DISCUSSION
Et-VOM may cause several complications, such as cardiac tamponade, stroke, anaphylactic shock, atrioventricular block, and left atrial appendage isolation.1 The left phrenic nerve injury, however, has not been reported as a complication of Et-VOM. Catheter ablation can injure the left phrenic nerve for its proximity to several heart structures. The left phrenic nerve is at risk of injury during radiofrequency application to a left posterolateral accessory pathway,2 and the left PNP is one of the critical complications during cryoballoon ablation of the left superior pulmonary vein.3
The left phrenic nerve runs dorsally to the left brachiocephalic vein and anterolateral to the aortic arch and pulmonary trunk.4 After that, it descends toward the cardiac apex following three courses: (1) along a course related to the anterior surface of the heart (anterior course), (2) pass leftward along a course related to the apex of the left atrial appendage and obtuse margin of the left ventricle (lateral course), or (3) pass posteriorly to the inferior surface of the left ventricle (inferior course). In particular, the inferior course shows the shortest distance to the left superior pulmonary vein.4 Scarring caused by Et-VOM was observed on the left lateral ridge anterior to the left superior pulmonary vein in this case (Fig. 2B). This finding presumes that Et-VOM directly injured the left phrenic nerve with an inferior course. Since the vein of Marshall is an epicardial structure, ethanol exuding from it may damage pericardial structures. The tissue staining around the vein of Marshall (Fig. 2A) after Et-VOM supports this hypothesis. However, epicardium insulation of the left phrenic nerve may have kept the left PNP transient.
To our best of knowledge, this is the first case report of the Et-VOM-related left PNP. Fortunately, the left PNP was transient in this case; however, the persistent left PNP might be caused in patients with a shorter distance between the left PNP and the vein of Marshall. We should know the risk of the left PNP and keep a close observation of the diaphragmatic movement during Et-VOM.