The utility of atrial pacing for identifying the electrical breakthrough sites between the left atrium and pulmonary veins

BACKGROUND Circumferential pulmonary vein (PV) isolation for atrial fibrillation (AF) is occasionally difficult to achieve because electrical breakthrough sites (EBSs) between the left atrium (LA) and PVs cannot be identified during ablation especially in the carina regions. METHODS The left PVs (Lt.PVs) of 60 AF patients and the right PVs (Rt.PVs) of 37 patients undergoing PV isolation were studied. When PV isolation was not achieved after the initial circumferential PV isolation, atrial pacing was repeatedly performed from the distal coronary sinus (CSd) and high right atrium (HRA), and the time interval from the stimulus to the earliest PV potential (stimulus-PV interval) was measured using circular mapping catheters at each PV until PV isolation was achieved. When PV isolation was achieved via local Radiofrequency (RF) deliveries, those regions were diagnosed as final EBSs. We classified the final EBSs into six segments for each PV (anterior and posterior PV walls of the roof, carina, and bottom) and investigated the relationship between the final EBSs and stimulus-PV intervals. RESULTS For Lt.PVs, the stimulus-PV intervals during CSd pacing were significantly shorter than during HRA pacing at the Lt.PV anterior carina and bottom (90±28 ms vs. 125±26 ms, P<0.001 and 84±20 ms vs. 148±24 ms, P=0.028, respectively), but there was no significant difference in the Lt.PV roof and any posterior segments. For Rt.PVs, the stimulus-PV interval from both pacing sites exhibited no significant difference between either segment. CONCLUSIONS This pacing method may help to identify whether EBSs are located in the anterior Lt.PVs. Improved recognition of EBSs through pacing from different sites would be helpful for achieving PV isolation.