The authors report the case of a patient with an automatic defibrillator implanted by an endocavitary approach. The device emitted a series of inappropriate shocks. They were triggered by the detection of myopotentials resulting from lesions of the lead due to Twiddler's syndrome. This was reproduced by telemetry in real time and confirmed by chest and abdominal X-ray and the peroperative findings. Treatment consisted of ablation of all implanted material which was replaced by a new retropectoral model.