Click on image to view larger version.

Figure 4 (A) Isopotential maps showing the activation sequence (frames 1 to 3) of atrial pacing before ablation. Color scale for each isopotential map has been set so that white indicates most negative potential and blue indicates least negative potential. The activation wavefront propagates downward from the superior anterior right atrium (RA) (frame 1) to middle anterolateral RA and splits into two wavefronts (frame 2); one passes through the gap (g) in the crista terminalis (CT) and activates superior posterolateral RA (frame 3), and the other passes through the lateral cavotricuspid isthmus. (B) Isopotential maps showing the activation sequence (frames 1 to 3) of atrial pacing after ablation. Color scale for each isopotential map has been set so that white indicates most negative potential and blue indicates least negative potential. The activation wavefront propagates downward from the superior anterior RA (frame 1) to middle anterolateral RA (frame 2) and splits, into two wavefronts (frame 3); one passes around the cranial end of the CT and activates the superior posterior RA, and the other passes through the lateral cavotricuspid isthmus. L10 to L15 represent the radiofrequency ablation lesions. (C) Before ablation the virtual electrograms near the conduction gap in the CT demonstrate fractionated potentials. (D) After ablation the virtual electrograms near the conduction gap in the CT demonstrate double potentials, suggesting conduction block. IVC = inferior vena cava; SVC = superior vena cava.