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.

METHODS AND 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.