Researchers at the University of British Columbia created a ‘smart stent’ empowered with sensors that can monitor and provide real-time feedback on blood flow to help decrease restenosis or the narrowing of arteries.
Cardiovascular disease is the top medical reason for deaths worldwide. Millions of patients have benefitted from stents placed in clogged arteries to improve blood flow and reduce the risk of heart attack. But there is also a risk associated with stents: plaque can build up, causing arteries to narrow again.
Researchers at the University of British Columbia in Vancouver, Canada, have figured out that stents could do a lot more than just be a dumb tube on the wall of an artery. They’ve created a ‘smart stent’ empowered with sensors that can monitor and provide real-time feedback on blood flow. The feedback can detect re-narrowing of stented artery, known as restenosis, a common complication of stent implantation. The researchers believe in‐stent restenosis can reach as high as 50 percent among patients with stents.
“The essence of the technology is its unique ability to provide early warning of re-narrowing, to address it before it becomes severe leading to heart attack,” says Kenichi Takahata, associate professor in the Department of Electrical and Computer Engineering at UBC. “Allowing for continuous monitoring, it can lower the cost for diagnosis as well. The technology can be applied to other types of stents beyond the cardiac area.”
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The smart stents provide an early-warning system that the researchers believe is a better way to diagnose restenosis. In‐stent restenosis in arteries is currently diagnosed through duplex ultrasound and angiography, usually done when patients complain of heart attack-related symptoms like chest pain. Stents in some cases are coated with slow-release medication to prevent plaque buildup, which can be effective in the short run, but it doesn’t protect against heart attack in the long run.
The smart stent detects signs of restenosis and also thrombosis, which is clotting inside a vessel. The stent has sensing and real-time communication ability via micro‐electromechanical systems (MEMS) and antenna functions. The signal sent by the stent is received by an external portable reader, and the readings can be used in diagnosis. The researchers tested the system using a live, anesthetized pig.
The smart stent integrates a micro-pressure sensor developed for chronic tracking of local blood pressure. The stent itself is designed to work as a radio-frequency antenna, in addition to its mechanical role as a vascular scaffold, for wireless telemetry of local blood pressure. The sensor microchip and the antenna stent are based on medical-grade stainless steel, type 316L, which is similar to that in commercial stents.
“This allows the sensor to be directly micro-welded on the stent, which has achieved not only excellent sensor-to-stent electrical interface, but also very high mechanical bonding strength between them as well,” Takahata says. “Our smart stent device is made entirely of biocompatible materials.”
Stenting is a mechanically demanding process. The stent is crimped on a balloon catheter, pushed through a tight hemostatic valve and guided through intricate blood vessels, and then expanded against the arterial wall. The smart stent, to the best of the researchers’ knowledge, is the first compatible with standard clinical procedure used for stenting, owing to its electromechanical robustness, Takahata says.
The researchers focused on designs compatible with standard angioplasty and stenting procedures. Stents typically vary in size depending on the patient, and flexibility was another consideration during the design process.
“Our plan is to further refine the prototype before putting it through clinical trials and bringing it to market which should take some years. We are seeking industry partners for this translation,” Takahata said.
A paper on the smart stents was published in the May issue of Advanced Science. Other researchers involved in the project included York Hsiang, a professor for vascular surgery at UBC, and university researchers Xing Chen and Babak Assadsangabi.
Agam Shah is associate editor of Mechanical Engineering magazine.
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