Cavotricuspid isthmus is constantly a zone of slow conduction: Data from ultra-high-resolution mapping

Whether cavotricuspid isthmus (CTI) is a region of conduction slowing during typical flutter has been discussed with conflicting results in the literature. We aimed to evaluate conduction velocity (CV) along the different portions of the typical flutter circuit with a recently proposed method by means of ultra-high-resolution (UHR) mapping.

Consecutive patients referred for typical atrial flutter (AFL) ablation underwent UHR mapping (Rhythmia, Boston Scientific). CVs were measured in the CTI as well as laterally and septally, respectively, from its lateral and septal borders.

A total of 33 patients (mean age: 65 ± 13 years; right atrial volume: 134 ± 57 mL) were mapped either during ongoing counterclockwise (n = 25), or clockwise (n = 3) AFL (mean cycle length: 264 ± 38 ms), or during coronary sinus pacing at 400 ms (n = 1), 500 ms (n = 1), or 600 ms (n = 3). A total of 13 671 ± 7264 electrograms were acquired in 14 ± 9 min. CTI CV was significantly lower (0.56  ± 0.18 m/s) in comparison with the lateral CV (1.31 ± 0.29 m/s; P < .0001) and the septal border CV of the CTI (1.29 ± 0.31 m/s; P < .0001).

UHR mapping confirmed that CTI CV was systematically twice lower than atrial conduction velocities outside the CTI.