1. Longitudinal Compression Second Generation DES: What You Need to Know
Ian T. Meredith
MBBS, PhD, FRACP, FCSANZ, FACC, FSCAI, FAPSIC, FAHA
Professor and Director of Monash Heart
Monash Medical Centre, Melbourne Australia

2. Ian T Meredith, MD, PhD Honoraria: Abbott Vascular
Boston Scientific Corporation
Medtronic, Inc.

3. What is Longitudinal Stent Deformation?
LONGITUDINAL / AXIAL
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, IVUS catheter or possibly another stent

4. Longitudinal Stent Deformation Should Not Be Confused With..
Foreshortening
Inherent change in stent’s length occurring during implantation and expansion.
Recoil
Change in stent’s diameter due to mechanical and radial forces.
Stent Fracture
Cracking or breaking of a stent strut.

5. Is Longitudinal Stent Deformation a New Problem?No
The axial shortening or lengthening of a stent after implantation, resulting from interaction with another device balloon or stent reported 18 yrs ago
Chalet et. al., Cathet Cardiovasc Interv 1994; 32: 376-9
Bhargava et. al., J Invasive Cardiol 1996; 8: 447-9
Experienced clinically and anecdotally with:
Wiktor Stent, GR 1 and GR 2, Cordis Tantalum Stent and others

6. Can Procedural Technique Contribute to Longitudinal Stent Deformation?
Yes shortening or lengthening probably occurs
when an ancillary device bumps or catches a mal-apposed strut during re-cross or subsequent withdrawal.
Likely procedural Factors
When nominal inflation pressure and diameter are not attained initially leading to under-deployment and mal-apposition of stent struts
When the lesion tapers, leading to malapposition of struts
When the stent is undersized
Where there is wire bias or significant curvature resulting in poor coaxial alignment of the second device
Deep seated guide catheter. .

7. Can Stent Design Contribute to Longitudinal Stent Deformation?
Yes potentially
Different stent designs do have different “longitudinal strength” and integrity in bench testing
* Ormiston
But stent performance is the sum or a number of interrelated and interdependent design features
* Ormiston et. al., J Am Coll Cardiol Intv 2011; 4:

8. Recent Attention to Stent Deformation
PROMUS® Element™, BioMatrix™, and Resolute Integrity™ Stents EuroIntervention 2011
Endeavor®/Driver® Stent EuroIntervention 2011
The issue of stent deformation has received much attention lately. Let us put this issue into perspective, particularly as it relates to the Platinum Chromium Stent Platform.
First, it is important to recognize that the frequency of stent deformation is a very low.* That said, there are lessons that have developed with the recent focus on this issue.
*sources: Boston Scientific Element platform clinical programs and complaints data on file; PLATNUM Trial: Stone G et.al., JACC 2011, 57; PERSEUS WH Trial: Kereiakes D et.al. JACC 2010, 56.

9. Are There Clinical Consequences of Longitudinal Distortion?
Yes may be, potentially
Luminal obstruction resulting in ST or enhancing risk or restenosis
Inadequate lesion coverage
Mal-apposed struts may predispose to stent thrombosis & restenosis
Ormiston TCT 2011

10. Are There Clinical Consequences of Longitudinal Distortion?
Yes may be, potentially
Luminal obstruction resulting in ST or enhancing risk or restenosis
Inadequate lesion coverage
Mal-apposed struts may predispose to stent thrombosis & restenosis
But
This assumes ìt is unrecognized and untreated
Post-dilatation to correct luminal obstruction and appose struts or additional stenting of uncovered lesion may suffice
Importantly the evidence thus far is anecdotal
Ormiston TCT 2011

11. Stent Design in Perspective (Delivery & Acute performance)
are a series of “sinusoidal hoops” and “connectors”
Hoops
may be “in phase” or “out of phase”
influence radial strength and scaffolding and to a lesser extent flexibility and conformability
Connectors
the number, orientation, shape, thickness and composition influence flexibility, deliverability and conformability and tissue coverage and influence longitudinal strength
Ormiston TCT 2011

12. Stent Design in Perspective (Outcome)
effects the vascular responses stent deployment
Strut orientation and cell design
influence magnitude of stent induced platelet activation and inflammatory neo-intimal response
Strut thickness and alloy composition
also influence extent of stent-induced vessel injury and inflammation
Strut thickness
RCT and registry evidence of a relationship between strut thickness and ISR
Ormiston TCT 2011

13. Stent Design Progression: Platform
Material
SSTL
CoCr / CoNi
PtCr
Architecture
Strength
Flexibility
Coverage
Optimization
Closed Cell
Open Cell
Hybrid
Strut Thickness

14. Design of the Stents Tested
Figure 1. Design of the Stents Tested
Shown are photographs of the stent designs, their names, the metal they are constructed from, strut thickness in microns, and the number of connectors between hoops for each design. The Cypher Select, cut from a stainless steel tube, has a strut thickness of 140 m. Its design is out-of-phase sinusoidal hoops linked by 6 sinusoidal bridges that are orientated about 30° from the stent long axis. The Liberte, cut from a stainless steel tube, has struts100 m thick. Its apparently complex design is fundamentally out-of-phase hoops (yellow line) that are joined directly by 3 links (red arrows). The Vision and MultiLink 8 and their drug-eluting counterparts, Xience V and Xience Prime, are cut from a cobalt chromium tube and have struts 81 m thick. The design is in-phase sinusoidal hoops linked by 3 bridges that are aligned with the stent long axis. Each connector has a U-shaped loop to improve flexibility. The 3-mm Driver (and the drugeluting version, Endeavor or Resolute) has sinusoidal, largely out-of-phase hoops linked by 2 welds (red arrows). The Integrity and its Resolute drug-eluting counterpart has a single sinusoidal cobalt chromium component that winds helically from 1 end of the stent to the other with 2 welds between adjacent “hoops” (red arrows). The Omega (bare-metal version) and Promus Element (everolimus-eluting version) and the paclitaxel-eluting version (Taxus Element, called “ION” in the United States) have sinusoidal hoops made from platinum chromium. These are linked by 2 straight bridges per hoop that are aligned at an angle of about 45° from the stent long axis (red arrows).
Ormiston et al J. Am. Coll. Cardiol. Intv. 2011;4;

15. Comparative Stent Longitudinal Shortening and Distortion With 0
Comparative Stent Longitudinal Shortening and Distortion With 0.5 N Compressing Force
Figure 4. Comparative Stent Longitudinal Shortening and Distortion With 0.5 N Compressing Force
The 0.5 N force did not compress the Cypher Select stent, and the Liberte was compressed 2 mm. The Vision/Xience and MultiLink 8/Xience Prime were compressed 1 mm with minimal distortion. The Integrity shortened by 2 mm, with a small amount of strut overlap. The most shortening was with the Driver/Endeavor (4 mm) and Omega/Element (5 mm), and these stents experienced the most longitudinal distortion, with strut overlap.
Ormiston et al J. Am. Coll. Cardiol. Intv. 2011;4;

16. Compressive Force and Stent Shortening
Figure 3. Compressive Force and Stent Shortening
Plotted is stent shortening (millimeters) against force (Newtons) for 3 examples of the 7 stent designs. Compression graphs are not smooth
but are complicated because of strut collision and over-ride.
Ormiston et al J. Am. Coll. Cardiol. Intv. 2011;4;

17. Flexibility and Axial Strength A Balancing Act
SSTL
PtCr
Closed Cell
Open Cell
Axial Strength
Flexibility

18. Conformability and Axial Strength Stent flexibility is inversely related to axial strength
Bending Moment
(Newtons/mm)
Here you can see the association between flexibility and axial stiffness. The Cypher stent is the stiffest stent and the Platinum Chromium platform provides the most flexibility.
More Flexible
Cypher® Stent
n=6
Xience V ®
(PROMUS®) Stent
n=10
Integrity® Stent
n=3
Driver® Stent
n=7
PtCr Element
Stents
n=15
Bench test results may not necessarily be indicative of clinical performance. Data on file at BSC. PROMUS Stent is a private-labeled Xience V Everolimus Eluting Coronary Stent System manufactured by Abbott and distributed by Boston Scientific Corporation.

19. Measured Stent Length in PERSEUS
Cumulative frequency distribution of the ratio of QCA stent length to nominal stent length – single lesion PERSEUS RCT workhorse pts with 1 implanted study stent (N=1152)
Quantiles
TAXUS Express
(N=289)
ION/TAXUS Element
(N=863)
100% Max
1.280
1.225
99%
1.173
1.059
95%
1.018
1.009
90%
0.998
75% Q3
0.989
0.988
50% Median
0.965
0.960
25% Q1
0.919
0.915
10%
0.850
0.860 5%
0.830
0.819 1%
0.730
0.745
0% Min
0.612
0.594
100 80
ION™/TAXUS Element™
TAXUS® Express® 60
Percentile 40 20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Ratio
No cases of longitudinal stent compression or deformation were seen in either group by the core laboratory
Presented by Gregg W. Stone, MD, TCT 2011.

20. Measured Stent Length in PLATINUM
Cumulative frequency distribution of the ratio of QCA stent length to nominal stent length – single lesion Platinum RCT pts with 1 implanted study stent and no non-target lesions in the target vessel (N=1251)
Quantiles
PROMUS
(N=612)
PROMUS Element
(N=639)
100% Max
1.146
1.310
99%
1.081
1.077
95%
1.006
1.020
90%
0.998
1.000
75% Q3
0.986
0.984
50% Median
0.943
0.950
25% Q1
0.877
0.897
10%
0.819
0.847 5%
0.748
0.802 1%
0.643
0.664
0% Min
0.426
0.559
100 80 60
Percentile 40
Promus Element™
Promus 20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Ratio
No cases of longitudinal stent compression or deformation were seen in either group by the core laboratory.
Popma JP. 20

21. PROMUS™ (Xience V™) Stent (n=762)
PLATINUM Workhorse (12 months) TLF rates with PROMUS Element™ and PROMUS™ Stents
P superiority =0.72
P noninferiority =0.0009
P=0.96
P=0.14
P=0. 51
P>0.99
Incidence Rate (%)
PROMUS™ (Xience V™) Stent (n=762)
PROMUS Element™ Stent
(n=768)
* Intent-to-Treat Population
*TLF=Ischemia-driven (ID) target lesion revascularization (TLR), or cardiac death/myocardial infarction (MI) related to the target vessel (TV). GW Stone, et. al., JACC 57;16, PROMUS Stent is a private-labeled Xience V Everolimus Eluting Coronary Stent System manufactured by Abbott and distributed by Boston Scientific Corporation. Xience V is a registered trademark of Abbott Cardiovascular Systems, Inc.

22. PROMUS™ (Xience V™) Stent (n=762)
PLATINUM Workhorse Less bail-out stenting with PtCr stents due to improved lesion coverage
Overall Rate
Cited Reason for Bail-out Stent
P=0.004
P=0.36
P=0.01
P=0.06
Incidence Rate (%)
PROMUS™ (Xience V™) Stent (n=762)
PROMUS Element™ Stent
(n=768)
Presented by Gregg W. Stone, MD, ACC PROMUS Stent is a private-labeled Xience V Everolimus Eluting Coronary Stent System manufactured by Abbott and distributed by Boston Scientific Corporation. Xience V is a registered trademark of Abbott Cardiovascular Systems, Inc.

23. Stenting Technique to Reduce Incidence
Take care when crossing a newly deployed stent
Visualize stent when crossing any ancillary device
Ensure proper apposition of the stent to the arterial wall
Avoid deep seating the guide catheter
Minimize wire bias where possible
Longer inflation and deflation times with long stents
Illustration for information purposes, not indicative of actual size or clinical outcome.

24. Longitudinal Stent Distortion
The potential ALC clearly exists with modern stents
Not all stents are equal wrt to this potential
Caution when focusing on one design feature in isolation
Stent performance and outcome are the sum of many features
All designs have trade-offs, strengths and weaknesses
Importantly clinical trials have not demonstrated an effect
Finesse rather than force is important when re-crossing stents. Elegant tools require delicate hands
Illustration for information purposes, not indicative of actual size or clinical outcome.

25. Thank You

26. SCAAR Registry Crude Restenosis Rates - Unadjusted0% 2% 4% 6% 6 12
Stents Implanted
November 2009 – March 2011
Cypher™ Stent n=782
Endeavor™ Stent n=747
TAXUS™ Liberté™ Stent n=1,393
PROMUS™ (Xience V™) Stent n=1,533
Endeavor™ Resolute™ Stent n=1,566
Xience Prime™ Stent n=4,832
Cumulative Rate of Restenosis
PROMUS Element™ Stent n=2,724
Total number of Stents n=13,577
Time in Months
Presented by Stefan James, MD, ACC PROMUS Stent is a private-labeled Xience V Everolimus Eluting Coronary Stent System manufactured by Abbott and distributed by Boston Scientific Corporation.

27. Stent Appearances After 5-mm Shortening
Figure 5. Stent Appearances After 5-mm Shortening
Shown are micro-computed tomographic images cut electronically longitudinally after the stents had been compressed by 5 mm. Of course, different magnitudes of force were required to compress different designs by 5 mm. The lower portions of the stents below the broken line were clamped, hence were not subjected to compressive forces, and serve as normal stent comparitors for insights into mechanisms of shortening. For the Cypher Select the hoops were able to bunch as the wavelength of the sinusoidal connectors shortened and the connectors angulated and became less aligned with the long axis. For the Vision and MultiLink 8 designs, the hoops were pushed together where there are no connectors. In addition, the connectors became angulated and less aligned with the long axis of the stent. Furthermore, especially with the MultiLink 8, the U-shaped loop in the connector closed up. The Liberte, Driver, and Integrity designs have only 2 connectors between hoops, and these are direct connections so there was little to prevent struts bunching and overlapping in response to compressive forces. With only 2 connectors between hoops, there is again little to prevent Omega/Element struts being pushed together. Additionally, connector orientation
changed, becoming more aligned with the stent long axis.
Ormiston et al J. Am. Coll. Cardiol. Intv. 2011;4;