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
Dr. Feldman 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.” (A copy of the editorial is available from Health Science Center External Affairs upon request.)

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.

The University of Texas Health Science Center at San Antonio is the leading research institution in South Texas and one of the major health sciences universities in the world. With an operating budget of $668 million, the Health Science Center is the chief catalyst for the $16.3 billion biosciences and health care sector in San Antonio’s economy. The Health Science Center has had an estimated $36 billion impact on the region since inception and has expanded to six campuses in San Antonio, Laredo, Harlingen and Edinburg. More than 25,600 graduates (physicians, dentists, nurses, scientists and other health professionals) serve in their fields, including many in Texas. Health Science Center faculty are international leaders in cancer, cardiovascular disease, diabetes, aging, stroke prevention, kidney disease, orthopaedics, research imaging, transplant surgery, psychiatry and clinical neurosciences, pain management, genetics, nursing, dentistry and many other fields. For more information, visit

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