Effect of right atrial isthmus ablation on the occurrence of atrial fibrillation: observations in four patient groups having type I atrial flutter with or without associated atrial fibrillation.

Background: The goal of this study was to test the hypothesis that the occurrence of atrial fibrillation (AF), in at least some patients with coexisting type I atrial flutter (AFL), is based on macro-reentry around the tricuspid valve orifice, including the right atrial (RA) isthmus, by evaluation of AF recurrences after successful ablation of AFL.

Results: Eighty-two consecutive patients with type I AFL, with or without concomitant AF, underwent radiofrequency ablation (RFA) of the RA isthmus by an anatomical approach. The results were analyzed in 4 groups of patients: group 1 (only AFL; 29 patients), group 2 (AFL >AF; 22 patients), group 3 (AF >AFL; 15 patients), and group 4 (developing AFL while receiving class IC antiarrhythmic drug therapy for AF, the "class IC atrial flutter"; 16 patients). In all groups, RFA of type I AFL was performed with a high (>/=93%) procedural success rate. In group 1, only 2 patients (8%) had AF after (18+/-14 months) AFL ablation. These figures were 38% (20+/-14 months) and 86% (13+/-8 months) in groups 2 and 3, respectively. Group 4 patients (4+/-2 months) had a 73% freedom of AF recurrences with continuation of the class IC agent.

Conclusions: The low incidence of new AF during long-term follow-up after RFA of type I AFL makes it unlikely that radiofrequency lesions promote the development of AF. The impact of isthmus ablation on AF recurrences differs according to the clinically predominant atrial arrhythmia and suggests a possible role of the RA isthmus in the occurrence of AF in some patients. Ablation of class IC atrial flutter in patients with therapy-resistant AF is a novel approach to management of this patient subset. Careful classification of AF patients plays a role in the selection of the site of ablation therapy.