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 (⌬d) were measured with a dedicated image processing system (IÔ version 3.1, IÔDP), while pulse blood pressure (⌬P) was measured. Diameter compliance (Cd) and distensibility coefficient (DC) were calculated as Cdϭ2⌬d/⌬P and DCϭ2⌬d/⌬P/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 (27.77Ϯ1.11, 27.38Ϯ1.08, 27.38Ϯ1.09ϫ10 Ϫ3 mm ⅐ kPa Ϫ1 ) than upstream (103.3Ϯ36.7ϫ10

Response:

“…Additionally, the authors observed a significant decrease in the distensibility coefficient of the stented region. 1 These are remarkable findings and are in accordance with others, in which the mismatch observed between the mechanical properties of the prosthetic graft and that of the adjacent native artery is conducive to the development of distal anastomotic intimal hyperplasia. 2 However, the study of Vernhet and coworkers did not reflect wall mechanics of stented carotid arteries as is suggested in the title.…”

Grading Carotid Intrastent Restenosis

“…In particular, the compliance mismatch between the native carotid artery and the stented segment, 23 the positive arterial remodelling (stent expansion), 24,25 and the enhanced stiffness of the stent-arterial wall complex 16 can induce alterations in compliance and in carotid hemodynamics and modifications of Peterson's elastic modulus of the stented vessel. 16 Moreover, changes in wall shear stress can bring endothelial dysfunction ultimately leading to intimal hyperplasia and restenosis 26 -28 (negative arterial remodelling).…”

Vascular Compliance Changes of the Coronary Vessel Wall After Bioresorbable Vascular Scaffold Implantation in the Treated and Adjacent Segments

“…34 Similar findings have been demonstrated in human carotid arteries after stenting. 35 It has also been shown that ring vortices with in-flow stagnation points and rapid variations of wall shear stress can form at the edges of the prosthesis. 3,26,36 All of these findings, in particular the increase in upstream compliance, have been related to the observation that late plaque rupture after stenting in human coronary arteries is more likely to occur at the stent inflow compared to elsewhere.…”

“…The lack of a control group testing a metallic stent is another limitation to fully interpreting the present findings; other investigators have, however, previously studied the phenomenon of mismatch compliance in vessel scaffolded with metal. 34, 35 …”