Click on image to view larger version.

Figure 8 High-density mapping of a tachycardia focus along the crista terminalis demonstrating the phenomenon of preferential conduction from origin-to-exit or breakout point to the remaining atria. This occurred in a 46-year-old man who presented with atrial tachycardia after having undergone pulmonary vein isolation, left atrial linear ablation, and cavotricuspid isthmus ablation for permanent atrial fibrillation (the crista terminalis had not previously been targeted by ablation). There is reversal of activation of potential on spine-C with the ectopic beat, which then spreads to the adjacent spine-B. At B5–6 continuous activity is observed followed by activation of the remaining atria. A second concealed beat is seen to arise from the origin (C10–11) and traverses to the exit point at B5–6. At this site conduction block is observed to the remaining atria. With longer coupling intervals, such ectopy was observed to excite the whole atria. CS = coronary sinus.