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dennis100
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« Reply #60 on: Today at 12:08:35 AM »

Model Number 302-20
Device Problem High impedance
Event Date 11/23/2015
Event Type  Malfunction   
Event Description
It was reported that high impedance was observed on vns patient's system on (b)(6) 2015. It was reported that the patient underwent generator replacement surgery on (b)(6) 2015 for prophylactic reasons. The diagnostic results in or and since have been good (dcdc 2), until on (b)(6) 2015 where the normal and system diagnostic testing showed high impedance (dcdc 7). X-rays were taken and sent to the manufacturer for review. The generator appears to be placed in the upper chest in normal arrangement. The pin connector is fully inserted. The electrodes appeared to be placed in normal arrangement. Strain-relief bend and loop seemed to have been used. One tie-down was found (visible) holding the lead but not as specified in labeling. A portion of lead behind the generator could not be assessed. No suspected lead break was found on the visible part of the lead. It was reported that the device was turned off on (b)(6) 2015. Review of manufacturing records confirmed that both, the generator and the lead passed all functional tests prior to distribution. No known surgical interventions have been performed to date. No additional relevant information has been received to date.
 
Event Description
Further information was received indicating that the patient underwent full revision surgery on (b)(6) 2015. The patient's vns system was tested upon connection of the new lead to the new generator and system diagnostics returned impedance results within normal limits with was 1345 ohms. It was reported that the generator was replaced due a generator issue. This event is reported in the medwatch number 1644487-2016-00042. Return of the explanted devices to the manufacturer is expected but they have not been received to date.
 
Event Description
The explanted lead was returned to the manufacturer on 01/08/2016. Analysis of the returned lead portions was completed and the reported allegations were confirmed. During the visual analysis of the returned 218mm portion quadfilar coil 2 appeared to be broken approximately 194mm from the end of the cut outer / inner silicone tubes. Scanning electron microscopy (sem) was performed on the connector end of the quadfilar coil 2 coil break (found at 194mm) 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 and evidence of a stress induced fracture (rotational forces) which most likely completed the fracture on one of the broken coil strands. The area on the remaining broken coil strands was identified as having evidence of a stress induced fracture with mechanical damage and no pitting. Determination could not conclusively be made on the fracture mechanism. Flat spots were observed on the coil surface. Sem was performed on the electrode (mating) end of the quadfilar coil 2 coil break (found at 194mm) and identified the area as being mechanically damaged (smooth surfaces) which prevented identification of the coil fracture type. Flat spots and pitting were 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. What appeared to be white deposits were observed in various locations. Eds (energy dispersion spectroscopy provides chemical or element identity/composition analysis) was performed on the deposit observed on the connector boot and identified the deposit as containing silicon, phosphorus, sodium, magnesium and calcium. 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. The setscrew marks found on the lead 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 the visual analysis, and no other discontinuities were identified. Based on the findings in the product analysis lab, there is evidence to suggest a discontinuity in the returned portions of the device which may have contributed to the stated allegations.

https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/detail.cfm?mdrfoi__id=5297221
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