Atrial fibrillation "unmasked" following flutter ablation
ROCHESTER, MINNESOTA. It is well established that patients with atrial flutter (AFL) treated with drugs are at high risk for the development of atrial fibrillation (AF). It is not clear, however, whether a successful right atrial flutter ablation (cavotricuspid isthmus [CTI] ablation) decreases the risk of future AF development in AFL patients with no previous history of AF.

Researchers at the Mayo Clinic now report the results of a trial aimed at determining if a CTI ablation is more effective than medical treatment in preventing AF development in AFL patients. The study involved 87 atrial flutter patients (group 1) with no structural heart disease (lone AFL), 50 atrial flutter patients (group 2) with structural heart disease, and a control group of 59 atrial flutter patients without structural heart disease who were treated with medication only (control group). All patients in groups 1 and 2 underwent a successful CTI ablation and were then, along with the members of the control group, followed for 5 years. During this time, 75% of the control group patients had one or more recurrences of AFL, while no patients in groups 1 and 2 had AFL recurrences. However, during follow-up, 32 group 1 members (37%) and 15 group 2 members (34%) developed AF. Most of the new AF cases were paroxysmal (85% in group 1 and 77% in group 2) and emerged within one year following the AFL ablation.

NOTE: There was no significant difference in the cumulative probability (Kaplan-Meyer) of AF development between the control group and groups 1 and 2, thus indicating that undergoing a CTI ablation does not reduce the risk of later AF development. However, the CTI-ablated patients did get rid of their AFL and, as a result, 56% of them were able to discontinue their antiarrhythmic medications (mostly flecainide and propafenone). The need for cardioversion was also dramatically reduced in groups 1 and 2 from 62% of patients needing one or more cardioversions in the 2 years prior to their CTI ablation to only 4% needing it after.

The Mayo Clinic group concludes that the natural history of AF development in AFL patients is not changed even by a successful CTI ablation.

Luria, DM, et al. Effect of radiofrequency ablation of atrial flutter on the natural history of subsequent atrial arrhythmias. Journal of Cardiovascular Electrophysiology, Vol. 19, November 2008, pp. 1145-50

Editor's comment: A right atrial flutter ablation is usually successful and, according to this study, materially reduces the need for cardioversions and antiarrhythmic medications. Therefore, in the case of atrial flutter, there would seem to be no valid reason to prefer ongoing medical therapy to an ablation, especially since both carry the same risk of the future development of atrial fibrillation.