Changes in low right atrial conduction times during pulmonary vein isolation for atrial fibrillation: correlation with inducibility of typical right atrial flutter.
Isthmus-dependent right atrial flutter (RAFL) is a common sequela of pulmonary vein isolation (PVI). It is unclear as to whether RAFL is a result of PVI or a concealed phenomenon unmasked by the elimination of atrial fibrillation (AF). We measured low right atrial conduction times (LRACTs) before and after PVI and examined their relationship to the inducibility of RAFL. Twenty consecutive patients with paroxysmal AF but no history of RAFL were studied during the initial PVI procedure by radiofrequency ablation. Antiarrhythmic agents were discontinued for at least five half-lives. The clockwise and counterclockwise LRACTs were measured before and after PVI by pacing the proximal coronary sinus or low-lateral RA. Programmed atrial stimulation was performed post-PVI. Right atrial flutter, if inducible, was confirmed by entrainment mapping. Right atrial flutter was induced in six patients (Group A). No arrhythmias or only AF was induced in the remaining 14 patients (Group B). The average change in the clockwise LRACT was 19.8±17.5 ms in Group A vs. 0.3±10.7 ms in Group B (P<0.05). The average change in the counterclockwise LRACT was 25.7±30.4 ms in Group A vs. 0.0±6.7 ms in Group B (P<0.05). There were no significant differences between the groups in absolute LRACT or number of ablation lesions around the right pulmonary veins. Right atrial flutter post-PVI is associated with prolongation of LRACTs. Ablation over the septal left atrium near the posterior right atrium during isolation of the right pulmonary veins may cause conduction delays that can lead to RAFL.