Current DES designs and expansion capacity testing

Transcription

1 construction of Sagrada Família basilica had commenced in 1882 anticipated completion date: 2026 Current DES designs and expansion capacity testing N. FOIN, MSc, PhD INTERNATIONAL CENTRE FOR CIRCULATORY HEALTH, IMPERIAL COLLEGE LONDON EBC COURSE 2012 February 2012

2 Drug Eluting Stent Design DES Stent Crowns and connectors design Material: alloy, polymer, Strut thickness Drug Coating: Polymer Primer, Drug Concentration+ Kinetics Mechanical Properties: -Radial Strength -Flexibility/Deliverability -Fatigue -resistance to fractures Vessel healing response

3 Stent design: engineering terminology Stent are designed with a succession of rings and connectors: Rings cell Connectors Peaks (or Crowns) XIENCE Prime 3.0 mm (6 crowns, 3 cells) Stent design: - Rings (hoops) provide radial support - Connectors hold rings together contributing to longitudinal stability Strut Length Number of crowns, strut and connector structure define each stent design and its mechanical characteristics Strut Thickness

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5 Stent terminology: workhorse/model designs SMALL & MEDIUM VESSEL XIENCE 6 crowns design (3 cells, 2 peaks/cell) mm LARGE VESSEL XIENCE 9 crowns design (3 cells, 3 peaks/cell) mm Stent design (crowns, cells) changes at different diameters Stents are manufactured in only 2 or 3 workhorse designs to cover the entire range of diameters

6 Cut-off between model designs is an important parameter for stent selection in bifurcation Promus Element 2.75 Promus Element 3.0 MV deployment 2.75 MV deployment KB KB model design is an important parameter for stent selection in bifurcation Model design impact stent expansion result Foin, 2011

7 DES model designs Element Xience Taxus Integrity BioMatrix Cypher 2.25 Very Small ( Small vessel workhorse (8 Medium vessel workhorse (6 crowns, 3 Small vessel workhorse (6 crowns, 2 crowns, Medium vessel workhorse ( Medium vessel workhorse (8 crowns, 2 Large vessel (9 crowns, 3 crowns, 3 Small vessel workhorse (7crowns, 2 connectors*) *1.5 in Endeavor Resolute Medium/Large vessel workhorse (10 crowns, 2 Medium vessel workhorse (6 crowns, 2 Large vessel (9 crowns, 3 Medium vessel workhorse (6 crowns, 6 Large vessel (7 crowns, Large vessel (10 crowns, 2 Large vessel (9 crowns, 3 Companies rarely provide data on cut-off diameter between stent designs Max DES size 4.0mm except in Taxus for which up to 5.0mm diameter were provided Labeled DES expansion usually limited to mm above largest nominal diameter Foin, Sen, Di Mario, Davies. 2012

8 Stent Model design and Maximal expansion capacity Expansion capacity depends on stent model design XIENCE STENT Large design (9 crowns) mm Large design (9 crowns) Small/Medium vessel (6 crowns) mm Small vessel (6 crowns) Data on expansion capacity beyond label use is not usually available

9 Overexpansion capacity testing XIENCE 6 crowns design XIENCE 9 crowns design Nominal = 3.0 mm Nominal = 3.5 mm Post-dil at 4.0 mm Post-dil at 5.0 mm Post-dil at 5.0 mm, MLD = 4.4 mm Post-dil at 6.0mm (14atm), MLD = 5.7 mm Straightening of the crowns, until physical limit Foin, 2012

10 alloon Max. size Post-dilatation expansion and DES designs Minimal stent LD excluding struts Limited to 6.0 mm SC balloon at 14 ATM Stent MLD (inner lumen) achieved after stepwise overexpansion and 2x final post-dilatation Foin, Sen, Di Mario, Davies. 2012

11 Impact for stent selection in bifurcation PCI Promus Element 2.75 Promus Element 3.0 MV deployment MV deployment KB KB In presence of a large diameter mismatch, we should look at workhorse design and maximal expansion capacity Or upscale to a larger diameter (at low pressure) Foin, 2011

12 Left-Main: impact of stent models 3.0 Xience Prime with 4.5mm proximal post dilation 3.5 Culotte Xience Prime Xience Prime from LCx to LM 3.5 (LWH) Xience Prime with 4.5mm Prox. Dilatation

13 Change in cell opening diameter with overexpansion Large cell opening diameter may impair drug concentration in the wall Potential risk of plaque prolapse

14 Changes in stent cell opening with overexpansion

15 Stent crowns deformations with overexpansion (largest design) Foin et al submitted

16 Stent maximal expansion capacity: a critical limiting factor for Left-Main treatment? LM-Ostial LAD Pre Post 4.0x38mm stent LAD to LM and 5.0 post 4.0/4.0 KB M Stent MLD = 4.70 mm KB with 4.0/4.0 mm OCT in LM after 4.0x38mm Stent MLD = 4.32 mm Resolute integrity and post-dil with 5.0 NC balloon Incomplete stent apposition in LM despite several post-dilatations > 5.0

17 XIENCE Prime after Overexpansion Potential hazard with stent Over-Expansion DES were not designed to be expanded beyond labeled use: little data is available from the industry on their performances/limitations above labeled use Unknown stent response: loss in structural integrity, impaired drug delivery, increased metal fatigue and risk of stent fracture Polymer damages can increase after extensive post-dilatations/over-expansion Dogbone effect with protruding balloon > can cause foreshortening of the proximal stent rings Strain on the vessel, risk of dissection? Risk of plaque prolapse?

18 Off-Label use means stepping into the unknown

19 Summary: Stent workhorse design Stent model design determines stent Maximal Expansion Capacity. Largest designs could be expanded at least > 5.4mm for all DES tested,.but risk of reaching expansion limit with smaller designs Therefore both DES platform and model design selection impact expansion and apposition of the struts, particularly important in Left Main PCI Limited data is available to document DES limitations in off label use

20 Summary 1. Apposition in Left Main is critical Risk of longitudinal compression at the ostium

21 alloon Max. size Summary 2: Knowing cut-off between model designs is critical Minimal stent LD excluding struts Limited to 6.0 mm SC balloon at 14 ATM Stent min. inner MLD achieved after overexpansion and 2x final post-dilatation of each workhorse design Foin et al. 2012

22 Thank you! We welcome your questions Acknowledgements: E. Alegria, S. Sen, R. Petraco, S. Nijjer, C. Di Mario, D.P. Francis, J.E. Davies.

23 Connector design with current platforms Foin, 2012