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Engineers work on medical device targeted to meet surgical needs

Two men in front of a computer.

A. Sherif El-Gizawy, a professor of mechanical engineering, and his graduate research assistant Amer Krvavac show a diagram of how the device will work.

No more risky open-heart surgery to replace failing aortic valves. That’s the ultimate goal of research by a collaborative University of Missouri faculty team from mechanical engineering and medicine.

The research project aims to create an easily inserted and withdrawn device to block any debris from reaching the brain during aortic valve replacement surgery in the practice of a less-invasive alternative valve replacement procedure for patients who might not recover from open-heart surgery.

Ahmed Sherif El-Gizawy, a professor of mechanical and aerospace engineering, is leading the research effort along with Raja Gopaldas, assistant professor of cardiothoracic surgery at the School of Medicine. El-Gizawy said he enjoys working with Gopaldas because of his practical focus on realistic solutions.

“He thinks engineering,” El-Gizawy said. “That makes me very comfortable working with this doctor in particular.”

Two men work on the model heart system.

Amer Krvavac, a graduate student working in mechanical engineering professor A. Sherif El-Gizawy’s lab, and Kyle Rood, an MU Biodesign Fellow and Bioengineering Department alumnus discuss the model heart system to measure pressure drops caused by the insertion of the device to block debris. Rood explains what he plans to do to measure the pressure changes with the more detailed model.

El-Gizawy and Gopaldas have been awarded $150,000 through the Coulter Translation Partnership Program. The program funds partnerships between medical professionals and engineers in order to speed the delivery of life-saving products from the research stage to the patient.

Open-heart surgery to replace a failing aortic valve, which reduces blood flow from the heart, is currently the standard practice. That’s because a non-invasive alternative carries a higher risk of stroke.

The non-invasive method relies on delivering a replacement valve through a catheter. When the new valve is placed, it may crush existing calcium deposits that can then flow up into any of the three arteries that lead to the brain, potentially causing a stroke.

The goal of the research is to create a device, nicknamed “The Embolisher,” that can be inserted through a catheter into the aorta. It will deploy a wire mesh to prevent calcium debris from flowing up to the brain. Instead it will be directed downward to other organs that can withstand the debris.

“The valve replacement until recently needed an open-heart operation that takes six or seven hours and has big risks,” El-Gizawy said. With this device, the risk of stroke from the non-invasive alternative valve placement will be lessened allowing it to be used more frequently.

Close up of the embolisher.

The Embolisher’s wire mesh will prevent calcium debris from flowing up to the brain.

“It’s a deployment device and a retrieval device,” said Amer Krvavac, a mechanical engineering graduate student working on the project. “We release it and the mesh deploys to cover the three arteries to the brain. It’s a filtering mesh and when the valve is placed, it stops any particles from going past and causing a stroke.”

Also working on the project with El-Gizawy is Kyle Rood, who graduated with his master’s of science in biological engineering in May 2013. Josh Arnone, who received his doctorate in mechanical engineering in 2011, serves as a consultant.

“I’m very happy that we found these two bright, young engineers to work together,” El-Gizawy said. “I am always fortunate at this place to have great students. The wealth of this university is the students.”

Krvavac and Rood are modeling the performance of the device using computer models and a physical model of the aortic arch. Krvavac will use computer modeling to make predictions about different situations and scenarios with such things as blood flow and blood pressure drop. When modeling is completed, it will move to the animal testing stage.

El-Gizawy said the pre-predictive methods used by mechanical engineers are different from clinical medicine’s trial-and-error based approach.

“In medicine, they look at a case and make a diagnosis based on past experience and then they try a solution based on their interpretation. If that doesn’t work, they try another,” El-Gizawy said. “In engineering we try to pre-predict using our tools — mathematics, mechanics, computer-aided techniques. Physics is behind everything. We are engineers, we don’t believe in just, okay, it works this way, it might not work this way every time.”

El-Gizawy is no stranger to applying an engineering philosophy to medical challenges. He and his research team have collaborated on several projects with faculty physicians at the medical school. One involved an improved device to separate the ribcage during surgeries, which showed him the importance of simplicity in design so doctors will find it easy to use in the field.

In 2011, he finished a five-year project with an orthopedic surgeon to build better implants. “I’ve been doing this since 1999,” El-Gizawy said.

He said that experience would help him on this project and hopes more such collaboration occurs in the future.

The heart is an extremely complex system and El-Gizawy said the team is relying on the medical expertise of Gopaldas to guide their efforts. The very first thing the doctor resolved for the team was the size of catheter that could be inserted through the femoral artery to deliver the device to the aorta.

“That saved us a lot of time and money,” Krvavac said.

While El-Gizawy emphasizes the importance of testing and modeling before moving to the animal testing stage, he doesn’t expect it to go perfectly the first time.

“Any problem that develops, we have to go back to our design and see what the causes of that are,” he said. “Reliability in design for medical devices is very, very important. It’s different from even when you design a car or a bike because here you are talking about somebody’s heart, and if failure happens — that’s the end of that life.”