Relationship of shear stress with in-stent restenosis: bare metal stenting and the effect of brachytherapy.

BACKGROUND The association of shear stress (SS) with in-stent restenosis after bare metal stenting is not clear. We investigated the significance of SS on predicting areas with neointima thickness (NT) in humans and the effect of vascular brachytherapy (VBT) following coronary artery stenting on the relationship of SS with NT. METHODS By using coronary angiography and intravascular ultrasound, we performed three-dimensional (3D) artery and stent reconstruction in 14 patients at 8-month follow-up after bare metal stenting with (stent&VBT group; 7 patients) or without (stent group; 7 patients) adjunctive beta-VBT. In-stent SS was calculated by applying computational fluid dynamics to the stent reconstruction and NT was determined in 3D space. RESULTS NT was significantly increased in the stent group (0.2+/-0.16 mm vs. 0.07+/-0.18 mm, p<0.001). The estimated intercepts and slopes regarding the relationship of NT with SS were 0.28 mm [95% confidence interval (CI): 0.20 to 0.36 mm, p<0.001] and -0.057 mm/Pa (95% CI: -0.062 to -0.052 mm/Pa, p<0.001) respectively for the stent group, and 0.15 mm (95% CI: -0.02 to 0.31 mm, p=0.082) and -0.017 mm/Pa (95% CI: -0.023 to -0.010 mm/Pa, p<0.001) respectively for the stent&VBT group. After pooling all data together, a significant effect of VBT on the relationship between NT and SS was found [estimate of interaction term (groupxSS) for stent&VBT vs. stent group: 0.04 mm/Pa; 95% CI: 0.032 to 0.049 mm/Pa, p<0.001]. CONCLUSIONS In-stent restenosis is inversely related to SS after coronary artery stenting and VBT diminishes the inverse relationship between NT and SS.