It was reported that high impedance was found during pre-operative vns generator checks.It was noted the generator was replace prophylactically and lead pin re-insertions were attempted during surgery; however, lead impedance continued to go up.Therefore, the lead was replaced and the high impedance resolved.The surgeon noticed an obvious lead break with lead dissolution upon explant.The explanted lead was received by the manufacturer for analysis.Product analysis is expected but has not been completed to date.Attempts for additional relevant information have been unsuccessful to date.
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Product analysis for the explanted lead was completed.It was noted that a portion of the lead assembly, including the electrodes, was not returned.Both stress induced fractures (fatigue fractures and rotational fractures) along with mechanical damage were found.Pitting was observed on the coil surface suggesting that stimulation was present for a certain period of time.Low magnification scanning electron microscopy analysis of the quadfilar coil shows characteristics typical of a lead discontinuity.Abraded openings were also found on the lead.With the exception of the observed discontinuity, the condition of the returned lead portions is consistent with conditions that typically exist following an explant procedure.No other obvious anomalies were noted except for the set of setscrew marks found near the end of the connector pin indicating the lead had not been fully inserted into the cavity of the generator at one point in time.Additional setscrew marks found on the connector pin provide evidence that, at one point in time, a good mechanical and electrical connection was present.Continuity checks of the returned lead portions were performed, during visual analysis, and no other discontinuities were identified.Based on the findings in the product analysis lab, there is evidence to suggest discontinuity in the returned portions of the device, which may have contributed to the stated allegations.
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Product analysis also determined that abraded openings in the inner and outer portions of the lead, along with the cut ends of the lead made during the explant process, most likely provided the leakage path for the dried remnants of what appeared to have once been body fluids found inside the outer and inner silicone tubing in the tubing 1 section of the lead.In the second section of the lead that was returned, tubing 2, there was no obvious path for fluid ingress other than the cut ends that were made during the explant procedure.
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