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Figure 3 Postoperative AFlut due to reentry around a lesion produced by radiofrequency ablation. (A) The pattern of endocardial activation during AFlut. Note that activation of the coronary sinus was from distal to proximal and activation of the septum was from low to high as recorded in the proximal electrode pairs of the tricuspid annulus (TA) catheter (proximal to distal). The TA catheter is in a proximal position with electrodes 16–20 close to the septum. The delay in conduction at TA 15,16 is due to the inferior vena cava to superior vena cava line of ablation, which diverts activation anteriorly around the superior vena cava. The larger delay between TA 11,12 and the distal TA electrodes is due to activation being diverted around the excised atrial appendage to the area lateral to the crista. There is, unexpectedly, minimal delay in conduction along the coronary sinus where a posterior left atrial line of ablation was placed intraoperatively. (B) Concealed entrainment of atrial electrograms during pacing of the distal coronary sinus during AFlut. Atrial activation in the two most distal coronary sinus electrograms is not visible owing to stimulus artifact. There is intact conduction along the coronary sinus from distal to proximal through the line of ablation. The right atrial decapole catheter has been moved from the TA position to the posterior right atrium. (C) and (D) The difference in coronary sinus activation during distal coronary sinus pacing before and after radiofrequency ablation. The 5-mm decapolar coronary sinus catheter is positioned with electrode 10 (the most proximal) at the coronary sinus os. Ablation was performed from within the coronary sinus at a site corresponding with electrode 3. This induced a reversal of the activation sequence in the proximal coronary sinus. Following this application of radiofrequency energy it was no longer possible to induce AFlut with burst pacing. (E) The likely circuit of this particular AFlut and the successful site of ablation (arrow).
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