Safety experts at the U.S. Food and Drug Administration have issued the most serious type of recall for malfunctioning pacemakers after at least four people have died and more than 2,500 others suffered “serious injuries.”

More than 1.3 million patients in the U.S. who have Boston Scientific pacemakers could be affected by the initial recall and an additional advisory. People with pacemakers have heart defects and count on their devices to keep their hearts pumping. Many may not realize that their devices could malfunction.

“If they are dependent on a pacemaker, and their pacemaker stops, there is a high likelihood that they might pass out or die suddenly,” said Dr. Rafay Sabzwari, a cardiac electrophysiologist who cares for patients at UCHealth University of Colorado Hospital and UCHealth Highlands Ranch Hospital.

To learn more about the pacemaker recall, we consulted with Sabzwari, who, much like an “electrician for the heart,” ensures that electrical signals are flowing properly to patients’ hearts.

Are these pacemaker recalls significant?

Yes, this pacemaker recall is significant, and patients with affected devices should contact their doctors, Sabzwari said.

Boston Scientific is one of the largest manufacturers of pacemakers in the world.

What do pacemakers do? And what happened with malfunctioning Boston Scientific pacemakers?

Pacemakers fire electrical signals that regulate and maintain healthy heart rhythms.

The pacemakers have been malfunctioning due to electrical interference that can suddenly reduce the device’s voltage and put it into emergency mode, meaning the device is in danger of failing.

Symptoms of a failing pacemaker include dizziness, low blood pressure and fainting. In the worst-case scenarios, patients could suffer cardiac arrest and death.

Fortunately, Sabzwari said very few patients with the recalled pacemakers have experienced severe symptoms.

In a New York Times investigation published earlier this year, however, journalists found that Boston Scientific identified the pacemaker battery problem as far back as 2021 and failed to notify affected patients.

Who is at risk, and what should patients do if they think they might have an affected pacemaker?

Cardiologists at UCHealth are working to help affected patients.

Patients who face the greatest risk of harm from the defective devices are those whose lives depend on their pacemakers working properly.

Officials with the Food and Drug Administration (FDA) first issued a recall of 203,000 pacemakers on March 18, 2026. Then, on May 8, FDA experts issued an advisory, separate from the recall, that puts the total number of defective Boston Scientific pacemakers at 1.3 million.

Sabzwari urged patients with pacemaker models that are part of the recall and advisory to contact their providers (unless they have already received help) so they can get information and schedule a mandatory software update that should mitigate the risk of adverse outcomes from the pacemaker defect. Some patients also are opting to get new pacemakers.

Patients can check to see if they have one of the recalled pacemakers by entering the device’s model and serial number on Boston Scientific’s Device Lookup Tool.

How and why pacemakers can malfunction: electrical interference leads to battery failure

The defect in the recalled pacemakers affects Boston Scientific’s Accolade family of devices. In these pacemakers, electrical impedance, or interference, suddenly spikes, causing the battery voltage to drop sharply.

This power defect caused some pacemakers to reset abruptly and unpredictably. According to representatives from Boston Scientific, with three resets in a 48-hour period, pacemakers automatically enter “Safety Mode,”a backup system designed to provide warning when a pacemaker is close to failure and must be replaced.

That’s a necessary safety feature. But in the recalled devices, normally routine operations that produce a surge of power sometimes depleted batteries enough to cause multiple resets and trigger Safety Mode. The abrupt changes in devices assumed to be functioning normally made it challenging for providers to respond quickly to the signs of failure.

The problem occurred, for example, during telemetry, a wireless or in-office communication between the pacemaker and a provider to get data about a patient’s heart rhythms and ensure it is working properly.

A pacemaker upgrade that reduces, but does not eliminate, risk

To address the electrical interference defect, Boston Scientific developed a software upgrade for specific Accolade devices that all patients must receive in the clinic in a relatively brief visit. This upgrade is automatic as soon as the device connects with a programming computer.

The upgrade mitigates — but does not fix — the electrical interference that snarls the pacemakers’ routine functions. Rather, it makes it easier for Boston Scientific and patients’ providers to detect when the power drain is happening, Sabzwari said.

“The software update is a mechanism to allow better, quicker and safer communication that the battery is at risk of getting early depletion,” he said.

Reducing the risk for the most vulnerable heart patients

Many people with recalled devices have been understandably worried since malfunctioning pacemakers can be a matter of life or death.

To help those who are affected, UCHealth doctors and support staff members have been reaching out via the UCHealth patient portal and with phone calls and letters, Sabzwari said.

While the software upgrade is a requirement for all patients with the recalled pacemakers, Sabzwari said that UCHealth follows a Boston Scientific-outlined strategy that places patients in tiers of risk.

Patients who should schedule the pacemaker update soonest and receive the closest monitoring are those who:

• Depend on their pacemakers.
• Have device batteries with fewer than four years of remaining life.
• Have devices that have reset or have gone into Safety Mode.
• Are not connected to remote monitoring to ensure their devices are operating safely.

Emergency pacemaker replacement recommended under specific circumstances

The recall does not recommend replacing all the defective pacemakers. However, a patient whose device entered Safety Mode should not wait to schedule an elective surgery to replace it, according to a guideline published in the Journal of the American College of Cardiology and recommended by Boston Scientific.

Sabzwari said UCHealth experts follow that directive. He added that providers normally have about three months of “wiggle room” to replace a pacemaker that is about to fail.

“Boston Scientific suggested we should not wait for those three months for the highest-risk patients,” he said.

It’s vital for patients to communicate with their providers

Sabzwari said that to date, as far as providers know, no UCHealth patients have suffered serious health problems tied to defective pacemakers. But many patients have reached out to their doctors to ask questions about the Boston Scientific recall.

He urged any patients with questions or concerns to contact their medical team right away.

“The most important takeaway from the recall is the way in which these adverse events are communicated to clinicians and patients,” he said. “It is much easier to explain things in a way that makes sense when the clinician communicates directly to their own patient regarding advisories and recalls.”

Sabzwari noted that as pacemakers become “smarter” and more sophisticated, the need for practical guidelines to manage them increases.

“The devices we use are increasingly indicated and technology continues to improve,” he said. “With this comes more complex devices with more complex components. They undergo a stringent approval process via the FDA but there is potential for issues that trigger an investigation to identify a root cause. As clinicians, our biggest commitment is to patient safety.”