Change Of Heart

As a member of a pioneering research team, Greg Burgreen is helping develop an artificial heart for infants

By Jim Raper

The challenges for the research team are immense. These devices must be hardworking and reliable, yet the children’s model is the size of an AA battery, and the infant model is only half that size.

Burgreen’s path from ODU to Mississippi State has been shaped by an interest in heart pumps and blood flow that may seem far removed from aerodynamics. But fluid dynamics involves the characteristics of anything that flows, such as gases or liquids, and can explain what happens when a flow comes into contact with a solid surface. To give two examples, fluid dynamics can account for the lift an aircraft generates from the flow of air above and below its wings, or can describe how the blade of a blender whips up a smoothie.

Indeed, Burgreen says that the image of a blender blade can help laymen envision how rotary artificial hearts and heart-assist pumps work. A small turbine is used in the devices to move blood – about five liters per minute for an adult and one-half liter for infants. “They have very fast spinning blades like a food blender’s,” he explains.

Heart pump designers seek to understand and to limit the shearing stress of the pump’s blade on blood cells. “If the red blood cells are torn apart, free hemoglobin, which is toxic, is released into the bloodstream. We desire to keep that to a minimum,” says Burgreen, who works at Mississippi State’s computer simulation facility called the SimCenter (www.erc.msstate.edu/simcenter).

There are other design requirements, as well. Blood flow must not be disrupted, producing stagnant areas inside a pump. Stagnant blood is more susceptible to clotting. “Also,” he says, “there are matters of attaining high hydraulic efficiency and good biocompatibility, which are often competing concerns.”

Burgreen’s contribution to the development of new implantable heart pumps involves computer modeling and testing of designs to guarantee fluid mechanical and medical viability. Computer simulations that predict the performance of a particular design or design component can decrease researchers’ reliance upon costly, time-consuming trial-and-error development processes.

His invitation to join the current National Institutes of Health child and infant heart pump project attests to his standing among CFD engineers who specialize in blood flow. The project is led by the famed artificial heart developer Robert Jarvik, whose Jarvik-7 was the first artificial heart to be implanted in a human. (The recipient of the 1982 implant was Seattle dentist Barney Clark, who lived for 112 days before succumbing to complications from the procedure.)

The NIH contracted in 2003 with JarvikHeart Inc. of New York on the miniature heart pump project and awarded $5 million to get development started. Because of the difficulties in downsizing adult heart pumps and of the relatively modest demand for infant implants, no commercial company in the United States had taken up the project on its own.

Dr. Bartley Griffith of the University of Maryland signed on as project co-director. Griffith and Dr. James Antaki of Carnegie Mellon University, both former colleagues of Burgreen when all were at the University of Pittsburgh School of Medicine, recruited the CFD expert to the design team.

“So far in the project, I have offered one-half of my input,” Burgreen says. “I have analyzed the child-sized version of the Jarvik pump and it is currently undergoing animal tests (implanted in sheep) at the University of Maryland Medical Center. A design and analysis phase for the infant-sized version is upcoming in 18 months.”

He says it could be late in the decade before either device is approved for use in humans. At present, external heart-lung machines are often used to keep alive babies with severely defective hearts, but many die before they can receive heart transplants.

Burgreen grew up about 20 miles outside of Huntsville, Ala., but close enough to the city’s NASA Marshall Space Flight Facility for him, as a 6-year-old, to hear the tests of rocket engines. “That piqued my interest” in engineering, he remembers. The interest only grew when he, beginning at the age of 14, was hired by his road-contractor father to operate bulldozers and scrapers. “That had a bearing on my mechanical interests, but working in road construction also taught me an invaluable lesson – you can break your back, or use your brain.”

He earned both bachelor’s and master’s degrees in mechanical engineering at the University of Alabama, Huntsville, whose alumni society honored him with its 2005 Alumni Achievement Award.

At ODU he was able to get cutting-edge experience in design optimization from his research at NASA Langley Research Center. He also formed enduring friendships at the university and at Immanuel Presbyterian Church, located just off campus.

“Arthur Taylor (ODU professor of mechanical engineering) epitomizes what a college professor should be,” Burgreen says. The two have stayed in touch over the years.

“Greg’s success is well deserved and doesn’t surprise me at all,” Taylor observes. “He was never actually under my supervision. I would have loved to have had him. I liked him a lot and I was very impressed with his work. He is a fine gentleman and a self-starter.”

Just before he received his doctorate, Burgreen says, he went to the NASA Langley library and researched artificial hearts. Not long afterward, one of his Ph.D. committee members told him about an opening at the University of Pittsburgh School of Medicine, which operated the McGowan Center for Artificial Organ Development (now McGowan Institute for Regenerative Medicine). The position that was advertised seemed tailor-made for his technical specialty and interests.

Burgreen eagerly sought the job and when he got it, he says, he realized how fortunate he was. His expertise in CFD was welcomed by his employer, and while offering his services he learned what he needed to know about physiology and the properties of blood related to fluid dynamics. He worked in the school’s Department of Surgery for eight years.
His move to Mississippi State was helped along by another friend he made at ODU, James C. Newman III, who earned bachelor’s and master’s degrees in mechanical engineering in 1993 and 1994. Newman joined the Mississippi State faculty in 1997 after completing a doctorate at Virginia Tech. Now an associate professor of aerospace engineering, Newman works in the area of computer simulation to predict performance capabilities of ships, aircraft and other vehicles. He was selected for a prestigious Office of Naval Research Young Investigator Award in 2002.

During that year, with Burgreen on a family vacation in Alabama, the two met for a serious talk. Was Burgreen interested in coming to Mississippi State? Before the year was out, he was in the job at the SimCenter.

“I was delighted,” he remembers. “Dr. Newman was a very good friend during the four years I was at ODU and we never lost touch. James has a rare combination of mathematical prowess, engineering instinct and earthy common sense.”

Newman is equally happy to have Burgreen in Starkville. “While at ODU, he was a constant source of friendship, fellowship and intellectual stimulation. He possesses a truly keen mind with the ability to arrive at innovative solutions to challenging problems, and the diversity to apply these techniques to applications outside traditional engineering disciplines,” Newman says. “This diversity was one of the main reasons the SimCenter at MSU aggressively pursued Dr. Burgreen.”

Another key SimCenter project for Burgreen is the development of unique simulation software. His goal is to integrate design and analysis research across diverse disciplines, ranging from computational structural mechanics to multicomponent fluid flow.

But his blood pump work is clearly his showcase project. In Pittsburgh, he swapped ideas about heart pumps with colleagues Griffith and Antaki, who literally sketched novel designs on paper napkins. Now they are continuing to work together to make miniature blood pumps a reality.