Further information was received from the surgeon's office that the lead was not detached from the vagus nerve and that upon opening the patient the lead was attached to the vagus nerve.The surgeon was not aware of the high impedance prior to the surgery and during intra-operative diagnostics the high impedance was observed resulting in the device explant.It was noted that out of the two electrodes and anchor tether only 2 items were removed.Generator product analysis was completed.The product analysis lab confirmed that the generator was at normal ifi (intensified follow-up indicator)=yes condition.Per the generator data dump, impedance changed from ok to high on 11/12/2018.There were no performance of any other type of adverse events found with the pulse generator.Lead product analysis was completed.Note that a large portion of the lead assembly (body) including the (-) green electrode was not returned for analysis; therefore a complete evaluation could not be performed on the entire lead product.During the visual analysis of the returned 38mm portion quadfilar coil 2 appeared to be broken approximately 19mm from the end of the cut outer / inner silicone tubes.Scanning electron microscopy was performed on the connector end of the quadfilar coil 2 coil break (found at 19mm) and identified the area on two of the broken coil strands as having evidence of a stress induced fracture (fatigue appearance) with mechanical damage, no pitting on one, with pitting and residual material on the other.The area on the remaining broken coil strands was identified as being mechanically damaged which prevented identification of the coil fracture type with pitting on one and residual material on the other.Pitting and residual material were observed on the coil surface.Pitting was observed on the coil surface.It is believed that stimulation was present for a certain period of time as evidenced by the presence of metal pitting.Low magnification sem analysis of the quadfilar coil shows characteristics typical of a lead discontinuity which may include: material fracture, rough or pitted surface, thinned material thickness, electro-etching or material dissolution.A set of setscrew marks were seen on the marked connector pin providing evidence that proper contact between the setscrew and the marked connector pin existed at least once.Other than typical wear and explant related observations as well as the noted observations, no other anomalies were identified in the returned lead portions.
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