Figure 4: Incisional Reentry in the Lateral Right Atrium in a Patient with Prior Repair of Atrial Septal Defect.

A: Electroanatomical map with the Rhythmia® system demonstrates reentry around a line of conduction block (indicated by blue tags) in the lateral right atrium (RA). B: Entrainment from poles 7–8 of a multipolar catheter loop in the lateral RA shows a post-pacing interval nearly identical to the tachycardia cycle length. Note that electrograms on more proximal poles RA 11–12 and 13–14, which are activated earlier, are entrained orthdromically with delay. This is an example of downstream overdrive pacing seen with reentrant arrhythmias. CS = coronary sinus.