velocity maps using the Ensite X navigator in magnetic mode with Omnipolar technology and HDGrid catheter compared to classical linear ablation. o Specific objectives: Fluoroscopy time, radiofrequency time, radiation dose, percentage of zero-fluoroscopy procedures, acute efficacy, complications rate. Secondary objectives: to increase the effectiveness of CTI ablation with 3 different strategies based in voltage and/or conduction velocity maps using the Ensite X navigator in magnetic mode with Omnipolar technology and HDGrid catheter compared to classical linear ablation. Specific objectives: Recurrences rate at 6 months.}}