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Sacks Leads Grant to Improve Replacement Heart Valve Durability

sacks nih improved valve

Deformations and strain fields of the aortic valve from the fluid–structure interaction computation. Note the different scale for each time. Credit: M.C. Hsu et al.

 

Professor Michael Sacks has received a $2.2 million National Institutes of Health grant to develop the first detailed computer simulations of how to improve bioprosthetic heart valves’ durability.

Roughly 300,000 Americans have one of the valves in their heart replaced annually because of aging, congenital defects or disease-related damage. The aortic valve is often the target, with follow-up surgeries occurring in about 9 years as the original replacement heart valve deteriorates from the work of opening and closing hundreds of millions of times. Yet little is known about how the material and shape of a bioprosthetic aortic valve contribute to its deterioration over time.

"Replacement heart valves have been used successfully for more than 50 years," says Sacks, a biomedical engineering professor, ICES core faculty member, and director of the ICES Center for Cardiovascular Simulation. "But a fundamental gap still exists in understanding their performance once inserted so that we can improve upon that."

Healthy heart valves open and close very quickly (in milliseconds), and do so under the pressure that builds up within a blood-filled heart chamber to force the valve to open. If a bioprosthetic aortic valve fails to close completely afterward as its once-living material deteriorates, less oxygen-rich blood will be pumped throughout the body for nourishment. This backflow process, called aortic valve regurgitation, puts the heart at risk of failure from working harder to compensate.

By creating advanced computer models of bioprosthetic heart valves as they operate under real physiological conditions, Sacks and colleagues seek to inform the development of new versions of these valves that function longer. The more durable heart valves would delay the time before a person receives another heart valve in what is often a complex, open-heart surgery.

The computer simulations of bioprosthetic heart valve function during wear that is developed could also suggest improvements in the durability of a new generation of replacement valves that are inserted during a simpler, less-invasive procedure than open-heart surgery. Called transcatheter valve-replacements, they are implanted in a much less invasive manner, and could become more common if the valves lasted longer.

“With the American population aging, the need for heart-valve replacements will continue to grow,” Sacks says, “making it urgent to develop improvements for traditional aortic replacement valves and alternative options.”

The four-year grant will build on Sacks’ 20-plus years experience in the modeling and simulation of cardiovascular systems. In addition to studying normal physiological flow conditions, his team will work with Dr. Keefe Manning, associate professor of biomedical engineering and surgery at Pennsylvania State University, to evaluate bioprosthetic aortic valves exposed to cycling 15 times faster than normal. Using this laboratory data, Sacks will refine mathematical models his team has developed to evaluate the novel fatigue-damage model of bioprosthetic aortic valves. In collaboration with Aerospace Engineering and Engineering Mechanics Professor and ICES core faculty member Thomas Hughes, these refined math models will then draw on the latest models of interactions between structures and fluids.

With input from Dr. Ming-Chen Hsu, an assistant professor of mechanical engineering at the University of Iowa, the data from the mathematical models will be converted into code for advanced computer simulations of valve function carried out using the Texas Advanced Computing Center at The University of Texas at Austin. This supercomputing data will allow the investigators to produce the first dynamic model of aortic heart valve function under normal conditions and under wear.

"These advanced simulations could have a tremendous impact on identifying novel, more durable bioprosthetic valve materials,” Sacks says, “which is key to improving the valves, and the lives of those who suffer from heart conditions in the future."

Learn about related research that Dr. Sacks is leading on computer modeling of replacement mitral valves.