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.