The study, detailed in a paper published in Science Advances, was directed by researchers in the Gutruf Lab at the University of Arizona, led by biomedical engineering assistant professor and Craig M. Berge Faculty Fellow Philipp Gutruf.
Pacemakers regulate the heartbeats of people with chronic heart diseases like atrial fibrillation and other forms of arrhythmia, but implantation is an invasive procedure and the lifesaving pacing the devices provide can be extremely painful.
Currently available pacemakers work by implanting one or two leads into the heart with hooks or screws. If the sensors on these leads detect a dangerous irregularity, they send an electrical shock through the heart to reset the beat.
"All of the cells inside the heart get hit at one time, including the pain receptors, and that's what makes pacing or defibrillation painful," Gutruf said in a statement. "It affects the heart muscle as a whole."
Yet to be tested on humans, the device, which uses light and optogenetics, would allow pacemakers to send much more targeted signals using a new digitally manufactured mesh design that encompasses the entire heart.
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Optogenetics modifies cells, usually neurons, sensitive to light, then uses light to affect the behaviour of those cells. This technique only targets cardiomyocytes, the cells of the muscle that trigger contraction and make up the beat of the heart. This precision will not only reduce pain for pacemaker patients by bypassing the heart's pain receptors, it will also allow the pacemaker to respond to different kinds of irregularities in more appropriate ways; during atrial fibrillation, the upper and lower chambers of the heart beat asynchronously, and a pacemaker's role is to get the two parts back in line.
"Whereas right now, we have to shock the whole heart to do this, these new devices can do much more precise targeting, making defibrillation both more effective and less painful," said Igor Efimov, professor of biomedical engineering and medicine at Northwestern University, where the devices were lab-tested. "This technology could make life easier for patients all over the world, while also helping scientists and physicians learn more about how to monitor and treat the disease."
To ensure the light signals can reach many different parts of the heart, the team created a design that involves encompassing the organ instead of implanting leads that provide limited points of contact.
The new pacemaker model consists of four petallike structures made of thin, flexible film, which contain light sources and a recording electrode. The petals, specially designed to accommodate the way the heart changes shape as it beats, fold up around the sides of the organ to envelop it.
"Current pacemakers record basically a simple threshold, and they will tell you, 'This is going into arrhythmia, now shock!'" Gutruf said. "But this device has a computer on board where you can input different algorithms that allow you to pace in a more sophisticated way. It's made for research."
Because the system uses light to affect the heart, the device can continue recording information when the pacemaker needs to defibrillate. In current pacemakers, the electrical signal from the defibrillation can interfere with recording capabilities, leaving physicians with an incomplete picture of cardiac episodes. Additionally, the device does not require a battery, which could save pacemaker patients from needing to replace the battery in their device every five to seven years.
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