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In cases of severe carotid artery stenosis (CAS), carotid endarterectomy (CEA) is performed to recover lumen patency and alleviate stroke risk. Under current guidelines, the decision to surgically intervene relies primarily on the percent loss of native arterial lumen diameter within the stenotic region (i.e. the degree of stenosis). An underlying premise is that the degree of stenosis modulates flow-induced wall shear stress elevations at the lesion site, and thus indicates plaque rupture potential and stroke risk. Here, we conduct a retrospective study on pre-CEA computed tomography angiography (CTA) images from 50 patients with severe internal CAS (>60% stenosis) to better understand the influence of plaque and local vessel geometry on local hemodynamics, with geometrical descriptors that extend beyond the degree of stenosis. We first processed CTA images to define a set of multipoint geometric metrics characterizing the stenosed region, and next performed computational fluid dynamics simulations to quantify local wall shear stress and associated hemodynamic metrics. Correlation and regression analyses were used to relate obtained geometric and hemodynamic metrics, with inclusion of patient sub-classification based on the degree of stenosis. Our results suggest that in the context of severe CAS, prediction of shear stress-based metrics can be enhanced by consideration of readily available, multipoint geometric metrics in addition to the degree of stenosis., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The prevalence of diverse animal models as surrogates for human vascular pathologies necessitate a comprehensive understanding of the differences that exist between species. Comparative passive mechanics are presented here for the common carotid arteries taken from bovine, porcine, ovine, leporine, murine-rat, and murine-mouse specimens. Data is generated using a scalable biaxial mechanical testing device following consistent circumferential (pressure-diameter) and axial (force-length) testing protocols. The structural mechanical response of carotids under equivalent loading, quantified by the deformed inner radius, deformed wall thickness, lumen area compliance and axial force, varies significantly among species but generally follows allometric scaling. Conversely, descriptors of the local mechanical response within the deformed arterial wall, including mean circumferential stress, mid-wall circumferential stretch, and mean axial stress, are relatively consistent across species. Unlike the larger animals studied, the diameter distensibility curves of murine specimens are non-monotonic and have a significantly higher value at 100 mmHg. Taken together, our results provide baseline structural and mechanical information for carotid arteries across a broad range of common animal models., Competing Interests: The authors have declared that no competing interests exist.

Mouse models of Marfan Syndrome (MFS) provide insight into the type and extent of vascular abnormalities manifested in this disease. Inclusion of the mgR mutation causes the otherwise normal extracellular matrix glycoprotein fibrillin-1 to be under-expressed at 15-25% of its normal level, a condition seen in MFS. Aortas in patients with MFS are generally less distensible and may experience dissecting aneurysms that lead to premature death, yet little is known about effects on other large arteries. In this study, common carotid arteries from mice heterozygous (R/+) and homozygous (R/R) for the mgR mutation were studied under biaxial loading and compared to results from wild-type controls (+/+). Carotids from +/+ and R/+ mice exhibited similar biomechanical behaviors whereas those from R/R mice were slightly stiffer in the circumferential direction while dramatically different in the axial direction. That is, R/R carotids were stiffer axially and had lower in vivo axial prestretches. Biaxial stress-stretch data were fit with a four-fiber family constitutive model. The fitted data yielded a lower value of an isotropic parameter for the R/R carotids, which reflects a compromised elastin-dominated amorphous matrix. Overall, it appeared that changes in axial mechanical properties afforded R/R carotids a means to compensate, at least early in maturity (9 weeks of age), for the loss of an important structural constituent as they attempted to maintain structural integrity in response to normal mean arterial pressures and thereby maintain mechanical homeostasis.