Inappropriate subcutaneous implantable cardioverter defibrillator shocks for bradycardia

Subcutaneous implantable cardioverter-defibrillators (S-ICD) have been shown to be noninferior to conventional transvenous ICDs with respect to device-related complications and inappropriate shocks.1 For patients who meet indications for an ICD and do not require bradycardia pacing, antitachycardia pacing, or cardiac resynchronization therapy, it is becoming an attractive option to avoid vascular complications. Complications such as lead malfunction and infection are more common with the transvenous ICD, whereas inappropriate shocks are more common with the S-ICD.1 The majority of inappropriate S-ICD therapies results from T-wave oversensing, but there are also reports of QRS double or triple counting, especially in times of electrolyte derangements. We report a case where oversensing of multiple components of a ventricular escape rhythm resulted in inappropriate shocks owing to a unique S-ICD algorithm.