Subcutaneous Implantable Cardioverter Defibrillator Lead Repositioning for Preventing Inappropriate Shocks Due to Myopotential Oversensing in a Post-Fulminant Myocarditis Patient.

A 28-year-old female presented with fulminant lymphocytic myocarditis. She developed cardiogenic shock, frequent sustained ventricular tachycardia, and fibrillation (VT and VF). The left ventricular ejection fraction improved from 5% to 40% after medical therapy, but the right ventricular systolic dysfunction and enlargement persisted. In addition, sustained VTs, requiring direct current cardioversion, occurred during oral administration of amiodarone following intravenous amiodarone, even after percutaneous stellate ganglion block. Standard body surface electrocardiogram (ECG) screening for an implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD) (EMBLEM™ S-ICD, Boston Scientific, Marlborough, MA, USA) demonstrated that two of the three sensing vectors were eligible in spite of very low-amplitude QRS complexes in the body surface ECGs. After implantation of the S-ICD, the patient experienced repetitive, inappropriate shocks due to pectoral myopotential oversensing, which could not be resolved by reprogramming the device settings. Thus, the S-ICD lead was changed from the standard left parasternal position to the midline of the sternum to reduce muscular noise due to myopotentials. Thereafter, the patient experienced appropriate ICD shocks for sustained VT and VF but no inappropriate ICD sensing or shocks. Lead repositioning may be one of the feasible solutions in S-ICD patients with low-amplitude QRS complexes and inappropriate shocks due to myopotential oversensing which cannot be resolved by reprogramming the device settings.