Class IC antiarrhythmic drug induced atrial flutter: electrocardiographic and electrophysiological findings and their importance for long term outcome after right atrial isthmus ablation

Objective-To describe the electrocardiographic and electrophysiological fin dings of new atrial flutter developing in patients taking class IC antiarrh ythmic drugs for recurrent atrial fibrillation, and to report the long term results of right atrial isthmus ablation in relation to the ECG pattern of spontaneous atrial flutter. Design-Retrospective analysis. Setting-Tertiary care academic hospital. Patients-24 consecutive patients with atrial fibrillation (age 54 (12) year s; 5 female, 19 male) developing atrial flutter while taking propafenone (n = 12) or flecainide (n = 12). Results-The ECG was classified as typical (n = 13; 54%) or atypical atrial flutter (n = 8) or coarse atrial fibrillation (n = 3). Counterclockwise atr ial flutter was the predominant arrhythmia. Acute success after isthmus abl ation was similar in patients with typical (12/13) and atypical (8/8) atria l flutter. After long term follow up (13 (6) months, range 6-26 months), co ntinuation of antiarrhythmic drug treatment appeared to result in better co ntrol of recurrences of atrial fibrillation in patients with typical atrial flutter (11/13) than in those with atypical axial flutter (4/8), but the d ifference was not significant. Ablation for coarse atrial fibrillation was unsuccessful. Conclusions-New atrial flutter developing in patients taking class IC antia rrhythmic drugs for recurrent atrial fibrillation has either typical or aty pical flutter wave morphology on EGG. The endocardial activation pattern an d the acute results of ablation suggest that the flutter circuit was locate d in the right atrium and that the isthmus was involved in the re-entry mec hanism. There appeared to be better long term control of recurrent atrial f ibrillation in patients with typical (85%) as compared with atypical atrial flutter (50%). Patients developing coarse atrial fibrillation may not be c andidates for this strategy.