Role of bipolar electrogram polarity mapping in localizing recurrent conduction in the isthmus early and late after ablation of atrial flutter

Objectives. Bipolar electrogram polarity was analyzed to localize the recurrent conduction site in the isthmus between the tricuspid annulus (TA) and inferior ven cav (IVC) in recurrent atrial flutter (AF). Background. Despite the initial successful linear isthmus ablation, recurrence of transisthmus conduction and AF is not uncommon. It is unclear how the recurrent conduction site can be identified. Methods. Fourteen patients with recurrent AF were studied: four with late recurrence remote from the first ablation and 10 with early recurrence within 60 minutes after the initial successful ablation. Bipolar electrogram polarity mapping was performed during low lateral right atrium (LLRA) pacing during sinus rhythm while recording bipolar electrograms from the septal portion of the isthmus along the previously ablated line. The septal side of the isthmus from T to IVC was arbitrarily divided into five sites, and the bipolar electrodes with cathode at the tip and anode at the second was placed at each site. The recurrent conduction site was localized by analyzing the polarity of the bipolar electrogram recorded at each site. Results. All recurrent AF was due to reentry around TA. During pacing from LLRA, as the mapping electrode was moved from T to IVC side, the major polarity of the electrogram changed from negative to positive in all patients. transitional electrogram with the equal amplitudes in positive and negative components was recorded between the sites showing mainly negative and positive electrograms, indicating electrogram polarity reversal at this site. Application of radiofrequency energy to this single site resulted in the elimination of transisthmus conduction in all patients with single application in 11 patients and 2 or 3 in the remaining 3. Conclusions. Bipolar electrogram polarity mapping with attention to the polarity reversal point is useful for identifying and ablating the recurrent conduction site.