The device fits in a syringe and melts away after use.
Scientists just unveiled the world’s tiniest pacemaker. Smaller than a grain of rice and controlled by light shone through the skin, the pacemaker generates power and squeezes the heart’s muscles after injection through a stint.
The device showed it could steadily orchestrate healthy heart rhythms in rat, dog, and human hearts in a newly published study. It’s also biocompatible and eventually broken down by the body after temporary use. Over 23 times smaller than previous bioabsorbable pacemakers, the device opens the door to minimally invasive implants that wirelessly monitor heart health after extensive surgery or other heart problems.
“The extremely small sizes of these devices enable minimally invasive implantation,” the authors, led by John Rogers at Northwestern University, wrote. Paired with a wireless controller on the skin’s surface, the system automatically detected irregular heartbeats and targeted electrical zaps to different regions of the heart.
The device could especially benefit babies who need smaller hardware to monitor their hearts. Although specifically designed for the heart, a similar setup could be adapted to manage pain, heal wounds, or potentially regenerate nerves and bones.
Achy Breaky Heart
The heart is a wonder of biomechanics.
Over a person’s lifetime, its four chambers reliably pump blood rich in oxygen and nutrients through the body. Some chambers cleanse blood of carbon dioxide—a waste product of cell metabolism—and infuse it with oxygen from the lungs. Others push nutrient-rich blood back out to rest of the body.
But like parts in a machine, heart muscles eventually wear down with age or trauma. Unlike skin cells, the heart can’t easily regenerate. Over time, its muscles become stiff, and after an injury—say, a heart attack—scar tissue replaces functional cells.
That’s a problem when it comes to keeping the heart pumping in a steady rhythm.
Each chamber contracts and releases in an intricate biological dance orchestrated by an electrical flow. Any glitches in these signals can cause heart muscles to squeeze chaotically, too rapidly or completely off beat. Deadly problems, such as atrial fibrillation, can result. Even worse, blood can pool inside individual chambers and increase the risk of blood clots. If these are dislodged, they could travel to the brain and trigger a stroke.
Risks are especially high after heart surgery. To lower the chances of complications, surgeons often implant temporary pacemakers for days or weeks as the organ recovers.
These devices are usually made up of two components.
The first of these is a system that detects and generates electrical zaps. It generally requires a power supply and control units to fine-tune the stimulation. The other bit “is kinda the business end” study author John Rogers told Nature. This part delivers electrical pulses to the heart muscles, directing them to contract or relax.
The setup is a wiring nightmare, with wires to detect heart rhythm threading through the skin. “You have wires designed to monitor cardiac function, but it becomes a somewhat clumsy collection of hardware that’s cumbersome for the patient,” said Rogers.
These temporary pacemakers are “essential life-saving technologies,” wrote the team. But most devices need open-heart surgery to implant and remove, which increases the risk of infection and additional damage to an already fragile organ. The procedure is especially difficult for babies or younger patients because they’re so small and grow faster.
Heart surgeons inspired the project with their vision of a “fully implantable, wirelessly controlled temporary pacemaker that would just melt away inside the body after it’s no longer needed,” said Rogers.
A Steady Beat
An ideal pacemaker should be small, biocompatible, and easily controllable. Easy delivery and multiplexing—that is, having multiple units to control heartbeat—are a bonus.
The new device delivers.
It’s made of biocompatible material that’s eventually broken down and dispelled by the body without the need for surgical removal. It has two small pieces of metal somewhat similar to the terminals of a battery. Normally, the implant doesn’t conduct electricity. But once implanted, natural fluids from heart cells form a liquid “bridge” that completes the electrical circuit when activated, transforming the device into both a self-powered battery and a generator to stimulate heart muscles. A Bluetooth module connects the implant with a soft “receiver” patch on the skin to wirelessly capture electrical signals from the heart for analysis.
Controlling the heart’s rhythm took more engineering. Each heart chamber needs to pump in a coordinated sequence for blood to properly flow. Here, the team used an infrared light switch to turn the implant on and off. This wavelength of light can penetrate skin, muscle, and bone, making it a powerful way to precisely control organs or tools that operate on electrical signals.
Although jam-packed with hardware, the final implant is roughly the size of a sesame seed. It’s “more than 23 times smaller than any bioresorbable alternative,” wrote the team.
Flashing infrared LED lights placed on the skin above the pacemaker turn the device on. Different infrared frequencies pace the heartbeat.
The team first tested their device in isolated pig and donated human hearts. After it was implanted by injection through a stint, the device worked reliably in multiple heart chambers, delivering the same amount of stimulation as a standard pacemaker.
They also tested the device in hound dogs, whose hearts are similar in shape, size, and electrical workings to ours. A tiny cut was enough to implant and position multiple pacemakers at different locations on the heart, where they could be controlled individually. The team used light to fine-tune heart rate and rhythm, changing the contraction of two heart chambers to pump and release blood in a natural beat.
“Because the devices are so small, you can pace the heart in very sophisticated ways that rely not just on a single pacemaker, but a multiplicity of them,” said Rogers. “[This] offers a greater control over the cardiac cycle than would be possible with a single pacemaker.”
Device Sprinkles
The team envisions that the finished device will be relatively off-the-shelf. Put together, a sensor monitors problematic heart rhythms from the skin’s surface, restores normal activity with light pulses, and includes an interface to visualize the process for users. The materials are safe for the human body—some are even recommended as part of a daily diet or added to vitamin supplements—and components largely dissolve after 9 to 12 months.
The devices aren’t specifically designed for the heart. They could also stimulate nerve and bone regeneration, heal wounds, or manage pain through electrical stimulation. “You could sprinkle them around…do a dozen of these things…each one controlled by a different wavelength [of light],” said Rogers.
The post World’s Tiniest Pacemaker Is Smaller Than a Grain of Rice appeared first on SingularityHub.