Fig. 2.

Intracardiac electrograms of the range of responses to HFS at ET-GP. All examples are from one patient. Map distal was used to pace and deliver HFS. Its positions in the LA at the time of stimulation are shown in the PA views of the CARTO™ geometry. The PV catheter was in the lower branch of the left common PV for all three ET-GP sites.

A) The Map catheter was positioned in the mid-roof, near to the posterior wall of the LA. After the first paced beat, the subsequent trains were synchronised HFS. The earliest ectopy activation was in PV 13–14. There were just two beats of the same ectopy before stopping both HFS and pacing.

B) The Map catheter was positioned near the anterior ostium of the upper branch of the left common PV. After the first paced beat, the subsequent trains were synchronised HFS. Again, the earliest ectopy activation was seen in PV 13–14. The PV rapidly fired causing few seconds of AF that regularised towards the end then terminated.

C) The Map catheter was positioned at the posterior ostium of the lower branch of the left common PV. This trace shows the first paced beat followed by one synchronised HFS train which triggered ectopy. The earliest ectopy activation was again in PV 13–14. This initiated sustained AF lasting >2min. The patient had direct DC cardioversion to restore sinus rhythm.

(L = left, CS = coronary sinus, ET-GP = ectopy-triggering ganglionated plexus, HFS = high frequency stimulation, LA = left atrial, LAA = left atrial appendage, Map = mapping catheter, PA = posterior anterior, RSPV = right superior pulmonary vein, RIPV = right inferior pulmonary vein, PV = pulmonary vein).