EMBOLIZATION AGENTS

EMBOLIZATION AGENTSDr.N.SundareswaranResident BIREmbolizationEmbolization is defined as the "therapeutic introduction of various substances into the circulation to occlude vessels, either to arrest or prevent hemorrhage to devitalize a structure, tumor, or organ by occluding its blood supply to reduce blood flow to an arteriovenous malformation.2Therapeutic goalsAn adjunctive goal (eg, preoperative, adjunct to chemotherapy or radiation therapy) A curative goal (eg, definitive treatment such as that performed in cases of aneurysms, arteriovenous fistulae [AVFs], arteriovenous malformations [AVMs], and traumatic bleeding) A palliative goal (eg, relieving symptoms, such as those of a large AVM, which cannot be cured by using embolotherapy alone)

Embolizing agentsNatural productsAutologus blood clot- temporary

Autologus muscle fragmentsAutologus fat semipermanent Lypophilized human dura mater

Particulate emboliBiodegradable particlesGel foamMicrofibrillar collagen temporaryStarch microspheresPermanent particlesPolyvinyl alcohol(PVA)Plastic,glass, and metal microspheresliquidsEthanolIodized oil(lipiodal,ethiodal)Glue or Cyanoacrylate, or N- -butyl-2-cyanoacrylate (NBCA)Onyx permanentSodiumtetradecyl sulfateBoiling contrastHypertonic glucoseMechanical embolic agentsMetal based agentsWires with threads(coil emboli)Bare wiresWires that induce electro occlusionMetal devices attached with occlusive plugsBalloons detachable non detachableOthers Devices for closing defects and shunt associated with congenital heart diseaseEnovascular grafts,plain threads, bristle brushesLaser that induce occlusionGel foam sterile gelatin sponge intended for application to bleeding surfaces for hemostasis or for use as a temporary intravascular embolic materialwater-insoluble, off-white, nonelastic, porous, and pliable material.Gelfoam is usually absorbed completely (depending on the amount used, degree of saturation with blood, and site at which it is used), with little tissue reactionDuration 2days to 6weeksTreating benign sources ofbleeding like trauma or temporary devascularization of mass

Tris-acryl gelatin microspheresbiocompatible, hydrophilic, nonresorbable, and precisely calibrated particles produced from an acrylic polymer and impregnated with porcine gelatinsizes of 40-1200 msupplied in a pyrogenic sterile sodium chloride solution.Polyvinyl alcoholPermanent mechanical occulusion of vessel lumen with ingrowth of thrombus and fibrinadministered in a mixture of contrast medium and isotonic sodium chloride solution under fluoroscopic guidanceAggregation of PVA particles can be minimized by using dilute contrast medium in a matched-density suspensionOmnipaque and sodium chloride solution can be used in a ratio of 1:0.4 for contour particle suspension. Used in Av malformation, tumours, BAE.

particle sizes ranging from 100-1200 m ethanoldirect toxic effect on the endothelium that activates the coagulation system and causes the microaggregation of red blood cells.damaging if it reaches the capillary bed of any given tissue (eg, skin), and it usually causes significant soft-tissue swelling, which may subsequently cause compartment syndrome (nerve compression).large amounts of absolute alcohol enter the systemic circulation, toxic effects can occur. central nervous system (CNS) depression, hemolysis, and cardiac arrest. Ethanol 1 mg/kg is the maximum amount that can be injected during a single session.Sodium tetradecylsulfatecontains 2% benzyl alcohol and is commonly used for VMs and varices.less painful for the patient, and it is considered to be less toxic then absolute alcohol.Cyanoacrylate,N- -butyl-2-cyanoacrylate (NBCA) is a rapidly hardening liquid adhesive often referred to as glue.substance hardens (polymerizes) immediately on contact with blood or other ionic fluid. Polymerization results in an exothermic reaction that destroys the vessel wall.Because of the rapid polymerization, coaxial catheterization, precise positioning of the delivery catheter, and considerable skill are required for NBCA embolization. When a suitable location is reached by using a microcatheter, the catheter is flushed with 5% dextrose to clear it of any blood or contrast medium.onyxliquid embolic agentmixture of ethylene vinyl alcohol co-polymer (EVOH) dissolved in dimethyl sulfoxide(DMSO).Micronized tantalum powder is suspended in the liquid polymer/DMSO mixture to provide fluoroscopic visualizationUpon contact with blood (or body fluids) the solvent (DMSO) rapidly diffuses away causing in-situ precipitation of a soft radiopaque polymeric embolus.onyxThe lower the concentration of the copolymer, the less viscous the agent and themore distal penetration can be achieved.Onyx is manufacturedas Onyx 18, Onyx 20, and Onyx 34Onyx 18 and 20are used for embolization of a plexiform nidus, Onyx 34 is used for embolization of large arteriovenous shunts in the AVM

coilsmicrocoils and macrocoilsMacrocoils, also called Gianturco coilsOcclusion occurs as a result of coil-induced thrombosis rather than mechanical occlusion of the lumen by the coil.To increase the thrombogenic effect, Dacron wool tails are attached to coilsCollateralization is a potential disadvantage of coil embolization, and it can result in the persistence of flow into the vascular territory of the vessel that was embolized with the coil.proximal occlusion occurs with coil embolization, repeat intervention via the same artery becomes difficult

IndicationsVascular anomalies (eg, AVM, AVF, venous malformation [VM], lymphatic malformation [LM], and hemangioma) Hemorrhage (eg, pseudoaneurysms and GI tract, pelvic, posttraumatic, epistaxis, and hemoptysis bleeding) Other conditions (eg, tumors, varicoceles, and organ ablation)

Vascular anomalies2 categories: hemangiomas and vascular malformations. Vascular malformations are categorized further as high-flow lesions (AVM, AVF), low-flow lesions (capillary malformation, VM, LM), or combined vascular malformations.hemangiomaRarely embolization may be necessary because of spontaneous hemorrhage or functional abnormality caused by the extreme size of the lesion or the particular anatomic location or because of significant congestive heart failure. patients in whom a hemangioendothelioma causes Kasabach-Merritt phenomenon (platelet trapping)goal of embolotherapy is to block a large percentage of the tumor vessels, thereby preventing further trapping and destruction of the platelets and hastening involution of the lesionAVMnidus of abnormal vessels in which shunting of arterial blood to veins occurstranscatheter embolization and/or sclerotherapyWhenever possible during primary embolotherapy, the nidus should be embolizedProximal embolization or ligation of the feeding arteries usually worsens matters because of subsequent recruitment of collaterals, and transluminal embolization of the nidus cannot be performed afterward.Gelfoam,PVA ,Steel coils useddirect percutaneous cannulation of the nidus can be attempted.

Pulmonary AVMshigh association with osler-weber-rendu syndrome (also called hereditary hemorrhagic telangiectasia syndrome).simple lesions, a single artery and vein are involved complex lesions, 2 or more supplying arteries and 1 or more draining veins are involved.Most pulmonary AVMs (80%) are simple.surgical approach (thoracotomy and resection) is the traditional mode of therapy, transcatheter embolization is currently a preferred alternative.Complications non target embolization in the systemic circulation (through the AVM shunt) or in other noninvolved pulmonary arteries. properly sizing the coil to the feeding (afferent) artery is essentialfeeding arteries larger than 3 mm should be embolizedcoil that is 2- to 3-mm larger than the feeding artery is usually selected. If the feeding artery is large in caliber (>12 mm), a balloon occlusion of the proximal artery via a second groin puncture can be used for a more controlled coil deployment.AVFcongenital or secondary to trauma, surgery, or underlying vascular abnormalityGelfoam or particles are not appropriate for use in AVF embolizationDetachable coils or balloons are ideal because these embolic materials can be positioned optimally before they are detacheddisadvantage of coil embolization is that the clot that forms around the coil may dissolve, resulting in recanalizationthrombosis can be augmented by soaking the coils in thrombin before deployment or by injecting sclerosants around the coils.Hemorrhageembolization can be particularly effective in hemorrhage, regardless of whether the etiology is trauma, tumor, epistaxis, postoperative hemorrhage, or GI hemorrhageIt can be performed anywhere in the body that a catheter can be placed, including the intracranial vasculature, head and neck, thorax, abdomen, pelvis, and extremities. With the availability of coaxial microcatheters, superselective embolizations can be performed. Selective and superselective angiography is more sensitive in finding the source of bleeding diagnostic angiography -Hemorrhage is identified by active extravasation of contrast medium outside of the confines of the vessel lumen. CECT radionuclide scans with technetium-99m (99m Tc)labeled red blood cells (RBCs) are important in guiding angiographic examination.Embolizing agents in hemorrhagecoils are typically the agent of choice advantages of coils - high radiopacity and they can be deployed with high accuracy.Particulate embolic agents useful in the setting of acute hemorrhage include polyvinyl alcohol (PVA) and absorbable gelatin sponge (Gelfoam).9,12 Trisacryl microspheres (EmbospheresGelfoam is generally a temporary occlusive agentGelfoam can be useful in trauma cases in whicha temporary occlusion is desired while either surgical repair of the injury is undertaken Absolute alcohol, small particles, and surgical gelatin powder not useful in the setting of hemorrhage they cause occlusion at the capillary level, leading to tissue necrosis. Because of tissue necrosis, these agents are typically reserved for tumor embolization where cell death is the intended resultBalloons are not routinely used in patients with hemorrhage

epistaxisAcute management includes chemical or electrocautery and nasal packingIf fails surgery or embolization next choiceadvantage of embolization over surgical ligation is the more selective blockade of smaller branchesComplications of embolization may include the reflux of embolization material outside the intended area of embolization, (stroke or blindness)

hemoptysisBronchial artery embolization is performed in patients with massive hemoptysis, defined as 500 mL of hemoptysis within a 24-hour period. bronchiectasis, cystic fibrosis, neoplasm, sarcoidosis, tuberculosis, and other infectionsMedical and surgical treatments for massive hemoptysis are usually ineffectivetranscatheter embolization has become the therapy of choice for massive hemoptysisEmbolization has an initial success rate of 95%, 5F reverse-curve catheter(eg, a Mikaelsson catheter or Shetty catheter) or adouble-curve catheter (eg, a cobra-shaped catheter or "headhunter" catheter)is used to cannulate the origins of the bronchial arteries, typically arise at the level of the T3-T7 thoracic vertebraemost common situation,1 artery supplies the right lung and2 arteries supply the left;Most importantly, spinal arteries must be identified during angiography. Spinal arteries can have common origins with intercostal branches and are identified by a characteristic "hairpin" loop overlying the vertebral column. The presence of spinal arteries may be a contraindication to embolizationPermanent embolic agents (eg, PVA) are typically used

Bronchial angiogram revealed

- hypervascularity - bronchial artery hypertrophy - hypervascularity with shunting - dense soft tissue staining - vascular abnormalities and - extravasation of contrast

GI hemmorhageupper GI tract hemorrhage are ulcer disease, gastritis, malory- weiss tears, and varices. lower GI tract hemorrhage are angiodysplasia, diverticulosis, and bleeding after endoscopic biopsy. Embolization is usually the first line of treatment in patients with upper GI tract bleeding and is used as the second line of treatment in patients with lower GI tract bleeding (usually used if vasopressin treatment fails).

If the bleeding source is identified on arterial angiogram , the patient is treated by using either intra-arterial vasopressin infusion (Pitressin) or embolization of the bleeding mesenteric arteryThe most commonly used embolic agents are coils (macrocoils or microcoils) and Gelfoam pieces ,PVAPelvic hemorrhageeither posttraumatic or postpartumDetailed angiographic examination with superselective injections in the branches of the internal iliac artery is mandatory.Embolization can be performed by using an autologous blood clot, Gelfoam torpedoes, PVA particles, cyanoacrylate (glue), coils, or detachable balloons.At the capillary level, embolization with small particles or Gelfoam powder is contraindicated (because of the elimination of collateral flow, which results in massive tissue necrosis).Chemoembolization commonly performed in hepatic malignancieswith unresectable liver tumors, particularly hepatocellular carcinoma and metastatic liver diseaseproceed with chemoembolization, the patent portal vein with hepatopedal flow is typically required. The bilirubin level should be less than 3 mg/dL The most commonly used chemoinfusion mixture consists of 10 mL of lipiodol ultrafluid , 5 mL of Omnipaque 300 and 50 mg of doxorubicin.The chemoinfusion is usually followed by embolization with a slurry of gelatin sponge powder (Gelfoam).

Utrine fibroid Transcatheter embolotherapy is a well-recognized therapeutic alternative to surgery with a high patient satisfaction rate PVA or microspheres are the embolic agents most often used in patients with uterine fibroids. Particle sizes of 355-500 m and 500-710 m are used most commonly. Embolization is usually performed with an initial angiographic examination of the internal iliac arteries, followed by catheterization of the uterine arteries and the delivery of particles under fluoroscopic guidance

Malignant tumoursIndications for embolotherapy in neoplastic conditions include preoperative embolization and palliative embolization, It alleviates symptoms, reduces further dissemination, and increases the response to other treatment modalities (eg, radiation therapy).Renal malignancy is the most common type of tumor treated with embolotherapypelvic malignancies and bone tumorsComplicationsPost embolization syndrome-fever,pain,nausea leukocytosis 3to 5 daysPainPulmonary or systemic embolizationAVM- Gelfoam,PVA ,Steel coils AVF- Detachable coils or balloonsEpistaxis,hemoptysis- PVA,GelfoamGIT,Pelvic hemorrhage- coils. Gel foam,PVAUterine fibroid- PVA or microspheres Chemoembolization- lipiodol +Omnipaque +doxorubicin Organ ablation- , PVA, ethanol , NBCAOnyx- brain AVM,anerysm.spinal AVM,angiomyolipomaTHANK U