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The benefits of induction at the end of implantation - Evera XT DR

Patient


Patient implanted with a dual-chamber defibrillator with a Fidelis lead undergoing a box change (Evera XT DR); induction protocol at the end of the procedure.


Trace


1- What do you think of this interval plot?
The plot initially shows an induction protocol with rapid pacing burst; the fact that the low-amplitude electric shock is delivered on the T wave is not indicated on the graph; induction of a probable ventricular arrhythmia detected in the VF zone (appearance compatible with a real ventricular arrhythmia); the first shock delivered (35 Joules) significantly alters the ventricular cycles, with evidence of a cloud of points (very short cycles and longer cycles with great variability); the second shock does not alter the appearance of the ventricular cycles.

2- What type of procedure is involved?
The EGM shows rapid ventricular pacing followed by a low-amplitude shock delivered on the T wave (in the vulnerable period) due to an induction protocol at the end of implantation to check for correct defibrillator function.

3- What is the effect of the first low output shock?
The electric shock induces rapid ventricular tachycardia, which is detected in the VF zone.

4- What is the effect of the second high output shock?
The electric shock terminates the ventricular arrhythmia but is followed by the over-detection of anarchic signals with saturation of the amplifiers, suggesting a diagnosis of lead dysfunction.

Comments

  • This plot shows the value of inducing ventricular arrhythmia when changing leads, particularly when the patient is implanted with a lead known to have an increased rate of dysfunction.
  • Lead fracture was unmasked in this patient following detection of an episode of induced VF and the delivery of an electric shock; the electric shock delivered sometimes stretches a lead which had already been stretched and weakened beforehand and causes a definitive fracture; the stimulation impedances were strictly normal prior to this episode and no episode of oversensing had previously been recorded in the device memory; therefore there was no warning sign of lead dysfunction and no other indication for this patient to have an induction protocol performed when the box was changed.
  • This young patient had the faulty lead removed and a new ipsilateral lead implanted.

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