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

DISCUSSION
3D reconstruction of stent geometry during balloon inflation allows characterisation of
the local deformation of stent units around the proximal and distal circumference. In
addition, measures used in previous studies employing 2D methods which provide a
more global assessment of changes in stent geometry have also been computed for
comparison. The results shown in figure 5a are in good agreement with the results
obtained by Kiousis et. al. [8]. The dog-boning ratio demonstrates greater deformation
at both the proximal and distal ends within the range 3 to 6 atmospheres. During
inflation of the 4mm stent the proximal end deformed first at an applied pressure value
of 3.75 atmospheres. Further increase in pressure to 4.5 atmospheres caused full
expansion of the stent, as shown in figure 5b.
For the two stents observed in the current study, it is clear that the local deformation of
individual stent units does not always correspond directly with changes in stent
diameter. It was not possible to assess all stent units due to the field of view and stent
rotation relative to the camera during balloon inflation. Figure 6 shows the expansion
of two proximal and one distal unit. Results from the 3 mm diameter stent (Fig.6a)
indicate that as the pressure load increased to 3 atmospheres the angle of the unit in the
distal part increased significantly. These results are in good agreement with the
computed dog-boning effect (Fig. 5a). However, the two units in the proximal part of
the stent expand more gradually. This occurs due to smaller separation of chosen units
and does not agree with the dog-boning response (Fig. 5a). Results from the 4 mm
diameter stent (Fig. 6b) indicate the angle of the units in the proximal part increased
significantly as the pressure load increased to 3.75 atmospheres whilst the distal unit
remained unexpanded. This is also depicted in Fig. 4. This behaviour agrees with the
dog-boning results (Fig. 5b) for both ends of the stent.
CONCLUSION
The present study computed both local and global measures of proximal and distal stent
deformation under applied pressure. It has been shown that local strut deformation does
not always correlate with changes in stent diameter. This may have implications for the
local strains generated during contact of the stent with the vessel wall. The methods
have been employed at coronary stent length scales and hence are appropriate for
extension to the study of stent-vessel wall interaction.
LIMITATIONS
The present study considers the free expansion of the stent and does not consider the
interaction of the stent with the vessel wall.
ACKNOWLEDGEMENTS
The research leading to these results has received funding from the European Union
Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 238113
(project MeDDiCA).
REFERENCES
1. European cardiovascular disease statistics (2008)
2. Duraiswamy, N, Schoephoerster, R. T., Moreno, M. R. and Moore J.E, Stented
Artery Flow Patterns and Their Effects on the Artery Wall, Annu Rev Fluid Mech,
2007, 39: p 357- 382.