Coronary Stent deformation in PCI

1. Longitudinal Stent Deformation
Satyam Rajvanshi

2. • More contemporary stent benefits
– increased deliverability and conformability
– Improved PCI outcomes

3. Improved stent deliverability achieved through
– Novel alloys (cobalt chrome or platinum chrome)
– Thinner struts
– Newer 3D designs
– in some stents—reduced number of connectors
between adjacent stent rings (crowns) – improves
SB access also

5. • Even with reduction in strut thickness,
innovative designs have enabled maintenance
of radial strength
• However, longitudinal (or axial) strength may
be lower with these new designs and is not
routinely reported by stent manufacturers

6. • Longitudinal stent deformation (LSD) is
defined as the accidental mechanical
distortion or shortening of a stent in the
longitudinal axis following stent deployment

7. THE ANGIOGRAPHIC
“WEDDING BAND”!

9. EuroIntervention 2012;8:267-274

10. EuroIntervention 2011

11. LSD
• 0.2% incidence – 0.2% of 4455 PCIs
• 0.09% stents deployed

12. • 12 published cases : 11 proximal crunch and 1
distal crunch
– 7 Promus Element (Pt-Cr)
– 2 Biomatrix (SS)
– 1 Endeavour (Co-Cr)
– 1 Taxus liberte (SS)
– 1 Resolute Integrity (Co-Cr)
• Average length of stents implanted – 30.7 mm

13. • Most common cause
– Unexpected or Excessive penetration of
• Guide catheter
• Guide catheter extension
• Proximal EPD in SVG-PCI
– Mechanical conflict between proximal
malapposed stent struts and Post-dialatation
balloon

16. EuroIntervention 2012

19. • Stents inflated to nominal pressure in a test
fixture
• Stent length 28-30 mm
• Longitudinally compressed by 14 mm
• Longitudinal compression force - measured as
a function of the compression distance
• Plot of the longitudinal compression force
versus amount of longitudinal compression
was generated

21. Clinically relevant force – 50 gms

22. Clinically relevant force – 50 gms

23. Column
Strength:
Key to less
LSD

24. • Recommendation
– Additional stent connectors be added to the
Element stent design
– Addressed in Promus Premier

25. • Major LIMITATION!
– All 6 authors – Abott vascular employees
– Clear conflict of interest!
• Also, clinicians said LSD is as common is all
platforms – but more recognised in ELEMENT
– the flipside of better visibility!

26. Circ Cardiovasc Interv February 2014

27. Point compression on proximal malapposed segment
Partial recoil
But
permanent
deformability

31. Biomatrix Flex - most resistant to deformation
Element - most easily deformed

32. SITUATIONAL EXAMPLES

33. • Withdrawal of a stent delivery system when the balloon gets
caught in struts of the deployed stent
• Crossing of a newly deployed stent with a stent delivery
system for treatment of a distal lesion
• Crossing of a balloon dilatation catheter through a deployed
stent for post-dilation of the stent
• Guide catheter contact with the stent after stent
deployment due to ostial location or deep-seating of the
guide
• IVUS pull-back during post-deployment inspection of the
deployed stent
Malapposition of struts – MC underlying pathophysiology

34. ANGIOGRAPHIC OUTCOME
AFFECTED? YES
BUT DOES IT AFFECT MACE?

44. AVOIDANCE AND TREATMENT

48. CONCLUSIONS

49. • Longitudinal stent deformation can occur
secondary to a variety of mechanisms
• Rare but also under-recognised and under-
reported
• More common in complex angiographic
disease
• Identification is important as, left untreated, it
may be associated with MACE
• Although seen with several different stents, in
the published series - more commonly
observed with the Promus Element stent.
Engineering studies also give scientific logic
behind this.

50. Before PCI

51. After PCI