Different Coronary stent design PPT

DIFFERENT CORONARY STENT DESIGN

DR AWADHESH KUMAR SHARMA DEPARTMENT OF CARDIOLOGY PGIMER & DR RML HOSPITAL,NEW DELHI

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

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

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

PALMAZ-SCHATZ

Balloon expandable; slotted tube

316 L stainless steel

J. clinical pathology.2005,aug;58(8):795-804

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.

STENT SELECTION

STENT SELECTION-PERFORMANCE & EASE OF USE

STENT SELECTION-GOOD ACUTE ANGIOGRAPHIC RESULTS

JACC 2003;41:1283-1288

TYPES OF STENTS Mechanism of expansion (self-expanding or balloon-

expandable)

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, photo-

etching)

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.

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;7:127-134

MATERIALS

Corrosion resistance

Biocompatibility

Adequately radio-opaque

Create minimal artifacts during MRI

STENT PLATFORMSSTENT 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 (paclitaxel-

eluting stent, Boston Scientific, Natick, MA)JACC 1996;27:53

CO-CR

Superior radial strength and improved radiopacity

Thinner stent struts

The second generation DES, Xience V (everolimus-

eluting stent, Abott Vascular, CA) and Endeavor

(zotarolimus-eluting stent,Medtronic Vascular,

Santa Rosa, CA).

JACC 1996;27:53

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

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

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;86:1073-1079

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;7:127-134

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

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

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

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.

COIL VS TUBE

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.

SLOTTED TUBE VS. MODULAR (TUBULAR)

MODULAR DESIGN

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

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

CYPHER STENT BY CORDIS

OPEN CELL

Some or all the internal inflection points of the

structural members are not connected by bridging

elements.

Periodic peak-to-peak connections, peak-to-valley

connections, and mid-strut to mid strut connections

The unconnected structural elements contribute to

longitudinal flexibility.

Ann Ist Super Sanita 2007;43,no1:89-100

OPEN CELL DESIGN

STENT DESIGN IMPACTS DRUG DELIEVERY

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 oneEuropean Heart Journal 2001;22:1585-1593

NUMBER OF STRUTS

More struts vs. less

Less struts induce less chance of restenosis

compare to more struts.

THIN STRUT VS THICK STRUT

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.)

In an effort to further reduce strut thickness while

maintaining adequate radiovisibility and radial

strength, novel metallic materials such as cobalt-

chromium alloy are being used for the production of

stent.

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

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

SQUARE VS. ROUND STRUT CROSS-SECTION

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

ELEMENT OF STENT DESIGN- BALLOON OVERHANG

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

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

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

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

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

OTHERS

Tacrolimus

Pimecrolimus

Curcumin

Resveratrol

CD 34 antibody

Anti-VEGF

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

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.

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)

COMMONLY USED CORONARY STENTS IN CLINICAL PRACTICE

XIENCE FAMILY OF STENTS

Stent Manufacturer

Drug Base Form/Design

Polymer Diameter Length

XIENCE Xpedition

Abott vascularFDA Approved

Everolimus100μg/cm2

L-605 CoCr Hybrid cellMultilink0.0032" strut thickness,laser cut

PBMANon erodible

SV-2.25MV-2.5,2.75,3.0,3.25,3.5,4.0LL2.5,2.75,3.0,3.25,3.5,4.0

8,12,15,18,23,28

33,38

XIENCE V Abott vascularFDA Approved

Everolimus100μg/cm2Multi-layer Coating

MULTI-LINK VISION CoCr stent

Hybrid cellMultilink0.0032" strut thickness,laser cut,

PBMANon erodible

2.25,2.5,2.75,3.0,3.5,4.0

8,12,15,18,23,28

XINCE PRIME

Abott vascularFDA Approved

Everolimus100μg/cm2

Cobalt Chromium

Hybrid cellMultilink0.0032" strut thickness,laser cut,

biocompatible fluorinated copolymer

SV-2.25MV2.5,2.75,3.0,3.5,4.0LL-2.5,2.75,3.0,3.5,4.0

8,12,15,18,23,28Same33,38

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.

Stent Manufacturer



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 Zotarolimus-Eluting10μg/mm

cobalt-based alloy (cobalt, nickel, chromium, and molybdenum)

Modular design,Sinusoidal form wire,helical wrap,laser fused

Phosphorylcholine 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

Stent Manufacturer



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-b-isobutylene-b-styrene)], a tri-block 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 Paclitaxel1μg/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


2.50, 2.75, 3.00, 3.50

8, 12, 16, 20, 24, 28, 32

Taxus Element Boston Scientific Paclitaxel1.0 μg/mm2

Platinum Chromium

Sinusoidal ring modules consisting of alternating long and short crowns linked via “Z” shaped elementsthin-strut coronary stent


2.25,2.50,2.75,3.0,3.5,4.0,4.5

8,12,16,20,24,28,32,38

Stent Manufacturer

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 Paclitaxel1μg/cumm

Stainless steel

Multicellular ring design,HybridSuperb radioopacity

P matrix-polysulfone coating

2.5,2.75,3.0,3.5,4.0

8,13,16,19,25,28,32

Cypher cordis Sirolimus100% drug release with in 1 month

Stainless steel

Tubular,laser cut,sinusoidal pattern,closed cell

two non-erodiblepolymers: polyethylene-co-vinyl acetate (PEVA) and poly n-butyl methacrylate (PBMA)

2.50, 2.75, 3.00, 3.50

8, 13, 18, 23, 28, 33

Stent Manufacturer



YUKON Choice 4DES

Translumina, GermanCE mark

Sirolimus Medical Stainless Steel, 316 LVM, Surface containing micro-pores1million pores/sqcmBalloon marker material Platinum / Iridium

microporous PEARL SurfaceStrut thickness 0,0034” / 87 μmHybrid design

NonpolymericShellac resin biocompatible resin6 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 acidpolymerUltrathin coating(3μm)Drug sudden release f/b release upto 40-50 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 drug-carrier ,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

Supralimus-Core

Sahajanand Medical Technologies Pvt Ltd, India

Sirolimus cobalt-chromium

Hybrid biodegradable drug-carrier ,50% drug release in 7 days next 50% in 41days

same same

Stent Manufacturer



YUKON Choice PC

Translumina, GermanCE mark

Rapamycin (Sirolimus)Release of sirolimus up to 4 weeks

Medical Stainless Steel, 316 LVM, Surface containing micro-pores1million pores/sqcmFavours better endothelialisationBalloon marker material Platinum / Iridium

microporous PEARL SurfaceStrut thickness 0,0034” / 87 μmHybrid 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

Stent Manufacturer



BioMatrix Biosensors Inc, Newport Beach, CalifCE mark

biolimus A9highly lipophilic, semisynthetic 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 platformOpen cell,quadrature link

Biodegradable,Polylactic acid (PLA) applied to the abluminal surface

2.25,2.50,2.75,3.0,3.5,4.0

8,11,14,18,24,28,33,36

Pronova Vascular concepts,UK

Sirolimus Co Cr HybridS shaped articulations

Biocompatible,biostable polymer,drug release upto 30 days

2.25,2.50,2.75,3.0,3.25,3.50,4.0

13,18,23,28,33,38

Biomime Meril Life Sciences, India

Sirolimus1.25μgm/sqmm of stent surface,30 day elution kinetics

Co Cr Hybrid cell design65μm strut thickness

Biodegradable polymer

2.5,2.75,3.0,3.5,4.0,4.5

8,13,16,19,24,29,32,37,40

Stent Manufacturer



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

EverolimusLow drug dose 1.2μg/sqmm

Co Cr Open cell,Sinosoidal strut design,alternative 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

INDOLIMUSCe 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

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Different Coronary stent design PPT

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