- The new pacemaker holds promise for newborn babies with congenital heart defects.
- The tiny pacemaker works along with a small wearable patch on the patient's chest.
- The patch detects irregular heartbeats and emits pulses of light matching the correct heartbeat pace.
Northwestern University researchers have engineered a temporary pacemaker so small that it can fit on the tip of a syringe and be injected, eliminating the need for surgery.
The smaller-than-a-grain-of-rice device doesn’t need to be retrieved when it’s no longer needed, either. Completely biodegradeable, it will simply dissolve in the body.
And while it works for patients of all sizes, that’s especially good news for babies, where size matters a lot. The tiny device delivers the same pacemaking power as a standard pacemaker, but can easily be used to pace the smallest patient’s heart, according to Northwestern Now.
The innovative pacemaker works in conjunction with a small, wireless, flexible patch on the patient’s chest. That patch responds to detection of an irregular heartbeat, shining a light pulse to activate the pacemaker. “These short pulses — which penetrate through the patient’s skin, breastbone and muscles — control the pacing," per the university release.
The device has been tested in large and small animal models and human hearts from deceased organ donors who had died, the results published in the journal Nature.
“We have developed what is, to our knowledge, the world’s smallest pacemaker,” said Northwestern bioelectronics pioneer John A. Rogers, who led the device development, in a written statement. “There’s a crucial need for temporary pacemakers in the context of pediatric heart surgeries, and that’s a use case where size miniaturization is incredibly important. In terms of the device load on the body — the smaller, the better.”
Added his colleague, Igor Efimov, an experimental cardiologist who co-led the study, “Our major motivation was children. About 1% of children are born with congenital heart defects — regardless of whether they live in a low-resource or high-resource country. The good news is that these children only need temporary pacing after a surgery. In about seven days or so, most patients’ hearts will self-repair. But those seven days are absolutely critical.
“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.”
Dangerous removal
Temporary pacemakers are used for a number of reasons, including after heart surgery to help the heart recover its way to a normal rhythm. Temporary pacemakers are also used as a bridge to a permanent pacemaker.
But disconnecting a pacemaker when it’s no longer needed is no joke. Surgeons sew the electrodes onto the heart muscle and thread the wires out the front of a patient’s chest, connecting them to an external pacing box that controls the heart rhythm.
When the device is no longer needed, the electrodes are removed surgically, with potential complications including infection, dislodgement, damaged tissue, bleeding and blood clots.
The release said that’s how Neil Armstrong died when the wires were removed from his temporary pacemaker after he had bypass surgery. The famed astronaut bled internally, per Northwestern.
The little pacemakers dissolve “like absorbable sutures.” The composition and thickness of the materials determine exactly how many days they can be used before they dissolve.
New technology on board
Northwestern researchers made a dissolvable pacemaker in the past, but it was the size of a quarter. It needed a built-in antenna because it operated using the same technology that smartphones use to make electronic payments. That kept them from shrinking it further.
The use of light pulses instead of radio frequency let them shrink the device to its injectable size.
Next, they tackled the power source. The tiny pacemaker uses a galvanic cell, which is a simple battery that turns chemical energy into electrical energy. The two different metals used as electrodes to deliver the electric pulses to the heart are activated by biofluids, creating a battery that can stimulate the heart.
“When the pacemaker is implanted into the body, the surrounding biofluids act as the conducting electrolyte that electrically joins those two metal pads to form the battery,” Rogers said in the release. “A very tiny light-activated switch on the opposite side from the battery allows us to turn the device from its ‘off’ state to an ‘on’ state upon delivery of light that passes through the patient’s body from the skin-mounted patch.”
The light the patch dispatches is infrared, which is safe and penetrates the body well. Efimov said it’s similar to putting a flashlight against your palm and seeing the light glow through. “It turns out that our bodies are great conductors of light.”
It takes very little to stimulate the heart and the rice-sized device delivers the same stimulation as a full-sized pacemaker.
Pondering the possibilities
The researchers said that doctors could put multiple tiny pacemakers across the heart, designed to be activated by different light colors so that changing the color would switch out the pacemaker. “Use of multiple pacemakers in this manner enables more sophisticated synchronization compared to traditional pacing,” per the university. “In special cases, different areas of the heart can be paced at different rhythms, for example, to terminate arrhythmias.”
The small size means it could be integrated into other implantable devices, as well. So it could be used, for instance, in transcatheter aortic valve replacement and activity if there was a post-surgery complication during the recovery period.
“The technology’s versatility opens a broad range of other possibilities for use in bioelectronic medicines, including helping nerves and bones heal, treating wounds and blocking pain,” per the university.