Optimizing Device Design is the Holy Grail of Stenting

An investigation of how blood flows through stents after opening clogged arteries has led a team of researchers at the Medical College of Wisconsin Cardiovascular Center in Milwaukee to suggest that stents designed with thinner and fewer linkages may be the basis of a new generation of stents. Their findings are published in the July 2004 issue of the Journal of Applied Physiology.

One of the most common methods for treating heart blockages is balloon angioplasty, inflating tiny catheters with miniature balloons to open clogged arteries. Stents, tiny metal scaffolds, are then placed at the newly opened site in the arteries to permanently prop them open. However, 30 percent of stent patients experience restenosis, where arteries narrow again due to scar tissue and cellular growth that forms around the device.

“Currently, eliminating restenosis is the holy grail of catheter-based procedures such as angioplasty and stenting,” says John LaDisa, Ph.D., of the Medical College, who studied the stent designs. “Current research has not identified all the contributing factors to restenosis,” says Dr. LaDisa. “Now our research has shown that a stent’s design and its alteration of the blood vessel anatomy influences blood flow in ways that can contribute to restenosis. Also, restenosis rates vary according to an individual’s vessel geometry at the site of stent insertion.”

Using 3D computational fluid dynamic modeling, Dr. LaDisa investigated specific factors of stent geometry that contribute to, or minimize, the likelihood of restenosis. “We tested the hypothesis that differences in the geometric design of an implanted stent — differences in number, width and thickness of the linkages that compose a stent — affects the forces exerted on cells lining the vessel walls and ultimately influences restenosis rates,” he says.

“Our investigation revealed that several factors, including the thickness and number of stent struts affect restenosis,” LaDisa says. “The results suggest that future stent designs that reduce strut number and thickness will be less likely to subject a patient’s vessel to the physiological events associated with restenosis.”

Basic science researchers such as Dr. LaDisa form the ground floor of developments that lead to improved medical devices. Last year, for example, drug-coated stents, a revolution in stent design, came to market after extensive basic science research. Other investigators that contributed to the forthcoming publication include Paul S. Pagel, M.D., Ph.D., Judy R. Kersten M.D. and David C. Warltier M.D., Ph.D. from the Department of Anesthesiology and Lars. E. Olson, Ph.D., and Said H. Audi, Ph.D., from the Department of Biomedical Engineering at Marquette University. The study was supported by the Medical College’s Department of Anesthesiology.