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Schiavone et al. Modelling of metallic and polymeric stents

Figure 4: Stress-stretch curves for the three artery layers: Holzapfel-Gasser-Ogden model vs. experimental data [25]
Mises stress in the Xience and Elixir stents relaxed to and localized rupture for plaque as evidenced in
706 MPa and 50 MPa, respectively [Figure 7B]. These numerous studies. [28,29] In our case, plaque rupture is
are also the residual stresses generated in the stent likely to happen towards the ends of plaque region, a
after crimping. And the diameter of both stents settled condition that can lead to heart attack (coronary artery)
at about 1.5 mm. or stroke (carotid artery). In addition, there could be

Stent expansion
Pressure-diameter plots in Figure 8 showed that Elixir
stent experienced a lower rate of expansion than
Xience stent. Both stents developed a saturation state
in expansion with the increasing pressure, but Elixir
stent reached the saturation earlier. At the maximum
pressure, the stent outer diameter was computed
as 2.66 mm and 2.61 mm for the Xience and Elixir
stents, respectively. The recoiling effect was 11% for
the Xience stent [Figure 8B], which is significantly
lower than that for the Elixir stent (20%; Figure 8B).
Consequently, a larger final diameter was achieved Figure 5: Illustration of assembly used in crimping simulation for
for the Xience stent (2.40 mm) when compared to the Elixir stent
Elixir stent (2.10 mm only). Consistently, the Xience
stent also showed considerably less dogboning effect
(24%) than the Elixir stent (45%).

High levels of stresses were developed in both stents
following their deployment in the artery [Figure 9].
Similar to the crimping process, the maximum von
Mises stresses were found in the U-bend districts, with
a value of 935 MPa for the Xience and 95 MPa for
the Elixir stent. In the artery, the peak stresses were
generally found on the plaque, especially towards
the ends of the stenosis. This was caused by the
dogboning effect of the implanted stent. There is Figure 6: Deformation of Elixir stent and balloon (A) before, (B)
a direct connection between stress concentration during and (C) at the end of the crimping process
16 Vessel Plus ¦ Volume 1 ¦ March 31, 2017