Update to 2021 Advisory Regarding Certain Boston Scientific Pacemakers with Potential for Entering Safety Mode with Inhibition of Pacing

Issue Summary

In June 2021, Boston Scientific communicated that the aforementioned family of pacemakers had the potential to exhibit increasing battery impedances over time. The high impedance that occurs later in device life may lead to decreased voltage during times of high power consumption, particularly during interrogations. This may trigger a system reset. If three system resets occur within a 48-hour period, the device will enter Safety Mode to maintain back-up pacing with pre-defined, non-programmable settings. The pre-specified Safety Mode settings (VVI 72.5, at 5.0 V at 1.0 ms, with sensitivity of 0.25mV, and unipolar sensing/pacing) may not be ideal for the patient's condition. Safety Mode might result in pacing inhibition/pauses due to myopotential oversensing, skeletal muscle or phrenic nerve stimulation, loss of AV synchrony, and heart failure.

Based on continued post-market surveillance, Boston Scientific has recently released an updated communication. The communication mentions the following:

1. The occurrence rate for this issue is 8% at 9 years, 12% at 10 years, and 49% at 11 years.
2. Most safety mode reports continue to be associated with telemetry operations (programmer, LATITUDE Communicator, or LATITUDE Consult), though 3.5% of reports are unrelated to interrogations by an external device.
3. There have been 15 reports of pauses during interrogations with a programmer or patient initiated LATITUDE interrogations, some have been up to approximately 20 seconds.
4. There have been 3 deaths in patients who are pacemaker dependent, which possibly may not have occurred if the devices were replaced per previous recommendations (outlined below). The estimated potential for life-threatening harm is 1 in 769 (0.13%) at 11 years for impacted devices if the generator is not replaced at the recommended interval.
5. When safety mode is initiated due to high battery impedance, previous estimates of battery time become invalid.

Boston Scientific Recommendations:

1. Individual patient evaluation: Identify patients who are at risk of harm due to Safety Mode's non-programmable parameters (particularly pacemaker-dependent patients).
2. Replacement:
   • If a device enters Safety Mode, perform emergent generator replacement for patients at significant risk of harm, and non-emergent replacement for others.
   • General prophylactic device placement is not recommended.
   • For patients who are at risk of harm if Safety Mode is triggered, device replacement is recommended as follows:
     • For DR EL pacemakers, schedule replacement when longevity remaining is four years or less
     • For CRT-Ps, schedule replacement when longevity remaining is three years or less
3. Follow-up interval:
   • Perform a system follow up via remote or in office interrogation at least every 12 months.
   • When longevity reaches one year remaining, follow up every three months until replacement is indicated.
   • Note: There is a potential for pacing pauses during in person checks and LATITUDE patient-initiated interrogation (PII) checks for pacing-dependent patients who remain implanted beyond the recommended replacement interval (within ≤4 years remaining for DR EL pacemaker or within ≤3 years remaining for CRT-P). During in-person device checks, consider patient recumbency and the availability of resuscitation equipment with qualified personnel. Consider disabling PII for patients on LATITUDE within these windows.

HRS Recommendations

HRS strongly encourages its members to read the updated Boston Scientific Safety Notification. We agree with Boston Scientific that the decision to replace the generator should be individualized based on patient risk. In high-risk patients the device should be replaced as outlined above when the benefits of replacement outweigh the risks. To limit potential out-of-pocket costs to patients in this clinical scenario, HRS strongly recommends use of Boston Scientific’s unreimbursed medical expense program (available to patients in the United States).

Reporting Adverse Reactions or Quality Problems

Adverse reactions or quality problems experienced may be reported directly to Boston Scientific or the FDAs MedWatch Adverse Event Reporting program at www.fda.gov/medwatch/report.htm or call 1-800-332-1088. Should you have any questions about this notice, please contact your local Boston Scientific Representative. In addition, please work with your device representative to return any explanted devices for product evaluation and analysis.