Anatomic evaluation of the left phrenic nerve relevant to epicardial and endocardial catheter ablation: Implications for phrenic nerve injury

Background/ObjectiveThe purpose of this study was to clarify the spatial relationship between the left phrenic nerve (LPN) and key cardiac structures in order to minimize the risk of phrenic nerve injury during interventions.MethodsThe course and relationship of the LPN to various cardiac structures were examined by gross dissection and histologic sections of 22 human cadavers.ResultsThe nerve descended on the fibrous pericardium along one of three courses: over the anterior surface of the left ventricle (18%), over the lateral margin of the left ventricle (59%), and in a posteroinferior direction (23%). The endocardium of the roof of the left atrial appendage was <4 mm from the LPN in 2 (9%) specimens. The nerve passed <2.5 mm from the epicardium of the apex of the left atrial appendage in 7 (31%) specimens. Regardless of the position of the nerve in relation to the high left ventricular wall, the nerve was <3 mm from the epicardial surface in 8 (36%) specimens and passed <6 mm from the epicardium of the right ventricular outflow tract in 2 (9%) specimens.ConclusionDuring electrophysiologic interventions, the LPN is especially at risk when procedures are performed in the vicinity of the left atrial appendage and high left ventricular wall.