Biomedical Engineering Reference
In-Depth Information
stent configuration was observed in model P2 where a lower distal orifice area was
reached. This result suggests that calcifications located close to the leaflet commis-
sures could potentially affect the performances of TAV, since in the real scenarios
TAV is often implanted in AVs with dense and thick calcifications [
28
], were critical
degrees of distortion could be expected.
Moreover, a different distribution of the contact forces between the stent and the
AR was observed in the three models: greater interaction with the stenotic AV was
found in the pathological models (P1 and P2). The interaction between the stent
and the surrounding tissues is a crucial aspect to take into account when evaluating
the possible damages induced on the cardiac structures [
29
]. From this point of
view, in the light of the present results, it can be speculated that the presence of the
calcifications on the AV has the effect of protecting the LVOT, where the stent radial
forces could damage the left bundle brunch, causing heart block events [
30
].
In conclusion, TAV simulations throughout the cardiac cycle were performed al-
lowing to evaluate the dynamics of TAV following implantation: results showed that
in all the three models a physiological behaviour was recovered. Nevertheless, some
differences were observed in terms of AOA between the pathological models, sug-
gesting a possible correlation between lower AOA and commissural calcifications.
5 Limitations and Future Perspectives
The present work demonstrated the potential of computational models to investigate
TAV implantation outcomes: the results showed how the influence of the calcifi-
cations of the native AV may affect the configuration of the implanted device and
consequently the global outcomes of the procedure. The findings give insights into
the interaction between TAV device and the stenotic AV and the AR, but further
improvements and studies are still needed to overcome some limitations.
First of all, the balloon for stent expansion was not modeled in order to reduce the
complexity of the analysis and its computational cost: although previous computa-
tional studies on percutaneous approaches simulated the deployment of the stent by
directly applying a pressure load on its inner surface [
11
], some authors revealed that
this strategy leads to different results when simulating coronary stent deployment
[
31
]. In the future, further efforts will be made in order to introduce the expanding
balloon model and to assess how it can affect the results of the performed analyses.
A second limitation is related to the AR models: despite the paradigmatic model
proposed by Sturla [
16
] has been obtained from in vivo data, it is based on the
hypothesis that the shape of the aortic annulus is circular. Many clinical studies
revealed that the eccentricity of the aortic annulus (that is frequent both in healthy
and pathological AR anatomies) has a great influence on the outcomes of TAV,
mainly on TAV insufficiency [
32
]. The application of the developed computational
models to different and more realistic AR models could significantly improve the
trustworthiness of the results and will be pursued in the next future.
