Wall Mechanics of the Stented Extracranial Carotid Artery

Abstract

Background and Purpose— Abrupt compliance changes and concomitant nonlaminar flow patterns may contribute to endothelial dysfunction and subsequent neointimal thickening. The aim of this study was to test the feasibility of wall mechanics measurement using B-mode ultrasound image analysis by dedicated software in the stented human carotid artery. Methods— Carotid Wallstents (Schneider) were placed in the extracranial carotid arteries of 15 patients. B-mode ultrasound examination was performed with a 7.5-MHz probe on the carotid artery upstream; at the proximal, mid, and distal stent levels; downstream from the stent; and on the contralateral internal and common carotid arteries. Carotid diameter (d) and systolic diameter changes (Δd) were measured with a dedicated image processing system (IÔ version 3.1, IÔDP), while pulse blood pressure (ΔP) was measured. Diameter compliance (Cd) and distensibility coefficient (DC) were calculated as Cd=2Δd/ΔP and DC=2Δd/ΔP/d and compared between measurement sites. Results— The evaluation could be completed in 8 of 15 patients. Compliance was significantly lower at the proximal, mid, and distal stent levels (27.77±1.11, 27.38±1.08, 27.38±1.09×10 −3 mm · kPa −1 ) than upstream (103.3±36.7×10 −3 mm · kPa −1 ), downstream (91.5±41.3×10 −3 mm · kPa −1 ), or on the contralateral internal (87.6±28×10 −3 mm · kPa −1 ) and common (149.3±47.6×10 −3 mm · kPa −1 ) carotid arteries. Conclusions— Stenting of the extracranial carotid artery induces a compliance mismatch between the native and the stented artery.