Figure 3. Periprocedural electrocardiograms: Termination of AT. (A, B) Surface and intracardiac electrocardiograms with the ablation catheter at the location of termination of the atrial tachycardia (AT) at the anterior wall. The black arrows indicate the sharp potentials on the microelectrodes. Small, fragmented potentials are visible on ablation (Abl) d electrodes at the same time. The cycle length of 400 ms was prolonged to 450 ms and stopped application of ablation application for 1200 ms (large arrow). The total radiofrequency ablation time at termination was 40 s. CS – coronary sinus catheter placed distal in the coronary sinus; spiral – spiral mapping catheter placed inside the left atrial appendage; Abl d – distal electrodes on the map catheter; Abl p – proximal electrodes on the map catheter; Abl u1–u2, Abl u2–u3, Abl u1–u3 – micro electrodes; A – atrium; V – ventricle; black triangle – start of ablation; black star – termination of AT. Speed 100 mm/s. (C) An electroanatomic map of the left atrium using CARTO 3, V7 (Biosense Webster). Left side, right anterior oblique and right side, left anterior oblique views during ablation at the anterior wall. Note the ablation catheter in the anterior wall during delivery of a very high-power, short-duration application of 90 W/4 s. The “bullseye” in the upper left corner shows the temperature of the ablation catheter tip. White arrow – application of AT termination. (D) An electroanatomic map of the left atrium with the final lesion set up with an anterior line and pulmonary vein isolation depicted by red dots with white points. Source: Property of C. Heeger.