A project with heart

Students research artifical heart valves

By Catie Hall
On April 9, 2013

  • Seniors Tim Roemer and Andrew Beland work on a pig’s heart as part of the Ex Vivo, or “out of body” portion of their senior project, which studies the flow of the human heart and artificial valve geometries. Courtesy

Instead of building Formula One racecars, model airplanes or off-road vehicles for their senior project, Tim Roemer's mechanical engineering group is going biomedical: studying the flow dynamics of the human heart and artificial valve geometries

Roemer's group is using Ex Vivo and PIV technologies for their project. The group includes seniors Roemer, Andrew Beland, Chloe Garrage, Greg Kopanski, and Jimmy Popovitch

So, why are mechanical engineer seniors researching the biomedical aspects of the human heart? Because heart valves can malfunction, tear and leak. Mitral valve regurgitation occurs when blood leaks into the heart and the flow is disrupted. It can lead to heart swelling, lethargy and activity restriction. 

Artificial valves can be designed to save lives.

According to the Mayo Clinic website, mitral valve regurgitation occurs when "the flaps (leaflets) of the mitral valve weaken, causing blood to leak backward into the left atrium of your heart. If not treated, it can result in heart muscle damage."

Roemer and his group compiled research from textbooks, published papers and medical websites on mitral valve regurgitation. During their research, they found that more than 3 million people in the United States have it. With over 300 million people in the United States, one percent of the population is affected. 

Christopher White is a professor of mechanical engineering. He is also Roemer's group advisor. Though the percentage is small, he does not think it explains the issue.

"I think the numbers are significant enough," White said. "So, if you put it in percentage, it's not a large percent, but it is a large number of people." 

Roemer's group also found that every year over 250,000 people are diagnosed with mitral valve regurgitation. In terms of surgeries worldwide, it translates to over 100,000 valve replacements every year. 

When mitral valve regurgitation is not treated, the heart can swell. In worst-case scenarios, MVR leads to heart failure. 

While this wasn't the case for Sean-Michael Dunphy, he still experienced a close call. As a baby, he had open-heart surgery.   

"When I was six months old, they did what's called a balloon operation," Dunphy said over the phone. Surgeons found that Dunphy's pulmonary valve was closed and not enough blood was getting to his heart. 

The solution was to put in a valve to open it up. However, the procedure left a tear. Doctors frequently checked on the status of Dunphy's heart as he aged, he said. 

At age 21, Dunphy's heart swelled and the tear in his heart spread. Doctors told him that his heart was 175 percent larger than it was supposed to be. They were worried about the elasticity of his heart, Dunphy said.

Because doctors noticed Dunphy's swollen heart, they performed surgery at Massachusetts General Hospital in Boston after his junior year. The surgery was a success. 

Dunphy is now 24 years old and ran a half marathon in Hampton last September. 

Dunphy's experience is just one example of how Roemer's project could be impactful in the biomedical community.

"The main goal of their project is to quantify the performance of various artificial mitral valve geometries," White said. "So, the measures of performance would be the pressure drops across the valve. So if you have a large pressure drop, your heart has to work harder." 

In other words, if the group can understand the blood flow through an artificial valve, they can figure out ways to reverse mitral regurgitation. 

Roemer's interest in the project started at the end of his junior year. Roemer took White's class, ME 646: Experimental Methods and Data Analysis, where he did preliminary work for his current project.

In ME 646, Roemer worked with three-inch-diameter valves. He used airflow to test the valves. For his current project, Roemer's group works with life-sized, one-inch-diameter valves and water, which acts like fast-moving blood. 

White was impressed with Roemer's group work in his ME 646 class, he said. 

"It was probably the best - or at least Top 5- projects that I've seen in the seven years that I've taught the class. And there's roughly about 30 projects a year," White said. "So, this is over 200 projects, and his group was certainly Top 5 that I've seen. So, certainly they surprise me by the quality of their work." 

Roemer's group has two separate projects that coincide. With Ex Vivo, or "out of body," the group looks at a real pig's heart that came from a butcher. They look at the atrium chambers and how blood would flow through the heart. 

More related to the mechanical aspect of their project is the Particle Image Velocimetry system. Two water reservoirs sit about 5 ½ feet apart with a hollow tube connecting them. A mechanical valve sits in the middle of the tube. 

A smaller water reservoir pushes water through the tube and back into the other reservoir. The water contains particles made of small, hollow glass beads. A Class 4 laser emits a wall of light and lights up particles. The laser allows the group to see how the particles move through the valve.

The group has to wear special goggles and avoids contact with the laser when it is in use. It is the type of powerful laser, Roemer said, that can blind you and burn holes in your skin. Roemer explained that the laser can make people nervous.

"When you do it for the first time, some people don't look at it all," Roemer said.

After the laser lights up the particles, a camera synchronizes with the laser and takes pictures. The pictures indicate where the particles were before and after they passed through the valve.

Though the group enjoys their experiment, there have been some roadblocks.

With the Particle Image Velocimetry and Ex Vivo projects, Roemer's group runs into graduate-level math that they need assistance with. The group often asks teacher assistants and graduate students for advice. 

Not only does advanced math occasionally trip them up, but only Kopanski has extensive knowledge about the biological side of their project. Whenever Roemer's group has a question, they ask him. 

"I haven't taken biology since high school," Beland said. He laughed about his limited knowledge toward the biological side of the project. 

"I didn't take biology in high school," Roemer chimed in, laughing along. 

Thankfully for Beland and Roemer, the PIV project has little biology involved.

Garrage faces other challenges, being the only girl in both the PIV and Ex Vivo projects. 

"It's definitely an experience," she said over the phone. "Guys are definitely the same smartness level, so that's easy. Sometimes they can be insensitive, but I get over it." 

The challenges in the group cover every aspect, from graduate-level math to playful gender politics.  

When Roemer's group gets results, he said, he hopes to have their work published. The key is to get the results.

White said that though artificial valves have been studied and researched before, the valves were likely studied in different geometries. He also said that it's the type of system where it almost needs to be studied case-by-case.

"Fluid flow is an interesting phenomenon because it's highly dependent on geometry," White said. "So, if you know a flow in one geometry, it doesn't necessarily mean you know anything about it in another geometry."

White said their project is the highest-level undergraduate project with which he has been involved. The math and instrumentation they use is complex. 

White emphasized that Roemer's small project in his ME 646 class became the cornerstone for his senior project today.

"It's good for them," White said. "And it's good for other students to see that small things can then develop into something that really can be impactful."


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