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Internal insulation breaches in an implantable cardioverter-defibrillator lead with redundant conductors

Open AccessPublished:February 14, 2019DOI:https://doi.org/10.1016/j.hrthm.2019.02.019

      Background

      Internal insulation breaches (IBR) may result in implantable cardioverter-defibrillator lead failure and adverse clinical events. Concerns exist that the Durata lead may be prone to IBR.

      Objective

      The goals of this study were to assess Durata failures in the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database and compare them to failures in MAUDE for Endotak Reliance and Sprint Quattro Secure (QS) leads.

      Methods

      We searched the MAUDE database from 2008 to 2018 for IBR and other failure modes. Included were explanted leads whose manufacturers found an insulation or conductor defect not caused by extrinsic factors.

      Results

      The MAUDE search found 1011 qualifying leads. The cause of failure differed among leads (P < .001). The primary cause of Durata failure was IBR (293 of 316 leads [93%]), with IBR accounting for 47% (137 of 293); few QS (9 of 523 [1.7%]) and no Endotak Reliance leads failed because of IBR (P < .001). Durata IBR were responsible for 11 failures to treat ventricular tachycardia/ventricular fibrillation, and all were caused by high-voltage (HV) shorts between the proximal superior vena cava coil and a distal right ventricular coil cable (n = 10) or sensing conductor (n = 1); low values of HV impedance were found in these leads during defibrillation threshold testing (n = 3), after a shock or aborted shock (n = 7), and by an alert (n = 1). Inappropriate therapy was caused by 51 Durata IBR, but no QS IBR.

      Conclusion

      Durata implantable cardioverter-defibrillator leads are susceptible to IBR that may result in failure to treat ventricular tachycardia/ventricular fibrillation or inappropriate therapy; such failures may occur without forewarning. HV testing of Durata leads may be indicated during pulse generator replacement or when an insulation defect is suspected.

      Keywords

      Introduction

      The Durata implantable cardioverter-defibrillator (ICD) lead (Abbott/St. Jude Medical [A/SJM], Sylmar, CA) was designed, in part, to mitigate the conductor cable externalization and internal insulation breaches (IBR) that resulted in the recall of the Riata and Riata ST ICD leads.
      • Carlson M.
      • Tsung P.
      Medical device advisory St. Jude Medical Riata and Riata ST silicone endocardial defibrillation leads. November 2011.
      For Durata, A/SJM added a siloxane-based polyurethane outer insulation (Optim). However, the dual conductor design was retained, whereby 2 cable conductors are confined within a single oblong lumen (Figure 1B).
      Figure thumbnail gr1
      Figure 1Lead models. (A) Sprint Quattro Secure, (B) Durata, and (C) Endotak Reliance. Dark blue ethylene tetrafluoroethylene insulation covers cable conductors. Light blue polytetrafluoroethylene insulation covers the inner coil.
      While cable externalization appears to be infrequent,
      • Slane S.J.
      Abbott product performance report 2018. 1st ed. p 322.
      reports of Durata failures
      • Swerdlow C.D.
      • Kass R.M.
      • Khoynezhad A.
      • Tang S.
      Inside-out insulation failure of a defibrillator lead with abrasion-resistant coating.
      • Schloss E.J.
      • Krebs M.E.
      • Gupta M.
      Catastrophic failure of Durata ICD lead due to high-voltage short during shock delivery.
      • Shah A.D.
      • Hirsh D.S.
      • Langberg J.J.
      User-reported abrasion-related lead failure is more common with Durata compared to other implantable cardiac defibrillator leads.
      • Goldstein M.A.
      • Badri M.
      • Kocovic
      • Kowey P.R.
      Electrical failure of an ICD lead due to presumed insulation defect only diagnosed by a maximum output shock.
      • Doshi R.
      • Ceballos
      • Mendez F.
      Is high-voltage lead integrity measurement adequate during defibrillator generator replacement?.
      • Leong D.P.
      • Van Erven L.
      Unrecognized failure of a narrow caliber defibrillation lead: the role of defibrillation threshold testing in identifying an unprotected individual.
      raise the possibility that the IBRs observed in Riata and Riata ST leads may be affecting Durata lead performance. The most serious IBRs are those that disrupt the silicone, abrade the fluorine-based protective coating, and short-circuit conductors to each other or to the shocking coils. These IBRs may be clinically silent or cause detectable malfunctions. A short involving a conductor to a pace-sense electrode may present as noise/oversensing with inappropriate therapy (IARx). A short between the proximal superior vena cava (SVC) shock coil and the cable to the distal right ventricular (RV) shock coil prevents delivery of a lifesaving shock; this mechanism was responsible for Riata device–related deaths.
      • Hauser R.G.
      • Abdelhadi R.
      • McGriff D.
      • Retel L.K.
      Deaths caused by the failure of Riata and Riata ST implantable cardioverter-defibrillator leads.
      To assess the occurrence and characteristics of Durata IBR and failure modes, we searched the Food and Drug Administration (FDA) Manufacturer and User Facility Device Experience (MAUDE) database for Durata returned product analyses (RPA) that A/SJM submitted to the FDA from 2008 to 2018. The results were compared to RPA data in MAUDE for Sprint Quattro Secure (Medtronic Inc., Minneapolis, MN) and Endotak Reliance (Boston Scientific, St. Paul, MN) ICD leads.

      Methods

       Leads

      Durata (Figure 1B) is a 6.8-F single- or dual-coil true bipolar 4-lumen active or passive fixation ICD lead. All models have redundant conductors for the shocking coils and ring electrode; the cables are coated with abrasion-resistant ethylene tetrafluoroethylene (ETFE), a fluorine-based plastic. Insulation consists of inner silicone and outer Optim; the inner coil is covered with polytetrafluoroethylene (PTFE) tubing.
      Sprint Quattro Secure (Figure 1A) is an 8.2-F active fixation true bipolar dual- or single-coil ICD lead with silicone insulation and polyurethane outer coating. Each high-voltage (HV) and pace-sense conductor occupies a lumen. The inner coil is covered with PTFE tubing, while other conductors are covered with ETFE.
      Endotak Reliance (Figure 1C) is an active or passive fixation dual- or single-coil lead that has an integrated bipolar pacing electrode. The 8.2-F lead body has an inner silicone trilumen core and an outer layer of silicone. Each lumen is occupied by a single conductor; 2 lumens contain a PTFE- or EFTE-coated HV cable, and the third lumen has a pace-sense coil insulated with PTFE. Reliance G and SG shocking coils are covered with Gore-expanded PTFE to prevent tissue ingrowth.

       FDA MAUDE database

      The MAUDE database contains reports of adverse events involving medical devices that are reported to US manufacturers by users worldwide. MAUDE medical device reports (MDR) are publicly available for the previous 10 years at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/search.CFM.
      During December 2018, the MAUDE database was queried for Durata, Sprint Quattro Secure, and Endotak Reliance leads using the simple search terms: breach, abrasion, under coil, noise and coil, short, receipt, analysis, returned, and exposed for the years 2008–2018.
      Implant time was estimated by subtracting 4.7 months from the time between the lead’s manufacturing date and the date when the manufacturer received the returned lead; this number was based on 215 Medtronic leads and 106 Boston Scientific leads in MAUDE that were inserted but not implanted for technical reasons; 4.7 ± 2.4 months was the mean time between the date of manufacture and the date a lead was received by the manufacturer. Similar data were not found for A/SJM leads.

       Study population

      A lead was included if (1) it was manufactured after January 1, 2008, implanted, removed, and returned to the manufacturer for RPA and (2) the manufacturer concluded that the lead was defective because its insulation was breached or a conductor was fractured. Excluded from the study were leads that were as follows: (1) not implanted, (2) extrinsically damaged during implant or explant by cuts or extraction techniques, or (3) damaged because of clavicle/rib forces or Twiddler syndrome. Also excluded were leads whose only defect involved the active fixation mechanism. Leads that were damaged near the suture sleeve were excluded if the breach was not caused by an internal lead defect.

       Definitions

      Insulation was breached if (1) the manufacturer so stated, (2) a coil conductor was exposed and the ETFE or PTFE was abraded, or (3) if the manufacturer concluded that insulation abrasion was causally related to a reported malfunction. An HV or pace-sense conductor was fractured if it was described by the manufacturer. The incidence of Durata IBR was estimated using the number of US registered implants in the manufacturers’ 2018 product performance reports (PPRs).

       Statistics

      For each model, categorical variables were summarized as count (percentage) and implant times as mean ± SD. Incidence of IBR and serious adverse events were compared among the 3 lead models using Poisson regression with log link and offset for the log total for each model. A similar approach was used to compare incidence of Durata IBR and major adverse events between dual and single coils. The differences in implant time among the 3 lead models were estimated from a linear regression model; assumptions were verified via residual analysis. The resulting estimates are reported with their 95% confidence intervals and P values. All the analyses were performed with R (version 3.4.1) in R studio environment (version 1.1.453).

      Results

      The MAUDE search returned 1044 leads that qualified for the study (Table 1). The causes of lead failure differed significantly among the 3 lead models (P < .001). For Durata, IBR was the predominant cause of failure, and 137 (47%) of these were IBRs. The principal cause of Sprint Quattro Secure failure was conductor fracture; 71% of these involved the pace-sense conductor. An equal proportion of Endotak Reliance leads failed because of an IBR or conductor fracture; 24% malfunctioned because of calcification of the shocking coil and/or the pacing electrode.
      Table 1Cause of failure and serious adverse clinical events
      VariableDurataQuattro SecureEndotak Reliance
      No. of leads316523205
      Implant time (y)
      Implant time was longer for Durata and Endotak Reliance than for Quattro Secure (P < .001).
      4.5 ± 2.23.6 ± 2.24.3 ± 2.3
      Primary cause of failure
      Leads differ as to the cause of failure (P < .001).
       Insulation breach
      The risk of a Durata internal insulation breach was 8.7 times higher than that of Quattro Secure (95% CI 5.8–13.6; P < .001) and 22.2 times higher than that of Endotak Reliance (95% CI 9.3–72.3; P < .001). The risk of a Durata outer insulation breach was 3.5 times higher than that of Quattro Secure (95% CI 2.6–4.6; P < .001) and 1.3 times higher than that of Endotak Reliance (95% CI 1.0–1.7; P = .05).
      293 (93)83 (16)78 (38)
      Internal1379
      Outer1565775
      Internal + outer173
       Conductor fracture10 (3)438 (84)77 (38)
      High voltage17919
      Pace-sense930957
      High voltage + pace-sense35
      Multiple (>2 fractures)151
       Coil and/or electrode calcification49 (24)
       Indeterminate13 (4)2 (<1)1 (<1)
      Serious adverse events/cause
      Risk of failure to terminate VT/VF for Durata was 2.6 times higher than that of Endotak Reliance (95% CI 0.8–11.4; P = .14). The risk of inappropriate shocks or ATP was 1.5 times higher for Durata than for Quattro Secure (95% CI 1.1–2.0; P = .005) and not different from that for Endotak Reliance (1.2 times, 95% CI 0.8–1.7; P = .28).
       Failure to terminate VT/VF123
      Internal insulation breach11
      Outer insulation breach12
      Calcification of the HV coil1
       Inappropriate shocks or ATP889647
      Internal insulation breach51
      Outer insulation breach34712
      Conductor fracture38936
       Syncope/asystole332
      Internal insulation breach1
      Outer insulation breach21
      Conductor fracture31
      Values are presented as mean ± SD or as n (%).
      ATP = antitachycardia pacing; CI = confidence interval; HV = high-voltage; VT/VF = ventricular tachycardia/ventricular fibrillation.
      Implant time was longer for Durata and Endotak Reliance than for Quattro Secure (P < .001).
      Leads differ as to the cause of failure (P < .001).
      The risk of a Durata internal insulation breach was 8.7 times higher than that of Quattro Secure (95% CI 5.8–13.6; P < .001) and 22.2 times higher than that of Endotak Reliance (95% CI 9.3–72.3; P < .001). The risk of a Durata outer insulation breach was 3.5 times higher than that of Quattro Secure (95% CI 2.6–4.6; P < .001) and 1.3 times higher than that of Endotak Reliance (95% CI 1.0–1.7; P = .05).
      § Risk of failure to terminate VT/VF for Durata was 2.6 times higher than that of Endotak Reliance (95% CI 0.8–11.4; P = .14). The risk of inappropriate shocks or ATP was 1.5 times higher for Durata than for Quattro Secure (95% CI 1.1–2.0; P = .005) and not different from that for Endotak Reliance (1.2 times, 95% CI 0.8–1.7; P = .28).
      Major adverse clinical events (MACE) affected 103 patients who had Durata leads, and the majority (61%) of these events were caused by IBRs (Table 1). Twelve Durata leads failed to terminate ventricular tachycardia/ventricular fibrillation (VT/VF); 11 were due to IBRs, and 1 was caused by a lead-to-can outer insulation breach. Twenty-five Durata IBRs that resulted in failure and/or inability of the ICD system to deliver therapy are presented in Table 2. All 25 leads were dual-coil Durata models, and the most common RPA finding in leads that failed to terminate VT/VF was abrasion under the proximal SVC coil that shorted it to an ETFE-abraded HV RV coil cable (Figure 2).
      Table 2Durata internal insulation defects resulting in failure and/or inability of the device to deliver therapy
      Patient no.MDR no.Model no.Implanted (mo)Sign/reason for failure outcomeResults of SJM returned product analysis
      177241717121Q83Low HV impedance after a shock

      Manual HV impedance test normal

      Subsequent failure to deliver therapy

      Patient died
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of the RV conductor abraded at 1 location

      Slight melting of the RV conductor
      23789553712070Low HV impedance during DFT testing

      Failure to convert VT/VF

      Patient rescued with an external shock

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of the RV conductor abraded at this location

      Internal insulation abrasions under the RV shock coil
      33669333712065Low HV impedance during cardiac arrest

      Failure to convert VT/VF

      Patient rescued by EMTs

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of the RV conductor abraded at this location
      43837067712031Low HV impedance alert after an aborted shock

      Failure to convert VT/VF

      Arrhythmia terminated spontaneously

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of the RV conductor abraded at this location

      The SVC shock coil and RV conductor melted
      53098216712153Low HV impedance transmission

      Failure to convert VT/VF during DFT testing

      Patient rescued with an external shock

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded at this location

      The SVC coil and RV conductor melted
      65059386712173Low HV impedance after a shock

      Unsuccessful shocks: overcurrent detection

      Patient treated for VT storm

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded at this location
      74232747712172Low HV impedance during DFT testing

      Failure to convert VT/VF

      Patient rescued with an external shock

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded and melted at this location
      865073167120Q69Noise/oversensing

      Inappropriate shocks

      Lead replaced
      Three internal insulation abrasions beneath the RV shock coil

      ETFE coating of the adjacent (unspecified) conductor cable abraded
      945873307121Q54Low HV impedance during DFT testing

      Failure to convert VT/VF: overcurrent detection

      Patient rescued with an external shock

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of 1 sensing conductor abraded and the conductor melted
      1036657227121 Q42Low HV impedance after alert during charging for HV lead issue

      Failure to shock arrhythmia

      Arrhythmia terminated spontaneously

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of 1 RV conductor abraded and the other RV conductor melted
      1125693817170Q33Low impedance and output circuit damage

      Failure to shock VF

      Patient survived

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      One RV conductor cable broken and the SVC shock coil shorted
      1233322637170Q33Vibratory alert after failure to shock VT/VF

      Low HV impedance and aborted charge

      Patient survive

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating of the RV conductor abraded

      RV conductors and shock coil melted at this location
      1347604337121Q27Noise/oversensing

      Pacing inhibited; patient symptomatic

      Lead replaced
      Internal insulation abrasions under the RV shock coil

      ETFE coating abraded at this location
      1475242877121Q60Noise/oversensing

      Pacing inhibited; patient symptomatic

      Lead replaced
      Internal insulation abrasions breaching the ring electrode cable lumen beneath the RV shock coil
      1529080347120Q16Noise/oversensing

      Pacing inhibited; patient symptomatic

      Lead replaced
      Internal insulation abrasions under the RV shock coil

      ETFE coating of 1 ring electrode conductor abraded at this location
      1661189877120Q74Low HV impedance observed

      Syncope

      Lead replaced
      Internal insulation abrasions under the SVC shock

      ETFE coating abraded at this location
      1760477127121Q3Noise/oversensing

      Pacing inhibited; patient symptomatic

      Lead replaced
      Internal insulation abrasions under the RV shock coil

      ETFE coating of the sensing conductor intact at these locations
      1826473967170Q21Output circuit damage

      Aborted shocks

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      The SVC shock coil and RV cable melted

      ETFE coating of the RV cable abraded

      Open circuit on the SVC coil cables due to melting
      1947603397120Q43Vibratory alert for low HV impedance

      Lead replaced
      Internal insulation abrasions under the RV shock coil with intact ETFE. Internal insulation abrasions under the SVC shock coil. ETFE coating of the RV conductor abraded at this location
      2041308097120Q34Low HV impedance alert

      IAS for rapid AF

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded at this location
      2156381497120Q11Low HV impedance alert after an aborted shock for VF

      Second shock successful

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded at this location
      223953770712047Alert at home for low HV impedance

      Lead replaced
      Internal insulation abrasion noted under the RV shock coil

      ETFE coating abraded. Internal insulation abrasions under the SVC shock coil. The RV conductor abraded at this location
      236098257712096Low HV impedance alert via Merlin

      Noise noted on the lead

      Lead replaced
      Two internal abrasions noted at the SVC shock coil

      Cable coatings for the ring electrode and RV cables abraded at this location
      245062157712072Vibratory alert at home for low HV impedance

      Lead replaced
      Internal insulation abrasions under the SVC shock coil

      ETFE coating abraded at this location
      254075525712170ICD in the backup mode after multiple shocks

      Alert indicating lead problem

      Lead replaced
      Pinhole internal insulation abrasions under the SVC shock coil. ETFE coating abraded and the RV conductor partially melted at this location
      AF = atrial fibrillation; DFT = defibrillation threshold; EMTs = emergency medical technicians; ETFE = ethylene tetrafluoroethylene; HV = high voltage; IAS = inappropriate shock; RV = right ventricular; SVC = superior vena cava; VT/VF = ventricular tachycardia/ventricular fibrillation. Merlin (Abbott/St. Jude Medical, Sylmar, CA).
      Figure thumbnail gr2
      Figure 2Durata lead showing location of an insulation breach under the proximal superior vena coil (arrow). The cable to the distal right ventricular shocking coil has abraded through the inner silicone from the inside-out and ethylene tetrafluoroethylene has been damaged, allowing the cable to short to the underside of the shocking coil.
      Table 3 lists the signs of failure and abrasion locations for Durata leads with IBRs. A third of leads had multiple abrasions. Failure to terminate VT/VF due to IBR was associated with a low HV impedance that was found during defibrillation threshold (DFT) testing (n = 3), after a shock or aborted shock (n = 7), and after remote transmission (n = 1). Except for the patient identified by home monitoring, MDRs did not specify whether the other leads were evaluated by painless low-voltage impedance testing before the clinical event. Four patients (patients 19, 22, 23, and 24, Table 2) received alerts for low HV impedance at home; their leads were replaced, and none experienced a serious adverse event.
      Table 3Signs of failure and location of Durata internal insulation breaches
      Durata model7120 & 7120Q

      Dual coil
      7121 & 7121Q

      Dual coil
      7122 &

      7122Q

      Single coil
      7170 &

      7170Q

      Dual coil
      Total
      Number76 (55)29 (21)27 (20)5 (4)137 (100)
      Primary sign of failure
       Low HV impedance16 (21)9 (31)3 (11)1 (20)29 (21)
       High HV impedance--1 (4)-1 (<1)
       Noise/oversensing49 (64)18 (62)22 (81)2 (40)91 (66)
       Abnormal pacing impedance4 (5)--1 (20)5 (4)
       High pacing threshold-1 (3)--1 (<1)
       Aborted charges after shock---1 (20)1 (<1)
       Insulation damage at revision2 (3)-1 (4)-3 (2)
       Unknown5 (7)1 (3)--6 (4)
      Insulation breach locations
       Under SVC coil27 (36)12 (41)na2 (40)41 (30)
       Under RV coil33 (43)15 (52)24 (89)2 (40)74 (54)
       Under both coils6 (8)1 (3)--7 (5)
       Under ring electrode1 (1)1 (3)2 (7)-4 (3)
       RV cable22 (29)9 (31)1 (4)2 (40)34 (25)
       Pace/sense conductor47 (62)18 (62)25 (93)3 (60)93 (68)
       Unspecified8 (11)2 (7)2 (7)12 (9)
       Leads with >1 abrasion25 (33)9 (31)5 (19)2 (40)41 (30)
      Values are presented as n (%).
      HV = high voltage; RV = right ventricle; SVC = superior vena cava.
      The estimated incidence of Durata IBRs based on the number of US registered implants is presented in Table 4. Dual-coil models had a 2-fold higher incidence of IBRs than did single-coil models (95% confidence interval 1.3–3.2; P < .001); this difference was primarily due to the presence of the SVC coil. Durata externalized conductors were described in 4 reports (MDR nos. 5486355, 4761044, 4761031, and 6919368). Two were identified after lead explant, and 1 was seen on the radiograph before lead removal. The fourth was found under the SVC coil during RPA and caused lead noise but no adverse events.
      Table 4Incidence of Durata lead internal insulation breaches and major adverse events
      VariableNo. of US registered implantsInternal insulation breaches
      Dual coil vs single coil: P < .001; the risk of internal breach in the dual-coil design is 2.0 (95% confidence interval 1.3–3.2) times higher than that in single-coil models.
      Major adverse events
      Dual coil vs single coil: P = .08; the risk of major adverse events in the dual-coil design is 1.7 (95% confidence interval 0.9–3.1) times higher than that in single-coil models.
      No.Rate/10,000NoRate/10,000
      Dual coil191,3021095.7482.5
      Single coil100,538282.8151.5
      All leads291,8401374.7632.2
      Dual coil vs single coil: P < .001; the risk of internal breach in the dual-coil design is 2.0 (95% confidence interval 1.3–3.2) times higher than that in single-coil models.
      Dual coil vs single coil: P = .08; the risk of major adverse events in the dual-coil design is 1.7 (95% confidence interval 0.9–3.1) times higher than that in single-coil models.
      Three Endotak Reliance leads failed to terminate VT/VF. One (MDR no. 5831679) resulted in death caused by a lead-to-can outer insulation breach that shorted the lead during therapeutic shock delivery for VF. The second (MDR no. 4654719) was due to a lead-on-lead outer insulation breach in a hospitalized patient who was rescued. The third (MDR no. 6024239) involved an Endotak Reliance SG lead that exhibited a slow rise in shock impedance, resulting in high HV impedance (>125 Ω). DFT testing was unable to convert the patient in most configurations, and the lead was replaced. The manufacturer concluded that the lead’s high impedance was caused by calcification of the distal shocking coil.
      IARx was the most frequent MACE, and it occurred more often in Durata and Quattro Secure leads than in Endotak Reliance leads (Table 1). For Durata leads, 51 IBRs involving a pace-sense conductor were the most common reported cause of noise and IARx. Of these breaches, 75% (n = 38) were under the RV coil, 24% (n = 12) under the SVC coil, and 1% (n = 2) were under the ring electrode.

      Discussion

      The results of this study show that Durata leads are susceptible to IBRs that may result in serious adverse events without forewarning, including failure to treat VT/VF and inappropriate shocks. These defects appear to be similar to those found in Riata and Riata ST leads,
      • Hauser R.G.
      • McGriff D.
      • Retel L.K.
      Riata implantable cardioverter-defibrillator lead failure: analysis of explanted leads with a unique insulation defect.
      and they occurred despite the addition of Optim to the Durata lead. These findings are important because an estimated 290,000 patients in the United States and others worldwide have active Durata leads.
      • Carlson M.
      • Tsung P.
      Medical device advisory St. Jude Medical Riata and Riata ST silicone endocardial defibrillation leads. November 2011.
      In contrast, the Sprint Quattro Secure and Endotak Reliance leads seldom exhibited IBRs, and none were found under a shocking coil or caused MACE. Low HV impedance and failure to treat VT/VF occurred exclusively in dual-coil Durata leads; the cause of failure was an HV short between the proximal SVC coil and the cable to the RV coil. Dual-coil Durata models had a 2-fold higher incidence of IBR than did single-coil models. Single-coil Durata leads were not associated with HV insulation breach, probably because the absence of an SVC coil removes a potential return circuit for a breach in the HV system. It has been recommended that the SVC coil be excluded from the shock pathway of dual-coil Riata leads.
      • Swerdlow C.D.
      • Kalahasty G.
      • Ellenbogen K.A.
      Implantable cardiac defibrillator lead failure and management.
      The same programming of Durata leads may similarly reduce the risk of Durata HV failure.
      IBRs may not be detected by painless HV conductor impedance measurements.
      • Schloss E.J.
      • Krebs M.E.
      • Gupta M.
      Catastrophic failure of Durata ICD lead due to high-voltage short during shock delivery.
      • Shah A.D.
      • Hirsh D.S.
      • Langberg J.J.
      User-reported abrasion-related lead failure is more common with Durata compared to other implantable cardiac defibrillator leads.
      • Goldstein M.A.
      • Badri M.
      • Kocovic
      • Kowey P.R.
      Electrical failure of an ICD lead due to presumed insulation defect only diagnosed by a maximum output shock.
      • Doshi R.
      • Ceballos
      • Mendez F.
      Is high-voltage lead integrity measurement adequate during defibrillator generator replacement?.
      • Leong D.P.
      • Van Erven L.
      Unrecognized failure of a narrow caliber defibrillation lead: the role of defibrillation threshold testing in identifying an unprotected individual.
      It is likely that a substantial number of Durata IBRs in our study were not detected by painless measurements of HV impedance. Low HV impedances were found during DFT testing in 3 patients and after shocks or aborted shocks in 7 patients. One patient had a low HV impedance identified during remote transmission, and subsequently the lead failed to convert VT/VF during DFT testing. Four other patients received alerts for low HV impedances and received new leads before a MACE occurred. Nevertheless, improved methods for detecting insulation defects are needed.
      • Kollman D.T.
      • Swerdlow C.D.
      • Kroll M.W.
      • Seifert G.J.
      • Lichter P.A.
      ICD lead failure detection through high frequency impedance.
      Until sensitive and specific lead diagnostics are available, it is reasonable to deliver a high-energy shock to assess Durata HV impedance at the time of generator change or when concerns exist about the lead’s insulation. In contrast to HV-to-HV breaches that may be occult, noise discrimination algorithms may identify breaches affecting pace-sense conductors before they cause IARx.
      The incidence of Durata IBRs may be estimated using data from the manufacturer’s PPRs. Since data in manufacturers’ PPRs indicate that only a small fraction of leads is returned for analysis, it is probable that the actual incidence of IBRs and MACE are much higher than our study suggests.
      We can only speculate why these defects occur, but the constant movement of the redundant conductor cables against the lumen’s silicone wall is a plausible mechanism.
      • Swerdlow C.D.
      • Kass R.M.
      • Khoynezhad A.
      • Tang S.
      Inside-out insulation failure of a defibrillator lead with abrasion-resistant coating.
      • Hauser R.G.
      Riata externalized conductors: cosmetic defect or manifestation of a more serious flaw?.
      Over time, the inner silicone is abraded from the inside-out beneath a rigid shocking coil. When ETFE is abraded, the exposed conductor cable contacts the coil (Figure 2). The result depends on the cable exposed: if it is a sensing cable, the likely consequence is noise and IARx; if it is an HV cable, a low impedance pathway shorts the cable to the coil and prevents the delivery of a shock. Importantly, these events may occur without forewarning.
      Durata’s Optim outer insulation is not present under the shocking coils and thus does not insulate or restrain cable movement in these locations. In this respect, Durata is similar to non-Optim Riata and Riata ST leads. The Optisure ICD lead (A/SJM) has Optim under the shocking coils; this may mitigate short-circuiting. However, 2 Optisure leads have exhibited IBRs beneath the RV shocking coil, causing noise and oversensing (MDR nos. 7127690 and 7601101).
      As reported by A/SJM,
      • Carlson M.
      • Tsung P.
      Medical device advisory St. Jude Medical Riata and Riata ST silicone endocardial defibrillation leads. November 2011.
      8264 Durata and 2866 Riata ST Optim leads have been studied prospectively, and data from 3 registries found an all-cause mechanical failure rate of 1.36%. The freedom from mechanical failure at 10 years was 96.5%. Older studies
      • Liu J.
      • Patel D.
      • Rattan R.
      • et al.
      Failure-free survival of the Durata defibrillator lead.
      • Kramer D.B.
      • Hatfield L.A.
      • McGriff D.
      • et al.
      Transvenous implantable cardioverter-defibrillator lead reliability: implications for postmarket surveillance.
      • Providencia R.
      • Kramer D.B.
      • Pimenta D.
      • et al.
      Transvenous implantable cardioverter-defibrillator (ICD) lead performance: a meta-analysis of observational studies.
      reported that Durata’s performance was comparable to that of Sprint Quattro Secure and Endotak Reliance leads. The results of this study should prompt a reexamination of Durata’s performance by independent investigators. Such studies should differentiate failures that are identified by sensitive alerts that prevent MACE from those that occur without warning and result in failure to deliver therapy.
      This study has limitations. Our search terms were restrictive; however, we used terms such as analysis and receipt that returned a range of MDRs from the 3 manufacturers describing defects other than insulation breaches. Another limitation is the US postmarket surveillance system, which relies on passive reporting that necessarily introduces bias. Our study assumed that the fraction of leads reported in MAUDE was the same for the 3 manufacturers and was independent of the cause or mechanism of failure. According to manufacturers’ PPRs, only 4%–10% of removed leads are returned for analysis. Furthermore, the majority of failed leads are abandoned in situ. Thus, it is highly probable that the actual number of Durata leads that have failed because of IBR is substantially higher than the 137 leads in this report. Moreover, we do not know how many additional HV failures might have been identified if all Durata leads had been subjected to HV shock testing. Unless HV shock testing is performed, a lead with an occult HV insulation defect may not be identified. IBRs resulting in death may go unreported unless a device interrogation is performed postmortem and the results communicated to the FDA. Similarly, MAUDE data did not allow us to assess the efficacy of painless HV impedance measurements for identifying critical insulation breaches.
      While the results of our study are concerning, they do not justify routine prophylactic replacement of Durata leads. Physicians who follow Durata leads should ensure that patient notifiers and alerts are activated and patients understand their significance. ICDs should be programmed to recognize nonphysiological noise and minimize IARx. As with Riata leads, programming to a single-coil shock configuration should be considered. All removed leads should be returned to the manufacturer for analysis, together with clinical and diagnostic data.

      Conclusion

      Durata ICD leads are uniquely susceptible to IBRs that may result in failure to treat VT/VF or IARx. These serious adverse events may occur without forewarning. The constant movement of redundant cables in a single lumen is a plausible mechanism of failure. Dual-coil Durata models are more likely to develop IBRs. It may be appropriate to exclude the SVC coil from the shock pathway. HV DFT testing of Durata leads appears to be a useful diagnostic technique.

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