Boston Scientific has issued a letter notifying affected customers that certain ENDOTAK RELIANCE Defibrillation leads with expanded polytetrafluoroethylene (ePTFE) coated coils may impact shock efficacy and/or require early replacement. Boston Scientific ENDOTAK RELIANCE leads are intended for pacing, rate-sensing, and delivery of cardioversion and defibrillation shocks when used with a compatible pulse generator.
Boston Scientific is aware of the association of calcified defibrillation lead coil(s) with a pattern of gradually rising LVSI measurements. This calcification phenomenon can biologically encapsulate and electrically insulate the defibrillation lead coil(s).
BSC has completed a comprehensive investigation of ePTFE RELIANCE lead performance to identify the early signs of this phenomenon, characterize its potential effect on shock efficacy, and provide recommendations to mitigate the associated risk. Key findings include:
- While cracking of calcified ePTFE coating has been observed, calcification of the shock coil(s) does not compromise the physical or electrical integrity of the lead.
- A trend of gradually rising LVSI is correlated with shock coil calcification and is more prevalent with BSC RELIANCE ePTFE defibrillation leads compared to non-ePTFE defibrillation leads from BSC and other manufacturers; leads may be implanted for eight or more years prior to manifestation of this trend.
- The shock coil encapsulant material may exhibit a polarity bias with Reversed (RV+) polarity having an elevated high voltage shock impedance (HVSI) relative to Initial (RV-) polarity. Reversed (RV+) polarity shocks are 4.5 times more likely to initiate a high, delivered shock impedance alert (Code-1005), and defibrillation systems programmed to Reversed (RV+) polarity exhibiting a gradual rising LVSI have a lower defibrillator-determined shock success rate.
- When managing leads with calcified coil(s), delivery of commanded shocks is neither effective at permanently mitigating rising impedance risk nor predictive of future impedance as LVSI may initially decrease but typically returns to pre-shock values in less than six months.
The most common harm is early lead replacement, and the most serious harm is death or need for cardiac resuscitation due to non-conversion of a sustained ventricular arrhythmia from a reduced shock energy due to high impedance.
As of July 24, Boston Scientific has reported 386 serious injuries and 16 patient deaths associated with this issue.
On July 24, Boston Scientific sent all affected healthcare providers a letter recommending the following actions:
- Continue routine follow-up of defibrillation systems with ePTFE leads either via in-person or remote monitoring (RM) per labeling or medical guidelines with consideration that RM can facilitate early detection of this pattern.
- 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 and data provided in the physician letter.
- If lead replacement is planned, carefully consider the risk/benefit of lead extraction versus abandonment. Based on implant time and likely coil calcification, these leads may pose an increased risk of extraction-related complications.
- There may be circumstances such as routine defibrillator replacement that merit complex decision making. Contact BSC Technical Services for further assistance if necessary.
- Distribute the provided letter to all healthcare professionals (HCPs) within your organization who need to be informed and include this letter in the patient’s medical record.
- A patient letter is available upon request, which can be distributed to the patient.
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