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1 Anesthesiology, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA; Biomedical Engineering, Maquette University, Milwaukee, WI, USA
2 Biomedical Engineering, Maquette University, Milwaukee, WI, USA
3 Boston Scientific Corporation, Maple Grove, MN, USA
4 Pulmonary and Critical Care, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA; Biomedical Engineering, Maquette University, Milwaukee, WI, USA
5 Anesthesiology, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA; Pharmacology and Toxicology, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA
6 Anesthesiology, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA; Medicine, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA; Pharmacology and Toxicology, Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, WI, USA
* To whom correspondence should be addressed. E-mail: jladisa{at}mcw.edu.
Restenosis limits the effectiveness of stents, but the mechanisms responsible for this phenomenon remain incompletely described. Stent geometry and expansion during deployment produce alterations in vascular anatomy that may adversely affect wall shear stress (WSS) and correlate with neointimal hyperplasia. These considerations have been neglected in previous computational fluid dynamics (CFD) models of stent hemodynamics. Thus, we tested the hypothesis that deployment diameter and stent strut properties (e.g. number, width and thickness) influence indices of WSS predicted using 3D CFD. Simulations were based on canine coronary artery diameter measurements. Stent-to-artery ratios of 1.1 or 1.2 to 1 were modeled and computational vessels containing 4 or 8 struts of two widths (0.197 or 0.329 mm) and two thicknesses (0.096 or 0.056 mm) subjected to an inlet velocity of 0.105 m/sec were examined. WSS and spatial WSS gradients (WSSG) were calculated and expressed as a percentage of the stent and vessel area. Reducing strut thickness caused regions subjected to low WSS (less than 5 dynes/cm2) to decrease by approximately 87%. Increasing the number of struts produced a 2.75-fold increase in exposure to low WSS. Reducing strut width also caused a modest increase in the area of the vessel experiencing low WSS. Use of a 1.2 to 1 deployment ratio increased exposure to low WSS by 12-fold compared to stents implanted in a 1.1 to 1 stent-to-vessel ratio. Thinner struts caused a modest reduction in the area of the vessel subjected to elevated WSSG, but values were similar for the other simulations. The results suggest that stent designs that reduce strut number and thickness are less likely to subject the vessel to distributions of WSS associated with neointimal hyperplasia.
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