VISCOELASTIC AND INELASTIC PROPERTIES OF THE PORCINE CAROTID ARTERY. IMPLICATIONS IN ANIMAL

CARDIOVASCULAR DEVICE TRIALS

Estefanía Peña (1,2), Alberto García (1,2), Miguel Angel Martínez (1,2)

1 Aragón Institute of Engineering Research (I3A). Universidad de Zaragoza, Spain. 2 Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y

Nanomedicina (CIBER-BBN), Spain.

Introduction

The present study focusses on the determination,

comparison of the elastic, viscoelastic and inelastic

mechanical properties of the swine carotid artery

over very long stretches in both proximal and distal

regions. Special attention is paid to the histological

and mechanical variations of these properties

depending on the proximity to the heart.

The results can have clinical relevance, especially

in the research field of intravascular device design.

Before the final clinical trials on humans, research

in the vascular area is conducted on animal models,

being swine the most common due to the

similarities between their respective cardiovascular

systems as well as the fact that the swine size is

suitable for testing devices, in this case

endovascular carotid systems. The design of

devices usually involves numerical techniques, and

an important feature is the appropriate modelling of

the mechanical properties of the vessel.

Material and Methods

Nine female pigs of 3.5 ±0.45 months (mean ± SD)

old were used in this study. In order to determine

the mechanical properties, initial stretches in axial

and circumferential directions were estimated and

cyclic and relaxation test were developed.

Simple tension tests in longitudinal and

circumferential directions with different loading

and unloading cycles were applied. On the other

hand, uniaxial stress-relaxation tests were

conducted with six stress levels with three

preconditioning cycles that preceded the 30 min

relaxation phases corresponding to 20, 40, 60, 80,

120 and 240 [kPa], Figure 1.

Results

The experimental tests reveal a highly anisotropic,

non-linear viscoelastic response and local

dependence of the samples. Therefore, a

constitutive law that takes into account the

fundamental features, including non-linear

viscoelasticity, of the arterial tissue is proposed.

The present results are correlated with the purely

elastic response and the microstructural analysis of

the tissue by means of histological quantification,

(García et al. 2011).

Figure 1: Representative uniaxial stress-stretch of

swine carotid obtained.

Discussion

We have evaluated the influence of the

microstructure and its function in the mechanical

response of the swine carotid artery and also its

relevance in animal trials in the research field of

intravascular device design. The statistical analysis

evidenced significant changes depending on the

position of the sample, mainly in elastin and SMC

quantification. Thus, we can conclude that the

specific stent deployment location along the length

of the porcine carotid could affect the final results

in animal trial studies.

Acknowledgements

The authors gratefully acknowledge research

support from the Spanish Ministry of Science and

Technology through research project DPI 2010-

20746-C03-01, and CIBER initiative. Finally, we

also thank the Spanish Ministry of Science and

Technology for the financial support to A. García

through the grant BES-2008-002951.

References

[1]García et al, Med Eng Phys, 33: 665-676, 2011.

Presentation 1748 − Topic 03. Arterial biomechanics S29

ESB2012: 18th Congress of the European Society of Biomechanics Journal of Biomechanics 45(S1)