Developing New Stents Through Computer Modeling of Their Performance

The National Science Foundation is profiling cardiac stent research being done by collaborators from University of Houston and University of Zagreb in Croatia. They’re using mathematical computer models to optimize for different characteristics that stents exhibit, helping to design new stents and help simulate ones that are on the drawing board.

Together with her collaborator, Josip Tambaca of the University of Zagreb in Croatia, and her doctoral student, Mate Kosor, Canic wrote a much simpler program that approximates stents as meshes of one-dimensional rods. This program let the researchers achieve the same result using just 400 nodes.
Using their simplified model, the researchers have examined the designs of several stents on the market to see which structures seem to be best for specific blood vessels or procedures. For instance, they found that stents with an “open design”–where every other horizontal rod is taken out–bend easily, which makes them good to put in curvy coronary arteries.

Canic and Tambaca have also used the model to design a stent with mechanical properties specifically tailored to an experimental heart-valve replacement procedure. She found that this specialized stent works best for the procedure when it’s stiff in the middle and less stiff at the ends. In addition, she has found that combining “bendiness” with radial stiffness–where you can bend the stent into a U shape, but you can’t squeeze the tube shut–produces a stent with less chance of buckling than those that are currently in use.
Today, Canic is helping a team at the Texas Heart Institute study an unusual source for stent coating: ear cartilage. The team believes this easy-to-harvest tissue will make stents more biocompatible, though they don’t yet know how ear cartilage cells grow or behave in environments like human blood vessels.
Canic is using her computer programs, developed together with Tsorng-Whay Pan, Roland Glowinski and students, to simulate how blood interacts with the stent-coating cartilage cells and how the cells stick (or don’t) to the stent surface. She plugs in different fluid thicknesses and shear forces of blood flowing over the stent to see what might encourage the cartilage on freshly coated stents to stabilize quickly. The models have helped her collaborators learn the best conditions to test in follow-up experiments as they search for ways to pre-treat stents before doctors implant them.