Protected: Update to Recommendations Regarding Boston Scientific RELIANCE G Defibrillation Leads Connected to Non-Boston Scientific ICD Generators

Previously Reported Recommendations for BSC ePTFE Leads Connected to a BSC ICD Generator

There are no changes to the scheduled follow-up interval for patients with ePTFE lead models.

1. Continue routine follow-up of defibrillation systems with ePTFE leads either via in-person or remote monitoring (RM) with consideration that RM can facilitate early detection of this pattern.
2. During routine follow-up of affected leads, determine the most recent approximate 28-day average LVSI that has not been influenced by the delivery of a shock and review HVSI for all shocks from the most recent episode since the last system check using the criteria in Table 1 below.
3. If lead replacement is planned, carefully consider the risk/benefit of lead extraction versus abandonment.
4. There may be circumstances such as routine defibrillator replacement that merit complex decision making. Contact BSC Technical Services for further assistance if necessary.

Table 1
Guidance for mitigating risk by assessing 28-day average LVSI and Code-1005 alerts of defibrillation systems with ePTFE leads

^†If the system includes a DC lead programmed RV2CAN, treat the system as a SC system; if DC lead programmed RV2RA treat as DC; if SC lead connected to SQ array treat as DC.

Medtronic Recommendations for BSC ePTFE leads connected to a Medtronic ICD Generator

After analysis of technical differences between Medtronic and BSC ICD generators (including analysis of Medtronic CareLink data), Medtronic engineers have indicated that their devices should not be at risk for a fault equivalent to the BSC Code-1005 shock truncation, regardless of shock polarity, since Medtronic ICD generators do not truncate to monophasic shocks.

Medtronic ICD generators have a lower tilt (50% versus 60% for BSC) and a longer pulse width (25 ms versus 20 ms). In this context energy delivery from these ICD generators should  accommodate higher shock impedance without truncation. Moreover, even if the first phase of energy is not fully delivered by 25 ms, the device will still move to the second phase to complete the biphasic shock (although delivered energy may be less than programmed). For these reasons, Medtronic does not recommend reprogramming high-voltage therapy polarity. This recommendation is particularly important as Medtronic ICD generators (with glassed feedthrough) are currently under a FDA Class I recall,^2,3 recommending only the B>AX configuration (equivalent to the “reverse polarity” in BSC generator). This is the opposite polarity that BSC advises for its own generators paired with these leads.

Medtronic’s retrospective analysis of CareLink patients with mixed systems (BSC ePTFE leads integrated with Medtronic ICD generators) indicated that shock therapy success rates were consistent with historical performance metrics. However, due to the limited sample size of this group compared to BSC’s data and the low overall failure incidence of ePTFE leads, this finding is considered non-definitive. Consequently, despite the absence of observed therapy truncation with Medtronic ICD generators, the extant recommendation for PTFE lead replacement in systems exhibiting a gradual rising LVSI exceeding 150 ohms remains in effect, aligning with prior guidance issued by Boston Scientific.

Specific Medtronic recommendations for BSC ePTFE leads associated with a Medtronic ICD generator (Summarized)

1. Medtronic devices are NOT known to be at risk of a BSC Code-1005 equivalent fault and its associated constraints on high-voltage therapy delivery, irrespective of shock polarity.
2. Medtronic does not recommend reprogramming high voltage therapy polarity of Medtronic devices connected to recalled BSC leads.
3. The BSC recommendation to consider lead replacement with LVSI > 150 ohms also applies to advisory leads attached to Medtronic devices.

Abbott Recommendations for BSC ePTFE Leads Connected to an Abbott ICD Generator

After analysis of technical differences between Abbott and BSC ICD generators (including review of Merlin.net data), Abbott engineers have indicated that their devices should not be at risk for a fault equivalent to the BSC Code-1005 shock truncation, regardless of shock polarity. Therefore, they are recommending no change in shock polarity.

Abbott ICD generators have the option to program shock waveform to fixed pulse width (aka Optimized Precision Shock Technology or DeFT Response) which allows programmed shock duration at any impedance and prevents delivery of shocks with extended pulse widths. In addition, Abbott devices do not switch to monophasic. At impedances > 115 ohms, Abbott delivers a biphasic shock with a 12 ms pulse width for each phase.  However, lead integrity at impedances > 150 ohms remains a concern.  The relatively small sample size of this population also limits definitive conclusions regarding the long-term course of these mixed systems.

Specific Abbott Recommendations for BSC ePTFE Leads Connected to an Abbott ICD Generator (Summarized)

1. The Abbott ICD generator should be programmed as follows:
   1. All HV therapies should be programmed to maximum output (40 J/896 V or 36 J/850 V), particularly if RV-Can shock impedance is above 90 ohms.
   2. Program Waveform Mode to fixed pulse width using DeFT Response.
   3. Maintain shock polarity as programmed, as Abbott devices are not subject to Code-1005 time-out error and do not automatically switch to monophasic.
   4. Set High Voltage Lead Impedance (HVLI) Monitoring Upper Limit to benefit from alerts for impedances (e.g., above 90 or 125 ohms). For remotely monitored patients, ensure the HVLI alert is enabled in Merlin.net.

2. Boston Scientific ePTFE leads with a low-voltage shock impedance value (i.e. High Voltage Lead Impedance (HVLI) on Abbott devices) >150ohms, particularly on RV-Can, should be considered for replacement.

Biotronik Recommendations for BSC ePTFE Leads Connected to a Biotronik ICD Generator

Similar to BSC ICDs, Biotronik devices (utilizing the default waveform) employ a configuration where the RV shock coil functions as the cathode (-) and the device housing acts as the anode (+) during the initial phase of shock delivery. Additionally, Biotronik ICD generators are susceptible to premature shock truncation, mirroring similar considerations with BSC ICD pulse generators. A 23-millisecond timeout for the first shock phase terminates energy discharge if reached, resulting in an incomplete monophasic shock. This truncation phenomenon persists even when programming the device to the “biphasic2” waveform (which incorporates a fixed, time-controlled 2ms second phase).

Biotronik’s “Last Shock Impedance” (which is the last daily shock impedance measurement) serves a function analogous to Boston Scientific’s LVSI. However, direct quantitative comparison is not recommended due to inherent differences in calculation methodologies and established reference ranges. For Biotronik ICDs, impedance values below 25 ohms or exceeding 150 ohms are categorized as out-of-range, indicative of a potential lead anomaly.  Shock impedance is continuously monitored and the daily mean value is transmitted via Home Monitoring Service Center (HMSC). In the HMSC, the events “daily shock impedance measurement out-of-range” and “shock impedance out-of-range” are <30 Ohms and >125 Ohms (programmable between >70 Ohms and >150) as standard settings for the alert-limits.

Out-of-range measurements trigger a clinical event message, accessible via both the programmer and the HMSC. While direct programmer interrogation with specific devices (Acticor, Rivacor, Ilivia Neo, Intica Neo) reveals detailed impedance trends across various pathways (e.g., RVcoil-Can, RVcoil-RVtip, RVcoil-SVCcoil, etc.) for enhanced technical diagnosis, these specific trend data are not available with the HMSC.  In the event of a failed shock due to a Shockphase timeout, detailed episode information and a clinical event message is generated and available on the programmer and uploaded to the HMSC.  Unlike Boston Scientific systems, a specific alert code (code-1005) is not generated in the Biotronik system.

Specific Biotronik Recommendations for BSC ePTFE Leads Connected to a Biotronik ICD Generators (Summarized)

1. Biotronik devices are subject to shock truncation (monophasic shocks) in cases of lead calcification and high lead impedances due to similar timeouts as BSC.
2. When possible, devices should be programmed to the default shock waveform (“normal polarity”) with RV shock coil serving as cathode (-) and the housing as anode (+) during the first shock phase as recommended by BSC for these leads
3. Biotronik’s “Last Shock Impedance” serves a function analogous to Boston Scientific’s LVSI. However, direct quantitative comparison is not recommended due to inherent differences in calculation methodologies and established reference ranges. For Biotronik ICD systems, impedance values below 25 ohms or exceeding 150 ohms are categorized as out-of-range, indicative of a potential lead anomaly. Lead replacement should be considered when “Last Shock Impedance” is out of range or in cases of a failed shock.