Transcript ENDOVASCULAR STENTS CAN WE RELY ON LONG

ENDOVASCULAR FEMORAL STENTS
CAN WE RELY ON LONG-TERM FRIENDSHIP ?
Emad A Hussein ; MD
Emad A Hussein
MD
Vascular
Surgery ;Department
Ain Shams University
Cairo - EGYPT
ENDOVASCULAR FEMORAL STENTS
CAN WE RELY ON LONG-TERM FRIENDSHIP ?
Emad A Hussein ; MD
Vascular Surgery Department
Ain Shams University
Cairo – EGYPT
MUSCAT ; OMAN IVC - March 2013
STENT

“ A device that supports against collapse
or deformity “
ENDOLUMINAL STENT

The stent is carried by a catheter to a
remote site inside the lumen

Use of metallic stents in Surgery
BACK TO 16th CENTURY
( Gold in dentistry ! )
ENDOVASCULAR STENTS
CURRENT STUATION
70-85 % of coronary interv.(>1million/yr)
 25-35 % of peripheral interv.

( Thierry; J Endovasc Ther 2003 )
> 50 types of stents/stent- grafts  FDA
 Worldwide market $ 2.5 billion
 Annual Growth rate 5 %

ENDOVASCULAR STENTS
CURRENT SITUATION
RESTENOSIS RATE


8-10 % for ideal lesions
30-50 % for complex lesions esp. diabetics
( Gershlick; Heart 2004)
INDICATIONS OF STENTING

1- Sub optimal PTA / Complex lesions

2- Recurrent stenoses post-PTA

3-To fix a PTA complication ; Bail-out
( Dissection , Thromb., Perf. )
Nonvascular
Vascular
- Coronary arteries
- Coronary vein bypass
- A. carotid
- A. subclavian
- A. Renal
- TIPPS
- Aorta
- Dialysis Fistula
- A. iliac
- A. femoral
- Veins
- Vena cava sup. syndrome
- Vena cava inf. syndrome
- Pulmonary stenosis
-
- Ureter
Bronchial
Biliary
Trachea
Oesophagus
STENTS - CLASSIFICATION
Stent ( Bare )
Material

Manufacture
Shape & Design

Mode of
Deployment

Rate of
Compliance

Special Types ( Covered & Drug Eluting )
Alloy
Stainless Steel
Nitinol
NITINOL.ppt
J&J
Palmaz Genesis
Medtronic
AVE
JoMed
Smart
Optimed
Memotherm
Expander
RadiMax
Cobalt – Titanium
WallStent
Material
normally stainless steel.
others:Tantalum (Strecker), Platinum
Most
prominent representative: PALMAZ
pre mounted on a balloon
Inflate
the balloon to a nominal diameter

Production usually out of a pipe tube

Cutting of the design through



- Laser cutting (cleanest technology)
- Water jet technology
Other cutting techniques
Advantages:




-
Balloon exp. is a known mechanism
clear radiopacity
precise placement
high radial force
Disadvantages:



- no self expansion (deformable from outside)
- may be too rigid.
? CRUSHABILITY
- may not be flexible enough.
Material
usually nitinol
- different stents on the market:
Memotherm, Sinus-Stent, Cragg-Stent,
Vascucoil, S.M.A.R.T.
Exception
- Wallstent
mediloy/cobalt alloy
Advantages:
- Flexible
- stable Form, not deformable
- Self expansion (own force)
Disadvantages:
- Misplacement is often criticized
- Lower radial force
S.M.A.R.T.Control
Stent Characteristics
Nitinol
Lasercut,electropolished
Multisegmented
Design
Micromesh Geometry
Micromarkers
Minimal Foreshortening
Clinical Results
Perfect Wall apposition with self
expandable stent
S.M.A.R.T.
Control
Wallstent
WHICH STENT FOR WHICH LESION ?
Site ( anatomy ) - Kinking, Ostial stnosis etc..
Carotid & fempop  Self exp
Renal  Balloon exp ( ostial )
Aorto-iliac  Balloon or self exp
Morphology
Calcified plaques, recoiling
Exact placement ( close import.branch etc..)
-
-
FURTHER FACTS ABOUT STENTS
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Bio stability

Bio compatibility
Available data derived
In-stent thrombosis from in-vitro testing !
In-stent stenosis
1ry & 2ry Patency
( Not only technique dependant ! )
Patency Rates Nitinol Stents
Fempop
-
AIN SHAMS UNIVERSITY
VASCULAR SURGERY . 2001-2012
Demerdash + Specialized Hospital
Stents Deployed – Balloon / Self Exp.
Iliac
Fempop
Tibial
Renal
Venous
143
132 ( including 5 hemo / viabahn )
33 ( CLLI-Limb salvage )
16 + Carotid 17 ( short-term F.U )
39
AIN SHAMS UNIVERSITY
VASCULAR SURGERY . 2001-2012

2010 …. To Date

MORE DEB
IN FEMOROPOP SEGMENT
&
LESS STENTS !
AIN SHAMS UNIVERSITY
VASCULAR SURGERY . 2001-2012
STENT REGISTRY
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Follow-up non uniform ( & so is patency ! )
Range 4-46 months
Different complications
( Restenosis/ Thromb./ Migration / Fr ? )
Occurring 8 months – 3 years
Determinant Factor ( ? Multifactorial )
AIN SHAMS UNIVERSITY
VASCULAR SURGERY . 2001 – 2012
STENT REGISTRY
( Femoropop )
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Total 127  All Self-Exp + 5
Hemobahn / Viabahn
Occlusions 93
Stenoses 39
1ry Patency ( 3 yrs ) 87 %
Lesion length 1.8 – 17.7 cm
AIN SHAMS UNIVERSITY
VASCULAR SURGERY . 2001 – 2012
STENT REGISTRY
( Femoropop )
Stent Fracture 2 ( Lesion > 9 cm )
In Stent Thrombosis 4 ( 3 % )
In Stent Stenosis 6 ( 4.6 % ) – Migration 1
Mortality ( unrelated / MI or CVA ) 3
FINAL RESULT POST-STENT
THE PROBLEM WITH STENTS ?
Metal inside blood vessels  permanent
 ? Body reaction

Chemical + Mechanical Factors
WHAT HAPPENS IN A FEW YEARS ?
To stent
To artery
To body
IN ALL STENTS
( including Nitinol )
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Pitting Corrosion
Fractures
?Allergy
Degradation Products
Pro inflammatory effects commonly
associated with RESTENOSIS !
FDA

( 2006 / 2007 )
“ Long – term biodegradation
of metallic devices remains a serious
issue ! “
BIO STABILITY
Are Alloys used in Endovascular Surgery
STABLE ?

Stainless Steel / Nitinol / Elgiloy / Tantalum

All release +ve ions ( esp.nickel ) & liable to
pitting corrosion but by the process of
passivation (electropolishing )
ion release
esp.nitinol ( 75 % less )
BIO STABILITY
? FURTHER COMPOUND PROBLEM
Physiologic Body Fluids Contain :
Dissolved O2
 Chloride/ Hydroxide /Sodium
 Potassium/ Bicarb/ Phosphate
 Magnesium/ Calcium ions

VERY CORROSIVE ELECTROLYTES !
BIO COMPATIBILITY
“ Blood-Device Surface Interaction “
OR
Biologic Response to Degradation Products
BIO COMPATIBILITY
Stent Deployed

What happens in the 1st few seconds ?
BIO COMPATIBILITY

Bio material  Blood
A hydration layer forms within seconds
Rapid adsorption of a layer of pl.proteins

 Triggers


Cellular invasion
Inflammatory response
BIO COMPATIBILITY

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Bare metal stents inherently thrombogenic
Rationale for adjunctive
Antiplatelets + Anticoagulants
? Metal hypersensitivity
? Cytotoxicity & Carcinogenicity
( concern in orthopedic implants )
NITINOL STENT FRACTURE ?

SIROCCO 1 Trial - Cordis  18.2 %
( Duda SH et Al ; Circulation. 2002 )

SIROCCO II  8 %
( J Vasc Interv Radiol. 2005 )
Long segment SFA Stenting ; 57 pts randomized
Sirolimus – Eluting vs Bare Nitinol Stents
F.U 6 ms – Radiologic Screening
In SIROCCO 1 , Longer lesions were addressed !?
SIROlimus Coated COrdis Self Expandable Stent
NITINOL STENT FRACTURE

LONG SEGMENT FEMPOP NITINOL STENT
( Sabeti S et Al ; J Endovasc Ther . 2005 )  15 %
( Scheinert B et Al ; J Am Coll Cadiol . 2005 )
93 pts ( 121 limbs )
F.U 10.7 ms
Global Stent Fracture 37.2 %
Stented Segment =< 8 cm
13.2 % Fr. Rate
> 8 – 16 cm
42.4 % Fr. Rate
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
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1st Study to demonstrate that
“ STENT FRACTURE
IS NOT A BENIGN
INCIDENTAL FINDING , BUT IS ASSOCIATED
WITH
INCREASED RESTENOSIS “
Kaplan Meier estimates for PATENCY at 12 ms
Non-Stent Fracture  84.3 %
Stent Fracture  41.1 %
ENDOVASCULAR STENTS
RECENT ADVANCES – CLINICALLY TESTED
NIH
Drug Eluting Stents DES  Selected indications
Drug Eluting Balloons DEB ( widely accepted )
Brachytherapy  Beta emitting radioactive stents
LIMITATION !
Subacute Thrombogenicity + Narrowing at Stent Edge
Candy – Wrapper effect
ENDOVASCULAR STENTS
NEW HORIZONS
Heparin & Hirudin coating
 Inorganic coating 
Diamond-like Carbon
& Titanium-NO2
TARGET

Diminish NIH & Release of ions
Improve Corrosion Properties
ENDOVASCULAR STENTS
NEW HORIZONS

Organic coating  Bovine peritoneum-lined stents
No progression of NIH 30-180 days
As compared to polyester-lined self-exp stents
( Carnevale K , Ouriel K et Al ; J Edovasc Ther. 2006 )
ENDOVASCULAR STENTS
NEW HORIZONS

Biodegradable Stents – absorbed in 60 days
( Heublein et Al ; Heart. 2003 / DiMario et Al ; J Interv Cardiol.2004 )

? Replace the Stents
Catheter-based local delivery of
Antimitotic Agents
L- Arginine ( Suzuki et Al ; Am J Cardiol. 2002 )
To diminish Cell. Proliferation & Restenosis
ENDOVASCULAR STENTS
CAN WE RELY ON LONG – TERM FRIENDSHIP ?
THANK YOU