An Inappropriate Shock Case Early after Implantation of a Subcutaneous Cardiac Defibrillator by Subcutaneous Entrapped Air.

A 17-year-old woman was resuscitated from cardiac arrest due to ventricular fibrillation and was diagnosed with concealed long QT syndrome. She underwent subcutaneous implantable cardiac defibrillator (S-ICD) implantation at our hospital. The device electrogram immediately after implantation was normal. Four days after implantation, she received an inappropriate shock. The device interrogation revealed a continuous baseline shift and frequent oversensing for low amplitude signals, followed by a shock. A chest radiograph in the orthogonal view showed entrapped subcutaneous air surrounding the distal electrode. Entrapped subcutaneous air can cause inappropriate shocks in the early period after S-ICD implantation.