The British Heart Rhythm Society (BHRS) and Arrhythmia Alliance (A-A) have produced a joint document to support the recent Boston Accolade field safety notice. This should be read in association with the original FSN.
This summary should not be used in isolation and clinical teams should also read the Boston Scientific’s Urgent Field Safety Notice: “Boston Scientific High Battery Impedance May Initiate Safety Mode in a subset of ACCOLADE™ Family of Pacemakers and CRT-Ps”, published 12 December 2024. It is an interpretation to aid clinical decision making. Document produced by British Heart Rhythm Society and Arrhythmia Alliance – March 2025.
Devices Affected
Boston Scientific has found that a subset of the ACCOLADE™ family of pacemakers and CRT-Ps may prematurely develop abnormal function of the pacemakers’ battery. Note that the manufacturers have determined that pacemakers in this group are only susceptible to this malfunction in the last four years of the pacemakers’ battery life. The pacemakers affected were all manufactured before September 2018 and approximately 13% of those devices may be affected. At risk devices can be identified by consulting this link: www.BostonScientific.com/lookup. Enter your language, as well as the model and serial numbers of the device.
Abnormal Pacemaker Function
In affected devices a manufacturing process, prior to September 2018, can result in a high battery impedance which may cause a device to exhibit transient voltage decreases in the last 4 years’ life of the battery. When the pacemaker’s battery is stressed, for example during telemetry operations or during other normal high power device operations such as automatic radio frequency telemetry circuit enablement and automatic memory checks, then the battery voltage may drop below a minimum threshold (that is during a high-power state). The pacemaker’s software then triggers an automatic system reset such that the conditions of the high-power state are interrupted. Further system resets may occur with further high battery impedance high-power states. If 3 such resets occur during a 48hour period the pacemaker’s software causes it to enter safety pacing mode, intended to maintain basic pacing functionality in the context of reducing battery capability.
Safety Mode Pacing
Safety mode pacing is intended to provide basic pacing treatment for 3 months, but this cannot be relied upon in the context of a high battery impedance, and neither is it as sophisticated as normal pacemaker function. It is only intended to be a bridge to pacemaker replacement. Pacing can be stopped altogether by external electrical factors (for example: pacemaker interrogation, myopotential inhibition, diathermy).
Thus, patients who are pacing-dependent (see below) are at risk of asystole and collapse. There have been two patients’ deaths in the affected population.
Importantly during box change, the safety mode’s non-programmable sensitivity setting, and unipolar pacing configuration, make the system susceptible to pacing inhibition during electrocautery and removal of the device from the pocket such that a temporary pacing wire may be required to cover the procedure in pacing-dependent patients.
Who Should Have a Pacemaker Box Change Because of this Problem?
The manufacturer is not recommending prophylactic pacemaker replacement in all patients with pacemakers that fall into the advisory population. However, many patients with affected devices may initially seek pacemaker replacement. Thus, the risk of pacing malfunction needs to be balanced against procedural risks (e.g., infection, lead damage etc.). This will always be a matter of individual clinical judgement but in summary and as a guide to the decision process:
If your patient has one of the affected pacemakers
and
If your patient’s pacemaker is in the last 4 years of its battery life
and
If your patient is “pacemaker-dependent” *
then
prophylactic replacement should be considered, because should their pacemaker have 3 resets in 48 hours, it will go into safety pacing mode and the patient will be at risk of asystole and collapse.
OR
If your patient has one of the affected pacemakers
and
If their device has already gone into safety mode pacing mode and is therefore not providing optimal pacing for your condition
then
the pacemaker should be promptly replaced, and urgently so if the patient is pacing dependent.
OR
If your patient has one of the affected pacemakers
and
If their pacemaker is in the last 4 years of its battery life
and
If you consider your patient to have another condition that you consider puts them at high risk, should they go into safety pacing mode eg. history of myopotential oversensing, likely poorly tolerating unipolar sense/pacing, high pacing burden.
then
consider prompt prophylactic replacement.
After a shared decision-making process, some patients may elect not to have a box change despite device having <4yrs longevity on battery.
Remote Monitoring
The FSN does not recommend deactivating remote monitoring even though the interaction with latitude may precipitate a safety mode event. It remains an important means to alert clinicians to the onset of safety mode which will allow prompt action to be taken. Some centres may choose to deactivate patient-initiated interrogation due to the possibility that this small additional number of latitude/device interactions could increase the number of higher current drain interrogations with latitude and potentially increase the risk of initiating a safety mode. This function can be deactivated and reactivated remotely via Latitude.
Financial Remuneration
Boston Scientific understands the ramifications this FSN has had on many of its UK customers and whilst there is no formal compensation scheme in place, on this exceptional occasion Boston Scientific is providing free of charge devices for replacement in specific UK patients as per the FSN, including for those devices that are outside of warranty. The company will liaise directly with implanting centres.
Reporting to MHRA
1. It is important that any devices which have entered safety mode are reported to the MHRA in the usual way in addition to returning the device to the manufacturer. If there are patients who have died suddenly or unexplained with a device affected by the FSN, efforts should be made to interrogate the device postmortem and the MHRA should be informed if the device has entered safety mode. Any adverse events suspected or confirmed to be related to the FSN should be reported to MHRA and Boston Scientific. https://yellowcard.mhra.gov.uk/
*Pacing Dependency
There are various definitions for pacing dependency. The prevalence of pacemaker dependency in a CIED population is determined by the definition used. The American Heart Rhythm Society defines pacemaker dependency as no intrinsic rhythm greater than 40bpm or haemodynamic instability with the intrinsic rhythm1. In clinical practice a patient is pacing dependent when they have an inadequate or absent intrinsic heart rhythm, which becomes symptomatic if there is a (sudden) failure of the CIED’s pacing function. A frequently used definition is the absence of any spontaneous ventricular activity (or the presence of low‐rate, clinically not tolerated, spontaneous activity when the CIED is transiently programmed in VVI 30‐40 bpm2. The majority of patients are not pacing dependent based on this definition, and as such, if their device was temporarily turned off or damaged, they would not come to serious harm or death from sudden CIED failure3.
1.Indik JH, Gimbel JR, Abe H, et al. 2017 HRS expert consensus statement on magnetic resonance imaging and radiation exposure in patients with cardiovascular implantable electronic devices. Heart Rhythm.2017;14:e97‐153
2.Zecchin M, Severgnini M, Fiorentino A, et al. Management of patients with cardiac implantable electronic devices (CIED) undergoing radiotherapy: A consensus document from Associazione Italiana Aritmologia e Cardiostimolazione (AIAC), Associazione Italiana Radioterapia Oncologica (AIRO), Associazione Italiana Fisica Medica (AIFM). Int J Cardiol. 2018;255:175‐183.
3.Panagiotis Korantzopoulos, Konstantinos P. Letsas, George Grekas, John A. Goudevenos, Pacemaker dependency after implantation of electrophysiological devices. Europace 2009;11:1151‐55
PUBLISHED: 12th March 2025