Researchers from The University of Texas Health Science Center at San Antonio (UTHSC) and UT Austin now can measure the strength or weakness of the mouse heart, thanks to a miniaturized catheter system they invented.
The rodent heart hums along at 700 beats a minute — 10 times faster than the human heart and about the rate of motion of a hummingbird's wings. The blood volume is the equivalent of one drop of human blood.
"The catheter system is threaded into the mouse heart. It sets up an electrical field that measures voltage as the heart contracts and relaxes," said Marc D. Feldman, M.D., associate professor of medicine and director of interventional research at UTHSC.
The invention is of great interest to the pharmaceutical industry, which seeks animal models for measuring the effects of new cardiac medications. Houston-based Millar Instruments has sold 50 to scientists and pharmaceutical companies, with each unit going for $6,000.
The standard measurement of heart muscle strength is performed with what scientists call pressure volume loops. The volume measurement has been performed with echocardiography, angiography and ultrasonic crystals. "These conventional measures cannot be done in the mouse because of the heart's small size and rapid rate," said Dr. Feldman, also associate director of the cardiac catheterization laboratory at University Hospital. "This is the first simple system to conquer those obstacles."
Dr. Feldman worked with colleagues at the UT Austin School of Bioengineering, where he is cross-appointed as assistant professor. A National Institutes of Health grant enabled the group to commercialize the invention. The researchers will improve the accuracy of the system in further studies. Their early work was reported in two articles in the American Journal of Physiology.