Abstract 2345: Radiofrequency Ablation of the Cavotricuspid Isthmus Independently Mitigates the Arrhythmogenicity of Remote Ectopic Atrial Beats
Background: Radiofrequency ablation (RFA) of isthmus-dependent atrial flutter (AFL) in patients with AFL and atrial fibrillation (AF) has been shown to decrease the future AF burden. The purpose of this study was to test the hypothesis that RFA of the cavotricuspid isthmus (CTI) renders ectopic atrial beats (EABs) less arrhythmogenic without effecting the frequency of EABs.
Methods: The study comprised patients who had drug-refractory paroxysmal AFL and AF without a transition of either arrhythmia to the other. The frequency of EABs and percentage of AF episodes per EAB were assessed before, during, and after CTI ablation. Atrial effective refractory periods (AERPs) were measured before and after RFA.
Results: Twenty-three patients were included (mean age, 56.3±7.4 y). During electrophysiology studies, the average number of EABs per minute was 4.8±3.8 before ablation and 4.5±1.8 after ablation (P=NS). Before ablation of the CTI, 35.2±10.7% of the EABs led to bursts of AF lasting at least 5 seconds. After ablation of the CTI, 10.7±11.8% of the EABs lead to bursts of AF (P<0.0001). The mean coupling interval of the EABs was 303±32 ms before ablation and 331±34 ms after ablation (P<0.0001). The mean right AERP (at a basic cycle length of 400 ms) was 203±15 ms before ablation and 218±18 ms after ablation (P<0.0001). During 4 weeks of outpatient monitoring, with the patients receiving the same regimen as they did prior to CTI ablation, the mean number of AF episodes per patient decreased from 16.2±7.2 before ablation to 3.2±2.8 after ablation (P<0.001).
Conclusions: RFA of the CTI may render EABs less arrhythmogenic without effecting the frequency of EABs and may be coincident with local vagal denervation. This phenomenon may be a newly recognized mechanism by which RFA of the CTI decreases the AF burden.