University of Rochester

Engineers Unravel the Forces that Shape Our Heart

April 21, 2000

Engineers at the University of Rochester are using their mathematical skills to learn more about one of the most remarkable machines of all: the human heart.

Renato Perucchio and his colleagues have been awarded $1.6 million to study how the heart develops from a feebly pumping, millimeter-long tube found in young embryos to the robust four-chambered organ that's present in many animals, including humans. The four-year project is funded by the National Institutes of Health and is led by former Rochester professor Larry Taber, now at Washington University in St. Louis. Perucchio, associate professor of mechanical engineering, is heading the portion of the project where engineers develop complex computer-based models to describe and predict with numbers the nuances of the heart's mechanics.

The team's work takes a pioneering look at the biomechanical forces that shape the heart in its earliest stages. In their studies the team is focusing on chicken embryos-eggs like those we eat, except that they've been fertilized. The hearts of chickens and many other animals are remarkably similar to those of humans, and any new findings in chick embryos should give physicians key information in treating heart disease in humans.

The human heart represents a superior work of mechanical engineering. With 2.8 billion beats during an average lifetime, our hearts move enough blood to fill the Washington Monument five times over. The heart becomes the first working organ in the human body, pumping by rhythmically opening and squeezing shut just 17 days after conception.

But it all begins modestly. At the very early stage being studied by Perucchio's team, a chick heart is a simple hollow tube the size of a grain of rice that squeezes together to push blood through the embryo. Stresses from the flow of blood, the heart's pumping action, and the growth of adjacent tissue all produce forces that affect how the heart will ultimately form.

"There are plenty of embryologists who study how the heart develops, but they almost always look at heart development from a genetic perspective," says Perucchio. "Genes certainly play an important role, but it's hard to deny that biomechanical stresses are also key factors in shaping the heart. We know that patterns of blood flow and the pumping-induced growth of cardiac muscle both affect the thickness of the walls in different parts of the heart. These effects, combined with the bending caused by the growth of nearby tissue, eventually cause the heart to assume its shape."

The team is using sophisticated image-processing techniques to compile digital images of embryonic chick hearts. Then Perucchio and his students apply powerful computer programs that they have developed to do sophisticated mathematical modeling of the mechanical forces involved. Using a technique known as finite element analysis, the team measures the forces involved and computes the stresses, strains, and deformations experienced by the beating heart.

Much of the engineers' attention is focusing on a time during development when the wall of the heart is transformed from a compact layer of cells into column-like structures that support the heart wall, almost like beams that are raised to support a barn. The engineers are turning to their models to compare how the mechanical behavior of the heart wall changes when the column-like structures, known as trabecula, are not present.

The work should help physicians understand the cardiac mechanics of heart disease patients with dangerously enlarged hearts, such as congestive heart failure sufferers. The research could also have important ramifications for much younger patients: One in 100 babies is born with a heart defect, making it the leading cause of congenital infant death in the United States.

Perucchio and Taber have been collaborating for several years. Now they take advantage of special software to have face-to-face meetings over the Internet, sketching out plans together and even sharing a cyberspace "white board" where they swap insights about the research.




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