Biomedical Engineering Reference
In-Depth Information
Fig. 7 a
Normalized stent external radius along the axial coordinate of the stent for the three
models (H, P1, P2).
b
Post-implantation configuration of the stent in model P2 where the distorted
longitudinal profile is shown
on the AV were lower; conversely, in both the pathological models (P1 and P2)
the interaction forces were lower on the LVOT and increased on the AV, reaching
higher values in model P2 were wider calcifications were present. The contact forces
computed on the LVOT were lower than those reported by Wang and collaborators
[
14
], who found values of 25 N: this difference can be justified by the more proximal
position of the stent simulated by Wang. The biomechanical interaction between the
stent and the anatomical structures is an important aspect with respect to the critical
issue of the impairment of the cardiac tissue, thus explaining the relevance of these
results.
In Fig.
8
a the TAV leaflet model after the positioning simulation in model P2
is depicted and TAV dynamics at the early systole and during diastole are shown
(Fig.
8
b, c).
All the three models reported physiological AOA values with systolic peak values
of 3.1, 3.1 and 2.7 cm
2
in model H, P1 and P2 respectively.
Moreover, those values were in agreement with in vivo measurements obtained with
Doppler echocardiography [
26
]. It is interesting to note that in model P2 AOA was
13% lower than in model P1, suggesting another potential implication of the dis-
tribution of AV calcifications on TAV performances. Negligible differences were
observed in terms of mechanical stresses and strains on the TAV leaflets of the three
models, where the average value of the first principal stress was 148, 145, 150kPa
in model H, P1 and P2, respectively. These values are lower than those found by
Auricchio and colleagues [
15
], but this difference can be explained by the different
constitutive models applied to the TAV leaflets: while in the present study a non linear
hyperelastic mechanical behaviour was used, in their work Auricchio and co-authors
approximated bovine pericardium as a linear elastic material.
