It was reported that the patient was referred for vns generator replacement due to battery depletion.It was stated that the battery was fully depleted and could not be interrogated prior to the surgery.However, upon connecting the new generator, high impedance was observed with two diagnostics tests.The surgeon removed the dual lead pins, cleaned them, and reinserted them into the generator.The high impedance did not resolve.It was reported that the surgeon visualized a lead fracture.The patient underwent a full vns replacement as a result.The newly implanted generator was replaced as well due to lead incompatibility.The two explanted vns generators and the vns lead were received by the manufacturer and are pending product analysis.No additional relevant information has been received to date.
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The initially implanted generator product analysis was completed.The reported low battery status was duplicated in the product analysis, or pa, lab.The generator would not interrogate during attempts at bench interrogation.Therefore, system diagnostics, vbat calculation, and the fet could not be performed.With the case removed and the battery still attached to the printed circuit board assembly, or pcba, the battery measured 0.811 v, confirming the end of service, or eos, condition.Postburn electrical tests confirmed that the pcba performed according to functional specifications.The second generator product analysis was completed.The generator performed according to functional specifications.There were no performance or other adverse conditions found with the generator.Lead product analysis was completed.The allegation of fractured leads was verified in the product analysis, or pa, lab.A break was identified in the positive and negative lead coils approximately 0.2 cm past the end of the electrode bifurcation.Abraded openings were noted on the silicone tubing of the lead coils.Scanning electron microscopy, or sem, images of the positive and negative lead coils identified pitting or electro-etching conditions had occurred at the breaks.Due to metal dissolution and mechanical distortions, the fracture mechanism could not be ascertained.The positive coil showed signs of wear in the vicinity of the break.A portion of the vns lead containing the furthest electrode to the bifurcation was not returned and, therefore, product analysis could not be made on that portion of the lead.The silicone tubing of the lead coils appeared to have been torn and abraded open at the location of the suspected coil break.The silicone tubing of the positive coil was cut open approximately 0.4 cm prior to the closest electrode.Remnants of what appeared to be body fluids were observed inside the inner and outer silicone tubing.No other obvious points of entry were noted other than the identified openings and the ends of the returned portions.
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