July 2019, ScientificAmerican.com 21FROM “SYMBIOTIC CARDIAC PACEMAKER,” BY HAN OUYANG ET AL., IN
NATURE COMMUNICATIONS,
VOL. 10, ARTICLE NO. 1821; 2019
BIOMEDICAL ENGINEERINGThe Beat
Powers On
An experimental pacemaker runs
off energy from a beating heartScientists have successfully tested a
heartbeat-powered pacemaker in living
pigs, whose hearts are similar to humans’
in size and function. Researchers say this is
an important step toward developing bat-
tery-free implantable medical devices.
Current pacemaker batteries have a life
span of seven to 10 years, and replacing
them entails expensive surgery.
The new “symbiotic pacemaker” con-
sists of three components: a wafer-sized
generator attached to the hear t that con-
verts the organ’s mechanical energy into
electrical energy; a power-management
unit that has a capacitor to store that ener-
gy; and the pacemaker itself, which stimu-
lates and regulates the heart muscle.
Zhou Li of the Beijing Institute of
Nanoenergy and Nanosystems and Zhong
Lin Wang of the Georgia Institute of Tech-
nology and their colleagues implanted
their device in two adult male pigs. In the
first animal (which had a healthy heart),
the team tested how well the generator
harvested energy; it powered the pace-
maker for a total of nearly three and a half
hours. The pig’s heart generated more
than enough energy to power a human
version of the pacemaker, the scientists
reported in April in Nature Communica-tions. In the second pig, they induced an
irreg ular heartbeat (arrhythmia) to test the
pacemaker’s therapeutic function. When
the device—which had been charged by
the pig’s heart for more than an hour—
was turned on, the animal’s heartbeats
prompt ly became regular and remained
so even after it was turned off.
Human testing is unlikely in the near
future because the device’s size, safety
and efficiency must still be optimized.
“The technology described is a significant
achievement,” says Patrick Wolf, a bio-
medical engineer at Duke University, who
was not involved in the study. But he cau-
tions that the size and efficiency hurdles
are significant, and the pacemaker’s effec-
tiveness in a less dynamic, diseased heart
is yet to be determined.
Another drawback is that the unit must
be attached directly to the heart’s surface
and could interfere with the organ’s func-
tions. A group at Dartmouth College and
the University of Texas at San Antonio
pre viously designed a pacemaker that
instead harnesses kinetic energy from its
own lead wire, which moves when the
heart pulses. The team is currently testing
it in dogs.
“The development of these batter y-
free technologies will revolutionize im -
plant able devices,” says Ramses Martinez,
a researcher in industrial and biomedical
engineering at Purdue University, who
was not involved in either study. “Soon
traditional rigid implants will evolve into
conformable systems capable of harvest-
ing the energy they need to function from
the patient.” — Harini BarathSymbiotic pacemaker runs
on a tiny generator ( pictured )
powered by the heart.Scientific American is a registered trademark of Springer
Nature America, Inc.