Colleen Witzenburg looks at the human heart and sees a wonderfully complex organ—one that’s built of layers of fibers running in different directions, that is mechanically and electrically active, and that can adapt to changes. But the mechanical engineer in her can also peer through the intricacy and awe of the heart and see it as a functional object.
“It’s a pump. It’s a really amazing and intricate pump, but it’s still a pump,” says the assistant professor of biomedical engineering, who joined the University of Wisconsin-Madison faculty in January 2019.
Witzenburg, whose bachelor’s, master’s and doctoral degrees are all in mechanical engineering, studies cardiovascular tissue structure and function. By gleaning quantifiable data, she attempts to predict the tears or ruptures that occur after sudden events, such as heart attacks, or conditions that develop over time, like congestive heart failure.
“The tissues we study are crucial to the load-bearing capacity of the cardiovascular system,” says Witzenburg, who completed a postdoctoral fellowship in biomedical engineering at the University of Virginia before coming to UW-Madison. “It is often life-threatening when these tissues are damaged or diseased and may require the replacement of an entire vessel or even the heart itself.”
Witzenburg is interested in how the heart responds to disease from a structural perspective and, ultimately, using those insights to inform clinical treatment plans.
In particular, she’s studying the tissue changes associated with genetic disorders that threaten to rupture the aorta, the body’s largest artery, and unexplained congenital heart defects such as hypoplastic left heart syndrome. Babies with the condition are born without a fully developed left side of their hearts, leaving their right side to do all of the work and necessitating three surgeries before age 3.
By predicting tissue growth and remodeling in hypoplastic left heart syndrome, Witzenburg hopes to provide clinicians with data that could more precisely inform when those surgeries are performed.
“Can we better optimize the timing of surgery? Can we make better predictions of ventricular size and shape over long periods of time?” she says. “If we can give physicians more tools to make these decisions, then we can start making them on a more patient-specific basis.”
Witzenburg is also exploring heterogeneity within tissues—the spatial variance in material properties, both in healthy and diseased tissue—and its implications for potential tearing or rupturing. The first step, she says, is characterizing a tissue’s heterogeneity, which her lab group will do through a combination of computational modeling and mechanical tests.
“We’re trying to understand heterogeneity to be able to predict where failure initiates and how it propagates through a tissue,” she says.
Just as Witzenburg stresses the importance of maintaining a strong connection between her modeling work and experimentation, she’s an ardent believer in more closely linking theory and practice in her teaching. She remembers struggling to bridge that gap early on as a graduate student, a situation she’s keen to help current students avoid.
She is starting off as an instructor for the junior-level undergraduate biomedical engineering design course in the spring 2019 semester, but she also has experience teaching a biomechanics course at Virginia. She says her favorite part of teaching is witnessing the moment a concept clicks for a student.
“I can tell you something, but until you discover it, it’s not quite the same,” she says. “So I love that part.”