Embolization Agents

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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 i