Boston scientific received information that during a routine follow-up, this right ventricular (rv) lead exhibited increased pacing threshold measurements, to 5.0v.The pacing impedance measurements were also trending upward, but remained within range.A microdislodgement was suspected and the patient was scheduled for a lead repositioning.During the revision procedure, unusual electrograms (egms) were observed during lead testing.Several positions were attempted, then the helix became stuck and the lead could no longer be used.The lead was removed and another lead of the same model was implanted successfully.No additional adverse patient effects were reported.
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(b)(4).Upon receipt at our post market quality assurance laboratory, visual inspection noted the helix was stretched, with dried blood observed in the helix housing.Resistance testing found the lead was not electrically continuous.Detailed analysis confirmed that the cathode conductor coil was fractured at the distal end of the terminal pin.Microscopic analysis confirmed that the lead became fractured due to torsional overstress.Based upon the clinical observations and the laboratory findings, we believe the conductor coil became fractured during attempts to extend/retract the helix during the revision procedure.
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