Vascular stents in IR

1. Overview of Vascular Stents in
Interventional Radiology
Presenter:Dr.Abhishek Gupta
Moderator :Dr.Praveen Singhal

2. Vascular stent
 Also k/s Vascular endoprosthesis
 Provides intravascular scaffold
– Allows for endothelialization
 – Provides intravascular rigidity
 □ Compresses atheroma, dissection flaps
 □ Resists elastic recoil
 Placed in diseased vascular structures
 – Arteries
 – Pulmonary arteries
 – Veins
 – Portal veins

3. Indications
 – Recanalization of luminal stenosis/occlusion, including
 □ Arterial atherosclerotic plaque [e.g., peripheral
 arterial disease (PAD), chronic mesenteric ischemia]
 □ Venous extrinsic compression (e.g., May-Thurner
 syndrome)
 □ Intimal hyperplasia/Fibrosis (e.g., hemodialysis access
 outflow narrowing)
 – Aneurysm/pseudoaneurysm exclusion
 – Traumatic/iatrogenic arterial perforation
 – Arteriovenous (AV) communications
 – Stent-assisted coil embolization

12. Vascular stent designs
 ○ Closed cell: Every stent segment connected by
link
 – Less flexible, may develop kinks
 – Occasional incomplete expansion
 – Better radial force/intravascular scaffolding
 ○ Open cell: Some stent segment connections
absent
 – Conforms to angled vessels/tortuous anatomy
 – Less radial force/intravascular scaffolding

13. Stent delivery systems
 ○ Balloon mounted:
 Externally mounted on percutaneous transluminal
angioplasty (PTA) balloon
 Risk of dislodgement; prevent by introducing through
guiding catheter/sheath
 Balloon inflation to deploy stent (Good for ostial
stenosis )
 More rigid stent design
 Conforms poorly to changing vessel diameters
 □ Over-the-wire (OTW)
 □ Rapid-exchange (monorail)

14. Self-expanding Metallic Stent
(SEMS ):
 Sheathed in retractable delivery system;
 spontaneously expands after retraction
 Most frequently constructed from nitinol
- Alloy regains original shape when no longer
compressed/constrained
 Requires appropriate oversizing to achieve secure
 intravascular fixation
 – Typically more flexible
 – Conforms to changing vessel diameters
 ○ 0.035" and 0.014"/0.018" delivery systems

18. Stent technologies
 Bare metal (BMS):
 Mesh-like scaffolding deployed in order to achieve
and maintain patency of vessel
 Not coated with polymers, medications, or fabric/graft
 ○ Drug eluting (DES):
 Stent coated with medication (e.g., paclitaxel,
sirolimus), which has antiproliferative effect on
smooth muscle cells, reducing neointimal hyperplasia

19. Covered (stent-graft):
 Metallic intravascular stent combined with fabric graft of either Dacron or
expanded polytetrafluoroethylene (ePTFE)
 Courses inside vascular lumen;
 Redirects blood flow through device rather than native vessel
 □ Radial force of metallic stent secures graft
 □ Catheter-mounted delivery system
 – Peripheral stent-graft examples
 Fluency (Bard ): Self-expanding nitinol stent encapsulated with
 ePTFE
 Covera BD international (The ONLY Covered Stent Indicated for AV Grafts and
Native AV Fistula)
 Bentely Begraft stent –biocompatible Co Cr alloy with ePTFE
 Viabahn: Inner ePTFE fabric graft attached to external self-expanding nitinol
stent(Not available in india
 Lifestream Balloon mounted stent graft (Bard International )

20. Flow diverter
Directs blood flow within parent vessel
 – Provides scaffolding to endothelial proliferation
 across diseased segment
 – Ability to maintain patency of critical perforator
 vessels
 – Pipeline embolization device (Covidien) approved
(in
 USA) for treatment of intracranial aneurysms

21.  Bioresorbable vascular scaffold (BVS): a.k.a.
absorbable
 – Scaffold artery while natural healing to occur;
 subsequently biodegrades
 – Stent may/may not deliver drug as degradation
proceeds

22. Things to check
 ○ Clinical history and physical examination
 – Emphasis on risk factors for PAD
 □ Should also evaluate carotid/coronary arteries; high
 incidence of concurrent disease
 □ Smoking cessation key for preventing/decreasing
 disease recurrence/progression
 – Detailed pulse examination/Doppler evaluation
 □ Document ankle-brachial index before/after
 stenting for lower extremity lesions
 – Current medications
 □ Any anticoagulants, antiplatelet agents, oral
 hypoglycemic agents, antihypertensives
 ○ Allergies

23. Laboratory parameters
 – Electrolytes, glomerular filtration rate (eGFR)
 □ Prefer normal Cr; eGFR > 60
 – Complete blood count (CBC) not routinely
 recommended
 □ Platelet count > 50,000/μL if evaluated
 – Coagulation profile
 □ International normalized ratio (INR) ≤ 1.5
 recommended
 □ Normal partial thromboplastin time (PTT)
 recommended for patient receiving IV heparin

24. Medications
 ○ Heparin
 – Various intraprocedural administration regimens Bolus dose of 2,500-5,000 U;
followed by infusion
 of 1,000 U/hr
 ○ Antibiotics
 – Prophylactic antibiotics not currently recommended in routine arterial stent placement
 – Consider antibiotics for patients at high risk for infection (i.e., cases of repeat
intervention within 7
 days, prolonged indwelling arterial sheath, prolonged procedure duration)
 ○ Vasodilator (e.g., nitroglycerin)
 – Typical bolus dose of 100-μg nitroglycerin
 – Prevents/treats catheter-induced vasospasm
 ○ Aspirin and Clopidogrel (typically only with arterial stents)
 – May electively give loading dose preprocedure 300-mg minimum loading dose
 – Continue maintenance dose post procedure

25.  Equipment list
 ○ Vascular access sheath
 – Sheath size depends on stent/catheter size
 – Permits catheter exchanges as necessary
 □ Reduces local complications at access site
 ○ Guiding catheter/sheath (typically 5-6 Fr)
 – Allows coaxial injection around stent delivery
 system/guidewire/angioplasty balloon
 – Use to precisely localize stent position
 ○ Selective catheter and guidewire
 – Configuration depends upon target vessel/lesion
 – Hydrophilic guidewire often used to cross lesion
 – Stiff guidewire: Provides stability across lesion during stent delivery/deployment (e.g., Amplatz, McNamara,
Lunderquist, Rosen)
 ○ Stent and stent delivery system: Dependent on target location, size, accessibility
 ○ Calibrated insufflator device
 – For precise atmospheric pressure inflation of balloon mounted stents and angioplasty
 ○ Angioplasty balloon catheter
 – May predilate lesion prior to stent placement
 □ May be necessary before balloon-mounted stent
 – May postdilate following stent placement
 □ May be necessary following self-expanding stent

26. Patient Position and Access
 Best procedure approach
 ○ Arterial stent
 – Usually retrograde common femoral artery access for
 pelvic, contralateral lower extremity, renal, visceral
 artery, great vessel lesions
 – Brachial/radial access for some upper extremity, some
 renal/visceral lesions (e.g., superior mesenteric artery)
 – Antegrade common femoral artery access may be
 used for ipsilateral lower extremity lesions
 ○ Venous stent

27. Venous stent
 Common femoral vein for pelvis, inferior vena cava
 (IVC), lower extremities; sometimes for superior vena
 cava (SVC)/central veins
 – Jugular vein access for some venous stenoses [e.g.,
 SVC, hepatic veins, transjugular intrahepatic
 portosystemic shunt (TIPS) stenosis]
 – Dialysis-related venous stenoses (peripheral and
 central) usually accessed through fistula/graft

28.  Crossing stenotic lesion
 ○ Gently advance guidewire across stenosis
 – Monitor fluoroscopically while crossing lesion
 □ May use roadmap when crossing lesion
 – Imperative to avoid vessel dissection
 – If resistance to guidewire passage
 □ Caution: Do not continue to advance guidewire;
 may cause dissection, vessel perforation
 □ Retract wire; reorient catheter; readvance wire
 □ Consider different catheter shape, guidewire
 – Keep catheter parallel to vessel centerline
 □ Direct guidewire through stenotic channel
 □ Advance catheter through lesion over guidewire
 □ Position catheter distal to lesion; remove wire
 □ Inject contrast; confirm catheter tip position
 – Follow sequence for stent placement

29. Venous stent
 Lesion location determines stent appropriateness:
 Repeated venous angioplasties may be more
appropriate for maintaining long-term patency
 Thoracic inlet:
 – May-Thurner: syndrome: often apparent with
 intravascular US (IVUS), suggesting stenting often
 appropriate
 – Central vein occlusion/stenosis:

30. POST PROCEDURE
 Things to Do
 • Arterial stent
 ○ Initiate dual antiplatelet regimen after procedure
 – Clopidogrel 75 mg daily for 4-6 weeks
 – Aspirin 81 mg daily, indefinitely
 • Venous stent
 ○ Consider systemic anticoagulation if stent placed
following thrombolysis
 Encourage lifestyle modification
 ○ Smoking cessation, cholesterol/diet control, exercise
 regimen

31. Complications
 ○ Vessel rupture-Most feared complication(s)
 – May be caused by stent oversizing/aggressive PTA
 □ Always maintain guidewire access across lesion
 until posttreatment DSA performed and reviewed
 – Stabilize by inflating balloon to tamponade
 – Requires covered stent or surgical repair
 ○ Other vascular injury
 – Dissection, perforation
 Immediate/periprocedural complication(s)
 ○ Access site complications: Hematoma, pseudoaneurysm,
 AV fistula
 ○ Stent migration: Stent too small
 – If still over wire, may tack down with larger stent
 ○ Contrast hypersensitivity reaction
 ○ Contrast-induced nephropathy
 Distal embolization of plaque (2-8% incidence) or
 thrombus

32.  Delayed complication(s)
 ○ In-stent restenosis (ISR)
 Stent fracture
 – Usually at site of repeated extrinsic compression (e.g.,
 subclavian vein)
 – Or sites of repeated torsion, compression, flexion
 (e.g., superficial femoral artery)
 ○ Immediate/delayed arterial stent thrombosis (2-10%)
 – Minimize with antiplatelet/anticoagulation agents

35. THE IDEAL VENOUS STENT
 The perfect venous stent will restore physiological blood flow without
modifying the vein's mechanical properties and function, thus allowing blood
return from the periphery to the heart and balancing blood volume and
pressure between organs.
 The following features will impact stent performance and treatment outcomes
and should be considered when treating venous diseases:
 Stent structure: material composition (stainless steel, alloys such as Elgiloy®,
nickel titanium/nitinol), stent size/design, strut thickness, cell design (laser
cut vs braided structures, closed vs open cell)
 Mechanical properties: radial strength, radial stiffness, acute recoil,
foreshortening, global and local crush resistance
 Deployment method: self-expandable versus balloon expandable
 Visibility under fluoroscopy and artifacts during computed tomography and
magnetic resonance imaging
 Bare-metal versus covered stents
 Presence of a drug

36. Dedicated Venous stents
 Venovo Venous Stent System (BD Interventional )
 Abre Venous Self-Expanding Stent System (Medtronic)
 Zilver Vena Venous Self-Expanding Stent (Cook
Medical )
 Sinus-Obliquus, sinus-Venous , sinus-XL Flex
(optimed )

51. TIPS reduction stent
 To increase the pressure gradient after TIPS procedure
 Repositionable self expanding nitinol stent

52. KEY POINTS
 There is a growing need for dedicated endovascular
devices to treat pathologies specifically affecting the
arterial and venous system.
 Stent material and structure, mechanical properties,
deployment method, visibility, and coating are crucial
features that must be analyzed and developed
specifically for angioplasty use and may differ
depending on whether the lesion is nonthrombotic,
acute thrombotic, or chronic thrombotic

53. Thanks