1. The role of biomechanics in advanced
atherosclerosis:
data of mice and men
Frank Gijsen
Biomechanics lab
Department of Cardiology
ErasmusMC Rotterdam
2. Image based biomechanical modelling of the cardiovascular
system to investigate the relationship between
biomechanical parameters and the development and
progression of atherosclerosis
Biomechanics lab
4. D = diameter of the tube
= viscosity of fluid
V = mean velocity
shear stress: SS = 8V/D
Shear stress (in a straight tube)
5. Shear stress (in arteries)
Steinman et al. 1999
Poiseuille can be useful, but:
arteries are not straight tubes
- bend
- stenosis
- bifurcations
flow in arteries is not steady
blood is not a Newtonian fluid
8. Atherosclerosis
Classification by Stary:
Circulation 1992, 85(1): A definition of the
intima of human arteries and of its
atherosclerosis-prone regions
Circulation 1994, 89(5): A definition of initial,
fatty streak, and intermediate lesions of
atherosclerosis
Circulation 1995, 92(5): A definition of
advanced types of atherosclerotic lesions and a
histological classification of atherosclerosis.
23. IVUS contours in 3D
c. d.
Van der Giessen et al., International Journal of Cardiovascular Imaging, 2010
van der Giessen et al., International Journal of Cardiovascular Imaging, 2009
Step 1: fusion of MSCT and IVUS
24. Step 2: add side branch lumen
data from MSCT only
Gijsen et al., Journal of Biomechanics 2014
29. ANGUS
3D wall thickness
ANGUS + CFD
3D shear stress
ANGUS + palpo
3D strain data
high
low
At index and at 6
months follow up
30. : wtnorm = 0.2
ANGUS data normalized wall
thickness (wtnorm)
flow
U
U: upstream
S S
S: shoulders
T
T: throat
D
D: downstream
Plaque definition
31. strain
31 plaques in 13
coronary arteries
were analyzed.
U
D
T
S S
U
D
T
S S
shear stress
average
normalized shear
stress
#
#
0
1
2
3
0
.
5
0
.
2
low medium high
shear stress
#
#
#
strain[%]
0.75
0.50
0.25
32. average normalized shear stress
U T S D
averageshearstress[Pa]
#
#
U T S D
0
1
2
3
0.5
0.25
averagestrain[%]
34. Shear stress vs strain
low medium high
shear stress
#
#
#
strain[%]
0.75
0.50
0.25
Gijsen et al., American journal of Physiology, 2008
35. Shear stress is low downstream of a plaque, but the complex 3D
shape of human coronary arteries does not allow to predict shear
stress distribution in other plaque regions.
Lower strain values can be observed downstream of a plaque, which
agrees with the observation that at those locations more SMC are
present. Other plaque locations show a heterogenuous strain
distribution.
The plaque regions exposed to the highest shear stress reveal
increased strain values, indicating that shear stress might have an
impact on plaque composition in the more advanced phases of the
disease.
Discussion and conclusions (1)
39. Follow-up studies are difficult!
Changes in strain -and thus plaque composition- over a six month
period are small.
No significant changes in plaque composition can be found if we
look at different plaque regions.
However, those plaque regions exposed to highest shear stress
levels show an increase in strain, confirming our hypothesis that
high shear stress might be involved in destabilizing advanced
atherosclerotic plaques.
Discussion and conclusions (2)
48. Plaques ruptures is induced by blood pressure, and it occurs where the plaque is
weakest.
The weakest plaque locations can be found:
Mostly proximal of the minimal lumen area (confirms findings from literature)
Mostly at the shoulder region
Where shear stress was high
healthy plaque rupture
0.8
1
1.2
1.4
1.6
1.8
shearstressratio
p=0.055
p=0.028
p=0.047
Discussion and conclusions (3)
49. fusion of cap thickness and shear
stress to assess plaque vulnerability
in human coronary arteries
Jelle Schrauwen, Guillaume Zahnd
55. • A. van der Giessen
• H. Schuurbiers
• A. van der Steen
• J. Wentzel
• J.Schrauwen
• P. Serruys
• E. Regar
• G. Zahnd
• T. van Walsum
• W. Niessen
• F. van de Vosse (TU/e)
• U. Hoffmann (Harvard)
• H. Samady (Emory)
Acknowledgements
62. TransWSS and athero
In cell culture, TransWSS is associated with increased inflammation
Chong Wang et al., Arterioscler Thromb Vasc Biol., 2013
Flow
OldrabbitsYoungrabbits
* Yumnah Mohamied et al., Annals
of Biomed Eng., 2015
63. To investigate the role of TransWSS in the prediction
of plaque progression and composition in human
coronary arteries
Aim
MaxP < -25.05
Type: Collagen
#of RO Is : 5
MaxP > -25.05
Type: Collagen
#of RO Is : 26
Int < -28.65
#of RO Is : 31
Int < -14.8
Type: Collagen
#of RO Is : 5
Int > -14.8
Type: Collagen
#of RO Is : 5
F at MaxP < 21.045
#of RO Is : 10
F at MaxP > 21.045
Type: Collagen
#of RO Is : 17
MB F < -65.09
#of RO Is : 27
Int < -4.195
Type: Calcium
#of RO Is : 6
Int > -4.195
Type: Collagen
#of RO Is : 5
MB F > -65.09
#of RO Is : 11
F at MaxP < 30.03
#of RO Is : 38
MaxP < -16.095
Type: Collagen
#of RO Is : 6
F at MaxP < 34.275
Type: Necr otic
#of RO Is : 6
MB F < -66.66
Type: FibroLipidic
#of RO Is : 5
MB F > -66.65
Type: Collagen
#of RO Is : 5
MaxP < -12.145
#of RO Is : 10
MaxP > -12.145
Type: Fibro-Lipidic
#of RO Is : 5
F at MaxP > 34.275
#of RO Is : 15
MaxP < -9.915
#of RO Is : 21
F at MaxP < 35.5
Type: Collagen
#of RO Is : 8
F at MaxP > 35.5
Type: Collagen
#of RO Is : 9
MaxP > -9.915
#of RO Is : 17
MaxP > -16.095
#of RO Is : 38
F at MaxP > 30.03
#of RO Is : 44
Int > -28.65
#of RO Is : 82
MB F < -55.695
#of RO Is : 113
MinP <-17.915
Type: Collagen
#of RO Is : 5
MB F < -53.15
Type: Calcium
#of RO Is : 8
MB F > -53.15
Type: Calcium
#of RO Is : 20
MinP > -17.915
#of RO Is : 28
MB F >-55.695
#of RO Is : 33
146
#of RO Is :
TREE
ROOT
media
fibrous
fibrofatty
calcium
lipid core
70. • Different results than expected from previous experiments
• Interaction effect of TAWSS and CFI
• Low shear stress + low CFI plaque progression
• High shear stress + high CFI characteristics of vulnerability
Discussion and conclusions (4)
