B-PO04-076 DIRECT IMAGING AND ANATOMIC RECONSTRUCTION OF THE RIGHT PHRENIC NERVE WITH INTRACARDIAC ECHOCARDIOGRAPHY: A MULTICENTER FEASIBILITY STUDY

Abstract

Right phrenic nerve (RPN) injury is a known risk of cardiac ablation. RPN pacing is commonly used as a surrogate to mark the course of the at-risk RPN during 3D electroanatomic (EA) mapping. The optimal method for anatomic localization and identification of the portion of the RPN at risk of injury during cardiac ablation is unknown. Ultrasound imaging of peripheral nerves is utilized in other fields of medicine, suggesting that this might be useful in cardiac electrophysiology. We evaluated the feasibility of intracardiac echocardiography (ICE) imaging and anatomic reconstruction of the RPN during EA mapping for AF ablation and compared this to traditional RPN localization with pacing. 27 consecutive patients undergoing initial or repeat AF ablation at 2 centers were studied prospectively in nonrandomized fashion. ICE imaging was performed from the superior vena cava (SVC) and right atrium (RA) to mark the location and course of the RPN using ultrasound based 3D mapping (Cartosound, Biosense Webster). RPN pacing (20 milliamperes @ 10 milliseconds) was then performed within the right pulmonary veins (RPVs) to identify and mark areas of capture by 3D EA mapping. The areas of capture were then compared to the course of the RPN visualized by ICE. The RPN course was successfully identified by ICE and confirmed by pacing in 26 patients (96%). Compared to pacing based localization, ICE based localization identified a greater degree of the RPN course adjacent to the right pulmonary veins in all 26 patients. Right pulmonary vein antral ablation was adjusted to avoid potential RPN injury in 5 patients (19%) based on pacing localization alone vs. 2 patients (7%) based on a combination of pacing and ICE localization. No serious complications, including phrenic nerve injury, pericardial tamponade, or other adverse events occurred. Direct imaging and anatomic reconstruction of the RPN by ICE is feasible and showed high correlation with capture by high output pacing. Further investigation is required to better understand if RPN ICE imaging allows for identification of additional areas of potential vulnerability near the RPVs, SVC, and RA; planning of safer ablation lesion sets; and/or reduction in incidence of RPN injury.