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

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