Lead fracture and multiple shocks
Tracing
Manufacturer Abbott
Device ICD
Field Sensing
N° 22
Patient
A 28-year-old, highly athletic swimmer with a family history of hypertrophic cardiomyopathy received a dual chamber ICD. He was seen for a routine follow-up.
Graph and trace
- Oversensing of rapid, non-physiologic signals of variable amplitude on the ventricular channel, with intermittent saturation of the amplifiers. A diagnosis of VF was made by the device and the capacitors, which were probably already charged, charged up very rapidly;
- Delivery of an electrical shock of maximum strength (HV, 830V) for detection of VF. Before delivery of the shock, ≥6 short cycles (F) needed to be detected since the start of the last charge, explaining the delay between the end of the charge and the shock delivery;
- Further oversensing and detection of VF after 6 F classified cycles. The charge markers (asterisks) are missing, indicating that a capacitor charge was in progress; the capacitors were already charged, though the shock was not delivered because the lead was fractured;
- Further attempted shock following an identical delay (≥6 cycles F needed); this shock was, once again, not delivered;
- Further unsuccessful attempt;
- Further unsuccessful attempt;
- Further unsuccessful attempt;
- Following 6 shocks of maximum strength, which, actually, were not delivered, the device concluded that VF was not terminated and abandoned further attempts (VF – no further therapy).
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In ICD recipients, sports that prominently mobilize the shoulders, such as freestyle or butterfly swimming, body-building, tennis, as well as contact sports and martial arts, may be avoided, as they are associated with a high risk of lead fracture, either from a direct trauma, or from repetitive compression of the defibrillation lead at the level of the costo-clavicular outlet. Likewise, extreme sports, including mountaineering, diving, parachute jumps, ultralight aviation, parasailing etc., where a syncopal event or an electrical shock might be fatal, are discouraged.
This kind of episode illustrates the benefit of limiting the delivery of therapy to 6 shocks in the VF zone. The occurrence of multiple, consecutive inappropriate shocks are particularly poorly accepted by patients. In this patient, the energy was not delivered and this episode remained asymptomatic.