By Brooke Struyk
Abstract
According to Yale University there are over 3 million people in the United States who use pacemakers to prevent or treat too slow, too fast, or irregular heartbeat. Pacemakers are small, implanted battery-powered devices that help regulate the rhythm of the heartbeat. They include electrodes that deliver electrical impulses to one’s heart to make it beat regularly. Depending on the pacemaker, its battery can last between 5 to 15 years. Battery life is essential for keeping the electrical impulses consistent. Without the battery, the pacemaker will not work and, depending on the person’s condition, may be life-threatening. What if the concern for battery life was no longer an issue? What if there was a way to avoid surgery to charge pacemaker battery? This blogpost delves into the newly discovered science behind a body rechargeable pacemaker and explores vulnerabilities brough about innovative and increasingly interconnected pacemaker technologies.
Introduction
Heart disease is the leading cause of death in the United States (U.S.).[1] In 2021 about 695,000 people died from heart disease in the US. About 3 million people in the United States use pacemaker.[2] Of these 3 million people about 70% of them are over the age of 65. Pacemakers are not only used in adults, on rare occasions children need pacemakers. In adults, pacemakers are usually found in patients with bradycardia (heartbeats too slow) and tachycardia (heartbeat is irregular or too fast).[3] Pacemakers in children are typically used for patients with congenital complete heart block, a rare condition that affects 1 in around 15,000 children.[4] The smallest child with a pacemaker has been recorded to be 11 days old and weigh 3.5 lbs.[5] This demonstrates that pacemaker technology has come a long way since it was first FDA approved in 2011. Pacemakers are important for keeping children and adults alive and for improving the quality of their lives. In fact, in individuals 65 years or older, a pacemaker was on average able to extend their lives 8 years.[6] While new pacemaker technology is in development to improve functionality, the automated and increasingly interconnected pacemakers create new concerns for providers, patients, and their wellbeing.
Batteries at the Heart of Pacemaker
Pacemakers usually last 5-15 years depending on the type of battery used. The most common type of battery in a pacemaker is lithium iodine batteries. Lithium iodine battery expectancy tends to range 5-10 years.[7] For patients to receive a new battery for their pacemaker, they must go under intensive surgery that carries significant risks. For example, the most common issue with these surgeries is that they are prone to infections and bleeding. This generally affects the patient’s overall quality of life and causes issues later with the pacemaker itself. Scientists and biomedical corporations have been working for years to improve upon pacemaker technology including to ensure a longer lifespan to reduce the need for additional surgeries. One such approach is to use piezoelectric energy to power a pacemaker.
Piezoelectric energy
What is piezoelectric energy?
Piezoelectric energy is the conversion from mechanical energy to electrical energy. It is also able to use vibrations from the environment to harvest the energy and be used for electrical energy. There are many materials that can be used to create this kind of harvester of energy. The most popular is Lead Zirconate Titanate, however, it cannot be used in the body for pacemakers, so scientists use materials like Zinc Oxide that is able to produce a high voltage coefficient and is biocompatible.[8] When looking for specific properties of a piezoelectric harvester, one would want to find materials that are biocompatible, biodegradable, flexible, and durable. Natural piezoelectric energy can be found in biological systems. For example, one can see it in vitamins, collagen, and chitin, which have natural piezoelectric materials.9
How is it used in pacemakers?
Piezoelectric generators are based on the intrinsic polarization of the material used for the pacemaker. This would mean that it would not require an extra voltage source, allowing for the generator to be smaller. Piezoelectric generators are also great regarding durability, reliability, and having a high voltage output[9]. They can use vivo energies, which are things like lungs motion, heartbeat, and muscle stretching to power the generator. This energy is then converted from mechanical energy into electrical energy that can power a pacemaker’s device. This conversion allows for the pacemaker to be batteryless and provides an alternative to leadless pacemaker.
Examples of piezoelectric energy use
The University of Washington Department of Medicine study created a leadless pacemaker with an outer shell of piezoelectric material. When testing their prototype, the researchers were able to generate about 10% of the energy necessary to pace a heartbeat. This would mean that the device is almost fully functional. The researchers aim to implement their device on pre-clinical models which would be a large step forward for this type of technology.[10]
In another study Chinese researchers successfully built a piezoelectric device that powers itself. The device uses a triboelectric nanogenerator, which is somewhat like a piezoelectric generator, but it uses static friction to make an electrical charge. The nanogenerator is placed onto the surface of the heart and generates electrical energy as the heart contacts. This device has been successfully tested on pigs, which have similar organs to humans and are used as animal models for testing biomedical devices. This type of device is one step closer to making a fully functioning pacemaker that would be able to work on humans.[11]
Alternative Methods to Power Pacemaker
Body Heat
The first method that is currently being studied is the usage of body heat to recharge pacemakers. Pacemakers need around 6 V of energy for it to work efficiently. In a 2010 J Pharm Study, scientists used a power generator with both piezoelectric elements and a thermocouple.[12] By using piezoelectric energy, a zinc oxide nanogenerator, and a thermocouple, the body heat from sources like the heartbeat, blood flow, and body motion would convert into electrical energy that would be used to power the pacemaker. Using a device like this could theoretically last a person 30 years, cutting the number of battery replacement surgeries and eliminating risks associated with lithium battery-powered pacemakers. This specific method, although functional, proves to be very costly.
Solar Energy
Another method that has been studied is using solar powered energy to recharge pacemakers. In a study from Switzerland,[13] researchers used a pacemaker made of a bipolar active pacemaker lead, a small lithium-polymer accumulator, and a solar module. In this experiment, researchers placed the pacemaker in the lateral neck of a pig underneath a layer of skin. They placed the pigs in three different conditions to see how the pacemaker performed: lots of light, some light, and no light. Pacemaker with medium light, meaning in and out of light and dark throughout the day, was able to have the best functionality. The pacemaker with the highest level of light was also able to perform well. The pig that stayed in the darkness was able to have a pacemaker that harvested some energy for about 40 days until the voltage dropped significantly. This indicates that solar powered pacemakers may be able to work in humans. Pig skin is a lot like human skin, an important detail when looking at how light can hit the skin. This specific method brings up issues, including the fact that the pacemaker is very big, it may need be individualized depending on the season, patient’s geographical location, and the level of sunlight it is able to get.
Pacemaker Vulnerabilities and Issues
Despite promising research on the new ways to power pacemakers, improve technology and resolve current shortcomings, there are several issues and vulnerabilities. For regular pacemakers, cybersecurity is a very important issue that needs to be addressed. Some vulnerabilities may include remote access, modification of pacemaker’s operation, and man-in-the-middle attacks. These potential threats create access for a person to change the way a pacemaker operates, leading the patient to be vulnerable. Another issue that may arise is wireless communication capabilities, which would allow for data transfer and remote control that can be used for harm. Data transfer may especially cause an issue with financial and patient information being sold on the black market for a lot of money. This gives criminals more of an incentive to get access to this data.[14] In 2017 over 500,000 implantable pacemakers were recalled because of potential vulnerability to hacking.14 When creating a rechargeable pacemaker to be sold on the market, researchers must take cybersecurity into account, so these vulnerabilities that are found in pacemakers will be more protected in rechargeable pacemakers.
There are many different issues that may come with using a piezoelectric device or any of the other devices listed above. With piezoelectric devices, there is still so much research that needs to be done on the different types of materials that can be used in the body and if there are any harmful effects, for example scar tissue buildup. Scar tissue buildup may occur in the body due to the initial surgery, or inflammation of the issue around that device. This may cause a potential issue on the implantation side of the device.
Research has also yet to get to actual human clinical trials, as this is a new technology that is still a work in progress for a lot of labs. Many of these labs have a long-term goal of testing these devices on humans and seeing how the heart will react with this new type of technology. However, there is still a lot to be learned from this type of device that is not known, and it may take years to fully understand and implement the device. It may also be an interesting find if there would be an increase in life years after implanting this device and comparing it to a lead-less pacemaker.
Another issue that may arise is the difference in cost. Depending on how a company may follow through with the device, this type of pacemaker may end up on the more expensive side, making the pacemaker harder to get than it already is. This type of issue may cause a lesser production in these devices due to the low demand with the price and even with this useful technology, it may not be used the best way it can.
Conclusion
Rechargeable pacemakers could be a great alternative for regular pacemakers. This type of new technology would allow for no extra battery replacement surgery and will allow for a device that lasts a long time. When taking the vulnerabilities and issues like cybersecurity, cost, insurance, tissue buildup, and pending human trials into account, one can see that the device still has a long way to go before it can be placed on the market. Once addressed, however, rechargeable pacemaker research can create opportunities for other medical devices like cochlear implants, pH sensors, bone graft materials, and seizure brain monitoring devices to make an advancement on their own technology. Body heat and solar energy devices are a great example of creations that may end up being more useful than the piezoelectric generators. Only time will tell where this research will be in the next 20 years, but new technologies like these are a great way to solve a very serious problem that patients with pacemakers have. Innovative research as described above must go forward with increased awareness of vulnerabilities and risks brough about the increasingly interconnected pacemaker technologies.
[1] "Heart Disease Facts." Centers for Disease Control and Prevention (2023). https://www.cdc.gov/heartdisease/facts.htm.
[2] "Cardiac Pacemakers." Yale Medicine (2024). https://www.yalemedicine.org/conditions/cardiac-pacemaker#:~:text=Up%20to%203%20million%20Americans,at%20least%2065%20years%20old.
[3] "Pacemakers: Who Needs Them." National Heart, Lung, and Blood Institute (2022). https://www.nhlbi.nih.gov/health/pacemakers/who-needs#:~:text=The%20most%20common%20reason%20people,fast%20(tachycardia)%20or%20irregular.
[4] Tomiyoshi, Tricia. "Doctor Pioneers Pacemaker Procedure in Kids." UCDavis Health (2022). https://health.ucdavis.edu/news/features/doctor-pioneers-pacemaker-procedure-in-kids/2022/02#:~:text=Pacemakers%20are%20typically%20placed%20in,about%2015%2C000%20to%2022%2C000%20children.
[5] Digitale, Erin. "Packard Children's Has Smallest Child yet to Get Pacemaker." Stanford Medicine (2012). https://med.stanford.edu/news/all-news/2012/02/packard-childrens-has-smallest-child-yet-to-get-pacemaker.html.
[6] Rajaeefard, A. Ten-year Survival and Its Associated Factors in the Patients Undergoing Pacemaker Implantation in Hospitals Affiliated to Shiraz University of Medical Sciences During 2002 - 2012. National Center for Biotechnology Information 2015.
[7] Mallela, V. S. Trends in cardiac pacemaker batteries. National Center for Biotechnology Information 2004.
[8] Anand, A. Design of Mems Based Piezoelectric EnergyHarvester for Pacemaker. Devices for Integrated Circuits 2019.
[9] Nurettin Sezer, M. K. A comprehensive review on the state-of-the-art of piezoelectricenergy harvesting. Nano Energy 2021. (acccessed 03/26/2023).
[10] Nazer, Dr. Babak. "New Pacemaker Recharges Its Battery with Energy from Natural Heartbeats." UW Medicine (2023). https://mednews.uw.edu/news/rechargeable-pacemaker#:~:text=New%20proof%2Dof%2Dprinciple%20research%20shows%20that%20an%20experimental%20pacemaker,power%20generated%20from%20natural%20heartbeats.&text=in%20Philadelphia%20by%20lead%20study,Study%20collaborators%20include%20Dr.
[11] J Jones, Lisa. "Self-Charging Pacemaker Breakthrough." British Heart Foundation (2019). https://www.bhf.org.uk/what-we-do/news-from-the-bhf/news-archive/2019/april/self-charging-pacemaker-breakthrough.
[12] Dinesha Bhatia, Sweeti Bairagi, Sanat Geol, Manoj Jangra. "Pacemakers Charging Using Body Energy." Journal of Pharmacy & BioAllied Sciences (2010). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146093/.
[13] Haeberlin, Andreas. "The First Batteryless, Solar-Powered Cardiacpacemaker." CrossMark (2015). https://www.sciencedirect.com/science/article/pii/S1547527115002520.
[14] C Clery, Daniel. "Could a Wireless Pacemaker Let Hackers Take Control of Your Heart?". Science (2015). https://www.science.org/content/article/could-wireless-pacemaker-let-hackers-take-control-your-heart.