Implantable cardioverter-defibrillator failure unmasked by a 'lucky' shock

A young woman with placement of a dual-chamber implantable cardioverter-defibrillator (ICD) and a history of prior cardiac arrest due to congenital long QT syndrome presented with defibrillation caused by a ventricular fibrillation arrest. Routine device interrogation revealed significant lead dysfunction. During device revision, breaches were detected in the insulation of both leads within the pre-pectoral pocket and an “arc mark” was observed on the ICD generator casing; these findings were consistent with a high-voltage discharge through a short circuit between the denuded right ventricular lead and the casing. In this case, system failure was unmasked only by interrogation after appropriate device activation, which highlights the importance of thorough evaluation after all ICD activations.