Patient - EN
This 31-year-old man presenting with Brugada syndrome, type 1 electrocardiogram, and syncope, was seen in routine follow-up after implantation of an Atlas single chamber ICD.
Main programmed parameters
- VF zone at 222 bpm
- 12 cycles in the VF zone were needed for the diagnosis
- Maximum sensitivity programmed at 0.3 mV
- VF zone: single 12.5-J shock followed by five 36-J shocks (maximum strength)
- VVI pacing mode at 40 bpm; VVI post-shock pacing mode at 60 bpm
Graph and trace
Episode of non-sustained VF with aborted shock.
Tracing
- Sinus rhythm;
- Oversensing of high-amplitude signals and saturation of the amplifiers consistent with lead fracture. The 2 mm/mV, 8.9 mV autogain indicates that signals >8.9 mV in amplitude were clipped and that the EGM were of very high amplitude;
- VVI episode pacing mode after 4 F classified cycles;
- Detection of VF episode (12 F classified cycles) and start of the capacitors charge;
- End of oversensing; diagnosis of return of sinus rhythm (5 consecutive VS).
The tracing suggests a lead fracture (short cycles, intermittent within the cardiac cycle, disorganized, of variable amplitude, sometimes saturating the amplifiers). In this asymptomatic patient, remote monitoring by telemedicine allows an early diagnosis and prevents the delivery of inappropriate shocks. Particular motions of the arm or shoulder might reproduce oversensing. The pacing impedance is not always changed; however, if it is <200 Ohm, it suggests an insulation breakdown, whereas if it is >2,000 Ohms, it suggests a lead fracture. Likewise, the shock impedance generally varies between 25 and 75 Ohm. A lower value suggests insulation breakdown, while a higher value suggests lead fracture. A sudden variation in the impedance curves is important to identify, even if it remains within the normal range.
An association between abnormal impedance and sensing of very short RR cycles (<140 ms) is highly suggestive of a lead dysfunction. Chest radiographs show fracture lines in <50% of instances of lead rupture. In this patient, the lead impedance was low and, and at lead extraction, an insulation breakdown was found with a worn area between the pulse generator and the fractured lead segment.