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Scientists develop a batteryless cardiac pacemaker

The new cardiac pacemaker is based on an automatic wristwatch and is powered by heart motion. It will avoid the surgical operations up until now necessary to substitute dwindling pacemaker batteries.

December 2014

Scientists develop a batteryless cardiac pacemaker. The new cardiac pacemaker is based on an automatic wristwatch and is powered by heart motion. It will avoid the surgical operations up until now necessary to substitute dwindling pacemaker batteries. IMA Lab

Various medical devices implanted inside the human body need electrical energy to make them work, in which case they are equipped with tiny batteries.
Pacemakers are one such device, and their average battery life lasts about seven years: when the batteries start to run low, they have to be substituted, and this involves a heart operation. This is obviously painful and exhausting for the patient, can potentially be risky, and is extremely expensive whether performed in private or public hospital contexts.

Professor Adrian Zurbuchen from the University of Bern in Switzerland, set out to try to find an alternative source of energy, deciding to revive and develop studies carried out by his colleague Rolf Vogel, a cardiologist and an engineer, who in 2000 had the idea of using an automatic wristwatch mechanism to harvest the energy of heart motion.

The basic concept is simple enough: the heart itself is an excellent source of energy which is both reliable and constant, since its contractions are repetitive and continue round the clock seven days a week. Automatic clockwork, first invented in 1777, also has a good reputation as a reliable technology for recycling energy obtained from motion.

The University of Bern research team’s first prototype is based on a commercially available automatic wristwatch. All the unnecessary parts were removed, in order to reduce weight and size. They then developed a custom-made housing with eyelets which make it possible to suture the device directly onto the myocardium. The prototype works the same way as it would on a person's wrist: when it is exposed to an external acceleration, the eccentric mass of the clockwork starts rotating. This progressively winds up a mechanical spring. When the spring is fully charged it unwinds and thereby spins an electrical micro-generator.

To test the prototype, the researchers developed an electronic circuit to transform and store the signal in a small buffer capacity. They then connected the system to a custom-made cardiac pacemaker. The system worked in three steps: firstly, the harvesting prototype acquired energy from the heart, secondly, the energy was temporarily stored in the buffer capacity, and finally, the buffered energy was used by the pacemaker to apply minute stimuli to the heart.

The researchers successfully tested the system through in vivo experiments with domestic pigs. The mechanism allowed them for the first time to perform batteryless overdrive-pacing at 130 beats per minute. "We have shown that it is possible to pace the heart using the power of its own motion. The next step for our prototype is to integrate both the electronic circuit for energy storage and the custom-made pacemaker directly into the harvesting device. This will eliminate the need for connecting leads," Zurbuchen said.

The research was presented on 31 August 2014 at the European Society of Cardiology (ESC) Congress in Barcelona and would appear to offer a solution to a problem that affects over a million people around the world, and over 440,000 in Europe. In a more general perspective, this invention reminds us yet again of the necessity and viability of studying and developing alternative sources of energy at all levels, which is and will increasingly become the most important and pressing scientific challenge facing our planet.