1. Understanding Stent Deformation
AXIAL
Understanding Stent Deformation
Keith Dawkins MD FRCP FACC FSCAI
Global Chief Medical Officer
Senior Vice President
Boston Scientific Corporation

2. Keith D. Dawkins, MD Salary: Boston Scientific Corporation
Ownership Interest (Stocks, Stock Options, or other Ownership Interest):

3. Stent Deformation: Initial Observations

4. Stent Deformation: Endeavor/Driver 7-Crown Stents
Pitney M: EuroIntervention 2011;7:

5. Stent Deformation: Endeavor/Driver 7-Crown Stents
Outcomes in Patients Demonstrating Stent Deformation
EVENT N %
Angiographic Success
13/14
93%
Re-Stent Required
9/14
64%
AMI (Tn >1.0)
7/14
50%
Stent Thrombosis 0%
Early Restenosis 2
14%
Usual Restenosis
Total Restenosis 4
29%
30-Day MACE 3
21%
6-Month MACE 5
36%
1000 patient, prospective, single-center registry of mm Endeavor/Micro-Driver stents
Pitney M: EuroIntervention 2011;7:

6. Hanratty CG: EuroIntervention 2011;7:872-877

7. Longitudinal Compression Manuscript
Three cases of Longitudinal Compression (ELEMENT, RESOLUTE INTEGRITY, BIOMATRIX)
‘In this particular case [Promus Element] the stent at the ostium of the vessel was crushed longitudinally as an Amplatz 1 guide catheter was advanced into the vessel to provide improved guide support. We did not feel this issue was related to the stent platform itself, as a braided guide catheter is capable of deforming any coronary stent’
‘In this case, the enhanced radiographic visibility of this platform [Element] meant that the complication was immediately apparent’
‘However we have since observed this phenomenon within our institution with all modern DES platforms from each of the major manufacturers’
Hanratty CG: EuroIntervention 2011;7:

8. What is Longitudinal Stent Deformation?
Longitudinal stent deformation is the axial shortening or lengthening of a stent after implantation, resulting from interaction with an ancillary device such as a guide catheter, post-dilatation balloon, or IVUS catheter
AXIAL

9. Longitudinal Stent Deformation Described with Eight Stent Types
Stent Name
Material
Strut Thickness
Connectors
BioMATRIX
Stainless Steel
112µm
2 or 3 
Endeavor
Cobalt chromium
(MP35N)
91µm
2 or 3
Micro Driver
PROMUS Element
Platinum chromium
81µm
(86µm for ≥4mm diam) 2
Resolute Integrity
1, 2 or 3
TAXUS Element
TAXUS Liberté
316L Stainless Steel
97µm 3
Xience V
(L605)

10. Longitudinal Stent Deformation
Created in a Model with Malapposed Struts

11. Ormiston JA: J Am Coll Cardiol Intv 2011;4:1310 –1317

12. Are these Bench Tests relevant?
Ormiston JA: J Am Coll Cardiol Intv 2011;4:1310 –1317

13. Longitudinal Strength In Perspective Is 0.5 Newtons Relevant?
Significant forces can be generated using normal procedural techniques
Force (Newtons)
0.5N
Embolize
a stent
Kink a
Hypotube
Deep-seat a
Guide Catheter
Catheter tip crossing
a deployed stent

14. Clinically Relevant Stent Compression Test
Ormiston Test
Relevant Test?
Internal Stent supported with a pipe
Constrained at base
Force applied 360O to full diameter of stent
Force value of 1N
Constrained by vessel
Open ended
Malapposed tapered section
Point force applied to stent
With a 1N load is there a clinical difference in procedural outcome?

15. 16mm WH ELEMENT
16mm WH XIENCE V
Pre
Post
Post
Pre

16. Prabhu S: EuroInterv 2011; published ahead of print

17. Is the ELEMENT Platform associated with a high rate of MACE Events?
PERSEUS Trial
PLATINUM Trial
MACE (%) 1-year
N=320
N=942
N=762
N=768
TAXUS
Express
TAXUS
Element*
PROMUS
PROMUS
Element
*ION
Kereiakes DJ: J Am Coll Cardiol 2010;56:
Stone GW; J Am Coll Cardiol 2011; 57:

18. Longitudinal stent deformation: QCA analysis from the PERSEUS & PLATINUM Trials
Kereiakes DJ: EuroInterv 2012 (in press)

19. Platform Innovation Leads to Lower Complaint Rates
Improvement in Stent Material & Design  65% Lower Complaint Rate
1.00
Normalized Complaint Rate
TAXUS Express
TAXUS Liberté
PROMUS
ELEMENT

20. PROMUS Element in SCAAR
Sarno G: Int J Cardiol 2012; doi.org/ /j.ijcard

21. PROMUS Element in SCAAR: Restenosis
Follow-up (months)
N=13,577 stents (PROMUS Element = 2,724)
Sarno G: Int J Cardiol 2012; doi.org/ /j.ijcard

22. PROMUS Element in SCAAR: Stent Thrombosis
Follow-up (months)
N=13,577 stents (PROMUS Element = 2,724)
Sarno G: Int J Cardiol 2012; doi.org/ /j.ijcard

23. Reducing Risk and Impact of Stent Deformation Similar DFU Verbiage Across Multiple Products
Inflation Pressure and Time
Care and Precaution Details
1. Care should be taken to control the position of the guide catheter tip during stent delivery, deployment and balloon withdrawal.
2. Care must be exercised when crossing a newly deployed stent with any wire, catheter or ancillary device to avoid disrupting the stent placement, apposition, geometry, and/or coating.
Nominal: 11ATM
Maintain inflation pressure for seconds for full expansion of the stent
ION™ Stent
1. Care should be exercised when crossing a newly deployed stent with an intravascular ultrasound (IVUS) catheter, a coronary guidewire, or balloon catheter to avoid disrupting the stent placement, apposition, geometry, and/or coating.
2. …a larger balloon may be used to expand the stent further… If this is required, the stented segment should be recrossed carefully with a prolapsed guidewire to avoid dislodging the stent.
Nominal: 9ATM
Maintain inflation pressure for seconds for full expansion of the stent
Endeavor® Stent
1. Care should be taken to control the guiding catheter tip during stent delivery, deployment, and balloon withdrawal.
2. When crossing a newly deployed stent with an intravascular ultrasound (IVUS) catheter, a coronary guide wire, a balloon catheter or delivery system, exercise care to avoid disrupting the stent placement, apposition, geometry, and/or coating.
3. The stent may be further expanded... the stented segment should be recrossed carefully with a prolapsed guide wire to avoid dislodging the stent.
Nominal: 8ATM for 2.5 and 2.75mm
9ATM for 3.0, 3.5, 4.0mm’s
Maintain pressure for 30 seconds
Xience V® (PROMUS®) Stent
All verbiage copied directly from U.S. Instructions for Use

25. Conclusions: Stent Deformation occurs rarely
Deformation is not unique to a particular stent: it has been described with 8 stent types
In vitro mechanical testing is of questionable relevance to clinical practice
Understanding the phenomenon, in particular avoiding the interaction between the stent and ancillary devices, is key
Adequately prepare the lesion
Initial stent implant at high pressure (≥ 12 atm)
Avoid guide-wire bias
Care with IVUS crossing
Wait for full balloon deflation (NB: Long balloons)