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The telltale heart: New invention helps to read its signals
Summary: Mice are often used in research, but the
frenetic beating of their hearts can make it difficult to measure their
strength. A new device offers a more accurate reading.
SAN ANTONIO (Nov. 10, 2009) — A mouse’s heart is the size of a pencil
eraser and beats 700 times a minute – 10 times faster than a human heart. For a
quarter-century, researchers have sought to more precisely measure the strength
of this frenetic heartbeat when testing potential therapies.
Now, a device that offers a far more accurate look at what is going on
in a mouse’s heart is on the market, thanks to collaboration between
cardiologists at The University of Texas Health Science Center at San Antonio
and electrical engineers at The University of Texas at Austin.
“Researchers all over the world are making gene alterations in mice to
observe the effect on the heart,” said co-inventor Marc D. Feldman, M.D.,
professor in the Janey and Dolph Briscoe Division of Cardiology at the UT
Health Science Center. “The Human Genome Project has given us a menu of gene
candidates, but determining which genes are responsible for the abnormal
function leading to heart failure will take years to determine. Gene-altered
mice offer us a tool to link gene changes with physiology. The problem is we
lacked the tools to study the impact of these gene alternations in the beating
mouse heart.”
Miniature catheter system
The invention is a miniature catheter system that establishes an
electrical field in blood and muscle. It then measures the voltage output, and
separates the blood and muscle components to evaluate pressure and volume from
the left ventricle, the major pumping chamber of the heart.
“We showed that measurements using the new technique are much closer to
truth than the older technology, both for normal mice and those with thickened
heart wall muscle,” Dr. Feldman said.
Presentation and editorial
He will speak about the
technology – called an “Admittance” system – at the American Heart Association
Scientific Sessions 2009, set for Nov. 14-18 in Orlando, Fla.
The device also was the subject of an editorial
published in October by the Journal of
Applied Physiology. Editorial author Maike Krenz, M.D., of the University
of Missouri, wrote that the “new Admittance approach clearly yields more
realistic data than the traditional ... techniques.”
Dr. Feldman and colleagues from the Health Science Center collaborated
with electrical engineers John A. Pearce, Ph.D., and Jonathan Valvano, Ph.D.,
of UT Austin.
In use around the world
The University of Texas institutions hold six patents on the technology
and reached a license agreement in 2008 with Scisense Inc., a biomedical
company in London, Ontario. The agreement is for studying cardiac function in
animals. Scisense combined the catheter technology with its own high-fidelity
pressure sensor, said Blair Poetschke, company president and CEO.
To date, dozens of laboratories from North America to Australia have
purchased the ADVantage™ admittance system, which sells for $30,000 or more. “We’re
very excited about the technology,” Poetschke said. “For the first time,
researchers can get a true measure of heart volume and a real-time measure of
cardiac function, and that is the real power of the system.”
Improving on the standard
Previous technology known as “Conductance” systems also used a catheter
and electrical current. However, these systems did not distinguish between
signals passing through blood and signals derived from the heart muscle wall,
and they underestimated ventricular blood volume. They also measured relative
changes in signals over time, rather than absolute blood volumes.
The Admittance system, on the other hand, distinguishes the returning
voltage signals that truly indicate the blood volume from “noise” signals
derived from the heart walls.
Affirmation from scientific
community
“This project represents translational research that came out of studies
in electrical engineering and cardiology, resulted in nine scientific
publications in peer-reviewed journals, and has been commercialized because
other scientists want to use it,” said Dr. Feldman, the interim Joaquin G.
Cigarroa Jr. Distinguished Chair in Medicine. “The ultimate proof of the value
of a technology is how many scientists are purchasing it for their own
research.”
Scisense hired Anil Kottam, Ph.D., a former doctoral student in
biomedical engineering at UT Austin, to help transfer the Admittance technology
to commercialization.
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