Successful radiofrequency catheter ablation of right sided accessory pathways during sustained atrial fibrillation

Up to now there have been no descriptions in the literature of endocardial catheter mapping and successful radiofrequency catheter ablation of the right sided accessory pathway during sustained atrial fibrillation. We attempted ablation of a right posterolateral and a right lateral accessory pathway during sustained atrial fibrillation with rapid anterograde conduction over the accessory pathway in two patients with Wolff-Parkinson-White syndrome. In both patients (aged 47 and 52 years), sustained atrial fibrillation occurred during the electrophysiological study to assess accessory pathway conduction properties. The mean ventricular rate during atrial fibrillation was 180 and 170beats. min− θ1, respectively. Both patients were successfully ablated with a single radiofrequency impulse. At the successful ablation sites, a potential of the accessory pathway was consistently recorded preceding the onset of preexcitation in the surface electrogram, by 25 ms in patient 1 and 30 ms in patient 2. The unipolar electro-gram recorded from the ablation catheter showed a QS morphology and the accessory pathway potential preceded the intrinsic deflection by 10 ms in both patients. Onset of the ventricular electrogram (patient 1: − θ20 mθ patient 2: − θ15 ms) and its activation time (patient 1: − θ15 mθ patient 2: ±5 ms) in relation to the onset of preexcitation in the surface electrocardiogram also indicated the close proximity of the ablation catheter to the accessory pathway. Preexcitation disappeared within 2 s after energy application in both patients. Thus, radiofrequency catheter ablation of right sided accessory pathways during sustained atrial fibrillation is feasible and may obviate the need for medical or electrical cardioversion. Appropriate target sites can be identified by the presence of an accessory pathway potential, early onset and activation of the local ventricular electrogram, and the QS morphology of the unipolar electrogram.