PO-04-060 FOUND WITH SOUND: INTRACARDIAC ECHOCARDIOGRAPHY CORRELATED WITH MEDIUM-OUTPUT PACING TO AVOID PHRENIC NERVE INJURY WITH RIGHT ATRIAL ABLATION

Abstract

Catheter ablation within the right atrium can be limited by proximity to the phrenic nerve and potential for hemi diaphragmatic paralysis. High output pacing is frequently employed to map phrenic position relative to endocardium, particularly in relation to the superior vena cava and the right superior pulmonary vein. The use of intracardiac echocardiography (ICE) in correlation with lower output pacing to rigorously map the course of the right phrenic nerve along the right atrium has not been previously described. We describe a case of incessant right atrial tachycardia successfully mapped and ablated close to the phrenic nerve using a combination of ICE imaging and medium-output pacing to rigorously map the phrenic nerve. n/a An 18-year-old man with incessant atrial tachycardia was referred for repeat ablation following unsuccessful attempt at ablation at an outside institution. Prior ablation was limited by proximity to the phrenic nerve and transient phrenic nerve palsy with cryoablation at the mid crista terminalis. Epicardial access to deflect the phrenic nerve was anticipated. Atrial tachycardia was mapped endocardially prior to obtaining epicardial access. An ICE catheter was advanced to the SVC and used to identify the phrenic nerve. The course of the phrenic nerve was rigorously mapped with ICE and integrated into the CARTO navigational system (Biosense Webster). Pacing along the course of the phrenic nerve was performed at 10 mA to further refine the course of the phrenic nerve within the SVC and right atrium. Regions in close anatomic proximity to the phrenic nerve with loss of pace-capture correlated with sites of physiologic effusion, where pericardial fluid was concentrated and separation of the phrenic nerve from the visceral epicardium was noted. After mapping the phrenic nerve, endocardial ablation of atrial tachycardia was successfully performed in the absence of phrenic nerve injury without the need for epicardial access. Phrenic nerve injury may be prevented by rigorous mapping of the phrenic nerve within the right atrium using intracardiac ultrasound with medium-output pacing.