A team at Northwestern University has developed a small pacemaker the size of a grain of rice. This innovative device, injected without any wires or surgery, could revolutionise the treatment of arrhythmias, especially in newborns. This is an important step towards safer, less invasive medicine, opening up new opportunities in the treatment of heart defects.
Up until now, regulating the heartbeat in patients with irregularities meant implanting a traditional pacemaker: a device that restores normal heart rhythm by sending electrical impulses directly to the heart. The entire system is inserted surgically, with a generator positioned under the skin and wires travelling through a vein and into the chambers of the heart. But things are now changing. In a revolutionary way.
An innovative wireless pacemaker
It is smaller than a grain of rice (1.8 millimetres wide, 3.5 millimetres long and 1 millimetre thick) and can be injected using a syringe, without any wires and bypassing the need for surgical insertion and removal. These are the highly innovative properties of the tiny pacemaker developed by the bioengineers at Northwestern University in Evanston (United States), who described the findings of their study in the scientific journal Nature. The device is much easier to handle than conventional pacemakers and could open the door to new treatment strategies, particularly in neonatal cardiology, but not only. Its efficacy has been demonstrated in animal tests performed so far on models of various sizes with heart problems.
“We have developed what is, to our knowledge, the world’s smallest pacemaker,” said John A. Rogers, bioelectronics pioneer and project leader. “There’s a crucial need for temporary pacemakers in the context of paediatric heart surgeries, and that’s a use case where size miniaturisation is incredibly important.”
A wireless pacemaker: more safety, fewer injuries
The system consists of two components: a tiny pacemaker, as well as a small external device worn on the patient’s chest to detect irregular heartbeats. If irregular heartbeats are detected, this device emits an infrared light pulse that penetrates the patient’s skin, bone and other tissues effectively to activate the pacemaker, with no wires or electrodes required.
Traditional pacemakers, on the other hand, normally – as we know – consist of a battery-powered impulse generator inserted under the skin, and leads that travel through a vein and into the heart.
The internal mini-pacemaker developed at Northwestern University is fully biocompatible and dissolves naturally in the body fluids when its work is done.
Pacemakers for newborns
“Our major motivation was children.” said cardiologist Igor Efimov, who co-authored the study. “About 1% of children are born with congenital heart defects, [and often] in about seven days or so [of temporary stimulation], most patients’ hearts will self-repair. But those seven days are absolutely critical.”
Traditional pacemakers are currently used in children, in miniaturised form. But they’re not as small as the one described in Nature. And they require surgery in order to insert and later remove them, which exposes the young patients to the potential risk of infections and other problems. The US researchers hope that these risks will be completely eliminated with the new device.
How does the wireless pacemaker work?
The team at Northwestern University had already created a resorbable pacemaker in 2021, but the bioengineers set about making it even smaller, achieving the micro-dimensions mentioned above. The solution stemmed from a brilliant idea: to power it with a micro-battery generated by the body fluids.
How does it work? The mini-pacemaker consists of two electrodes of different metals which, when in contact with the body’s fluids, spontaneously generate an electrical current capable of stimulating the heart when necessary. The tiny pacemaker can be positioned directly onto the external surface of the heart muscle using a syringe, by means of a percutaneous injection. Its soft and flexible structure allows it to fit onto the heart wall, where it stays in place without the need for stitches or invasive fastenings.
Further studies will be undertaken, but this kind of miniaturisation opens up new possibilities: cardiologists will be able to deploy several pacemakers at once, enabling them to control single areas of the heart with pinpoint precision.
Photo credit: John A. Rogers/Northwestern University
