Biomedical Engineering Reference
In-Depth Information
the implant that need design changes. Preformed scaffolds were determined to have
significantly lower stresses in comparison to flat ones. The method of tensile trian-
gles suggests shape changes for notable stress reduction. Furthermore, new scaffold
shapes were developed and simulated. Two of them are recommended for further ex-
aminations through in vitro and in vivo tests. A completely new alternative scaffold
concept is also proposed.
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Keywords
Numerical simulation
FEM
Tensile triangles
LA63
Left ventricle
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Heart attack
Tissue substitution
Supporting structure
1 Introduction
Despite the fact that the incidence of severe coronary artery diseases is decreasing
in industrial nations, they are still one of the leading causes of death. Approximately
280,000 heart attacks occur every single year in Germany alone. A heart attack does
not necessarily lead to death, but it will likely cause long term negative effects on the
heart. Stenosed arteries can result in death of the myocardial tissue they supply. This
necrotized tissue will be replaced by scar tissue. A loss of myocardial tissue means
a loss of contractile tissue, resulting in reduced heart performance, which eventually
results in congestive heart failure. Congestive heart failure often leads to a secondary
end organ failure such as liver insufficiency, renal failure, and severe edema. Surgical
treatment is required to restore sufficient hemodynamic performance of the heart.
Therefore, current available techniques strive to restore the physiological shape and
volume capacity of the ventricle [
1
-
3
]. However, reconstruction of large lesioned
areas of the ventricle still results in a less than optimal ejection fraction [
4
,
5
].
Thus, the ideal myocardial reconstructive therapy would utilize regenerative tissue
prostheses that could restore full contractile ability of the lesioned cardiac tissue.
One research direction is to reduce the scar tissue size by injecting cardiac stem cells
and bone marrow mesenchymal stem cells [
6
]. Even though a slight boost of the
heart's performance can be detected, this cell based enhancement most likely will
remain a secondary treatment. However, replacement of the scar tissue with solid
innovative and regenerative grafts promises to provide a more effective solution that
will be available sooner [
7
].
The use of artificial grafts lacks the problems of non-contractility and susceptibil-
ity to infections. Biological grafts appear to be a preferable solution. A few tissues
showed a good potential, such as the urinary bladder [
8
], pericardium [
9
], skele-
tal muscle [
10
] or myocardium [
11
]. Tudorache et al. had success with autologous
small intestine segments without mucosa [
12
]. After substitution of a limited area
of right ventricular tissue with vascularized autologous small intestine, repopula-
tion of these decellularised grafts with cardiomyocytes was shown in animal studies.
This gave evidence of myocardial remodeling processes [
12
]. In a similar approach,
Badylak et al. detected cardiomyocytes in urinary bladder matrixes used as a recon-
structive myocardial patch [
13
]. However, these studies were done for use on the
