This tracing illustrates typical noise oversensing due to a lead fracture : noise signals in this situation are often intermittent. Noise signals are often oversensed by the ICD as RR intervals close to the sensed ventricular blanking period (120-140ms). Such short intervals do not occur with VT or VF. The signal also presents very high amplitude that saturates the amplifier. Overall, this episode lasted for 35 seconds and would have lead to the delivery of an inappropriate shock if the noise detection algorithm was not present (nominal programming : ON). The therapy is suspended since the noise criterion is met. However, it works only for the initial detection of the tachycardia and not for its redetection. This patient underwent the extraction of this defect lead and got a new ICD lead.