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Takeaway: As a result of this project, investigators determined pacemaker dependency was associated with a high risk of major complications for Veterans with pacemakers recalled in 2024. This study was then able to inform clinician-patient decision-making about how best to address the risks of this recall.
When an individual’s heart cannot maintain a normal heart rhythm and other treatments do not help (i.e., medication), healthcare providers may recommend a cardiac pacemaker be placed in the chest. A pacemaker is a medical device that corrects certain heart rhythm problems by prompting the heart chambers to beat. A pacemaker can sense when an individual’s heartbeat is not normal (too fast, too slow, irregular) and will deliver electrical impulses to correct the rhythm. It does not deliver a shock.
Currently, as many as 3 million Americans have pacemakers and more than 70% of those with pacemakers are at least 65 years old. In 1960, VA researchers—led by Dr. William Chardack—created the cardiac pacemaker, a small electronic device that can be implanted in a patient’s chest to help stabilize abnormal heart rhythms. Chardack described the original pacemaker as a “battery-operated gadget about twice as big as a spool of Scotch tape and much the same shape.” Today, VA continues to provide state-of-the-art pacemakers to Veterans.
On December 12, 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. The FDA classified this as a class I recall, meaning there was a “reasonable probability that the… product will cause serious adverse health consequences or death.” This recall affected a large number of VA and non-VA patients. However, although hundreds of thousands of patients were at risk, including Veterans, there were no data about the risk of complications from Safety Mode initiation for physicians and patients to weigh against the 2% to 4% risk of major complications and generator replacement [surgical procedure in which the battery-powered unit (pulse generator) of the pacemaker is replaced].
In Safety Mode, the pacemaker permanently enters a non-programmable, high output, unipolar ventricular sensing/pacing mode at 72.5 beats per minute. Of greatest concern is the risk that unipolar sensing can over-sense skeletal muscle signals as cardiac activity, leading to the inappropriate inhibition of life-sustaining pacing.
HSR Career Development Awardee, Sanket Dhruva, MD, MHS, and colleagues sought to identify the severity of complications and risks to patients associated with these recalled pacemakers. They used VA National Cardiac Device Surveillance Program data, which included device data and remote monitoring transmissions, for all Veterans with pacemakers followed by 121 VA device clinics, to identify devices affected by the recalls from June 1, 2014, to January 1, 2025. To broadly identify all Safety Mode initiations, 2,952 Veterans with recalled pacemakers were screened for Safety Mode initiation at any battery life and with any length of VA follow-up.
Through VA electronic health record chart review, investigators identified complications that were acute onset and concurrent with Safety Mode initiation. Complications were categorized as major (i.e., associated death, syncope, presyncope, falls with trauma, documented oversensing with asystole) or other (i.e., dizziness, shortness of breath, heart failure, muscle stimulation, or fatigue). Of 47 Veterans with Safety Mode initiation, 31 (66%) had any complication and 15 (32%) had a major complication.
Among the 29 patients with Safety Mode initiation who were pacemaker-dependent, 23 (79%) had any complication and 15 (52%) had a major complication, compared with 8 (44%) and 0, respectively, in patients who did not depend on pacemakers. [Pacemaker dependency occurs when an individual’s heart cannot beat on its own without relying on an implanted pacemaker to maintain a safe rhythm.]
Among patients with recalled Boston Scientific pacemakers who entered Safety Mode, investigators found a high risk of major complications among pacemaker-dependent patients, including death and syncope (fainting), associated with asystole (heart stops beating) caused by over-sensing. This new information helped inform physician recommendations for preventive generator change in pacemaker-dependent patients affected by the recalls, who reach the specified battery longevity criteria.
HSR Career Development Awardee, Sanket Dhruva, MD, MHS, whose CDA award focuses on better understanding the safety of cardiovascular implantable electronic devices, with the goal of developing interventions that improve patient safety.
Caughron H, Dhruva S, and Raitt M. Complications associated with safety mode initiation in recalled Boston Scientific pacemakers. Journal of the American College of Cardiology. May 6, 2025;85(17):1709-1712.
