Embolizing Agents

Presenter:
Swastika Pandit
B.Sc.MIT 4th year
NAMS,Bir hospital
Embolization

• Embolization refers to lodging of an embolus within the bloodstream.

• It may be of natural origin embolism (Pathology),for example pulmonary embolism.
Or Artificially induced.
• Therapeutic introduction of substances into circulation, to arrest or prevent
hemorrhage, to devitalize a structure, tumor or organ by occluding blood supply.
• Embolization means: “obliteration of a vessel by introducing into the bloodstream
an occlusive agent (foreign body, biological tissue, sclerosing fluid, etc.), which
produces the deliberate interruption of vascular flow, mechanically or by
producing an intense inflammatory reaction of the vessel wall”.
• Deliberate occlusion of a blood vessel to achieve a therapeutic result.
Therapeutic goals of Embolization

• An adjective goal : preoperative, adjunct to chemotherapy or radiotherapy.

• A curative goal : definitive treatment in case of aneurysm, AVFs, AVMs and
traumatic bleeding.
• A palliative goal : relieving symptoms such as large AVMs
 Embolic agents

Temporary Permanent

• Gel Foam Others Liquid agents

Particles Coils
• Collagen • PVA • Pushable • Ampltser • Glue
• Thrombin • Embospheres • Injectable Plugs • Onyx
• Detectable • Detectable
• Alcohol
-Mechanical Ballons
• AL GEL
-Electrolytic • GGVOD
-Hydrolytic
Device selection

• Vascular territory to be embolized

• Degree of occlusion—proximal or distal—desired
• Permanence of occlusion i.e Temporarary or Permanant
Permanent Large-Vessel Occlusions

• Coils- Pulmonary AVM

• Balloons
• Amplatz Vascular Plug
• Guide wires
• Silk suture material
Permanent Small-Vessel Occlusions

• Particles
• Liquid sclerosants
• Liquid adhesive
• Ethiodol
• Thrombin
• Onyx
Temporary Large-Vessel Occlusions
• Gel foam sponge
• Autologous clot

Temporary Small-Vessel Occlusions

• Gel foam powder
• Starch microspheres
• Fibrillated collagen
Temporary embolic agents
Gelfoam (Gelatin Foam)

• It is the most widely used temporary embolic agent, is an absorbable bioprosthetic material available
as a block (sponge or sheet) or as a powder. Gel-foam powder particles range from 10 to 100 μ.
• It provides a temporary occlusion lasting approximately 3 to 6 weeks.
• It is made up of purified skin gelatin
• First used for cortico-cavernous fistula(1964)
• It is available in sterile sheets & powder.
• Gel foam is cut into 1-2 mm pieces
• Mixed with dilute contrast
• Injected as pledgets/ prepared as slurry
Mechanism of action of gel foam

Its aggregates or swells on hydration into larger particles

Mechanical obstruction

Slowing of blood flow

Hastening thrombus formation

Advantage
• As it is temporary in nature advantageous in haemoptysis & trauma
• Low cost
• widely available
• and easily modified to the size of the target artery
Disadvantage
• Can cause infection due to the trapped air bubbles
• Can lead to ischemia due to small size (< 70 µm)
Used for
• embolization of pelvic trauma or postpartum hemorrhage, (especially when there are
multiple punctuate bleeding sites from various branches of the internal iliac artery.)
Setup for particle embolization. Larger
syringe is reservoir and smaller is for
injection. Open end of the three-way
connects to the catheter. This setup is
for all particles as well as gelfoam
slurry.
 Embolization material and substance

• 1st agent used was

• Autologous blood clot (temporary occlusive agent)
Method:
• Aspirate roughly 20 mL of the patient's blood and allow it to clot, then discard the supernatant and
reintroduce the clot through the catheter. If desired, the clot can be opacified by adding sterile tantalum
powder.
Advantage:
• Easily and quickly obtained
• Absence of cost.
• Lack of adverse reaction(biocompatible).
Disadvantage:
• Recanalization occurs within hours to days due to body’s natural clot lysis mechanism
 Uses:
• Autologous blood clot seal (ABCS) after biopsy of lung lesions can reduce or prevent pneumothorax.
• Epidural blood patch to relieve post Dural puncture headaches caused by lumbar puncture.

Schematic display of thrombin injection in a false aneurysm.

Permanent embolizing agent

Particles: Polyvinyl Alcohol Particles

• First used in 1974
• it is a plastic sponge that is fragmented and filtered to a
certain size range. They produce permanent occlusion by
adhering to the vessel wall and causing an inflammatory
reaction and vessel fibrosis
• Particles are made from PVA sheets – vacuum dried & rasped
into particles
• Particles are filtered with sieves(filtering devices) and PVA is
available in sizes between 50 and 2000 µm, the typical size
ranges used clinically are 300 to 500 µm or 500 to 700 µm.
Mechanism of action PVA
• PVA particles are irregular in shape which (oval, oblong, irregular and angulated) promote aggregation.
• PVA particles :
Adherent to vessel wall

Stagnation of flow

Inflammatory reaction

Vessel fibrosis

Permanent occlusion
Uses
• Uterine fibroid embolization -either for preoperative devascularization or as definitive treatment.
• JNA (Juvenile nasopharyngealAngiofibroma) embolization.
• Bronchial artery embolization.
• Portal vein embolization. Etc
Disadvantage
• Occludes vessels from proximally due to irregular size.
• Can cause catheter occlusion which can lead to non targeted embolization when catheter is flushed.
• Smaller particles have a significant risk of tissue infarction due to their distal level of occlusion.
Microspheres (embospheres, biosphere medical )
• They are perfectly round and slightly deformable embolic agents, they can be compressed approximately
20% of their diameter.
• They have the advantage of having a uniform size, which decreases the risk that smaller spheres may end up
in distal vessels and cause ischemic complications.
• Its diameter varies between 50 and 1,200 microns.
• They are not radiopaque, so they must be mixed with contrast medium
Embosphere: Tris-acryl Gelatin Microspheres

• Embospheres are precisely calibrated, spherical, hydrophilic, micro porous beads made of an
acrylic co-polymer, which is then cross-linked with porcine gelatin.
• The hydrophilic surface prevents aggregation, allowing a more predictable, uniform vessel
occlusion than PVA, as well as easier delivery through small catheters.
• Embospheres are available in six size ranges: 40 to 120 μm, 100 to 300 μm, 300 to 500 μm, 500
to 700 μm, 700 to 900 μm, and 900 to 1200 μm. Embospheres are packaged in 20-mL prefilled
syringes containing 2 mL of spheres in saline . Embosphere gold particles are colored for
visibility.
Diagrammatic representation
 SIR Spheres

• SIR-Spheres microspheres contain resin based microspheres with

an average diameter between 20 and 60 micrometre. The
microspheres are impregnated with 90Y, a beta radiating isotope of
yttrium
• Once injected into the hepatic artery via a catheter the
microspheres will preferably lodge in the vasculature of the
tumour. The radiation will lead to damage of tumour tissue and, in
the best case to a complete elimination of the tumour. Due to the
half-life almost all of the radiation is delivered within 2 weeks.
After 1 month almost no radioactivity will remain.
• used to treat patients with unresectable liver cancer.
SIR Spheres microspheres
• Provide internal radiation of hepatic malignancies.
 Mechanism of microsphere

• Same as PVA Particles. That is they:

Adherent to vessel wall

Stagnation of flow

Inflammatory reaction focal angio-necrosis Vessel fibrosis

Permanent occlusion
Advantage
• Particles accumulation in catheter tube is uncommon.
Disadvantage
• Needs intermittent brisk stirring to prevent sedimentation.
• Embospheres are composed of porcine gelation which has
allergic potential
• Careful attention in sizing is required because same size
embosphere will penetrate more deeply compared with
PVA which could cause unintended ischemia.

Uses
• In the treatment of fibroid by uterine artery embolization
• liver embolization in patients with metastatic Microspheres in uterine Fibroids treatment
neuroendocrine tumors
• In the preoperative embolization of meningiomas
• Embolization of facial AVM
 Coils
• Coils are permanent embolic agents that come in a variety of shapes and sizes .First embolic coils consisted of
pieces of stainless steel guide wires onto which strands of wool had been woven to add a matrix for thrombus
formation.
• They are typically used for occlusion of larger vessels and cause complete occlusion equivalent to surgical
ligation .
• Stainless-steel coils are best suited for high-flow applications due to their high radial force, which helps
prevent dislodging.
• Coils are generally made of steel or platinum. Although more expensive, platinum coils are more malleable and
radiopaque and are easier to see under fluoroscopy compared with similarly sized and shaped steel coils
• Platinum coils are highly visible under fluoroscopy and are much softer than stainless steel. This facilitates
accommodation of the coil to the vessel.

• Appropriate sizing is important to ensure occlusion of the vessel at the intended location.
 MECHANISM OF ACTION

Coils in blood vessel

Slowing of blood flow Thrombogenesis Clot formation Vessel wall damage

Release of thrombogenic factors

Thrombogenesis

Clot formation
 Coils
• Size - 0.008 to 0.052 inches

• Length – 1 to 300 mm

• Diameter – 1 to 27 mm

• Shape – J or C shaped, helical, conical, straight and complex 3D shapes.

• Coils may be bare or fibered with material such as dacrum, nylon fiber, polyster, wool, silk or PVA (to increase
thermogenicity)

• In general coils should be sized 20 to 30 % larger than what the vessel measures on pre deployment angiogram
to prevent distal embolization / migration.
Advantage
Easy to see, control and display
Causes complete occlusion of vessels
Disadvantage
Occlusion of non target vessels
Coil migration
Vessel dissection/ perforation
Vessels rupture(soft coils are used to reduce incident)
Infection
Allergic reaction
Uses of coil

• Applications for coil embolization include treatment of hemorrhage – Aneurysm.

• Occlusion of arteriovenous fistulas.
• Preoperative or pre-stent graft vessel occlusion.
*The main goal is prevention of rupture in unruptured aneurysms, and prevention of rebleeding in
ruptured aneurysms by limiting blood circulation to the aneurysm space
* Embolization with coils produces a focal occlusion, leaving the vessel distal to the coil patent, similar
to surgical ligature. Therefore, coils are utilized in almost any application in which precise vessel
occlusion.
Coils
Methods of delivery

• Pushable coils
• Injectable coils
• Detachable coils
 Mechanical
 Electrolytic
 Hydrolytic
Pushable coils
• Most commonly used
• Special guide wire with bulbous tip is used to physically push the coil through an end hole catheter
into a desired position
Advantage
• Ready availability
• Relative cost and easy to use
Disadvantage
• Reposition is not possible
• Can be trapped at sharp curves of vessels.
• If incompatible with the catheter, can become irretrievably jammed in the catheter
Pushable coil. Left to right: package, loaded introducer, initial
introducing stylet.
Injectable coils(liquid coils)
• These are the soft, non fibered platinum coils of 0.008 to 0.016 inch in diameter.
• Injection through a catheter via a small syringe with saline.
• Quicker method.
• Liquid coils are deployed by forceful injection of contrast through the catheter after loading the coil.
Advantage
• Tight coil compaction Ability to accommodate to tortuous anatomy
• Ability to flow to a target distal to the catheter if required
Disadvantage
• Vigorous injection can result in pushing the catheter back substantially and risking non target
embolization
Detachable coils

• The first detachable coil was described in 1977 by Professor Cesare Gianturco.
• Cesare first used these coils to embolize renal tumors
• These coils are not routinely used.
• It is non fibered, extremely soft.
• Uncoated platinum coil fixed to a stainless steel delivery wire.
• They come in a variety of shapes such as– 3D basket type,2D helical type.
• Current detachable coils deploy by a variety of mechanisms including mechanically, by electrolysis, and via hydrostatic
means.
• Used in AVM and Aneurysms.
Disadvantage
 expensive,
 large setup time
 the coil can rotate or flip at detachment by inadvertent detachment during wire manipulation .
• The disadvantage of this system is that there is often friction between the microcoil and
microcatheter
Mechanically detached coil (hinge
mechanism).
A. Mechanical coils
Mechanical detachment includes interlocking mechanical detachment and screw-
release mechanisms. The interlocking mechanism uses small metal beads, or hinge,
at the proximal coil tip and end of the wire. The coil is fastened by overlapping the
beads hinge .Within the catheter the coil is attached, but once out of the catheter the
beads separate and the coil is released.
Disadvantage:
• friction between the microcoil and microcatheter
B. Electrolytic coils(GDC-Gugliemi detachable coil)
• Electrolytic detachment coil was designed and first used by Dr. Guido Guglielmi
in 1991 .
• The original GDC is a non-fibered, extremely soft, uncoated platinum coil affixed
to a stainless steel delivery wire.
• Coil is welded to the pusher wire in the desired position.
• The wire is attached to a battery device.
• The current melts the welded connection between the coil and the wire and detaches the coil.
• Currently, the platinum coil is welded to platinum- tungsten alloy and has a highly successful
deployment rate
• A 1-mA current is used to detach the coil at the weld point. A 2-mA current can alternatively be
used to detach the coil more quickly
Advantage :
• Minimally invasive
• Requires less time than surgery
Disadvantage :
• Expensive
C.HYDROGEL COILS

• It is a detachable platinum coils(0.008-to-0.016-inch diameters) coated with an

expandable polymer.
• When detached in the vasculature > polymer expands> coil diameter increases from
0.014 to 0.027 inches.
• Complete expansion occurs within 20 minutes.
• These are extremely soft, non fibered platinum coils . Although made of metal, liquid
coils can be delivered across tight bends and conform to the space into which they are
injected
 Advantage :
• greater volume expansion & occlusion than regular coil
• Do not depend on thrombus formation
• ability to accommodate to tortuous anatomy, and ability to flow to a target distal
to the catheter if desired
Disadvantage :
• coil can get struck in the catheter if the coil is not compatible with the delivery
system.
Others

1)Detachable balloon
• It was first used in 1974
• Balloon is made up of latex of size 6 to 14 mm and silicon size 6 to 10
mm.
Uses
• cortico- cavernous fistula, pulmonary AVMs, large vessel occlusion.
Advantage
• Ability to occlude large vessel. possible reposition.
Disadvantage
• Rupture of vessels, deflation, migration and premature detachement.
2)Amplatzer vascular plug
• It is a new device (expandable nitinol mesh occlusion device)
• Amplatzer I – simple thick disk 4 to 16 mm
• Amplatzer II – thin disk 3 to 22 mm
• They have stainless steel screw attachment to delivery wire & radio- opaque marker bands at both ends.
Uses
Internal iliac artery, mesenteric artery, Renal artery, Portal vein, Splenic Artery.
Advantage
• reduces need for multiple coil hence saves money and time.

Disadvantage
• used in straight segment of vessel which dose not taper. Does not cause immediate thrombosis . They
are not fibered & depend on patient’s ability to form thrombus.
 DETACHABLE SACK VASCULAR OCCLUSION DEVICE

• First described by Dr. Ronald G. Grifka and Prof. Cesare Gianturco, the detachable
sack Grifka-Gianturco vascular occlusion device.
• (GGVOD) incorporates a flexible nylon sack in varying diameters attached to a
4.5F sack catheter . Coils are advanced into the sack and then the filled sack is
released from the catheter by advancing a release catheter up against the neck of the
sack. The sack catheter is the withdrawn firmly, which releases the sack. The
GGVOD allows repositioning of the device before release; coils can be pulled out
of the sack and the sack can be pulled back into the sack catheter
Permanent liquid agents

1.Glue
• Glue (N-BUTYL- 2 CYNOACRYLATE - NBCA)
• Preparation:
 1 gm. of tubes of NBCA – free monomer, when expended to anionic
environment(blood & water ) polymerization occurs.
 10 ml ethiodized oil(Made from iodine and poppyseed oil) – vehicle and acts as a
polymerization occurs.
 1gm of tantalum powder – provides radiographic opacification and initiates
polymerization
 These are mied immediately before use.
N-butyl-cyanoacrylate (NBCA)
• N-butyl-2-cyanoacrylate (NBCA), also commonly known as “glue,” is a clear free-flowing
radiolucent liquid
• It is one of the main liquid adhesive agents used mainly in the treatment of high-flow arteriovenous
malformations, highly vascular tumors and lymphatic malformations.
• It polymerizes rapidly on contact with ionic solutions such as blood or normal saline and forms a
cast of the vessel.
• Although in principle it was used without radiopaque agents, it is currently used in combination
with oils such as Ethiodol in a ratio of 1: 4 (Ethiodol: NBCA).
• Due to the viscosity of this component, it occludes the vessels, and also generates an acute
inflammatory process in the wall of these, which subsequently progresses to chronic in
approximately four weeks .
Mechanism of action

Glue adherent to vessel wall

Inflammatory reaction

Chronic inflammation

Polymerization of glue starts immediately on contact with anion

Glue
• To avoid unintended polymerization by premature contact with anion catheter should be flushed with 5%
dextrose in water intermittently.
• That is why it requires special set up i.e 3 way stopcock (syringe for NBCA and 5% dextrose)
• Immediately after glue injection, catheter tip is retracted to avoid catheter adhesion .

Advantage
• permanent
• completely occludes the vessels
• works instantly
Disadvantage
• Can get entrapped in the occluded vessel.
• Require expertise,
• Polymerization can spread distally or reflux proximally to the intended lesion.
2.Onyx (Ethylene Vinyl Alcohol Co-
polymer-evoh)

• First used as embolic agent by Dr taki in 1990

• Co-polymer of ethylene vinyl alcohol, prepared with dimethyl

sulfoxide solvent .Tantalum powder is added for opacity.
• On contact with blood, the DMSO diffuses away allowing
polymerization of the EVOH, which forms a cast of blood
vessels

• After Onyx is injected into the target lesion, the dimethyl

sulfoxide solvent rapidly diffuses away, causing precipitation
of the polymer and formation of a spongy cast.

• Used mainly in Cerebral and Peripheral AVM emboization

 Mechanism of action

Onyx / EVOH on contact with blood

DMSO (dimethyl sulfoxide) diffuse away

Polymerization of EVOH

Forms a cast
Procedure
• EVOH comes with separate vail of DMSO and DMSO compatible
catheters should be used for procedure.

Catheter is placed in place

DMSO is injected to fill the catheter dead space

Which inhibits in catheter polymerization of EVOH

EVOH is injected under fluoroscopy guidance

Advantage
• Non adhesive allows longer injection times and ability to temporally suspend embolization which allows further
procedure during angiography.

Disadvantage
• Need DMSO compatible catheter
• DMSO is toxic and rapid injection causes vasospasm and necrosis.

Use
• in cerebral AVM
• Injection Rate : < 0.3 ml/ > 40 seconds
Sclerosing agents

3.Absolute alcohol (ethanol)

• Ethanol is the most commonly used sclerosant and causes protein denaturation, which leads to
endothelial damage and permanent vascular occlusion .
• Inadvertent introduction of alcohol into a normal vascular territory can result in serious
complications.
• Latex occlusion balloon catheters are often used to control the flow of ethanol, prevent reflux of
ethanol, and keep ethanol in place for a few minutes, allowing the ethanol to interact with the
endothelium.
• Peripheral indications for ethanol use include renal tumor ablation and portal vein embolization
before partial hepatectomy
• Cause protein denaturation, leading to endothelial destruction and vascular occlusion. Occlusion by
sclerosants is usually permanent.
• Sodium tetradecyl sulfate (Setrol) and Polidocanol

Uses
• ablation of tumours, solid organs, veins, or vascular malformations.
Absolute Alcohol
Mechanism of action

Absolute Alcohol

Denaturation of proteins

Thrombosis

Fibrosis

Infarction
Advantage

• Less cost, easily available

Disadvantage
• Difficulty to control placement ,Lack of opacity and rapid dilution by vascular inflow
4.Calcium Alginate Gel (Algel)

• It is polymer of alginic acid

• Procedure:

Calcium alginate

Liquide alginate (premixed with contrast for visibility)

Calcium chloride

Forms a non adhesive gel foam

Advantage

• Unlike coils, gel fills the entire structure to be occluded

• Catheter occlusion is less likely because two components are injected separately

Disadvantage

• Requires expertise.
References
• Diagnostic imaging : Interventional procedures 2nd edition by Brandt C.Wible .
• Sandeep Vaidya, M.D, Kathleen R. Tozer, and Jarvis Chen .An Overview of Embolic
Agents. Semin Intervent Radiol. 2008 Sep; 25(3): 204–215.doi: 10.1055/s-0028-1085930
• María A L, Alejandra D V, Luis F A, Jorge R U and Alejandro R. Transcatheter Embolization
. Rev. Colomb. Radiol. 2017; 28(4): 4773-81.
• Avinash M, Albert Z, Philip O et.al .A Case-Based Approach to Common Embolization
Agents Used in Vascular Interventional Radiology. American Journal of Roentgenology.
2014;203: 699-708. 10.2214/AJR.14.12480.
• Slideshare
Thank you