Phrenic Nerve at Greater Risk: Congenital Absence of Pericardium Exposing the Nerve

Abstract

A14-month-old girl child was admitted for an elective repair of sinus venosus atrial septal defect. Through a routine sternotomy, it was realized that there was no pericardium covering the heart anteriorly. There were very minimal thymic tissues on the side of superior vena cava, and there was an additional ridge of tissue across the heart from the left side going down to the diaphragm (Fig 1). Dissection on the right side confirmed a free pericardial edge, confirming deficiency of pericardium anteriorly. The right phrenic nerve was close to the edge of the pericardium on the superior aspect and it deviated to its normal course inferiorly. The ridge seen anteriorly is the left phrenic nerve, as traced both superiorly and inferiorly to the diaphragm (Figs 2, 3). This places this nerve to be at its greatest risk for damage during potential dissection (Fig 3), if the island of tissue were to be freed for cardiac repair. The island of pericardium on the right inferior aspect, which was seen anterior to the right phrenic nerve, was