Carotid Geometry as a Predictor of In-Stent Neointimal Hyperplasia　― A Computational Fluid Dynamics Study ―

Abstract

Background: Carotid angioplasty and stenting (CAS) is emerging as an alternative treatment for carotid stenosis, but neointimal hyperplasia (NIH) remains a drawback of this treatment strategy. This study aimed to evaluate the effect of variations of carotid bifurcation geometry on local hemodynamics and NIH. Methods and Results: Hemodynamic and geometric effects on NIH were compared between 2 groups, by performing computational fluid dynamics (CFD) simulations both on synthetic models and patient-specific models. In the idealized models, multiple regression analysis revealed a significant negative relationship between internal carotid artery (ICA) angle and the local hemodynamics. In the patient-derived models, which were reconstructed from digital subtraction angiography (DSA) of 25 patients with bilateral CAS, a low time-average wall shear stress (TAWSS) and a high oscillatory shear index (OSI) were often found at the location of NIH. Larger difference values of the OSI percentage area (10.56±20.798% vs. −5.87±18.259%, P=0.048) and ECA/CCA diameter ratio (5.64±12.751% vs. −3.59±8.697%, P=0.047) were detected in the NIH-asymmetric group than in the NIH-symmetric group. Conclusions: Changes in carotid bifurcation geometry can make apparent differences in hemodynamic distribution and lead to bilateral NIH asymmetry. It may therefore be reasonable to consider certain geometric variations as potential local risk factors for NIH.

Hemodynamic and Geometric Risk Factors for In-Stent Restenosis in Patients with Intracranial Atherosclerotic Stenosis

“…From the hemodynamic point of view, the increased tortuosity might induce disturbances of local hemodynamic environment characterized by low wall shear stress that have been demonstrated to associate with the initiation and progression of atherosclerosis [44][45][46]. For coronary [23,47,48] and carotid stents [11,21,24,42,49], geometry of the blood vessels, especially tortuosity, had been suggested to attribute to not only atherogenesis but also instent NIH [1]. The current study showed an ISR rate of 17.95% in severe ICAS patients and also revealed the important role of vessel tortuosity.…”

“…Stent implantation induced vessel straightening, significantly decreased vessel curvature, remodeled the vessel, and changed hemodynamic patterns [ 10 , 29 ]. In coronary and carotid atherosclerosis, stenting showed its ability to change the vessel geometry and the local hemodynamics [ 23 , 24 , 30 ]. In intracranial arteries, previous studies have described the effect of stent-induced straightening of vessels [ 31 ] and vascular angel remodeling [ 32 – 34 ] during stent-assisted coiling of intracranial aneurysms.…”

“…With a 6.81% to 31.18% occurrence rate [11][12][13][14][15][16][17][18][19], the in-stent restenosis (ISR) in ICAS might be affected by features of the lesion and characteristics of the stent, which was controversial and not definite [11,15,16,20]. In carotid and coronary arteries, local hemodynamic changes caused by geometric variations had been suggested to govern the risk and mechanism of ISR [21][22][23][24]. However, the hemodynamic and geometric features prone to adverse events, especially ISR in ICAS, had never been studied before.…”

“…Oxidative Medicine and Cellular Longevity stenting [23,47] and carotid stenting [24,49]. For intracranial arteries, elevated focal WSS at ICAS lesions significantly increased the risk of recurrent stroke despite optimal medical treatment [55].…”

<p>Influence of Stent Flexibility on Artery Wall Stress and Wall Shear Stress in Bifurcation Lesions</p>

“…Third, the CFD simulation was performed as a steady flow and WSS was used as a hemodynamic parameter, but there are studies reporting that neointimal hyperplasia is not associated with WSS 34 or is associated with oscillatory shear index. 35,36 However, in a systematic review, 37 nine of eleven reports visually comparing maps of hemodynamic parameters and hyperplasia supported the low WSS (steady flow) theory, suggesting that CFD simulation was appropriate. Lastly, any effects on the side branch geometrically changed by straightening the mother artery with stenting in bifurcations were not investigated in this study.…”