A Beating Heart May Produce Energy to Power
Pacemaker or Defibrillator
Microgenerator captured enough surplus heart energy
to provide 17% of power needed to run implantable
pacemaker
Nov. 11, 2008 - Surplus energy generated by the
heart may one day help power pacemakers and defibrillators implanted in
cardiac patients, according to research presented at the American Heart
Association’s Scientific Sessions 2008. In a trailblazing experiment, a
microgenerator powered by heartbeats produced almost 17 percent of the
electricity needed to run an artificial pacemaker.
“This was a proof-of-concept study, and we proved
the concept,” said Paul Roberts, M.D., first author of the study and a
Consultant Electrophysiologist at Southampton University Hospital in the
United Kingdom. “Harvesting surplus energy might be a major transition
in implantable pacemakers and defibrillators because engineers will have
more energy to work with.”
● At a heart rate of 80 beats per minute (bpm),
the device yielded an average harvested energy of 4.3 microjoules per
cardiac cycle.
● Increasing changes in the heart rate produced
corresponding increases in energy. At 104 to 128 bpm, the harvested
energy level increased 140 percent.
● Decreases occurred when the researchers slowed
the heartbeat or lowered blood pressure.
● Implantation and surplus energy harvesting
caused no significant injury to the lining of the heart’s chambers.
“What this might mean is that in the next era of
pacemakers, you’d get devices that lasted significantly longer and we
could add more functions to help monitor the heart,” Roberts said. “It’s
possible they could be efficient enough to allow complete and indefinite
powering of pacemakers.”
Since their introduction into clinical medicine,
implantable pacemakers and defibrillators have saved lives and become
more sophisticated. However, adding new monitoring capabilities to the
devices has led designers to a critical point.
“The small devices now are really very good, but
power consumption must increase if we want to take them to the next
level,” Roberts said. “Battery technology has plateaued and the only way
we are going to increase power is to increase size.”
This, in turn, would increase the units’ weight,
making them more uncomfortable and less cosmetically acceptable to
patients because the devices are implanted under the skin.
The innovative generator — called the
self-energizing implantable medical microsystem (SIMM) — helps the heart
produce more than enough energy with each beat to pump blood.
The SIMM uses two compressible bladders and a
microgenerator mounted on the lead of a pacemaker or defibrillator, the
wire that connects the device to the heart.
The lead is attached to the end of the right
ventricle, and the bladders relay the energy from the pressure of each
heartbeat to the microgenerator, which transforms it into electricity
for use by the battery.
A consortium of companies including InVivo
Technology, Perpetuum and Zarlink Semiconductor developed and tested the
SIMM microgenerator with United Kingdom government funds. Researchers
used an in-vivo porcine model to evaluate the study. The researchers are
now working to improve the materials used in the SIMM microgenerator.
“With different materials, we’re seeing even
greater energy harvesting,” Roberts said. “While at the moment we see
about 20 percent harvesting, we’re anticipating that will be
significantly more in the next iteration of the device.”
Co-authors are: Giles Stanley, M. Sc., and John
Mark Morgan, M. D.
Roberts and Morgan hold ownership interests in
InVivo Technology and serve on its Scientific Advisory Board. Other
disclosures can be found in the abstract.
The United Kingdom Technology Strategy Board funded
the SIMM project.
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Nov. 11, 2008 - Surplus energy generated by the
heart may one day help power pacemakers and defibrillators implanted in
cardiac patients, according to research presented at the American Heart
Association’s Scientific Sessions 2008. In a trailblazing experiment, a
microgenerator powered by heartbeats produced almost 17 percent of the
electricity needed to run an artificial pacemaker.