When they were introduced in 2002, drug-eluting stents exploded onto the market and have since been implanted in millions of patients worldwide. Drug-coated stents have proven to be safe in the vast majority of patients, but they have been linked to sometimes-fatal blood clots in some patients.
A recently developed computer model developed at MIT shows that uneven diffusion of drugs is likely the cause of the blood clotting in those patients. The model, which simulates the dynamics of blood flowing around a stent, shows how the drug coating of stents can diffuse unevenly in some scenarios. While the drug prevents restinosis (or narrowing of the arteries), excessive drug buildup promotes clot formation. “There are some areas with too much drug, and areas where there are no drugs,” says Kinam Park, a professor of biomedical engineering at Purdue University. This uneven diffusion can lead to tissue damage and, in some cases, death, Park explains.
The software could be used to develop stents that promote more-even diffusion of drugs within the arteries—improving their safety as well as their efficacy. “The model allows us to change the stent–the design, dimensions, materials, drug, and the way it is released,” says Elazer Edelman, a professor of Health Science and Technology (HST) at MIT and the principal investigator of the project.”Then we can place the stent, alone or adjacent to other stents, in arteries with different diseases or in different natural states. By rapidly considering thousands of different design features, the model can do things that can otherwise not be done.”
The 3-D simulation enables the scientists to change the parameters such as materials, stent configurations, drug-flow properties, and the shape of the arterial wall. “We created an automatic algorithm so that we have the flexibility to visualize different elements without having to start from scratch,” says Vijaya Kolachalama, a postdoctoral associate at HST working on the program.
Seeking to make computer modelling part of the US FDA regulatory process, the MIT researchers say the model could help the US FDA in its approval processes by helping regulators determine which stents are most likely to be safe based on their size and shape.
More informationon the computer model is available from the Technology Review.Brian Buntz