The occurrence of atrial fibrillation during an electrophysiologic study in patients with Wolff-Parkinson-White syndrome is a common problem and it is time-consuming to terminate it either with the use of drugs or by electrical cardioversion. The purpose of this report is to assess the feasibility of successful radiofrequency catheter ablation of and mapping for overt left-sided accessory pathway during atrial fibrillation. During an electrophysiologic study, pre-excitation was lost and the patient developed sustained atrial fibrillation either spontaneously or during catheter manipulation. We decided to map during this arrhythmia because we noted that the patient had maximally pre-excited beats which might increase the possibility of accessory pathway potential recording and a successful ablation site. With the ablation catheter in the left-lateral region we recorded an early ventricular electrogram and a rapid deflection preceding the onset of ventricular activation that was not observed in non pre-excited beats and we considered it the Kent potential. At this site we applied one pulse of radiofrequency current with temperature control at 70 degrees C and eliminated anterograde conduction over the accessory pathway during the first 3 seconds and continue the radiofrequency current for a total of 2 minutes. The procedure time was 60 minutes. We conclude that mapping and radiofrequency catheter ablation can be successfully performed during pre-excited atrial fibrillation and this could shorten the procedure and obviate the need for several electrical cardioversions.
