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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.
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