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Qiu et al. Vessel Plus 2018;2:12 I http://dx.doi.org/10.20517/2574-1209.2018.13 Page 11 of 15

A

B

C

D

E

Figure 9. Contour plot of the maximum principal stress on the media layer at a degradation time of 0 day (A), 189 days (B), 365 days (C),
659 days (D) and 729 days (E) [41]

of stress for the whole scaffold-plaque-artery system. This work offered valuable insights into interactive
behaviour between a bioresorbable stent and diseased artery during a 2-year period of in vitro degradation,
which is helpful for developing new-generation BRSs for treating artery stenosis.

The work of Qiu et al. highlighted that for percutaneous coronary intervention, stent deployment causes
[41]
severe stresses to the artery, which will induce negative influence such as damage to arterial tissue. Thus, it
is of importance to assess the stress state produced in the artery-plaque system during stent implantation
process. A desirable process of stent implantation requires an outcome of expansion which is enough to relieve
vessel obstruction and also causes least damage to the arterial walls , as unsuccessful deployment may trigger
[42]
ISR. Here, unsuccessful deployment includes injury and excessive stretch of arterial walls, under-expansion of
stent and structural failure of struts. A strong correlation between severe wall stresses and high restenosis rate
has been confirmed by literature . Clearly, it is also necessary to assess the safety and efficacy of polymeric
[43]
stents during degradation, especially stent-artery interaction. The work of Qiu et al. is the first attempt to
[41]
model the mechanical interaction of BRS with stenotic artery over the full process of stent degradation.
A general reduction of stresses was shown for the plaque and vessel layers over stent degradation, which can
be beneficial for the natural healing of stented artery.

So far, computational work has focused on the development and validation of material constitutive models
that can predict the mechanical behaviour of degradable polymer or implant [44,45] . There is not a model
available yet to model the degradation process as well as property changes, especially to predict both
biodegradable implant mechanics and its interaction with blood vessel. For instance, finite-element models
were used to predict the recoil and collapse behaviour of polymer stent design by considering the elastic
and/or inelastic behaviour of the polymer [46,47] , but neglecting any changes of material properties that occur