Materials and their distinctive

characteristics that are used for

stents in endovascular treatment of

Iliac arteries.

Konstantinos Spanos, MD, MSc, Athanasios Athanasoulas, MD, MSc, Christos

Karathanos, MD, MSc, PhD, Athanasios D Giannoukas, MD, MSc, PhD, FEBVS.

Vascular Surgery Department, University Hospital of Larisa, Faculty of Medicine, School of Health

Sciences, University of Thessaly, Greece.

Charles Thomas Stent, 1807,

London dentist

Studies in Plastic Surgery of the Face

Annals of Surgery , 1917

Mulliken JB, Goldwyn RM: Impressions of Charles Stent.

Plastic & Reconstructive Surgery 62:173–176, 1978.

Dotter CT: Transluminally placed coilspring endarterial tube grafts. Invest Radiol 4:327–

332, 1969.

ILIAC ARTERY FEMORAL ARTERY

10 stents

3 Iliac arteries

4 Femoral arteries

The question remains

Who first used (published) the word stent for the vascular prosthesis?

1964: Dotter and Judkins proposed the use ofpercutaneously introduced prosthetic

devicesto maintain the luminal integrity of

diseased blood vessels

1977: Grüntzig, coronary angioplasty

1985. Palmaz et al. introduced the use of balloon mounted stents in peripheral arteries

Nitinol coil stent used by Dotter

A coil wound to a small diameter and delivered

through a catheter into the vessel would expand to a

larger diameter, upon warming with 60°C saline

solution

His

tory

1986 Schatz et al. modified the Palmaz stent, which led to the development of the first commercially successful stent, the Palmaz–Schatz stent.

1986 Puel & Sigwart were the first to implant a stent in humans they used a self expanding mesh device.

1987 Puel & Sigwart They were also the first to describe the use of this stent for emergency vessel closure during balloon angioplasty, on the basis of the ability of the device to act as a scaffold to move intimal and medial flaps away from the lumen and maintain radial support to offset elastic recoil

To oppose to artery recoiling

Treat dissection

2000

2007Endovascular therapy is the treatment of choice

2000

2007

Endovascular treatment

is the preferred treatment

TASC C lesions

2000

2007

Surgery is the preferred treatment for

good-risk patients with type C lesions

TASC D lesions

2000

2007

Surgery is the treatment of choice

Method of deployment

Flexibility

Crush (not crush) on external pressure

Radial strength, Hoop stress

Radiopacity

Predictability of final deployment location and length

Ability to be repositioned prior to complete deployment

Material of construction

Most pronounced characteristic

Method of deployment

Self expanding

Balloon expanding

Balloon expanding stents

Non mounted

Pre-mounted

Spring load

Plastic deformation

Thermal memory

A stent with an expansibility ratio of 4 and an optimal expanded diameter of 5 mm will have an unexpanded diameter of 1 .25 mm, or 3.75 French.

(the ratio shows how short can be a stent in non expanded form)

The strength and elasticity of the diseased arterial wall may vary considerably

the hoop stress (residual circumferential elasticity)

that follows balloon dilatation may result in the collapse of a relatively weak stent after its placement.

• High radiopacity for clear visualization, which facilitates accurate placement

• High hoop strength to resist arterial recoil• Minimal or no foreshortening in deployment, for precise placement• Simple and easy-to-use delivery system• Longitudinal flexibility to cross tortuous vessels and aortic

bifurcation with the contralateral approach• Radial elasticity to resist external compression without permanent

deformation, especially at flexion sites• High expansion ratio and low profile for passage through small

introducers or guiding catheters or through tight stenoses• Retrievability in case of faulty deployment• Side branch accessibility• Minimal induction of intimal hyperplasia• Resistance to thrombosis and corrosion• Durability

The stent material are negative charged, while the endovascular surfaces are positive charged.

Passivation is the –spontaneous- formation of a hard non-reactive surface film that inhibits further corrosion and thrombogenity

High expandability

Final diameter depends on the size of balloon used to deploy it

Ability to use in areas of vessel size changes e.g. common to external iliac artery?

Risk of dislodgment

Calcification

Risk of balloon rupture during deployment

Risk of delivery fail at aortic bifurcation

Flexibility related

Use only short length balloons

The Assurant Cobalt Iliac stent, with its unique cobalt chromium modular design, provides excellent conformability without sacrificing radial strength

http://www.peripheral.medtronicendovascular.com/us/product-type/stents/assurant-cobalt/index.htm

A next generation Cobalt Chromium stent proven in challenging iliac cases1. CoCr + Multi-Link Design create a strong and highly flexible stent that conforms to tortuous anatomies and supports a superb healing environment2

1. The MOBILITY Clinical Study. Data on file with Abbott Vascular.2. The ISAR-STEREO and ISAR-STEREO-2 trials studied stents designed with Multi-Link technology. Kastrati, et al. Intracoronary stenting and angiographic results strut thickness effect on restenosis outcome (ISAR-STEREO) trial. Circulation 2001; 103:2816-2821.Pache, et al. Intracoronary stenting and angiographic results: strut thickness effect on restenosis outcome (ISAR-STEREO-2) trial. JACC 2003; 41:1283-8

The FLEXIVEᵀᴹ Cobalt-Chromium Endovascular Stent System is the new treatment option for tortuous iliac lesions. This highly visible Cobalt Chromium stent with thin struts is designed to provide outstanding flexibility and conformability

The EXPRESS Vascular LD Iliac Pre-mounted Stent System is a stainless steel balloon expandable stent, well known for its superior resistance to compression and great conformability.

Best conformability to changing vessel diameters

Best flexibility in undeployed and deployed state to pass or stent tortuous vessels

Smaller sheath requirements

ConstructionCoil wire

Braided wires

Thermal memory metals

1st self-expandable stent Braided wires

Made of a cobalt (Co)–chromium (Cr) alloy (Elgiloy), Mo was clinically applied in 1986

Low strength at end-points Corrosion resistance Narrow range of expansion (large inventory of

stents) Maximal foreshortening , Accuracy only

distally Can be recaptured during deployment

Wallstent

Good flexibility

Apposition to vessel wall fair, may not make adequate wall contact

Modular designs (Laser cut Nitinol ) offer better apposition

The Jaguar is a self-expandable stent made of NITINOL. The stent is made of a special wire knitting NITINOL. This allows a unique flexibility and elasticity even in the toughest stenoses. It is used with 0.035" wire and is Over The Wire. It passes through 6 and 7 Fr sheath and the length of the catheter is 80cm, 135cm and 165 cm. Available in diameters of 4 - 10 mm and length of 15 -120mm.

The 5F Nitinol Peripheral Stent System is self expandable and features a radial force that is perfectly suited for prevention of elastic recoil settled in the Iliac arteries. The SilkenFlex Iliac also proves useful bilary procedures and provides stellar pushability and dependability. This technology helps easy access to the lesions and easy to use and smooth deployment thanks to the Pin and Pull' system.

The EverFlex™ Self-expanding Peripheral Stent System is indicated for use in occlusions, lesions at high risk for abrupt closure or threatened closure following percutaneous transluminal angioplasty (PTA);

They are superelastic

(crush recoverable)

Flat unloading curve over a wide

deflection (strain) range

Exert a gentle “chronic”

outward force

Nitinol Properties

Kink Resistance

Memory formation

Nitinol stents with a transition temperature of 30°C

Weak when squeezed at low temperature.

Much stiffer when squeezed at T above 30°.

Temperature - dependent stiffness.

ZA stent (Cook) Symphony stent (Boston Scientific)

wire formed design with struts

welded to form hexagonal cells

Braided or weld wire struts: larger catheters

When Nitinol sheet became available, Angiomed (Bard) developed the first laser-cut Nitinol stent bycutting a pattern from sheet, rolling it up, and welding at specific strut locations

Memotherm stent

EndoTex stent

Nitinol sheet to produce a series of windows and a locking feature at one edge. It is rolled up to a small diameter

roll and placed onto a PTCA balloon. The assembly is then placed into the vessel and the diameter of the stent is

adjusted by inflating the balloon. As the balloon expands, the stent uncoils to the desired diameter to prop open

the vessel. The stent is locked into place by unique tabs that slide into the stent “windows” upon balloon deflation.

This design provides a wide range of diameters to custom fit for each treatment. It combines balloon expandability

with the superelasticity after deployment

Presently

Most self-expanding Nitinol

stents are produced by laser

cutting of Nitinol tubing.

Laser-cut Nitinol tubular stents.

Top: Memotherm (Bard Angiomed)

bottom: SMART (Cordis)

Laser-cut Nitinol tubular stents.

Top: Jostent SelfX (Jomed)

bottom: DynaLink (Guidant)

To improve the fluoroscopic visibility of the Nitinol

stents, radiopaque markers are often attached or

integrated into the design of the stent.

Compatibility issues have to be considered

when using these material combinations

Coined Tantalum markers of the

SMARTeR stent (Cordis)

Radiopacity enhancements

Radiopacity enhancements

The GORE VIABAHN Endoprosthesis is a flexible, metallic (made from Nitinol) tubular-shaped device (stent) which is lined with plastic (made from expanded polytetrafluoroethylene [ePTFE]). The device is mounted on the end of a delivery catheter and held in place by a release mechanism.

Covered stent graft

Components of a drug eluting stent

a)Platform (stent itself)

b)Carrier (usually a polymer)

c)Agent (drug)

The bioabsorbable magnesium-alloy stent(BIOTRONIK AG) was first implanted safely

ininfrapopliteal and human coronary arteries

POLYMERSPolylactic, polyglycolic acid

LimitationLower strengthGreater bulkAtrophic changes of the arterial wall may lead to aneurysmal

dilatation

METALSMg

Metals Limitation:Inflammatory response elicited after implantation

Second generation AMS is under development

Optimization of the Mg alloy resulting in a

longer degradation time

Stent design with increased radial force

Stent sizes should be better adapted to

peripheral lesions.

During Abdominal Aortic Aneurysm study

Stent fracture

Iliac artery flow study

Thank you