Embolization: Therapeutic technique using direct/transcatheter introduction of intravascular agent for hemorrhage control/devascularization/occlusion
Various available agents
Subclassified as temporary and permanent agents
Temporary embolic agents
Gelatin sponge
Inexpensive, readily available, rapid preparation and effect
May be prepared as single torpedo or slurry
Recanalization of embolized vessel is unpredictable, usually occurring within weeks to months
Consider use for rapid embolization of arterial hemorrhage, combine/sandwich with coil embolization, temporarily occlude shunting prior to definitive treatment, occlude percutaneous transhepatic access, or when permanent embolization not ideal
Not ideal for small vessel embolization
Gelfoam
Sheet form; can cut into pledgets/create slurry
Surgifoam
Sheet form similar to Gelfoam
Powder form (40- to 60-μm particle diameter) causes distal occlusion; possible ischemia/infarction
Autologous clot
Delivery of patient's thrombosed blood products
Short effective duration (hours)
Permanent embolic agents
Coils: Mechanical metal occluding device; assumes coiled configuration upon exiting catheter, blocks vessel with fibers, swelling hydrogel; various sizes, configurations, and shapes (e.g., straight, helical, tornado-tapered, 2D, or 3D)
Consider coil use when catheter can be advanced to targeted vessel
Platinum: Compliant, pack well, microcatheter delivery possible
Nitinol: Highly flexible, shape memory
Bioactive coils: Surface modifications added to coil to aid thrombogenicity
Fibered coils
Polymer-coated coils
Hydrogel-coated coils
Protein-coated coils
Pushable 0.035" or 0.018" coils: Inexpensive, straightforward delivery
May be advanced and deployed through catheter with "coil-pusher" wire or careful (semiforceful) injection with 1- to 3-cc syringe of saline
May not be possible to remove/snare if malpositioned
Examples
Azur HydroCoil
Nester, Hilal, and Tornado coils
VortX embolization coils
Detachable 0.035" or 0.018" coils: May be retrieved if in suboptimal location/configuration
Consider detachable coil use in critical vessels, high-flow shunts, or areas where nontarget embolization could inadvertently occur (e.g., gastroduodenal artery)
Used in conventional transarterial chemoembolization where it acts as fluoroscopically visible chemotherapeutic delivery agent and transient arterial embolic
Can occlude lymphatic leaks (50-75%) during lymphangiogram
Added to other embolics during delivery (e.g., ethanol, "glue")
Solidifies on contact with ionic medium (e.g., blood)
Liquid "glue" polymer is mixed with Lipiodol immediately prior to delivery
Ratio with more Lipiodol (5:1) slows rate of glue polymerization/solidification; ratio with less Lipiodol (2:1) increases rate of polymerization/solidification
Nonionic preparation of table, gloves, catheters, syringes vital
All equipment must be meticulously flushed with nonionic solutions (e.g., D₅W)
"Glue" is deployed between nonionic solution
Small volumes of n-BCA:Lipiodol necessary
Caution: Catheter can become "glued" to vessel
Has nonvascular applications, since occlusion does not require platelets/coagulants
Onyx
Ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide (DMSO)
Radiopaque-suspended, micronized tantalum powder added for increased visibility; tantalum may become visible through skin if treating superficial vascular malformations
Precipitates from outside in on contact with aqueous solution as DMSO dissipates
Forms "foam" with lava-like flow pattern
Nonadhesive; catheter very unlikely to stick to vessel during delivery; allows slower, more deliberate injection vs. n-BCA "glue"
Thrombin solutions
Rapidly converts fibrin to fibrinogen, activates coagulation cascade; causes thrombotic occlusion of target
Extremely small volumes (0.2-0.5 cc) typically necessary
Severe potential effects of nontarget embolization; Doppler distal pulse during delivery in extremity
Aneurysm occlusion off-label use
Caution: Do not use if patient had prior allergic reaction to thrombin
Examples of topical thrombin
Surgiflo
Floseal
Sclerosing agents
Detergents: Causing vessel occlusion via inflammation/thrombosis
Consider use in varicose veins, venous malformations, pelvic congestion syndrome, balloon-occluded retrograde transvenous obliteration
Can use as liquid, or mix with air (or CO₂) to form foam
Advantage of foam: Increased contact with wall, requires decreased sclerosing agent
Examples
Ethanolamine oleate iopamidol (Ethamolin): Widely used in Japan
Polidocanol: Widely used in Europe
Sodium tetradecyl sulfate-STS (Sotradecol): Mild sclerosant; typically 3% STS (available in 2-mL vials) is mixed with air/CO₂ (3 mL air: 2 mL STS: Add 1 mL Lipiodol for visualization as needed)
Sodium morrhuate (Scleromate): Fallen out of favor
Examples of other sclerosants
Ethanol: Immediate protein denaturation and cell death
Boiling contrast: Not often used due to patient pain, operator risk
Lymphocele sclerotherapy
Doxycycline: Intracavitary injection effective for treatment of lymphatic malformations; inexpensive, widely available
Tetracycline, bleomycin, talc and fibrin glue intracavitary injection have also been described
Oncologic agents
Drug-eluting beads: Chemotherapeutics are bound to spheres ionically (irinotecan) or osmotically (doxorubicin) and delivered to tumor where chemotherapeutics release from beads, resulting in significantly higher concentrations at tumor bed than can be achieved via IV delivery
Examples
LC Beads (DC Beads in Europe): Blue tint, sizes include 100-300 µm, 300-500 µm, and 500-700 µm
QuadraSphere: Spheres enlarge over time: 30-60 µm, 50-100 µm, 100-150 µm, and 150-200 µm
Radioactive particles: β-emitting particle, Y-90 embedded on microspheres
Selective internal radiation therapy (SIRT)
Examples
SIR-Spheres; resin microspheres, increased particles per dose
TheraSpheres; glass microspheres with increased activity per particle
Stents: Used in association with embolization coils
Stent-assisted coil embolization: Noncovered stent placed across wide neck aneurysm
Coils introduced through stent interstices into aneurysm/pseudoaneurysm using microcatheter
PREPROCEDURE
Indications
Contraindications
Getting Started
PROCEDURE
Patient Position/Location
Procedure Steps
Alternative Procedures/Therapies
POST PROCEDURE
Things to Do
Things to Avoid
OUTCOMES
Problems
Complications
Expected Outcome
Selected References
Doucet J et al: The feasibility of degradable glass microspheres as transient embolic medical devices. J Biomater Appl. 35(6):615-32, 2021
Altun I et al: Blood-derived biomaterial for catheter-directed arterial embolization. Adv Mater. 32(52):e2005603, 2020
Hu J et al: Advances in biomaterials and technologies for vascular embolization. Adv Mater. 31(33):e1901071, 2019
Horbach SE et al: Sclerotherapy for low-flow vascular malformations of the head and neck: a systematic review of sclerosing agents. J Plast Reconstr Aesthet Surg. 69(3):295-304, 2016
Spiotta AM et al: Comparison of techniques for stent assisted coil embolization of aneurysms. J Neurointerv Surg. 4(5):339-44, 2012
Etezadi V et al: Endovascular treatment of visceral and renal artery aneurysms. J Vasc Interv Radiol. 22(9):1246-53, 2011
Zhu X et al: Utility of the Amplatzer Vascular Plug in splenic artery embolization: a comparison study with conventional coil technique. Cardiovasc Intervent Radiol. 34(3):522-31, 2011
Lee BB et al: Management of arteriovenous malformations: a multidisciplinary approach. J Vasc Surg. 39(3):590-600, 2004
de Giovanni JV: The use of Amplatzer devices to occlude vascular fistulae. J Interv Cardiol. 14(1):45-8, 2001
Jackson JE et al: Treatment of high-flow vascular malformations by venous embolization aided by flow occlusion techniques. Cardiovasc Intervent Radiol. 19(5):323-8, 1996
Jander HP et al: Transcatheter gelfoam embolization in abdominal, retroperitoneal, and pelvic hemorrhage. Radiology. 136(2):337-44, 1980
Related Anatomy
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Related Differential Diagnoses
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References
Tables
Tables
KEY FACTS
Terminology
Preprocedure
Outcomes
TERMINOLOGY
Definitions
Embolization: Therapeutic technique using direct/transcatheter introduction of intravascular agent for hemorrhage control/devascularization/occlusion
Various available agents
Subclassified as temporary and permanent agents
Temporary embolic agents
Gelatin sponge
Inexpensive, readily available, rapid preparation and effect
May be prepared as single torpedo or slurry
Recanalization of embolized vessel is unpredictable, usually occurring within weeks to months
Consider use for rapid embolization of arterial hemorrhage, combine/sandwich with coil embolization, temporarily occlude shunting prior to definitive treatment, occlude percutaneous transhepatic access, or when permanent embolization not ideal
Not ideal for small vessel embolization
Gelfoam
Sheet form; can cut into pledgets/create slurry
Surgifoam
Sheet form similar to Gelfoam
Powder form (40- to 60-μm particle diameter) causes distal occlusion; possible ischemia/infarction
Autologous clot
Delivery of patient's thrombosed blood products
Short effective duration (hours)
Permanent embolic agents
Coils: Mechanical metal occluding device; assumes coiled configuration upon exiting catheter, blocks vessel with fibers, swelling hydrogel; various sizes, configurations, and shapes (e.g., straight, helical, tornado-tapered, 2D, or 3D)
Consider coil use when catheter can be advanced to targeted vessel
Platinum: Compliant, pack well, microcatheter delivery possible
Nitinol: Highly flexible, shape memory
Bioactive coils: Surface modifications added to coil to aid thrombogenicity
Fibered coils
Polymer-coated coils
Hydrogel-coated coils
Protein-coated coils
Pushable 0.035" or 0.018" coils: Inexpensive, straightforward delivery
May be advanced and deployed through catheter with "coil-pusher" wire or careful (semiforceful) injection with 1- to 3-cc syringe of saline
May not be possible to remove/snare if malpositioned
Examples
Azur HydroCoil
Nester, Hilal, and Tornado coils
VortX embolization coils
Detachable 0.035" or 0.018" coils: May be retrieved if in suboptimal location/configuration
Consider detachable coil use in critical vessels, high-flow shunts, or areas where nontarget embolization could inadvertently occur (e.g., gastroduodenal artery)
Used in conventional transarterial chemoembolization where it acts as fluoroscopically visible chemotherapeutic delivery agent and transient arterial embolic
Can occlude lymphatic leaks (50-75%) during lymphangiogram
Added to other embolics during delivery (e.g., ethanol, "glue")
Solidifies on contact with ionic medium (e.g., blood)
Liquid "glue" polymer is mixed with Lipiodol immediately prior to delivery
Ratio with more Lipiodol (5:1) slows rate of glue polymerization/solidification; ratio with less Lipiodol (2:1) increases rate of polymerization/solidification
Nonionic preparation of table, gloves, catheters, syringes vital
All equipment must be meticulously flushed with nonionic solutions (e.g., D₅W)
"Glue" is deployed between nonionic solution
Small volumes of n-BCA:Lipiodol necessary
Caution: Catheter can become "glued" to vessel
Has nonvascular applications, since occlusion does not require platelets/coagulants
Onyx
Ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide (DMSO)
Radiopaque-suspended, micronized tantalum powder added for increased visibility; tantalum may become visible through skin if treating superficial vascular malformations
Precipitates from outside in on contact with aqueous solution as DMSO dissipates
Forms "foam" with lava-like flow pattern
Nonadhesive; catheter very unlikely to stick to vessel during delivery; allows slower, more deliberate injection vs. n-BCA "glue"
Thrombin solutions
Rapidly converts fibrin to fibrinogen, activates coagulation cascade; causes thrombotic occlusion of target
Extremely small volumes (0.2-0.5 cc) typically necessary
Severe potential effects of nontarget embolization; Doppler distal pulse during delivery in extremity
Aneurysm occlusion off-label use
Caution: Do not use if patient had prior allergic reaction to thrombin
Examples of topical thrombin
Surgiflo
Floseal
Sclerosing agents
Detergents: Causing vessel occlusion via inflammation/thrombosis
Consider use in varicose veins, venous malformations, pelvic congestion syndrome, balloon-occluded retrograde transvenous obliteration
Can use as liquid, or mix with air (or CO₂) to form foam
Advantage of foam: Increased contact with wall, requires decreased sclerosing agent
Examples
Ethanolamine oleate iopamidol (Ethamolin): Widely used in Japan
Polidocanol: Widely used in Europe
Sodium tetradecyl sulfate-STS (Sotradecol): Mild sclerosant; typically 3% STS (available in 2-mL vials) is mixed with air/CO₂ (3 mL air: 2 mL STS: Add 1 mL Lipiodol for visualization as needed)
Sodium morrhuate (Scleromate): Fallen out of favor
Examples of other sclerosants
Ethanol: Immediate protein denaturation and cell death
Boiling contrast: Not often used due to patient pain, operator risk
Lymphocele sclerotherapy
Doxycycline: Intracavitary injection effective for treatment of lymphatic malformations; inexpensive, widely available
Tetracycline, bleomycin, talc and fibrin glue intracavitary injection have also been described
Oncologic agents
Drug-eluting beads: Chemotherapeutics are bound to spheres ionically (irinotecan) or osmotically (doxorubicin) and delivered to tumor where chemotherapeutics release from beads, resulting in significantly higher concentrations at tumor bed than can be achieved via IV delivery
Examples
LC Beads (DC Beads in Europe): Blue tint, sizes include 100-300 µm, 300-500 µm, and 500-700 µm
QuadraSphere: Spheres enlarge over time: 30-60 µm, 50-100 µm, 100-150 µm, and 150-200 µm
Radioactive particles: β-emitting particle, Y-90 embedded on microspheres
Selective internal radiation therapy (SIRT)
Examples
SIR-Spheres; resin microspheres, increased particles per dose
TheraSpheres; glass microspheres with increased activity per particle
Stents: Used in association with embolization coils
Stent-assisted coil embolization: Noncovered stent placed across wide neck aneurysm
Coils introduced through stent interstices into aneurysm/pseudoaneurysm using microcatheter
PREPROCEDURE
Indications
Contraindications
Getting Started
PROCEDURE
Patient Position/Location
Procedure Steps
Alternative Procedures/Therapies
POST PROCEDURE
Things to Do
Things to Avoid
OUTCOMES
Problems
Complications
Expected Outcome
Selected References
Doucet J et al: The feasibility of degradable glass microspheres as transient embolic medical devices. J Biomater Appl. 35(6):615-32, 2021
Altun I et al: Blood-derived biomaterial for catheter-directed arterial embolization. Adv Mater. 32(52):e2005603, 2020
Hu J et al: Advances in biomaterials and technologies for vascular embolization. Adv Mater. 31(33):e1901071, 2019
Horbach SE et al: Sclerotherapy for low-flow vascular malformations of the head and neck: a systematic review of sclerosing agents. J Plast Reconstr Aesthet Surg. 69(3):295-304, 2016
Spiotta AM et al: Comparison of techniques for stent assisted coil embolization of aneurysms. J Neurointerv Surg. 4(5):339-44, 2012
Etezadi V et al: Endovascular treatment of visceral and renal artery aneurysms. J Vasc Interv Radiol. 22(9):1246-53, 2011
Zhu X et al: Utility of the Amplatzer Vascular Plug in splenic artery embolization: a comparison study with conventional coil technique. Cardiovasc Intervent Radiol. 34(3):522-31, 2011
Lee BB et al: Management of arteriovenous malformations: a multidisciplinary approach. J Vasc Surg. 39(3):590-600, 2004
de Giovanni JV: The use of Amplatzer devices to occlude vascular fistulae. J Interv Cardiol. 14(1):45-8, 2001
Jackson JE et al: Treatment of high-flow vascular malformations by venous embolization aided by flow occlusion techniques. Cardiovasc Intervent Radiol. 19(5):323-8, 1996
Jander HP et al: Transcatheter gelfoam embolization in abdominal, retroperitoneal, and pelvic hemorrhage. Radiology. 136(2):337-44, 1980
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