Lessons from ablation responses to preferential wavefront in typical atrial flutter.

Background: The heterogeneous conduction properties through the cavotricuspid isthmus (CTI) in typical atrial flutter (AFL) have not yet been well elucidated.

Objective: We sought to investigate preferential conduction through the CTI and the efficacy of ablation targeting preferential wavefront (PW) guided by ultra-high-resolution mapping.

Methods: In retrospective study, 28 patients were enrolled. Wavefront propagation patterns through the CTI and ablation responses at the location of PW were evaluated. In the following prospective study, 23 patients with predominant PW across the CTI were enrolled and assigned to the arm of PW prior ablation and the arm of conventional ablation.

Results: Five activation patterns were noticed in the retrospective study. The termination sites were exactly located at the PW in 18 of 28 patients (64.3%). The width of the PW in direct termination group was significantly narrower than that in the CL prolongation before termination group (16.6 ± 1.0 mm vs. 23.3 ± 3.4 mm, respectively, p = 0.025). In the prospective study, the voltage of PW region was significantly higher than non-PW regions both from unipolar and bipolar mapping. 21 of 23 patients (91.3%) were terminated at PW. AFL could no longer be induced immediately after termination. The time from radiofrequency application to AFL termination and to achieve bidirectional conduction block was significantly shorter in PW prior ablation arm than that in conventional ablation group (p < 0.05).

Conclusions: Ablation targeting the PW first could be more efficient to terminate typical AFL and to achieve the endpoint of bidirectional conduction block.