Mapping and localization of the left phrenic nerve during left atrial appendage electrical isolation to avoid inadvertent injury in patients undergoing catheter ablation of atrial fibrillation

Background: A significant role of the left atrial appendage (LAA) in the genesis of atrial fibrillation (AF) has been described. Left atrial appendage electrical isolation (LAAEI) confers substantial long-term clinical benefits. Nevertheless, the left phrenic nerve (LPN) is in the vicinity of the LAA and can be injured during radiofrequency ablation at the ostial level. Objective: The purpose of this study was to describe our experience mapping the LPN, its anatomic relationships to the LAA and alternative approaches to isolate this structure when the LPN is located at the LAA ostium. Methods: Patients undergoing LAAEI for nonparoxysmal AF were included in this study. We attempted to localize the LPN with high-output pacing (20 mA/2 ms). Cases were classified into 4 groups (distal, middle, proximal segment and unmappable) based on the position of the LPN in electroanatomic mapping in the posterior wall of the LAA. Results: A total of 66 cases were included in this study. The LPN was mapped in the distal segment in 27 cases (40.9%); in the middle segment in 22 (33.3%); and at the proximal segment/ostium in 3 (4.5%); the LPN was unmappable in 14 cases (21.2%). In the 3 patients in whom the LPN was at the ostial level or crossing the ostium, segmental LAAEI was attempted in 2, with successful LAAEI achieved in 1 case. There was no LPN injury. Conclusion: LPN mapping is feasible and should be routinely performed to prevent LPN injury during LAAEI.