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Transmission

When looking at the overview screen, the attention is immediately drawn to the Device management section where the “leads” is marked as a RED alert. In the warnings and observations, we observe that it is the low P-wave amplitude (1.0 mV) which is associated with the RED alert. The real time EGM does not show intrinsic P-waves which may help us verify this observation. The ventricular lead seems to be functioning properly with sensing at 14.9mV, normal and stable impedance and normal EGM.

The most important observation however, is the presence of an untreated arrhythmia episode. For any ICD, this type of episode may be associated with self-terminating ventricular arrhythmia, however it may also signify impeding inappropriate shocks due to oversensing of noise. When looking at the episode, we see very fast high-amplitude (with clipping) artifacts on the ventricular lead with oversensing. The signals are certainly non-physiological of nature, and suspicious of RV lead fracture. The abnormal signals are not typical for oversensing of 50 Hz (too high amplitudes). Electromechanical interference or use of electrocautery knife should be excluded as sources of the noise by contacting the patient.

Next steps

The patient should be contacted to ask what actions were performed at the moment of the episode, if any. The patient in this case was sitting on the sofa, without any mention of large movements. The next step is to call the patient into hospital (forbidden to drive a vehicle), to deactivate the therapies, perform manual lead check-up with maneuvres with the goal to reproduce the noise. A chest X-ray may help in order to look for signs of conductor failure or insulation breach. In this patient, manual lead tests were normal but the suspicion of RV lead dysfonction remained very high, motivating the planning of a RV lead implantation. During the waiting period, the patient showed more similar RV oversensing episodes, typical of progressing RV lead fracture.