On December 13, 2024, Boston Scientific recalled 203,000 ACCOLADE™ family pacemakers and cardiac resynchronization therapy-pacemakers (CRT-Ps) because of an increased risk of initiating Safety Mode when the battery life is ≤4 years.1,2 The Food and Drug Administration classified this as a Class I recall2,3 meaning “reasonable probability that the… product will cause serious adverse health consequences or death.”4 This follows a June 2021 Class I recall for 48,000 Boston Scientific INGENIO™ family pacemakers and CRT-Ps, also for increased risk of Safety Mode.5,6
In Safety Mode, the pacemaker permanently enters a nonprogrammable, high output (5.0V), unipolar ventricular sensing/pacing mode at 72.5 beats/minute. Of greatest concern, unipolar sensing can oversense skeletal muscle signals as cardiac activity, leading to inappropriate inhibition of life-sustaining pacing. The resultant asystole is the presumed cause of three deaths associated with the INGENIO™ recall7 and 832 injuries with two deaths associated with the ACCOLADE™ recall.1,2
For these recalls, Boston Scientific recommends identifying patients at risk of harm from Safety Mode and promptly performing prophylactic generator replacement when pacemaker battery life is ≤4 years for the ACCOLADE™ and INGENIO family pacemakers and ≤3 years for the INGENIO family CRT-Ps.1,5,6,8 While hundreds of thousands of patients are at risk, there are no data about the risk of complications from Safety Mode initiation for physicians and patients to weigh against the 2–4% risk of major complications with generator replacement.9
Methods
We used the Veterans Affairs National Cardiac Device Surveillance Program (VANCDSP), which includes device data and remote monitoring transmissions for all patients with pacemakers followed by 121 Department of Veterans Affairs device clinics,10 to identify devices affected by the INGENIO™ and ACCOLADE™ recalls from 6/1/2014–1/1/2025. To broadly identify all Safety Mode initiations, 2952 patients with recalled pacemakers were screened for Safety Mode initiation at any battery life and with any length of VA follow-up. We identified Safety Mode through remote monitoring transmissions (pacemakers that initiate Safety Mode automatically trigger a transmission), keyword search of the VA electronic health record (EHR) for “Safety Mode,” and chart review of patients who had received generator replacements to evaluate for Safety Mode initiation before generator change. Two authors independently abstracted all data, with any disagreements resolved by consensus with the third author.
Through VA EHR chart review, we identified complications that were acute onset and concurrent with Safety Mode initiation. We stratified these complications as major (associated death, syncope, presyncope, falls with trauma, documented oversensing with asystole) or other (dizziness, shortness of breath, heart failure, muscle stimulation, or fatigue). We used descriptive statistics to compare patients with complications and those without, stratified by pacemaker dependency. In accordance with the Department of Veterans Affairs Office of Research & Development Program Guide 1200.21 “VHA Operations Activities That May Constitute Research,” data were collected as part of a quality improvement study for patient safety and did not require institutional review board approval.
Results
Forty-seven patients had Safety Mode initiation during the study period. Mean age was 78.5 years, 47 (100%) were male, and 29 (62%) were pacemaker-dependent (Table). The mean (±standard deviation) battery life at Safety Mode initiation was 15.5±8.0 months; all occurred when battery life was ≤4 years and 92% when battery life was ≤2 years. Safety Mode was identified and potentially triggered during pacemaker interrogation within a healthcare setting in 9 patients (19%) and via remote monitoring in 38 (81%).
Table:
Outcomes for patients with recalled Boston Scientific pacemakers who experienced Safety Mode initiation
| Overall N= 47 |
Pacemaker- Dependent N= 29 (62%) |
Non Pacemaker-Dependent N= 18 (38%) |
P-value | |
|---|---|---|---|---|
| Baseline Characteristics | ||||
| Age, years (mean ± standard deviation) | 78.5±10.1 | 79.4±9.2 | 77.0±11.5 | 0.44 |
| Male | 47 (100%) | 29 (100%) | 18 (100%) | - |
| Comorbidities | ||||
| HFrEFa | 16 (34%) | 13 (45%) | 3 (17%) | 0.05 |
| Atrial fibrillation and/or flutter | 26 (55%) | 14 (48%) | 12 (67%) | 0.22 |
| Coronary artery disease | 18 (38%) | 9 (31%) | 9 (50%) | 0.19 |
| Cerebrovascular event | 6 (13%) | 2 (7%) | 4 (22%) | 0.14 |
| Pacemaker implant indication | ||||
| Complete heart blockb | 16 (34%) | 16 (55%) | 0 (0%) | <0.001 |
| High grade or Mobitz II AV block | 9 (19%) | 7 (24%) | 2 (11%) | |
| Sinus node dysfunction | 20 (43%) | 4 (14%) | 16 (89%) | |
| Combined AV block/ sinus node dysfunction | 2 (4%) | 2 (7%) | 0 (0%) | |
| CRT-P | 7 (15%) | 7 (25%) | 0 (0%) | 0.03 |
| Any complication from Safety Mode | 31 (66%) | 23 (79%) | 8 (44%) | 0.014 |
| Major complications | 15 (32%) | 15 (52%) | 0 (0%) | <0.001 |
| Deathc | 2 (4%) | 2 (7%) | 0 (0%) | 0.26 |
| Syncope | 8 (17%) | 8 (28%) | 0 (0%) | 0.014 |
| Presyncope | 3 (6%) | 3 (10%) | 0 (0%) | 0.16 |
| Fall with trauma, no syncope | 3 (6%) | 3 (10%) | 0 (0%) | 0.16 |
| Pauses or asystole from oversensing documented on telemetry | 11 (23%) | 11 (38%) | 0 (0%) | 0.003 |
| Other complications | ||||
| Dizziness without syncope or presyncope | 8 (17%) | 5 (17%) | 3 (17%) | 0.96 |
| Heart failure exacerbation | 3 (6%) | 3 (10%) | 0 (0%) | 0.16 |
| Shortness of breath | 10 (21%) | 7 (24%) | 3 (17%) | 0.54 |
| Fatigue | 8 (17%) | 6 (21%) | 2 (11%) | 0.40 |
| Pectoral stimulation | 5 (11%) | 2 (7%) | 3 (17%) | 0.29 |
| Diaphragmatic stimulation | 1 (2%) | 1 (4%) | 0 (0%) | 0.43 |
| Clinical characteristics | ||||
| Emergency department presentation | 29 (62%) | 24 (83%) | 5 (28%) | <0.001 |
| Self-presented to emergency department due to symptoms | 20 (43%) | 16 (55%) | 4 (22%) | 0.03 |
| ICU admission | 10 (21%) | 10 (34%) | 0 (0%) | 0.005 |
| Early generator change | 45 (96%) | 27 (93%) | 18 (100%) | 0.26 |
| No generator change | 2 (4%) | 2 (7%) | 0 (0%) | 0.26 |
| Patient death during hospitalization | 1 | 1 | - | - |
| Patient transitioned to hospice | 1 | 1 | - | - |
Abbreviations: HFrEF, heart failure with reduced ejection fraction; AV, atrioventricular; CRT-P, cardiac resynchronization therapy pacemaker; ICU, intensive care unit
Heart failure with prior or current ejection fraction ≤ 40%
Two patients had prior AV node ablation
One patient with asystole from oversensing and resulting falls was transitioned to hospice during hospitalization in the setting of intractable symptoms and multi-morbidity and then died.
Of 47 patients with Safety Mode initiation, 31 (66%) had any complication and 15 (32%) had a major complication. Of 29 pacemaker-dependent patients, 23 (79%) had any complication and 13 (52%) had a major complication, compared to 8 (44%, p=0.01) and 0 (0%, p<0.001), respectively, in non-pacemaker-dependent patients. Major complications in pacemaker-dependent patients included 2 (7%) associated deaths, 8 (28%) syncope, 3 (10%) presyncope, 3 (10%) falls with trauma, and 11 (38%) documented oversensing with asystole. Among all patients with Safety Mode initiation, the other most common complications included 10 (21%) patients with dyspnea, 8 (17%) dizziness, 8 (17%) fatigue, and 5 (11%) pectoral stimulation. Twenty-nine (62%) patients presented to the emergency room related to Safety Mode and 10 (21%) required intensive care unit admission.
Discussion
Among patients with recalled Boston Scientific pacemakers who entered Safety Mode, we found a high risk of major complications among pacemaker-dependent patients, including death and syncope associated with asystole due to oversensing. This new information should prompt physicians to more strongly recommend prophylactic generator change in pacemaker-dependent patients affected by the INGENIO™ and ACCOLADE™ recalls who reach the specified battery longevity criteria.
Our study of broadly screened patients cannot (and should not be used to) estimate the incidence of Safety Mode initiation, which relies on duration of total risk exposure for an individual patient, with a weighted, escalating risk as the device ages and nears ERI; many patients had not reached the threshold at which Safety Mode initiation has been reported. Screened patients may also have had prophylactic generator changes, generator changes for other reasons (e.g., infection, upgrade), variable follow-up within VA, or death during the study period. However, estimates for the lifetime risk of conversion to Safety Mode are relevant to the decision to perform prophylactic generator change. In the INGENIO™ recall, at least one-third of recalled pacemakers were expected to enter Safety Mode before the elective replacement indicator (ERI)5 and, per the July 2024 manufacturer post-market data, the observed risk is 8% at 9 years and 49% at 11 years.7 The risk of Safety Mode initiation in pacemakers covered by the ACCOLADE™ recall is currently reported as 0.4%−2% at 9 years.1–2 However, given the pattern of escalating risk for INGENIO devices, the risk is likely to significantly increase as the pacemaker battery ages and nears ERI.
Safety Mode initiation can be triggered by high power operations such as in-person device interrogations and remote interrogations. Given that most Safety Mode initiations were not identified in a clinical setting, patients with recalled devices should be counseled to seek care immediately if they experience symptoms that could be associated with Safety Mode, including syncope, lightheadedness, and muscle stimulation.2 Further, for patients at high-risk of complications, clinicians may consider disabling patient-initiated transmissions to reduce the risk of ambulatory Safety Mode initiations.1
This study is limited to a male Veteran population and may underestimate complications when patients presented to non-VA clinicians. However, the vast size of the VANCDSP patient population uniquely enables this analysis and the risks are likely generalizable to all patients with affected Boston Scientific pacemakers.
The high risk of major complications among pacemaker-dependent patients can inform patient-physician discussions about prophylactic replacement of hundreds of thousands of pacemakers and CRT-Ps affected by the Boston Scientific recalls.
What is the clinical question being addressed?
What are the risks for patients with recalled Boston Scientific pacemakers who experience Safety Mode initiation?
What is the main finding?
Major complications, including syncope and death, are associated with Safety Mode initiation, specifically in patients with pacemaker dependence.
Acknowledgements:
We thank Gary Tarasovsky, BS for collecting data to identify patients who might have had Safety Mode initiation through electronic health record keyword search. Dr. Dhruva was supported by the Veterans Affairs Health Systems Research 1IK2HX003357.
Disclosures:
Dr. Dhruva currently receives research funding from Arnold Ventures and reports serving as a member of the Institute for Clinical and Economic Review California Technology Assessment Forum and Medicare Evidence Development and Coverage Advisory Committee. Drs. Caughron and Raitt have nothing to disclose.
References
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