Catheter ablation is recommended as first-line therapy for most patients with typical atrial flutter. The most common approach is to create an ablation line across the cavotricuspid isthmus (CTI). Traditionally, atrial flutter ablation has been performed with a conventional approach using two catheters, an ablation catheter and a duodecapolar catheter that is placed at the level of the tricuspid annulus to confirm the CTI block. Recently, a single catheter approach has been described using the behavior of PR interval change during differential pacing over the ablation line to prove CTI block. This prospective, randomized, multicenter study analyzes the effectivity of a single catheter approach compared with conventional approach in terms of clinical outcomes.

Typical atrial flutter is a reentrant rhythm in the right atrium that is constrained anteriorly by the tricuspid annulus and posteriorly by the crista terminalis and eustachian ridge. Catheter ablation is the first-line therapy for most patients with typical atrial flutter. The most common approach is to create an ablation line across the CTI, from the tricuspid annulus to the inferior vena cava. Traditionally, atrial flutter ablation has been performed with a conventional approach using two catheters, an ablation catheter and a duodecapolar catheter that is placed at the level of the tricuspid annulus that allows to evaluate the right atrial activation sequence to confirm the CTI block. Recently, a single catheter approach has been described using the behavior of PR interval (PRI) change during differential pacing over the ablation line to prove CTI block. The PRIs is measured for three different pacing site, 5 o'clock (medial to CTI line), 7 o'clock (lateral to CTI line), and 9 o'clock position. CTI block was assumed when the PRI at 7 o'clock was >80ms longer than that at pacing sites of 5 o'clock and the PRI at 9 o'clock was shorter than the PRI at 7 o'clock. However, a direct comparison between this approach and the conventional one was not yet performed. This prospective, randomized, multicenter study analyzes the effectivity of a single catheter approach compared with conventional approach in terms of clinical outcomes. Our research hypothesis is that a single catheter approach has the possible advantages of being a faster, more efficient and cheaper procedure than the conventional approach. Moreover, as it only requires a single venous access, the risk of complications is decreased.

Inclusion Criteria:

• Patients admitted at any of the centers to perform a CTI ablation.
• Signed informed consent

Exclusion Criteria:

• Age < 18 years.
• Pregnancy.
• Impossibility to perform CTI ablation.
• Impossibility to measure PRI (complete atrioventricular block).
• Ablation of other cardiac arrhythmias during the same procedure.
• Medical, geographical and social factors that make study participation impractical, and inability to give written informed consent. Patient's refusal to participate in the study.