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09, 1, 2-7
Published Online June 2009 in SciRes. http://www.scirp.org/journal/health
Finite element analysis of a percutaneous aortic valve
Gideon Praveen Kumar1*, Lazar Mathew1
1School of Biotechnology, Chemical & Biomedical Engineering, VIT University, Vellore, India.
*Corresponding author: Tel: +919894292348, Email: email@example.com
Received 15 April 2009; revised 28 April 2009; accepted 30 April 2009.
Aim: This paper discusses the design and Finite
Element Analysis (FEA) of a Percutaneous Aor-
tic Valve Stent. The aim of this study was to
model a percutaneous aortic valve stent and
subject it to finite element analysis. The design
process was carried out to meet the functional
and surgical requirements. Methods and Results:
Analysis was done with different materials with
loads ranging from 50 kgf/mm² to 73 kgf/mm².
These forces were selected because these val-
ues are far greater than the normal human blood
pressure which ranges from 10kPa to 16kPa. It
was also to understand the mechanical behavior
of different stent materials under such high
pressures. A stent model was generated and its
physical, mechanical and behavioral properties
were studied. Finite element analysis and
simulation of the model enhanced the designer
to optimize the geometry suitable for perform-
ance during and after implantation. The design
objective for the stent is to have long term du-
rability, low thrombogenicity, resistance to mi-
gration and paravalvular leak. Conclusion: The
analysis performed in this paper may aid in
understanding the stent’s tolerable pressures
ranges in comparison with the physiological
pressures exerted by the heart and cardiac
blood flow during abnormal cardiovascular
Keywor ds: stent; finite element analysis; blood flow;
aortic valve stenosis; port size
The treatment of stenotic valvular diseases consists of
routine procedures in interventional cardiology. To date,
surgical approach is the only option to replace diseased
cardiac valves. Recently stenosis of mitral, aortic or
pulmonary valves is treated by percutaneous valve re-
placement and has opened new perspectives on tran-
scatheter placement of cardiac valves. Aortic valve re-
placement was generally accomplished by using open
heart valve surgery, whereas endovascular procedures
for valve replacement may provide an alternative to car-
diac surgery. Such endovascular procedures require
minimal invasion of the human body, and there is con-
siderable reduction and, in some instances, even elimi-
nation of general anesthesia and intensive care unit stay.
In Percutaneous replacement, the diseased valve is re-
placed by a biological valve (porcine) via a catheter
driven through the femoral artery to the aortic position.
The valve is mounted on the stent, which is crimped into
the catheter and is guided to the parent position of the
aorta and deployed. Thus it pushes the diseased valve
aside to position itself. Post operative complications are
very minimal and the patient can get discharged within
days after the procedure. The stents that are used give
adequate support and stability to the valve and also pre-
vent the valve from getting migrated either in the ante
grade or retro grade direction. These stents also help in
preventing paravalvular leaks. So modeling of an ideal
stent design was done and the subjected to finite element
analysis with loads much greater than the expected blood
pressures even during adverse conditions.
2. STENT DESIGN
The design of the stent depends on many unique pa-
rameters, which include stent length, stent diameter,
number of struts, strut diameter and port angle. The de-
sign was an attempt to model a stent which would be an
ideal partner to the tissue valve that replaces the diseased
one . Solid 3D models (Figure 1) were created using
repeating unit geometry of each design using Solidworks
Modeling Software. The unit consisted of 8 lips with two
non crossing struts making a circular diameter of 16mm.
Two struts join to form a lip creating a diamond shaped
port. The port angle is 45 degrees and the distance be-
tween the two struts at the center is 6.25mm, with 8 lips
joining at the center to form the circular stent. The stent
design has a constant strut thickness of 0.5 mm and a
height of 18 mm.
G. P. Kumar et al. / HEALTH 1 (2009) 2-7 3
SciRes Copyright © 2009 HEALTH
STENT DIA 16mm
WIRE DIA 0.5MM
Figure 1. Model geometry of the stent.
3. MATERIAL MODEL
Stainless steel 316L was the material that was used for
analysis as it has a high strength to weight ratio and
excellent biocompatibility when used in humans .
The material properties ideal for analysis are tabulated
in Table 1. The material properties were assumed to
be bilinear, elasto-plastic model with isotropic hard-
ening. All materials were also assumed to follow
Hooke’s Law, and frictional forces neglected due to
the magnitude of this force being much less than the
applied force. The implant was assumed to transmit
all absorbed energy to the surrounding environment.
The amount of energy transfer to and from the implant
is zero. The effects due to body heat were also ne-
glected to optimize effects.
4. FINITE ELEMENT ANALYSIS
Finite element analysis with 316L stainless steel was
performed using visual Nastran, a FEA package. Visual
Nastran, a powerful general purpose finite element
analysis solution for small to complex assemblies, was
used for the entire analysis . Stresses ranging between
50 kgf/mm2 and 73 kgf/mm2 were loaded on to the stent
in the transverse direction. These pressures were selected
as they are far greater than that of the normal human
blood pressure which ranges from 10kPa to 16kPa. Ini-
Table 1. List of properties used for analysis.
Material Name 316 L Stainless Steel
Young’s modulus (E) 201 GPa
Poisson’s ratio 0.3
Yield stress 170 MPa
tially the loads were given as a centripetal pressure
around the circular stent in the transverse direction.
The reason for choosing this direction is because of
the fact that the pulsatile contraction of the aorta is in
the same direction. The model was constrained to-
wards one end of the stent. Owing to the direction of
load application and the stent being constrained to-
wards one end, the stent was able to crimp and
re-expand without stent fracture even when the load
applied was far greater than that of the normal physio-
logical pressures. The model was then constrained
towards the lower end of the stent. The upper portion
of the stent is somewhat free and is along the longitu-
dinal axis of the ascending aorta and the lower portion
bears the aortic valve and is fixed to the aortic annulus.
Similar pressures were applied in the upward direction
to understand the mechanical and physical behavior of
the stent. In the same position, pressures were applied
in the downward direction to understand the behavior
4 G. P. Kumar et al. / HEALTH 1 (2009) 2-7
SciRes Copyright © 2009 HEALTH
of the stent.
5. RESULTS AND DISCUSSION
The stent design was subjected to finite element analysis
and its mechanical behavior was studied. The load for all
the analyses ranged from 50 kgf/mm2 to 73 kgf/mm2.
Table 2. Displacement for load in the crimped stent model.
Force (kgforce/mm2) Displacement
Figure 2. Displaced shape of the stent.
Figure 3. Equivalent stress contours during crimping.
G. P. Kumar et al. / HEALTH 1 (2009) 2-7 5
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A contour plot of the equivalent von Mises stress
shows the location of the maximum stress is repre-
sented in Figures 3, 5 and 6. Correlative displace-
ments of the stent during various positions are repre-
sented in Figures 2, 4 and 7. The maximum stresses
applied to the stent, and its displacements in different
positions were compared. It can be noted that the stent
was able to withstand loads that were far greater than
the stress that may be exerted by the heart and blood
even during pathological conditions. Table 2 gives the
displacement for the given load on the stent model
which is fully crimped and Table 3 gives the dis-
placement for the given load on the stent model which
is fixed at the bottom.
Figure 4. Displaced shape with the stent constrained towards the lower end.
Figure 5. Equivalent stress contours with the stent constrained towards the lower end.
6 G. P. Kumar et al. / HEALTH 1 (2009) 2-7
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Figure 6. Equivalent stress contours when a force in the downward direction is applied.
Figure 7. Displaced shape of a single lip.
G. P. Kumar et al. / HEALTH 1 (2009) 2-7 7
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Table 3. Displacement for load in the stent model fixed at the
The stent design modeled and subjected to Finite ele-
ment analysis proved to be having ideal behavior for
percutaneous replacement by withstanding loads that are
well above the required level. The displacement was
good enough to prove mild contractions during cardiac
systole and diastole.
 C. M. Allison, D. Crossman, and J. Gunn, (2004) The
influence of physical stent parameters upon restenosis,
 K. W. Lau, A. Johan, U. Sigwart, and J. S. Hung, (2004)
A stent is not just a stent: stent construction and design
do matter in its clinical performance, Singapore Medical
 D. R. McClean and N. Eigler, (2002) Stent design: Im-
plications for restenosis, MedReviews, LLC.
 (2004) Stent design properties and deployment ratio in-
fluence indexes of wall shear stress: A three-dimensional
computational fluid dynamics investigation within a
normal artery, J Appl Physiol, 97, 424-430.
 (2000) An overview of superelastic stent design, Min
Invas Ther & Allied Technol, 9(3/4), 235-246.
 (2007) Engineering aspects of stents design and their
translation into clinical practice, Ann Ist super sAnItà,
 (2005) To stent or not to stent aortic dissection:good
news for a chosen few, but who? European Heart Journal,
26, 431-432, doi:10.1093/eurheartj/ehi119.
 J. Q. Zhou, A. F. Corno, C. H. Huber, P. Tozzi, and L. K.
von Segesser, (2003) Self-expandable valved stent of
large size: off-bypass implantation in pulmonary position,
Eur. J. Cardiothorac. Surg., 24(2), 212-216.
. P. Kumar and L. Mathew, (2009) New stent design for
percutaneous aortic valve replacement, International
Journal of Cardiovascular Revascularization Medicine,