Relationship between neointimal thickness and shear stress after wallstentimplantation in human coronary arteries

Background-In-stent restenosis by excessive intimal hyperplasia reduces the long-term clinical efficacy of coronary stents. Because shear stress (SS) is related to plaque growth in atherosclerosis, we investigated whether var iations in SS distribution are related to variations in neointima formation . Methods and Results-In 14 patients, at 6-month follow-up after coronary Wal lstent implantation, 3D stent and vessel reconstruction was performed with a combined angiographic and intravascular ultrasound technique (ANGUS). The bare stent reconstruction was used to calculate in-stent SS at implantatio n, applying computational fluid dynamics. The flow was selected to deliver an average SS of 1.5 N/m(2). SS and neointimal thickness (Th) values were o btained with a resolution of 90 degrees in the circumferential and 2.5 mm i n the longitudinal direction. For each vessel, the relationship between Th and SS was obtained by linear regression analysis. Averaging the individual slopes and intercepts of the regression lines summarized the overall relat ionship. Average Th was 0.44 +/-0.20 mm. Th was inversely related to SS: Th =(0.59 +/-0.24)-(0.08 +/-0.10)xSS (mm) (P<0.05). Conclusions-These data show for the first time in vivo that the Th variatio ns in Wallstents at 6-month follow-up are inversely related to the relative SS distribution. These findings support a hemodynamic mechanism underlying in-stent neointimal hyperplasia formation.