Click on image to view larger version.

Figure 1 Arrangement of the electrodes for recording and pacing. Multiple atrial electrograms were recorded by 96 bipolar electrodes (open circles) placed at 1-mm interpolar and 2-mm interelectrode distances. A pair of electrodes (filled circles) placed at a 1-mm interpolar distance in the center of the mapping electrodes served for pacing. A bipolar electrode (hatched circles) adjacent to the stimulation electrodes was used for sensing. An electrode (double circle) next to these electrodes was used for recording unipolar atrial electrograms from which local activation intervals were measured.