by Andrew Mullins
It’s 20 millimetres long. It weighs less than 50 milligrams. It was inspired by snakes. How a new stent is going to radically improve the lives of children suffering from pulmonary artery stenosis.
Supply and demand—it’s a simple rule of economics. But try telling that to the parents of children born with congenital heart defects. While millions of dollars can be made treating adult coronary artery disease with stents—small metal tubes inserted into arteries to improve blood flow—kids with cardiovascular abnormalities just don’t deliver enough market share to financially justify developing pediatric-specific technology.
Rosaire Mongrain, a professor in the Department of Mechanical Engineering and Co-director of the Cardiovascular Engineering Lab at the Montreal Heart Institute, reports that four out of a thousand children are born with a condition called pulmonary artery stenosis, a narrowing of the large artery that sends blood to the lungs to be oxygenated. Stenosis restricts blood flow, causing poor oxygenation, laboured breathing and low energy. In extreme cases, poorly oxygenated blood will turn patients blue. As the child ages, the condition worsens. Treatments vary and range from angioplasty to heart surgery; more and more, doctors are employing a stent to prop open the artery, a minimally invasive procedure.
So far, pediatric surgeons have been forced to use the equivalent of Oldsmobile parts to repair a Smart Car, making do with stents designed for adults. With 54 per cent of all adult cardiovascular deaths in Canada caused by coronary artery disease, medical technology multinationals aren’t terribly interested in developing a device needed by only 0.4 per cent of newborns.
It’s a far from ideal situation. A regular adult stent is a rigid scaffold, designed to be expanded in an adult artery that has narrowed and stiffened with plaque. Insert it into a child, and complications can set in as the child grows. According to Richard Leask, a William Dawson Scholar and professor in the Department of Chemical Engineering, that’s not the only problem, either. “Because the blood vessel is so elastic in a child,” says Leask, “it can cause the artery to repeatedly rub at the ends of the stent. You can actually injure the vessel and even rupture it. And the child can die from that.”
Leask and Mongrain are poised to remedy this problem. In collaboration with a Montreal company, Baylis Medical Inc., the team is developing a revolutionary prototype pediatric stent.
In order to best understand cardiologists’ needs, the team worked closely with two doctors at Hôpital Laval in Quebec City. Exasperated by the lack of a properly designed stent, Dr. Olivier Bertrand and Dr. Josep Rodés posed a simple question: “Would you put it in your kid?” These words became the team’s guiding principle.
The design process began by cutting an adult stent lengthwise on one side, creating a scaffold that could open gradually as the vessel grew. The team then gave their creation a twist—literally.
Sitting in Leask’s office, Mongrain holds up a small plastic cylinder that contains “generation three” of their carefully planned prototype. To the non-professional, it looks like a tiny spring that’s popped out of a toy. In reality, it’s a laser-cut piece of medical-grade stainless steel, its design sparked by an unusual muse.
“The inspiration came from a snake skeleton,” explains Mongrain. A snake skeleton features a rib cage to protect internal organs, “but it is also flexible and it has no sternum. It’s open on the other face. So it’s kind of a cut stent from the start.”
Their prototype, however, has a spiral “backbone.” “It’s what we call bio-inspired, not bio-mimicked,” Mongrain continues. “You take the snake and you twist it, so that now the backbone forms a helix.”
To help bring their design to fruition, the two professors turned to a Montreal business that knows firsthand how necessity can inspire innovation. In 1986, an enterprising nurse named Gloria Baylis, frustrated with her hospital’s inability to procure proper neurology equipment, founded her own distribution company. Baylis Medical Inc. soon grew to include designing and manufacturing high-tech medical equipment. Now run by engineer Frank Baylis, Gloria’s son, the company’s products include a line of pediatric cardiology equipment. When Leask and Mongrain approached Baylis about collaborating on their stent, they learned the company was working on a similar project. And so a partnership was born.
Baylis Medical provides financial investment—matched by a cash grant from NSERC’s Collaborative Research and Development initiative—as well as some equipment, facilities and engineering time. “It’s a relatively modest budget of around $225,000 over three years,” says Mongrain, “which is pretty cheap for any medical device.”
The company also provides connections to industry for laser-cutting their stent prototypes, says Leask, “and they’ve been involved in all the brainstorming, all the design discussions. They’ve been fantastic to work with.”
Working with university researchers provides an advantage for Baylis Medical, too. “They have good expertise and they have equipment as well,” says Frank Baylis. “If they have unique knowledge in a certain area, then we can tap into that.”
The stent project is now moving into the animal trials phase; if those succeed, the playing field suddenly becomes much bigger. While the team’s initial budget is small, bringing a medical device to market through clinical human trials and lengthy certification processes means costs can soar into the millions. Still, Frank Baylis is ready: “If the design, prototypes and animal testing are promising, then we foresee that we would have the financial resources to do it ourselves.”
Mongrain and Leask are grateful that this research collaboration puts them on the front lines, helping patients and the doctors who care for them. “There are a lot of people who do biomedical engineering but never actually get close to a doctor or the clinical side,” says Leask.
“This is where Rosaire and I think our strength is: we have very good connections and collaborations.
We don’t work for industry, we work together. That’s really what’s been the success and drive behind this project.”