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 electrical engineers at The University of Texas at Austin and cardiologists at The University of Texas Health Science Center at San Antonio.
The university's electrical engineers John A. Pearce, Ph.D., and Jonathan Valvano, Ph.D., collaborated with Dr. Marc D. Feldman, M.D., and colleagues from the Health Science Center.\
“Researchers all over the world are making gene alterations in mice to observe the effect on the heart,” said co-inventor Feldman, 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.
The group showed that measurements using the new technique are significantly more accurate than the older technology, both for normal mice and those with thickened heart wall muscle.
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.”
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.
Scisense hired Anil Kottam, Ph.D., a former doctoral student in biomedical engineering at UT Austin, to help transfer the Admittance technology to commercialization.
