incremental modulus E (kPa)

(1)

Centre for Centre for Centre for

Centre for Health Health Health Health Engineering Engineering Engineering Engineering CNRS UMR 5146

Prof. St Prof. St Prof. St

Prof. Sté é é éphane Avril phane Avril phane Avril phane Avril

What do we know about aortic arch arterial wall biomechanical

properties?

(2)

ESVB - 2011/05/13 - Prof Stéphane AVRIL

2

Introduction

Pathologies affecting the arch

Numerical modeling Design of vascular biomaterials

Questions?

Literature survey

Elastic properties Comparison with other locations

Failure properties Fracture properties Summary of data

Personal input

Method: Inflation tests Materials

Method: Digital image stereocorrelation

Results: characterization of rupture

Results: local stress strain curves

Results: stress at rupture Conclusions

Acknowledgements

(3)

3

The study includes the ascending thoracic aorta (A) and the descending thoracic aorta (C)

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(4)

4

Aneurisms including proximal or distal arch

Pathologies affecting the arch

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(5)

5

Dissection is a tear that develops in the intima of the aorta, the blood enters at the site of the tear, separates the layers of the aorta, and spreads the dissection

Pathologies affecting the arch

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(6)

6

Numerical modeling

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(7)

Shahcheraghi N, Dwyer HA. Unsteady and Three-Dimensional Simulation of Blood Flow in the Human Aortic Arch. J Biomech Eng 2002; 124(4):378-388.

Numerical modeling

(8)

8

Design of vascular biomaterials

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(9)

9

- To set up numerical models - To design appropriate devices

BIOMECHANICAL PROPERTIES OF THE ARTERIAL WALL MUST BE CHARACTERIZED

WHAT DO WE KNOW ABOUT THE AORTIC ARCH?

Questions?

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(10)

10

Literature survey

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(11)

11

DC h R R

R h p R

E /

/

/ =

∆ ∆

=

0 200 400 600 800 1000 1200

Isnard et al, 2001, normal

Muhs et al, 2006 and Lu et al,

2009

Lénàrd et al., 1999, < 35

Lénàrd et al., 1999, >35

Isnard et al, 2001, hypertensive

in c re m e n ta l m o d u lu s E ( k P a )

10% volume variation between diastole and systole

→ Windkessel effect

Elastic properties

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(12)

12

Haskett D, Johnson G, Zhou A, Utzinger U, van de Geest J. Microstructural and biomechanical alterations of the human aorta as a function of age and location. Biomech Model Mechanobiol 2010; 9:725–736.

Comparison with other locations

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(13)

13

longitudinal

circumferential

σ = F/S =1.7 MPa

Vorp DA, Schiro BJ, Ehrlich MP, Juvonen TS, Ergin MA, Griffith BP. Effect of aneurysm on the tensile strength and biomechanical behaviour of the ascending thoracic aorta. Ann Thorac Surg 2003; 75(4):1210-4.

Failure properties

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(14)

14

W < 10 mJ/cm ²

Sommer G, Gasser TC, Regitnig P, Auer M., Holzapfel G.A. Dissection properties of the human aortic media: an experimental study. ASME J Biomech Eng 2008; 130:021007.

Fracture properties

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(15)

15

Relatively Relatively Relatively Relatively good good good good knowledge knowledge knowledge knowledge of of of of average average average average properties properties properties properties ((((elasticity elasticity elasticity elasticity, fracture) , fracture) , fracture) , fracture)

Few data about Few data about Few data about Few data about hyperelastic hyperelastic hyperelastic hyperelastic models models models based models based based based on the on the on the on the local microstructure (

local microstructure ( local microstructure (

local microstructure (Holzapfel Holzapfel Holzapfel Holzapfel))))

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variations due to variations due to

variations due to curvature curvature curvature curvature and branches and branches and branches and branches

No No No No knowledge knowledge knowledge about how knowledge about how about how about how remodelling remodelling remodelling remodelling affects the affects the affects the affects the biomechanical

biomechanical biomechanical

biomechanical properties properties properties properties of the of the of the of the aortic aortic aortic aortic arch arch arch wall arch wall wall wall....

Need Need Need Need of of of of local local local mechanical local mechanical mechanical characterization mechanical characterization characterization characterization with with with with advanced

advanced advanced

advanced measurement measurement measurement techniques measurement techniques techniques techniques

Summary of data

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(16)

16

Personal input

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(17)

inflation device cylinder

pressure gage

simulates in vivo loading environments

(biaxial stress state due to internal pressure) can be generated

Method: Inflation tests

(18)

18

an excised cylindrical aneurismal aortic tissue

a square specimen removing loose connective tissue

finding an appropriate location to separate

specimen is mounted on the inflation test device

making a speckle pattern separated layers two layers are pulled each other to separate cut

adventitia media

media

adventitia

x y

diameter: 30mm

Materials

(19)

19

camera

Instron machine protector

Undeformed Deformed

x y

tracks the gray value pattern

in each subset during deformation Method: Digital image

stereocorrelation

(20)

20

the failure of aneurismal aortic tissue is caused principally by axial stress σσσσ yy

A

y B

ε

Results: characterization of rupture

x

y

(21)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

0 0.2 0.4 0.6 0.8 1 1.2

0 0.1 0.2 0.3 0.4

strain

stress (MPa)

I

II

I

II

I II

III IV

I II

III IV

Media Adventitia

circumferential direction ( σσσσ

xx

) axial direction ( σσσσ

yy

)

Results: local stress strain

curves

(22)

22

0 200 400 600 800 1000 1200

media 1 media 2 media 3 media 4 adventitia 1 adventitia 2

u lt im a te s tr e s s ( k P a )

Reminder - Strength of healthy aortic wall: 1700 kPa

Vorp DA, Schiro BJ, Ehrlich MP, Juvonen TS, Ergin MA, Griffith BP. Effect of aneurysm on the tensile strength and biomechanical behaviour of the ascending thoracic aorta. Ann Thorac Surg 2003; 75(4):1210-4.

J Kim, S. Avril, P Badel, A Duprey, JP Favre. Characterization of failure in human aortic tissue using digital image correlation. Computer Methods in Biomechanics and Biomedical Engineering, 2011, in press

Results: stress at rupture

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(23)

23

To To To To be be be be continued continued continued… continued … … …

To To To To be be be be correlated correlated correlated with correlated with with with the the the the in vivo in vivo in vivo in vivo biomechanical biomechanical biomechanical biomechanical behaviour

behaviour behaviour behaviour… … … …

Towards Towards Towards Towards statistical statistical statistical statistical inter inter inter inter- - - -individual individual individual individual comparison comparison comparison comparison ((((age age age age effect effect effect, effect , , , disease disease disease disease, , , , treatment treatment treatment treatment))))

To To To To be be be be implemented implemented implemented in implemented in in in numerical numerical numerical models numerical models models models for for for for fundamental

fundamental fundamental

fundamental investigation of investigation of investigation of aortic investigation of aortic aortic arch aortic arch arch arch biomechanical

biomechanical biomechanical

biomechanical behaviour behaviour behaviour behaviour

Conclusions

Introduction

Questions?

Literature survey

Personal input

Acknowledgements

(24)

24

incremental modulus E (kPa)

Centre for Centre for Centre for

Centre for Health Health Health Health Engineering Engineering Engineering Engineering CNRS UMR 5146

Prof. St Prof. St Prof. St

Prof. Sté é é éphane Avril phane Avril phane Avril phane Avril

What do we know about aortic arch arterial wall biomechanical

properties?

Introduction

Introduction

Literature survey

Personal input

The study includes the ascending thoracic aorta (A) and the descending thoracic aorta (C)

Introduction

Introduction

Literature survey

Personal input

Aneurisms including proximal or distal arch

Pathologies affecting the arch

Introduction

Literature survey

Personal input

Dissection is a tear that develops in the intima of the aorta, the blood enters at the site of the tear, separates the layers of the aorta, and spreads the dissection

Pathologies affecting the arch

Introduction

Literature survey

Personal input

Numerical modeling

Introduction

Literature survey

Personal input

Numerical modeling

Design of vascular biomaterials

Introduction

Literature survey

Personal input

- To set up numerical models - To design appropriate devices

BIOMECHANICAL PROPERTIES OF THE ARTERIAL WALL MUST BE CHARACTERIZED

WHAT DO WE KNOW ABOUT THE AORTIC ARCH?

Questions?

Introduction

Literature survey

Personal input

Literature survey

Introduction

Literature survey

Personal input

DC h R R

R h p R

E /

/

/ =

∆ ∆

=

0 200 400 600 800 1000 1200

Isnard et al, 2001, normal

Muhs et al, 2006 and Lu et al,

2009

Lénàrd et al., 1999, < 35

Lénàrd et al., 1999, >35

Isnard et al, 2001, hypertensive

in c re m e n ta l m o d u lu s E ( k P a )

10% volume variation between diastole and systole

→ Windkessel effect

Elastic properties

Introduction

Literature survey

Personal input

Comparison with other locations

Introduction

Literature survey

Personal input

longitudinal

circumferential

σ = F/S =1.7 MPa

Failure properties

Introduction

Literature survey

Personal input

W < 10 mJ/cm 2

Fracture properties

W < 10 mJ/cm ²