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

^a Division of Cardiology, Kumamoto City Hospital, Kumamoto, Japan
^* Second Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki, Japan

View larger version (20K): [in a new window]   Figure 1 (A) A schema showing the tricuspid valve annulus (TA) and electrogram recording sites. Orifices of the inferior vena cava (IVC) and superior vena cava (SVC) are shown. Mapping of 9 atrial sites around the TA was performed during pacing from the septal portion of the isthmus (S-IS) and from the lateral portion of the isthmus (L-IS) at a rate 10 beats/minute faster than the sinus rate in order to examine the conduction pattern in the IVC-TA isthmus. A-TA = anterior portion of the TA, AL-TA = anterolateral portion of the TA, CSOS = coronary sinus ostium, HB = His bundle potential recording site, L-TA = lateral portion of the TA, M-IS = medial portion of the isthmus, PL-TA = posterolateral portion of the TA. (B) Mapping catheter position for bipolar electrogram polarity mapping is shown in an open view of the floor of the right atrium. The septal portion of the isthmus extending from the TA to the IVC adjacent to the previously performed ablation line was arbitrarily divided into five sites. Mapping of these sites was performed during pacing from the low lateral right atrium (LLRA) with a mapping catheter being positioned parallel to the ablation line. (C), Mapping catheter position for bipolar electrogram polarity mapping performed before the initial ablation.

View larger version (19K): [in a new window]   Figure 2 Atrial electrograms obtained from each mapping site during bipolar electrogram polarity mapping performed after recurrence of isthmus conduction. The data are shown for all patients. Asterisks denote the transitional electrograms. Scale bars indicate 0.2 mV and 100 milliseconds.

View larger version (14K): [in a new window]   Figure 3 Atrial electrograms obtained from each mapping site during bipolar electrogram polarity mapping performed before the initial ablation in 10 patients. The atrial electrogram at each site shows the transitional electrograms in all patients. Scale bars indicate 0.2 mV and 100 milliseconds.

View larger version (25K): [in a new window]   Figure 4 Activation patterns around the tricuspid annulus before and after application of radiofrequency energy to the recurrent conduction site in the isthmus identified by bipolar electrogram polarity mapping. Scale bars indicate 0.2 mV and 100 milliseconds. (A) During pacing from the septal portion of the isthmus (S-IS) before application of radiofrequency energy, the impulse propagated in both a clockwise and a counterclockwise directions, causing a collision of wave fronts near the anterior portion of the tricuspid valve annulus. Abbreviations as in Figure 1. (B and C) Activation around the tricuspid annulus after radiofrequency energy application. Counterclockwise and clockwise activation around the tricuspid annulus were observed during pacing from the septal portion of the isthmus (S-IS) (panel B) and from the lateral portion of the isthmus (L-IS) (panel C), respectively. A double potential was recorded in the medial portion of the isthmus. Abbreviations as in Figure 1.

View larger version (19K): [in a new window]   Figure 5 A schema showing the relationship between the electrogram pattern obtained at each site and recurrent conduction site. Sites 1, 2, 4, and 5 are activated by the wave front originating from the recurrent conduction site, resulting in mainly negative (site 1 and 2) and positive deflection (site 4 and 5). Site 3 is activated by the wave front perpendicular to the bipole, resulting in the transitional electrogram. Abbreviations as in Figure 1.