PSI - Issue 10

I.D. Gavardinas et al. / Procedia Structural Integrity 10 (2018) 18–24 I.D. Gavardinas and A.E. Giannakopoulos / Structural Integrity Procedia 00 (2018) 000 – 000

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Nomenclature W

strain energy density first strain invariant principal stretches

I 1 λ i E R θ b h a P ν

Poisson’s ratio

Young’s modulus of elasticity radius of spherical tip indenter

half apical angle of the cone body indenter

indentation transition radius

indentation depth

indentation contact radius indentation applied vertical load

t

specimen thickness

H M

material hardness number

The deposit causing artery occlusion is called atherosclerotic or atheromatous plaque. Plaque hardens over time and narrows the lumen of arteries. It consists of fat, cholesterol, calcium, and other substances found in the blood. Moderate and severe (50%-99%) carotid artery stenosis affects approximately 10% of the general population by the 8 th decade of their life and causes about 10% of all strokes, as mentioned by Abbott et al. (2007). Carotid endarter ectomy (CEA) is one of the treatments currently available. Currently, the three principal approaches to CEA are: i) primary arteriotomy closure, ii) patch angioplasty and iii) eversion CEA (eCEA). Patch angioplasty and eCEA have been more popular among vascular surgeons, in contrast to primary arteriotomy closure, because of reportedly reducing the incidence of restenosis and including theoretical technical advantages, e.g. as per Ren et al. (2013). A schematic of CEA is illustrated in Fig.1.

Fig. 1. Schematic of human carotid endarterectomy and patch angioplasty.

Carotid patch angioplasty is a well-accepted technique among vascular surgeons and entails a longitudinal arterio tomy which extends beyond the plaque, both proximally and distally, see for example Awad and Little (1989) and the North American Symptomatic Carotid Endarterectomy Trial (1991). This is typically followed by the use of a patch angioplasty closure technique. Closure of the arteriotomy with a patch minimizes the effect of neointimal hyperplasia and scarring, maintaining the arterial lumen diameter after the procedure. A broad variety of materials, each bearing its own advantages and disadvantages, is available, according to Muto et al. (2009). The objective of the study is to provide a methodology for the mechanical characterization of tissue patches used in vascular surgery. Under this viewpoint, an indentation approach is developed. The material mostly used for this case is bovine pericardium, the tough tissue sac that surrounds the heart of a cow. Bovine pericardial patches possess several advantages compared with other types of patches, including superior biocompatibility, easy handling, less