Inappropriate shocks from a subcutaneous implantable cardioverter-defibrillator due to oversensing during periods of rate-related bundle branch block.

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is a novel technology with proven efficacy in sudden cardiac death prevention; however, there is a lack of long-term safety data. We describe the case of a 55-year-old female patient implanted with an S-ICD due to idiopathic ventricular fibrillation, who subsequently presented with inappropriate shocks leading to ventricular fibrillation that was successfully terminated by another shock. Inappropriate shocks were due to intermittent T wave oversensing during periods of rate-dependent right bundle branch block. Assessment of the S-ICD electrograms during an exercise test allowed successful reprogramming of the device׳s sensing vector with no further events.