Category: Press Releases

This alert was developed in collaboration with the European Heart Rhythm Association (EHRA) and Boston Scientific Corporation (BSC).

On July 24, 2025, Boston Scientific Corporation (BSC) began informing clinicians of the potential for gradually rising low-voltage shock impedance (LVSI) associated with shock coil calcification in RELIANCE™ defibrillation leads [both single coil (SC) and dual coil (DC)] coated with expanded polytetrafluoroethylene (ePTFE/GORE). This gradual impedance rise could reduce shock efficacy, and instances of failed shock therapy have been reported. Sensing and pacing performance of these leads are not known to be compromised.

HRS Recommendations

1. HRS strongly encourages its members worldwide to read the Boston Scientific Safety Notification.
2. Given the highly technically nuanced nature of this advisory, clinicians should maintain a low threshold to discuss lead concerns with BSC technical services for additional guidance to support informed lead replacement decision-making.
3. Gradual impedance rises are defined by 28-day averages based on visual estimates (from the shock impedance graph) and excludes rapid changes that may indicate a need to investigate other causes of lead malfunction, such as lead conductor fracture or connection issues. Gradual impedance rise includes a 20Ω rise from baseline, at least three (3) years post implant, to an average of >90Ω for SC leads, >70Ω for DC leads (excluding average rises in excess of 30Ω per quarter). Boston Scientific Technical Services may assist with estimates. All impedances described below are 28-day averaged LVSI.
4. Patients should be followed by remote monitoring, if possible.
5. Enhanced follow-up should be considered in patients who are not participating in remote monitoring, at a minimum of every 6 months, or if gradual impedance rises are observed to LVSI of >90 ohms for SC and >70 ohms for DC leads then every 3-6 months.
6. In patients who meet criteria for gradual LVSI consistent with lead calcification, clinicians should program Shock Polarity to Initial (RV-) and all shocks to maximum energy.
7. In patients who cannot be programmed to initial (RV-) shock polarity, but exhibit gradual rise to LVSI of >90 ohms for SC and >70 ohms for DC leads, clinicians should have a discussion with Boston Scientific Technical Services, and consider initiating shared decision making for potential future lead replacement if impedance continues to rise.
8. Lead replacement should be strongly considered in all patients (irrespective of the programmed polarity) with LVSI > 150 ohms or for whom HVSI Code-1005 alert has been detected.
9. There is no recommendation for commanded shocks/ DFT testing to assess HVSI. LVSI can be lower immediately post shock delivery, but again rise, thus providing a false sense of security. In addition, shock success at DFT testing is not predictive of future success in the setting of ongoing lead calcification.
10. The final decision to replace a lead should be made with the patient via a shared decision-making model based on individual patient characteristics, care goals, and preferences and the data provided by BSC.
11. If lead replacement is planned, clinicians should 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. However, this must be balanced by potential complications of abandoned leads and that extraction risk may be higher with longer lead dwell times. At this time, there are little data on whether these leads are at higher risk for extraction than other leads. When appropriate, alternative strategies such as a non-vascular ICD system or addition of another transvenous lead should be considered.
12. As always, patients and providers seeking financial assistance for services (including replacement) related to products under warranty, should contact their local representative. Boston Scientific’s RELIANCE Gore (ePTFE) includes a limited lifetime warranty. Terms and conditions are available online at www.BostonScientific.com/warranty. Boston Scientific’s warranty administration team is available to answer questions at warranty@bsci.com.

More Information

HRS Article: Boston Scientific Advisory Regarding the Potential for Shock Coil Calcification and Reduced Shock Efficacy for RELIANCE G Defibrillation Leads with Gore ePTFE Coated Shock Coils Manufactured Between 2002 and 2021

Boston Scientific Full Advisory notice