Lead electrical parameters may not predict integrity of the Sprint Fidelis ICD lead

Abstract

The reported failure rate of the Medtronic Sprint Fidelis defibrillator lead continues to increase over time. Clinicians and patients count on the electrical analysis of leads through device interrogation to determine whether a lead is functioning "normally." Most importantly, this analysis is often the basis for decision making around the ongoing use of this lead at the time of generator change. Can clinicians count on this analysis and feel confident that this "advisory" lead is "normal?" To describe the incidence of unexpected lead abnormalities among Sprint Fidelis leads removed without prior evidence of electrical abnormalities. We performed a retrospective cohort study of Medtronic Sprint Fidelis (6930, 6931, 6948, 6949) leads extracted at a single high-volume center. Medtronic analyzed all returned leads for abnormalities. The presence and type of lead abnormalities in addition to patient characteristics, indications for extraction, implant duration, and use of extraction sheath assistance are reported. Between September 2005 and January 2011, 209 Sprint Fidelis leads were extracted from 208 patients. The average duration of implant was 38.9 months (range 0.2-67.2). Of the analyzed leads, the majority of the extracted leads (63.1%) were active, normal functioning leads (83.8% prophylactically, 9.1% infection, and 7.1% other indication) while 36.9% had clinical evidence of a fracture. Extraction was achieved with simple traction in 39.5% of the leads; extraction sheath assistance was employed in 94 cases (59.9%), and surgical extraction at the time of transplant occurred in 1 case. Analysis of the 99 functionally "normal" leads removed determined that 20 leads had evidence of fractures (20.2%) not related to extraction. Of the fractured leads, 4 leads (20%) had more than 1 fracture and 1 lead had 3 separate fracture sites. There were 17 pacing conductor (10 proximal and 7 distal conductor) and 6 high-voltage conductor (1 superior vena cava and 5 right ventricle defibrillator conductor) fractures observed. Five additional leads (5.2%) had evidence of explant damage. Functionally "normal" Fidelis leads demonstrate an alarmingly high rate of "subclinical" fractures. Recommendations regarding prophylactic Sprint Fidelis lead extraction, especially at the time of generator change, may warrant reconsideration. To aid in the design of better leads, all leads should be returned for analysis, regardless of the indication for extraction.