Routine exercise testing could not predict T-wave oversensing in a patient after a subcutaneous implantable cardioverter-defibrillator implant.

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are susceptible to T-wave oversensing (TWOS) caused by high rate-dependent QRS-T morphology changes. We experienced an inappropriate S-ICD shock due to TWOS, which could not be predicted by routine exercise testing. A newly available high-pass filter might be effective for avoiding this.