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Different coronary stent design

Different coronary stent design

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  • 1. DIFFERENT CORONARY STENT DESIGN DR AWADHESH KUMAR SHARMA DEPARTMENT OF CARDIOLOGY PGIMER & DR RML HOSPITAL,NEW DELHI
  • 2. BACKGROUND    The introduction of angioplasty led to the development of a completely new approach to treat CAD. Until 1994, the percutaneous transluminal coronary angioplasty (PTCA) was the alone treatment for coronary artery disease. However, the incidence of restenosis of coronary arteries was an important problem, necessitating repeated interventional procedures in 30% of patients treated with PTCA alone. NEJM 1994;331:489-95
  • 3.  Coronary artery stents were developed to provide a metal scaffolding for the angio-plastied vessel, in an attempt to limit negative re-modelling.  Sigwart et al first reported the efficacy of stents in reducing restenosis rates in 1987.  By 1994, the Food and Drug Administration (FDA) had approved two stents (Gianturco-Roubin stent and the Palmaz- SchatzTM stent). Journal of Invasiv Cardiology.2001;13:634-639
  • 4. GIANTURCO-ROUBIN II    Flat wire coil attached to a single longitudinal strut 316 L stainless steel The first coronary stent approved by the FDA in June 1993. J. clinical pathology.2005,aug;58(8):795-804
  • 5. PALMAZ-SCHATZ Balloon expandable; slotted tube  316 L stainless steel  J. clinical pathology.2005,aug;58(8):795-804
  • 6.  The wide acceptance of coronary stenting was based on the results of the BElgian NEtherlands STENT (BENESTENT) and the STent REStenosis Study (STRESS) trials, which showed the superiority of stenting over balloon angioplasty.  After the wide acceptance of coronary stents the primary concern of stent development is the need to reduce device profiles and to increase flexibility to facilitate safe delivery. N Engl J Med,1994;331:489-95.
  • 7. STENT SELECTION
  • 8. STENT SELECTION-PERFORMANCE & EASE OF USE
  • 9. STENT SELECTION-GOOD ACUTE ANGIOGRAPHIC RESULTS
  • 10. JACC 2003;41:1283-1288
  • 11. TYPES OF STENTS  Mechanism of expansion (self-expanding or balloonexpandable)  Materials (stainless steel, cobalt-based alloy, tantalum, nitinol, Pt,Ir,Cr, inert coating, biodegradable)  Forms (sheet, wire or tube)  Manufacturing methods (laser cut, water-jet cutting, photoetching)  Geometrical configurations/design (mesh structure, coil, slotted tube, ring, multi-design)  Addition to stent (grafts, radio-opaque markers, coatings) Min Invas Ther & Allied Technol 2002;11:137-47.
  • 12. STENT GEOMETRIC DESIGN  MECHANISM OF EXPANSION  Balloon-expandable stents  The stent is pre-mounted on a balloon and the inflation of the balloon plastically expands the stent with respect to the balloon diameter.  Self-expanding stents- The smart material auto expands to a calculated size. Journal of invasive cardiology 1995;7:127134
  • 13. MATERIALS  Corrosion resistance  Biocompatibility  Adequately radio-opaque  Create minimal artifacts during MRI
  • 14. STENT PLATFORMS STENT MATERIALS- NON DEGRADABLE MATERIAL  316L stainless steel-  Excellent mechanical properties and corrosion resistance  Ferromagnetic nature and low density make it a non-MRI compatible  Poorly visible fluoroscopic material  First generation DESs, Cypher (sirolimus-eluting stent, Cordis, Warren, NJ) and Taxus (paclitaxeleluting stent, Boston Scientific, Natick, MA) JACC 1996;27:53
  • 15. CO-CR  Superior radial strength and improved radiopacity  Thinner stent struts  The second generation DES, Xience V (everolimuseluting stent, Abott Vascular, CA) and Endeavor (zotarolimus-eluting stent,Medtronic Vascular, Santa Rosa, CA). JACC 1996;27:53
  • 16. TA- TANTALUM  Excellent corrosion resistant material  Coated on 316L SS to improve corrosion properties and biocompatibility  High density and non-ferromagnetic properties  Fluoroscopically visible and MRI compatible  Higher rates of recoil- poor mechanical properties JACC 1996;27:53
  • 17. TI  Excellent biocompatibility and corrosion resistance  Low tensile strength and ductility  Ti alloys in combination with Ni-Ti  Ti-nitride oxide coating on 316L SS JACC 1996;27:53
  • 18. NI-TI  Good biocompatibility, radial force and shape memory  Coated by some materials such as polyurethane, Ti nitride and polycrystalline oxides to improve the corrosion resistance  Inadequate visibility under fluoroscopy American J of cardiology.2008;86:10731079
  • 19. PT-IR  Pt-Ir alloy of 90% platinum and 10% iridium  Excellent radiopacity and a reduction in both thrombosis and neointimal proliferation with less inflammatory reactions  Recoiling percentage was much higher (16%) than the 316L SS stents Journal of invasive cardiology 1995;7:127134
  • 20. BIODEGRADABLE METALLIC MATERIALS  Pure Fe  Oxidation of Fe into ferrous and ferric irons  Mg alloys  There are two Mg alloys, AE2153 and WE4357, used for making stents  Radiolucent Biomaterials.2006;27:1728-1734
  • 21. RATIONAL FOR BIODEGRADABLE STENTS Metal stent drawbacks  Cause permanent physical irritation  Risk of long term endothelial dysfunction and chronic inflammation  Metal have thrombogenic properties  Inability for the vessel to restore its a normal physiology Biodegradable stent advantages  May eliminate early and late complications of bare-metal stents  Restore the vasoreactivity  Allow a gradual transfer of the mechanical load to the vessel  Higher capacity for drug incorporation and complex release kinetics The need for a permanent prosthesis decreases dramatically 6 months post-implantation
  • 22. STENT DESIGN  On the basis of design, stents can be divided into three groups: coil, tubular mesh, and slotted tube.  Coil stents are characterised by metallic wires or strips formed into a circular coil shape  Tubular mesh stents consist of wires wound together in a meshwork, forming a tube.  Slotted tube stents are made from tubes of metal from which a stent design is laser cut. Eur Heart J 1997;18:1536–47
  • 23. COIL VS. TUBE  Coil design had greater strut width with gaps and fewer or no connections between struts  The strut width is greater; there are gap between struts, and no connections between struts which give it more flexibility.  However, the design lack radial strength, and the wide gap allow tissues to dangle. Singapore Medical Journal, 2004.
  • 24. COIL VS TUBE
  • 25.  As a result, coil design has become obsolete and replace by the more superior in radial strength, the tube design.  In tubular, there are two type of specification, a slotted tube and modular tube. Singapore Medical Journal, 2004.
  • 26. SLOTTED TUBE VS. MODULAR (TUBULAR)
  • 27. MODULAR DESIGN
  • 28. SLOTTED TUBE VS. MODULAR (TUBULAR)  Slotted tube stents resisted restenosis more than the modular stents (22.1% vs 25.2%)  Slotted tube- Closed cell design, and open cell design
  • 29. CLOSED CELL  Sequential ring construction  All Internal inflection points of the structural members are connected by bridging elements.  Regular peak-to-peak connections.  Optimal scaffolding and a uniform surface, regardless of the degree of bending.  Less flexible than a similar open-cell design. Ann Ist Super Sanita 2007;43,no1:89-100
  • 30. CYPHER STENT BY CORDIS
  • 31. OPEN CELL  Some or all the internal inflection points of the structural members are not connected by bridging elements.  Ann Ist Super Sanita 2007;43,no1:89-100 Periodic peak-to-peak connections, peak-to-valley connections, and mid-strut to mid strut connections  The unconnected structural elements contribute to longitudinal flexibility.
  • 32. OPEN CELL DESIGN
  • 33. STENT DESIGN IMPACTS DRUG DELIEVERY
  • 34. LENGTH & DIAMETER OF STENT  Long vs. Short  Stent length is associated with restenosis rate and clinical events (mainly target lesion revascularization)  Short stent has lower cases of restenosis than long stent.  Wide vs. Narrow  The wide diameter stent is more favorable than the narrow one European Heart Journal 2001;22:15851593
  • 35. NUMBER OF STRUTS  More struts vs. less  Less struts induce less chance of restenosis compare to more struts.
  • 36. THIN STRUT VS THICK STRUT
  • 37. STRUT THICKNESS  Although the immediate stent performance may be improved by increasing strut thickness (which increases radiovisibility, radial strength and arterial wall support) excessive strut thickness, on the other hand, may impart more vascular injury, trigger more intimal hyperplasia, and engender a higher risk for restenosis than thinner struts.  Strut thickness was observed to be an independent predictor of in-stent restenosis ISAR STEREO study(Circulation 2001;103:2816-21) ISAR-STEREO-2 trial(J Am Coll Cardiol 2003;41:1283-8.)
  • 38.  In an effort to further reduce strut thickness while maintaining adequate radiovisibility and radial strength, novel metallic materials such as cobaltchromium alloy are being used for the production of stent.
  • 39. THICK VS. THIN STRUTS  The stents with thinner struts is preferred for the design of new stents as they can reduce angiographic and clinical restenosis more than those with thicker struts ISAR-STEREO and ISAR-STEREO 2 trials
  • 40. SQUARE VS. ROUND STRUT CROSS-SECTION  The round strut cross-section without corners or sharp edges is popular at present  Round strut cross-section area is ideal for smoothness design.  Square strut cross-section area in not recommend because it interferes with blood flow due to their sharp edge which can slice blood cells. Kluwer Academic Publishers 2012
  • 41. SQUARE VS. ROUND STRUT CROSS-SECTION
  • 42. ROUGH VS. SMOOTH SURFACE  Smoothness of a stent can affect the performance and biocompatibily of the stent.  Smooth surface can reduce thrombus adhesion and neointimal growth.  To obtain smoothness, the stent need to be treated with acid-pickling and then electrochemical polishing.  The process removes slag which includes depositions and burrs, formed on the surface of stents due to the laser cutting production process. Seminars in interventional cardiology1998;3:139-144
  • 43. ELEMENT OF STENT DESIGN- BALLOON OVERHANG
  • 44. DRUG DELIVERY VEHICLES – COATING POLYMER- DRUG CARRIERS IN DESS  Nonbiodegradable and biodegradable polymers  Non biodegradable polymers  First and the second generation of DESs  The first generation of DES  Cypher - polyethylene-co-vinyl acetate (PEVA)/poly-n-butyl methacrylate (PBMA)  Taxus - polystyrene-b-isobutylene-b-styrene (SIBS)  The second generation of DES   Xience V – fluoropolymer Endeavor - phosphorylcholine (PC) Eurointervention,2005;1:266-272
  • 45.  Biodegradable polymers  Polylactic acid (PLA)  Polyglycolic acid (PGA)  Polylactic-co-glycolic acid (PLGA)  NON POLYMER  Titanium–nitric oxide alloy  Microporous stainless steel stent (Yukon, Translumina, Germany)  A nanoporous hydroxyapetite (a biocompatible crystalline derivative of calcium phosphate) coating  Magnetic nanoparticles (MNPs) Eurointervention,2005;1:266-272
  • 46. YUKON Choice DES system: Translumina modified stent surface containing micropores to enable the adsorption of different organic substances. Abizaid A , and Costa J R Circ Cardiovasc Interv 2010;3:384-393 Copyright © American Heart Association
  • 47. THERAPEUTIC AGENTS  Sirolimus (Rapamycin)  A macrocyclic lactone  Inhibits the migration and proliferation of SMCs  Zotarolimus  The sirolimus analogues  Developed by Abbott laboratories  Extremely lipophilic property and low water solubility  Everolimus  Sirolimus analogue  Immunosuppressive agent  Absorbs to local tissue more rapidly and has a longer celluar residence time and activity  Biolimus
  • 48. PACLITAXEL AND ITS ANALOGUES  Paclitaxel  Promoting tubulin polymerization and cell cycle arrest  Inhibiting the migration and proliferation of SMCs  Coroxane  Nanoparticle albumin bound paclitaxel (nab-paclitaxel)  To improve the solubility  Docetaxel  Semi-synthetic analogue  Better anti-proliferative properties
  • 49. OTHERS  Tacrolimus  Pimecrolimus  Curcumin  Resveratrol  CD 34 antibody  Anti-VEGF
  • 50. RADIO-OPACITY ENHANCEMENTS  Stainless steel or nitinol - hard to see fluoroscopically  To improve X-ray visibility, markers are often attached to the stents.  These additions are typically made from gold, platinum or tantalum  Electroplating (with gold) is also being used to enhance X-ray visibility
  • 51. COATINGS  To increase biocompatibility  Heparin was one of the first. Its mode of action is to reduce the coagulation cascade (and thus possibly the thrombogenic risk) after the deployment of a stent.  Phosphorylcoline and silicon-carbide have been used in order to reduce platelet activation and interaction, thus possibly controlling their adhesion to the stent struts during the acute phase of stent re-endothelization.
  • 52.  Passive coverage has been also shown to be useful.  Indeed, covered stents have been created, in which a PTFE layer was put between two stents (Jostent graft, Jomed) or one stent was covered by a inner and an outer layer of PTFE (Symbiot, Boston Scientific)
  • 53. COMMONLY USED CORONARY STENTS IN CLINICAL PRACTICE
  • 54. XIENCE FAMILY OF STENTS Stent Manufactu rer Drug Base Form/Desi gn Polymer Diameter Length XIENCE Xpedition Abott vascular FDA Approved Everolimus 100μg/cm2 L-605 CoCr Hybrid cell Multilink 0.0032" strut thickness, laser cut PBMA Non erodible SV-2.25 MV2.5,2.75,3.0,3. 25,3.5,4.0 LL 2.5,2.75,3.0, 3.25,3.5,4.0 8,12,15,18,23 ,28 33,38 XIENCE V Abott vascular FDA Approved Everolimus 100μg/cm2 Multi-layer Coating MULTI-LINK VISION CoCr stent Hybrid cell Multilink 0.0032" strut thickness, laser cut, PBMA Non erodible 2.25,2.5,2.75, 3.0,3.5,4.0 8,12,15,18,23 ,28 XINCE PRIME Abott vascular FDA Approved Everolimus 100μg/cm2 Cobalt Chromium Hybrid cell Multilink 0.0032" strut thickness,las er cut, biocompatibl e fluorinated copolymer SV-2.25 MV 2.5,2.75,3.0, 3.5,4.0 LL2.5,2.75,3.0, 3.5,4.0 8,12,15,18,23 ,28 Same 33,38
  • 55. THE XIENCE XPEDITION EVEROLIMUS ELUTING CORONARY STENT SYSTEM (ABOTT VASCULAR) FDA, CE MARK      The drug-coated stent and the balloon expandable delivery system 22% less force used to deliever than prime. Ultra low distal seal technology for outstanding crossability. Unique 3.25mm diameter for more accurate vessel sizing. More flexible multilayered balloon with flatter compliance.
  • 56. Stent Manufactur er Drug Base Form/Desi gn Polymer Diameter Length Promus element Plus Boston scientific Everolimus Platinum Chromium Tubular open cell,thin strut,high radial strength,good delieverality & trackability Thin, fluorinated copolymer matrix for controlled drug release (100% drug elution in 120 days) 2.25,2.5,2.75,3.0 ,3.5,4.0 8,12,16,20,24,28 ,32,38 Endeavor Sprint Medtronic ZotarolimusEluting 10μg/mm cobalt-based alloy (cobalt, nickel, chromium, and molybdenum) Modular design,Sinusoid al form wire,helical wrap,laser fused Phosphorylcholi ne polymer 2.25,2.5,2.75,3.0 ,3.5,4.0 8,12,14,18,22,26 ,30,34,38 Resolut Integrity Medtronic Zotarolimus eluting cobalt-based alloy (cobalt, nickel, chromium, and molybdenum) Modular design,Sinusoidal form wire,helical wrap,laser fused BioLinx biocompatible polymer 2.25,2.5,2.75,3.0 ,3.5,4.0 8,12,14,18,22,26 ,30,34,38
  • 57. Stent Manufactur er Drug Base Form/Desi gn Polymer Diameter Length Taxus Liberte Boston Scientific Paclitaxel 1 μg/mm2 paclitaxel in a slow release (SR)* 316L surgical grade stainless steel Sinusoidal ring modules linked via curved link elements SIBS [poly(styrene-bisobutylene-bstyrene)], a triblock copolymer (trade name: Translute) 2.50, 2.75, 3.00, 3.50, 4.00 8, 12, 16, 20, 24, 28, 32 TAXUS Express Boston Scientific Paclitaxel 1μg/mm2 paclitaxel in a slow release (SR) 316L surgical grade stainless steel modular ring strut pattern consists of two separate module designs: short, narrow sinusoidal Micro elements linked via straight articulations to long, wide sinusoidal Macro elements SIBS [poly(styrene-bisobutylene-bstyrene)], a triblock copolymer (trade name: Translute) 2.50, 2.75, 3.00, 3.50 8, 12, 16, 20, 24, 28, 32 Taxus Element Boston Scientific Paclitaxel 1.0 μg/mm2 Platinum Chromium Sinusoidal ring modules consisting of alternating long and short SIBS [poly(styrene-bisobutylene-bstyrene)], a triblock copolymer 2.25,2.50,2.75,3. 0,3.5,4.0,4.5 8,12,16,20,24,28 ,32,38
  • 58. Stent Manufactur er Drug Base Form/Design Polymer Diameter Length Coracto Alvimedica Rapamycin Stainless steel Tubular,open cell design Ultrathin polymer layer absobes 100% in 10-12 week 2.5,2.75,2.90,3 .00,3.5,4.0 9,13,17,21,26, 28,32 Coroflex please B.Braun Paclitaxel 1μg/cumm Stainless steel Multicellular ring design,Hybrid Superb radioopacity P matrixpolysulfone coating 2.5,2.75,3.0,3. 5,4.0 8,13,16,19,25, 28,32 Cypher cordis Sirolimus 100% drug release with in 1 month Stainless steel Tubular,laser cut,sinusoidal pattern,closed cell two non-erodible polymers: polyethylene-covinyl acetate (PEVA) and poly n-butyl methacrylate (PBMA) 2.50, 2.75, 3.00, 3.50 8, 13, 18, 23, 28, 33
  • 59. Stent Manufactu rer Drug Base Form/Desi gn Polymer Diameter Length YUKON Choice 4DES Translumina, German CE mark Sirolimus Medical Stainless Steel, 316 LVM, Surface containing micro-pores 1million pores/sqcm Balloon marker material Platinum / Iridium microporous PEARL Surface Strut thickness 0,0034” / 87 μm Hybrid design Non polymeric Shellac resin bio compatible resin 6 to 8 weeks release 2.0,2.25,2.50,2 .75,3.0,3.5,4.0 8,12,16,18,21, 24,28,32,40 GEN X Sync MIV therapeutics India pvt ltd Sirolimus Co Cr Open cell, alternate S link,uniform sinusoidal strut design Bio resorb PLLA-poly L lactic acid polymer Ultrathin coating(3μm) Drug sudden release f/b release upto 4050 days. 2.0,2.25,2.50,2 .75,3.00,3.50,4 .0,4.5 8,13,16,19,24, 29,32,37 Supralimus Sahajanand Medical Technologies Pvt Ltd, India Sirolimus Sainless steel Hybrid biodegradable drugcarrier ,50% drug release in 7 days next 50% in 41days 2.5,2.75,3.0,3. 5 8,12,16,20,24, 2832,36,40 SupralimusCore Sahajanand Medical Technologies Pvt Ltd, India Sirolimus cobaltchromium Hybrid biodegradable drugcarrier ,50% drug release in 7 days next 50% in 41days same same
  • 60. Stent Manufactur er Drug Base Form/Desi gn Polymer Diameter Length YUKON Choice PC Translumina, German CE mark Rapamycin (Sirolimus) Release of sirolimus up to 4 weeks Medical Stainless Steel, 316 LVM, Surface containing micro-pores 1million pores/sqcm Favours better endothelialisatio n Balloon marker material Platinum / Iridium microporous PEARL Surface Strut thickness 0,0034” / 87 μm Hybrid design The biodegradable components polylactide and shellac 2.0,2.50,2.75,3.0 ,3.5,4.0 8,12,16,18,21,24 ,28,32,40
  • 61. Stent Manufactu rer Drug Base Form/Desi gn Polymer Diameter Length BioMatrix Biosensors Inc, Newport Beach, Calif CE mark biolimus A9 highly lipophilic, semi synthetic sirolimus analogue (≈15.6 μg/mm of stent length) S-Stent (316 L) stainless steel stent with a strut thickness of 0.0054 inches (137 μm) laser-cut, tubular stent S-Stent platform Open cell, quadrature link Biodegradabl e, Polylactic acid (PLA) applied to the abluminal surface 2.25,2.50,2.7 5,3.0,3.5,4.0 8,11,14,18,24 ,28,33,36 Pronova Vascular concepts,UK Sirolimus Co Cr Hybrid S shaped articulations Biocompatibl e,biostable polymer,drug release upto 30 days 2.25,2.50,2.7 5,3.0,3.25,3.5 0,4.0 13,18,23,28,3 3,38 Biomime Meril Life Sciences, India Sirolimus 1.25μgm/sqm m of stent surface,30 day elution kinetics Co Cr Hybrid cell design 65μm strut thickness Biodegradabl e polymer 2.5,2.75,3.0,3 .5,4.0,4.5 8,13,16,19,24 ,29,32,37,40
  • 62. Stent Manufactur er Drug Base Form/Desi gn Polymer Diameter Length ACTIVE& ACTVE small IHT Paclitaxel Stainless steel Open cell,tubular P5 Biocompatible polymer 2.0,2.25,2.5,2. 75,3.0,3.5,4.0, 4.5 9,14,18,19,23, 28,36 EVERLITE Unimark remedies Everolimus Low drug dose 1.2μg/sqmm Co Cr Open cell,Sinosoidal strut design,alternativ e S link,ultrathin strut 65μm Biodegradable 2.25,2.5,2.75,3.0 ,3.5,4.0,4.5 8,13,16,19,24,29 ,32,37,40 Flexy Rap Lancer medical technology Rapamycin 1μg/sqmm Co Cr Open cell, Radial star segments combined with flexible links,Strut 65μm, Biodegradable polymer 2.25,2.5,2.75,3.0 ,3.5,4.0 7,10,13,15,17,20 ,24,28,33,38,42 INDOLIMUS Ce mark Sahajanand medical sirolimus Co Cr Open cell,laser cut,seamless tube,60 micm strut thickness Biodegradable polymer matrix 2.5,2.75,3.0,3.5 8,12,16,20,24,28 ,32,36,40
  • 63. THANKS