Inappropriate Shocks With Subcutaneous Implantable Cardioverter-Defibrillator in a Young Patient: A Case Report

Implantable cardioverter-defibrillators (ICDs) are increasingly used for the primary and secondary prevention of sudden cardiac death (SCD). Currently, transvenous (TV) and subcutaneous (S) ICDs are the two different types used. Preservation of central venous vasculature, no risk of vascular or myocardial injury during implant, easier explantation, and lower risk of systemic infections have driven the increased use of S-ICDs. The shocks delivered by ICDs for non-life-threatening arrhythmias or because of oversensing T waves or noise are known as inappropriate shocks. Here, we present the case of a 33-year-old man who had an S-ICD implanted in 2019 for hypertrophic cardiomyopathy. He had a TV-ICD implanted in 2010 which was explanted in 2013 due to infective endocarditis, and the patient underwent a mechanical mitral valve replacement. He was at intermediate risk for SCD over the next five years. He had an S-ICD implanted in 2019 and had never received any shock before. Electrocardiogram showed normal sinus rhythm, left axis deviation, QRS 110 ms, hyperacute T waves in inferior leads, and T-wave inversion in lateral leads. He then began experiencing inappropriate shocks three years after S-ICD placement due to a drop in R wave amplitude secondary to noise oversensing in October 2022. Despite reprogramming the device from the primary vector to an alternate vector, the patient had further inappropriate shocks two months later due to noise oversensing. The patient was discussed in a multidisciplinary team meeting and the S-ICD was explanted according to the patient’s wishes and a loop recorder was implanted.