Tiny Pacemaker Dissolves When No Longer Needed

The world’s tiniest known pacemaker, a device smaller than a grain of rice, can be implanted using minimally invasive techniques and dissolves when no longer needed. Researchers described their invention today in the journal Nature.

Pacemakers are implantable devices that electrically stimulate cardiac muscles to control heart rates. Many patients require temporary pacemakers for short-term heart problems, such as slow heart rates during recovery from cardiac surgery.

Conventional temporary pacemakers require invasive surgeries to implant them and then remove the devices. These procedures pose significant risks, such as infection or damage to heart muscles. Such complications are why Neil Armstrong died. He received a temporary pacemaker after a bypass surgery, but when the wires were removed he experienced fatal internal bleeding, says Igor Efimov, a professor of biomedical engineering and cardiology at Northwestern University, in Chicago.

To avoid problems resulting from pacemaker removals, Efimov and his colleagues developed the first dissolvable pacemaker in 2021. Although this quarter-size device performed well in animal experiments, cardiac surgeons asked if it was possible to further miniaturize such pacemakers for pediatric use.

“We were motivated by an unmet need: children born with congenital heart defects,” Efimov says.

Roughly 1 percent of children are born with congenital heart defects, Efimov explains. After surgeries treating such defects, children generally only need temporary pacemakers, as their hearts usually repair themselves after seven days or so. The goal was to make a temporary pacemaker that was as tiny as possible for the small, fragile hearts of newborns, Efimov says.

How the Tiny Dissolving Pacemaker Works

The new 13.8-milligram pacemaker is just 1.8 by 3.5 by 1 millimeter in size, capable of fitting inside the tip of a syringe. In their experiments, the researchers could implant it with an injection through a skin incision less than 3 mm wide.

“The small size of the pacemaker is without precedent,” Efimov says.

The quarter-sized pacemaker from 2021 was powered with the help of a built-in antenna that limited attempts at further miniaturization. In contrast, the new device has electrodes that when exposed to body fluids generate an electrical current. This design eliminates the need for an external power source, wires leading out of the body, and an antenna.

The new device is biodegradable, dissolving and being absorbed by the body after its useful lifetime—no surgical removal is required. The new pacemaker also does not interfere with magnetic resonance imaging and computed tomography scans, which is of benefit for patients who require routine medical imaging.

The researchers paired the new pacemaker with a small, soft, flexible, wearable patch that sits on a patient’s chest. When this patch detects an irregular heartbeat, it automatically emits pulses of near-infrared light. These shine through a patient’s skin, breastbone, and muscles to wirelessly control the pacemaker, flashing on and off at a rate that corresponds to the desired heart rate.

In experiments, the scientists found their new pacemakers proved effective in small and large animals such as mice, rats, dogs, and pigs, as well as human hearts from organ donors. Despite its size, it delivered as much stimulation as a full-size pacemaker.

The pacemakers are so tiny that the researchers could safely deploy arrays of multiple devices across the heart. This setup could enable more-complex stimulation of multiple areas of the heart to restore a regular heartbeat. The scientists add that they could also incorporate the new pacemakers into other medical devices, such as heart-valve replacements to help cardiologists address complications that might occur during a patient’s recovery.

The researchers note that these small biodegradable implants might have a number of uses beyond the heart. For instance, they say the devices could find use as electrical stimulators used in nerve and bone regeneration, wound therapy, and pain management.

This article appears in the June 2025 print issue as “Tiny Pacemaker Dissolves When No Longer Needed.”