Stent choices for paediatric cardiac catheterisation Shakeel A Qureshi Evelina Children’s Hospital London GHA/SHA, Riyadh, February 2013
Stents in Congenital Heart Disease Issues:
• Used in many defects – Aorta – Pulmonary arteries – Vena cava – Pulmonary veins – RVOT – Arterial ducts
Vessel recoil
Vessel kink
Vessel extrinsic obstruction
Vessel stretch
Acute post-operatove lesions
Ideal stent characteristics – High radial strength to avoid recoil of the vessel – Low profile of stent and delivery system (Premounted stents) – Flexibility – Good visibility – Ability to redilate in future for growth – Minimal foreshortening – Retrievable – Open cell design and wide struts to allow access to side branches – Rounded edges – Biodegradable
Requirements in Paediatric Cardiology – Ability to dilate to larger diameters
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Recent designs focus on: •
Foreshortening
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Flexibility
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Radial strength
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Low profile
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Trackability
– Flexibility
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Biodegradability
– Retrievability
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Rounded edges
– Maintain radial strength at large diameters – Low profile for use in smaller children
– Access to side branches
Stent designs • Stents made of: – Stainless steel 316L – used for balloon-expandable stents – Cobalt-based steels (cobalt alloyed with chromium and molybdenum) – Tantalum – Platinum (alloyed with iridium or tungsten) – Nickel-titanium alloys – Polymers – Biodegradable materials
Stents in Paediatric Cardiology Many balloon expandable stents are available: • Palmaz Genesis • Intrastent • Valeo • Cheatham-Platinum (bare and covered) • Andrastent • V12 Atrium (bare and covered) • Sinus Superflex
Stent : designs Material: stainless steel, cobalt, platinum, titanium, biodegradable material Self expandable: flexible, lower profile, conforms to vessel, less radial strength Bare stent/Covered stent: Unmounted (Hand-crimped) or Premounted Cell design: closed or open cells Open cell: flexible, less shortening, access to side branches Disadvantages: less scaffolding, more tissue prolapse, more recoil
Closed cell
Open cell
Courtesy: Caroline Ovaert
Stent designs •Bare stent – Covered stent Unmounted (Hand-crimped) or Premounted •Cell design: closed or open or hybrid cells
Hybrid cells (closed and open)
CP stents (bare or covered)
Stent designs Closed cell • Palmaz generations: Corinthian, Genesis, Palmaz Blue • Cheatham-Platinum • Advanta V12
On expansion cells maintain consistent shape Cell geometry consistent and cells complete
Stent designs Open cell • Intrastent Doublestrut LD • Jomed Wavemax • AVE Bridge • Herculink • Omnilink • Valeo
Stents Balloon expandable stents: •
Small - expandable to 4-5 mm diameter – Wide range of stents available
– Rapidly evolving technology – Covered or bare – Usually premounted – Primarily used in coronary arteries and other peripheral vessels – In ducts or RVOT in neonates
– Medium - expandable to 10-12 mm diameter – Large - expandable to 18 mm diameter – Extra large - expandable to 25 mm diameter
Small stents – cannot be overexpanded 8.0mm balloon
6.0mm balloon
8.0mm balloon 5.0mm balloon
M ax diameter 6.4 mm Courtesy: Frank Ing
Comparison of Genesis medium and large stents Max balloon size: 10 mm Max stent diam: 8.0 mm
Max balloon size: 14 mm Max stent diam: 12.3 mm
Extra large stents at 24 mm diameter
Maxi LD
Palmaz XL
CP 8-zig
Variety of stents • Medium – Genesis medium, Visipro – up to 10 mm • Large – – Genesis XD, Doublestrut LD, Mega LD, Andrastent XL – up to 18 mm – Jomed – up to 14 mm
• Extra large – P4014, 5014, Maxi LD, CP, Andrastent XXL
Stent: medium Dilatable up to 10 or 12 mm Omnilink (Guidant): stainless steel, length 12-58 mm premounted, 5-10 mm balloon, min 6F dilatable to 12 mm with no FS, open cell Valeo ‘medium’: stainless steel, open cell design premounted on 6-8 mm balloons: 6F length: 18, 26, 36, 56 mm dilatable to 13 mm (fracture > 13 mm), no foreshortening, open cell
Courtesy: Caroline Ovaert
Stent : Large Palmaz Genesis XD (19,25,29,39,59)
Dilatable up to 18 mm
Intrastents LD Mega (16,26,36)
Valeo ‘large’ (18,26,36,56)
Unmounted
Unmounted
Premounted (9 or 10mm): 7F
Stainless steel
Stainless steel
Stainless steel
10-12 18mm
9 18mm
9 or 10 20 mm
Flexible, rounded edges
Flexible, rounded edges
Flexible
Closed cells
Open cells
Open cells
good radial strenght
less radial strength
poor strength
FS: 35-38% (serial) at 18 mm
FS: single 35%, serial 8.5% at 18 mm
No FS if serial
circumferential fractures
easy distortion or fracture
Courtesy: Caroline Ovaert
Stent : Extra Large:
Dilatable up to 25 mm
Palmaz XL 4014, 5015
Intrastents LD Max (16,26,36 mm)
CP 8 zigs (16,22,28,34,39,45 mm)
Andrastent XL & XXL (13 to 57 mm)
Unmounted
Unmounted
Unmounted or premounted
Unmounted
Stainless steel Stainless steel
Platinum/iridum
Cobalt chromium
14 to 25
9 to 25
8 to 24
15-25 mm 20-32 mm
Closed cells
Open cells
Closed cells
Hybrid cell design
Rigid
Flexible
Robust, flexible, rounded edge
flexible
FS: 25% at 25 mm
FS: < 20% when serial
FS: 35% at 24 mm, 14% at 18 mm
FS XL: 35% at 25 mm, < 10% at 18 mm
Foreshortening of stent Closed cells serial vs direct dilation Genesis XD 2510 (large stent): serial dilation
Ing et al.
Foreshortening of stents Open cells Mega LD: serial vs direct dilation (18 mm)
Serial
Direct
Ing et al.
Foreshortening Open cells
Valeo large stent : effect of serial dilation
Ing et al.
Side branch occlusion Open vs Closed cell design 10 mm balloon
Mega LD
6 mm balloon
Genesis
Palmaz
Maximum dilation of cells in large stents
Ing et al.
Stent shortening at 12 mm diameter
Stents in pulmonary artery stenosis Naturally occurring RPA stenosis
Pulmonary artery stenosis post trunk repair In an infant
Oversized Palmaz stent
Covered stent in coarctation & PDA
Stents in IVC pathway
IVC stenting after Fontan operation
Corinthian PDA stent after RF
Bilateral PA stenting
Simultaneous bilateral PA stenting
Genesis closed cell stents
Bare stents and intimal proliferation Factors affecting histological restenosis studies due to intimal hyperplasia •
Stent design (strut thickness, number of struts per crosssection, and strut design)
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stent material
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surface smoothness
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Thin struts with a corrugated ring stent design found to induce the least intimal hyperplasia thickness between tested metal stents. Hoffmann R, et al. Relation of stent design and stent surface material to subsequent in-stent intimal hyperplasia in coronary arteries determined by intravascular ultrasound. Am J Cardiol 2002;89:1360–1364
Open cell stent in pulmonary artery
Open cells allow tissue prolapse, so may allow intimal proliferation
Intimal proliferation
Covered Stents ePTFE : stretchable Gor-Tex
Covered CP stent (Numed)
Advanta (V12) (Atrium)
Graftmaster Jostent (ABOTT, coronary stent, 3-4 & 4,5-5,5)
Cheatham-Platinum stents
unmounted
Length 16,22,28,34,39,45 mm Anything longer is custom made
premounted
Advanta V12 OTW LD (Atrium) •Stainless steel encapsulated by ePTFE on both sides •Guidewire lumen : 0.035” •Balloon: 12, 14, 16 mm •Sheath: 9Fr (12) - 11Fr (14-16) •Usually better to have 1Fr more •Length: 29, 41, 61 mm •Can be expanded up to 22 mm in steps of maximum 4mm (foreshortening 25%) •Flexible but recoil is an issue
Balloon has long shoulders
Advanta V12 RX (Atrium) • Premounted 5-7 mm, lengths 16, 21, 24 mm •Low profile (6, 7 Fr) •0.014” guidewire •Can be post-dilated to 8 mm
Advanta V12 OTW (Atrium) • Premounted 5-10 mm, lengths 16, 22, 38, 59 mm •Low profile (5, 6 Fr) •0.038” guidewire •Can be post-dilated to 12 mm
Andrastent (Andramed) •
Cobalt chromium stent
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Hybrid cell design (open and closed cells) makes it more flexible
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XL and XXL stents Stent lengths available: 13 mm , 17 mm, 21 mm, 26 mm, 30 mm, 35 mm, 39 mm, 43 mm, 48 mm, 57 mm
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XL – dilation between 15 and 25 mm
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XXL – dilation range between 20 and 32 mm
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Has been used in most indications for CHD
Andrastent (Andramed) • 12 zig or 15 zig design • Used also in RVOT prestenting prior to Melody valve • No fractures so far
Self-expanding stents • Very flexible • Low profile • Cannot be crushed • Conform to the curved vessel • Made of nitinol or cobalt-chromium alloy • Less radial strength than balloon expandable stents
Wallstent Braided wire tube of cobalt-chromium
SMART/Precise stent One piece laser cut nitinol tube construction
0.087â&#x20AC;? Peak to valley design
0.13â&#x20AC;?
6 Tantalum micromarkers at each end
Self-expanding stents Wallstent Design Metal alloy Sizes Sheath Foreshortening Radial strength
Braided wire tube Elgiloy (cobalt-cromium) 5-24mm diam;
6-11 Fr
SMART/Precise stent Single piece laser cut tube;MicroMesh geometry / segmented design
Nitinol 5-10 mm diam;
5-6 Fr sheath
Significant! Less than balloon expandable stents
Approx 8%
Sinus superflex stents • Self-expanding • Low profile • Used in stenting PDAs in duct-dependent circulation
Sinus Superflex DS stents •
Radio-opaque markers, braided sheath
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Anti-jump mechanism, self-expanding
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Low profile
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Used in hybrid procedures
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7-9 mm diameter, 15 – 20mm lengths, 0.018” guidewire
Hybrid procedure for HLHS
Sinus Superflex DS stents Hybrid PDA stent
Conforms to the vessel curve
Sinus Repo DS stents •
Radio-opaque markers, braided sheath
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Anti-jump mechanism, self-expanding
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Low profile
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Used for coarctation (or PDA stenting in ductdependent pulmonary circulation)
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5-6 mm diameter, 9 mm length, 0.018” guidewire
Biodegradable stents • Stent designs to overcome growth of patient • Degradable stents e.g polylactic acid – PLLA (Igaki-Tamai stent) – self expanding) • Magnesium stents (AMS biotronik, Mg stability for 8 days only) • PDS (polydiaxonone suture)
After subclavian flap
After AMS stent (3.5x10mm)
After 2 weeks
After AMS stent (4x10mm) Schranz CCI 2006
Biodegradable stents SX Ella stent • Used in bronchi and oesophageal strictures • Made of PDS • Integrity and radial strength maintained for 6-8 weeks • Degrades after 11 – 12 weeks
Biodegradable stents Ella stent • Available between 18 – 25 mm diameter for oesophagus (18 – 28 Fr sheath) • Custom made 6 to 8 + mm diameter for bronchi (16 Fr sheath)
Stents in Congenital Heart Disease •
Aortic coarctation and
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recoarctation
Older children, adolescents and adults
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Branch pulmonary arteries
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Any age
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Caval veins – superior and
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Older children, adolescents
inferior
and adults
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Right ventricular outflow tract
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Any age
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Patent arterial duct
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Neonates
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Aorto-pulmonary collaterals
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Any age
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Bronchi
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Usually in infancy