ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

SPATIAL AND TEMPORAL VARIATION OF VESSEL STRESS AS A
STIMULUS FOR NEOINTIMAL GROWTH
1. ABSTRACT
C.M. Amatruda 1 , P.V. Lawford 2 , D.R. Hose 3 and A.J. Narracott 4
Stent implantation in stenotic arteries is a technique used to restore blood perfusion to
downstream tissues; unfortunately neointimal tissue growth leading to in-stent
restenosis often occurs a few months after this procedure. Previous studies have
considered the stress within the vessel as one of the factors acting to stimulate this tissue
growth. In this context, the compressive stress imposed by the contact between stent
struts and the wall and the hoop stress in the stretched wall are believed to be relevant.
An evaluation of the distribution and magnitude of stress within the vessel wall is
important to improve our understanding of the stimuli for tissue growth. This study
develops a structural model of a stented vessel. The relative influence of a number of
parameters on the stress distribution within the vessel wall is considered. The initial
conditions prior to stent expansion are examined to include the combination of in vivo
blood pressure and longitudinal pre-tension. The contribution of viscoelastic effects is
included along with pulsatile pressure variation. Application of initial pre-stretch and
systolic pressure increases the peak compressive stress generated by the stent by 280%.
The viscoelastic effects influence both the magnitude of stress within the stented region
and the area of the vessel wall subjected to high compressive stress outside the stented
region. Such spatial and temporal variations in stress distribution may contribute to the
stimulus for neointimal formation.
2. INTRODUCTION
The most common cause of death and disability in western countries arises from arterial
diseases. These can occur as an occlusion of the vessel, resulting in an insufficient
blood supply to the tissues, or as aneurysms, local enlargements which might evolve in
rupture of the vessel [1]. Obstructive coronary artery disease, in particular, is due to the
formation of an atheromatous plaque within the wall of the coronary artery and reduces
the oxygen supply to the heart.
In many cases coronary artery stenosis can be treated by angioplasty, the inflation of a
balloon mounted on a catheter in order to expand the occluded vessel, followed by the
1 Marie Curie Early Stage Researcher, Department of Cardiovascular Science, Medical Physics Group,
Faculty of Medicine, Dentistry and Health, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX,
Sheffield, UK
2 Senior Lecturer, Department of Cardiovascular Science, Medical Physics Group, Faculty of Medicine,
Dentistry and Health, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, Sheffield, UK
3 Professor, Department of Cardiovascular Science, Medical Physics Group, Faculty of Medicine,
Dentistry and Health, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, Sheffield, UK
4 Research Associate, Department of Cardiovascular Science, Medical Physics Group, Faculty of
Medicine, Dentistry and Health, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, Sheffield,
UK