The Mission - June 2002

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Photo of a mouse on a pressure indicator panel

Biomedical engineering
Of Mice and Men
by Amanda Gallagher with Will Sansom

Photo of wire thin device compared with a lincoln penny

The tip of the device is smaller than the Lincoln Memorial etched on the back of a penny.

A wire-thin device snakes its way out of a box, through the hands of a lab technician and into a rapidly beating heart. It sends out an electrical signal, called a pressure volume loop, telling researchers about the strength of the heart.

The tip of the device is smaller than the Lincoln Memorial etched on the back of a penny. The four electrodes on the tip are barely discernible to the naked eye. The device is not much larger than a human hair, but its implications are so fantastic, scientists from around the world are calling the Health Science Center to get their hands on one. It is the SEGNO Mouse Catheter System, and it begins part two of The Mission’s special series on biomedical engineering.

Biomedical engineering combines the basic principles of science, medicine and engineering to rebuild or repair the human body. Biomedical engineers start with ideas and end with miracles — the very miracles designed at the Health Science Center and featured on the following pages.

The average mouse scurries about on four feet, whipping a pipe-cleaner tail and twitching a seemingly insignificant set of nostrils. Its chest rapidly heaves up and down and beneath its sleek fur, a heart drums out 600 beats a minute. The heart is tiny, smaller than a pinkie nail, and resembles a beating baked bean. But it’s a heart of gold — and doctors across the globe are tapping into it. They can, thanks to Marc D. Feldman, M.D.

Dr. Feldman is an associate professor of medicine and director of interventional research. He invented the SEGNO mouse catheter, technology that will change the way we understand heart genes, heart drugs and devices and even heart transplants.

"The catheter enables us to determine how strong or weak the heart is by measuring blood volume in the heart," Dr. Feldman said. "Scientists and pharmaceutical companies are buying it to figure out what individual genes do, or to screen compounds to see if those compounds make the heart weaker or stronger. We can do this in mice and then apply the knowledge to humans."

Dr. Feldman actually began designing catheter systems for humans back in 1993. But what he calls the "DNA revolution" forced him to modify his plans.

"In the mid- to late ’90s we began to have a road map of every gene. Because of the Human Genome Project, we can now figure out which genes cause heart muscles to weaken with the hope of one day altering those genes," Dr. Feldman said.

Scientists traditionally use mice for genetic experiments because the genetic code of a mouse is similar to that of humans. But researchers ran into trouble when they tried to measure the strength of the mouse heart.

"If we altered a gene, we couldn’t tell what we’d done because the heart is so small," Dr. Feldman said. "Conventional measures like echocardiography, angiography and ultrasonic crystals didn’t work because of the heart’s small size and rapid rate. This is the first simple system to conquer those obstacles."

Houston-based Millar Instruments manufactures the catheter system. So far, 60 models have sold to scientists and pharmaceutical companies in the United States, Europe, Australia and Japan. The whole system, including software, costs $20,000.

Dr. Feldman has two U.S. patents issued on the second-generation model, which provides a more accurate reading of blood volume by mathematically removing the heart muscle reading from the electric signal. Next, Dr. Feldman will design a similar catheter system for use in humans.

"Eventually, we will be able to use the catheter in patients who are candidates for a heart transplant. We can test the blood volume and muscle strength to see if new mechanical devices and operations actually strengthen the heart," Dr. Feldman said. "We will be able to see if a new heart medication, used in people, actually makes the heart stronger or just shifts blood volume out of the heart."

Dr. Feldman worked with colleagues at the UT Austin School of Bioengineering, where he is cross-appointed as an assistant professor. A National Institutes of Health grant enabled the group to commercialize the invention — an incredible feat considering only three of every 100 biomedical inventions are successfully marketed.

"This project involves classical bioengineering," Dr. Feldman said. "We are using electricity to study physiology. It’s a perfect marriage." And a perfect tale of mice and men.