Noncontact Mapping System (EnSite) Was Useful to Determine Optimal Ablation Site for the Origin of Atrial Tachycardia: A Case Report

The patient was 22-year-old female. She underwent catheter ablation for the treatment of Wolff-Parkinson-White syndrome (WPW) at the time of 17 years old. There was an accessory pathway located in the posterior septum which was successfully ablated at the first session. Since the discharge after this ablation procedure, the patient did not suffer from symptom of tachycardia for 4 years, but she again started to suffer from palpitation from the last year. In the electrophysiologic study (EPS), no recurrence of accessory pathway conduction was confirmed, but atrial tachycardia (AT) was induced by programmed electrical stimulation under isoproterenol infusion. The activation map in the EnSite system revealed preferential conduction nearby the His bundle area. In this analysis, the earliest activation site was located in the site close to His bundle (<5 mm) and the break-out through the preferential pathway was observed at the coronary sinus ostium. Because the earliest activation and preferential pathway were too close to His bundle, the ablation was performed against the break-out point, and it successfully interrupted the AT and prevented AT induction. In this case, the EnSite system was useful to determine an appropriate ablation target by precise evaluation of origin of AT.