Researchers at Northwestern University have developed the world’s smallest temporary pacemaker. The device can be non-invasively injected via a syringe and naturally dissolves into the body after use, which may make it pivotal in treating babies born with heart defects. The details of this development were published in Nature on April 2, 2025.
“Our major motivation was children,” said Northwestern Professor of Biomedical Engineering and Cardiology Igor Efimov. “About 1% of children are born with congenital heart defects—regardless of whether they live in a low-resource or high-resource country.” In most cases, it will only take seven days for the heart to self-repair. However, having a temporary implant during that time is crucial for the baby’s survival. This is where the pacemaker being smaller than a grain of rice comes into play. The less load the device has on the body, the better the projected outcome for the patient, especially with newborn babies, who are at their most vulnerable.
The current procedure for temporary pacemaker implants involves surgeons sewing electrodes directly onto the heart. Those electrodes are then attached to an external pacing box which delivers an electrical current to control the heart’s pacing using wires that exit a patient’s chest.
Aside from the bulky wires and external devices being uncomfortable for patients, there are complications involving the invasiveness of the process. Placing foreign matter into the body presents the risk of infection. On top of this, if scar tissue forms on the wires by the time a physician goes to remove the device, removal could damage the heart muscle. The first man to walk on the Moon, Neil Armstong, died in 2012 from complications following the removal of a temporary pacemaker.
Solving these problems is what drove teams led by Northwestern Professor of Neurological Surgery and Biomedical Engineering, John A. Rogers, to create the first iteration of this device in 2021, published in Nature Biotechnology. They were able to remove the wiring and large batteries required in current pacemakers. The replacement for wiring was a built-in antenna that relayed radio frequency commands and also helped provide power, which required them to keep the pacemaker at least the size of a quarter.
Still too large for a non-invasive implant, Rogers’ team worked to find an alternative to the antenna that allowed them to go even smaller. Their solution was a light-based method that works with a small patch attached to a patient’s chest. When the patch detects an irregular heartbeat, it flashes a light that dictates what heartbeat the pacemaker should stimulate. The new power supply is a type of battery that transforms chemical energy into electrical energy called a galvanic cell, generating power through chemical reactions with surrounding bodily fluids. With these changes, they have created a pacemaker that is 1.8 millimeters wide, 3.5 millimeters long, and 1 millimeter thick.
“Now, we can place this tiny pacemaker on a child’s heart and stimulate it with a soft, gentle, wearable device. And no additional surgery is necessary to remove it,” Efimov said.
The incredible feat they have achieved has the team hoping that they can use the pacemaker in more ways than intended. “We can deploy a number of such small pacemakers onto the outside of the heart and control each one,” Efimov explained. “Then we can achieve improved synchronized functional care. We also could incorporate our pacemakers into other medical devices like heart valve replacements, which can cause heart block.”
