Endovascular treatment of experimental aneurysms by use of a combination of liquid embolic agents and protective devices

BACKGROUND AND PURPOSE: The use of liquid embolic agents for embolization of cerebral aneurysms has been reported in the neurosurgical literature. The most important limitation of this technique is the relatively poor control of migration of the liquid embolic agent into the parent artery. We performed an experimental aneurysm study using a liquid embolic agent and different protective devices to evaluate the safety and technical feasibility of this endovascular technique. METHODS: Forty lateral aneurysms were surgically constructed on 20 common carotid arteries of swine. Onyx alone was used to obliterate eight aneurysms. Onyx was also used in combination with microcoils (n = 11), microstents (n = 6), balloons inflated proximally to the neck of the aneurysm (n = 6), and across the neck of the aneurysm (n = 7). One control aneurysm was embolized with Guglielmi detachable coils (GDCs) alone. RESULTS: The use of a microballoon across the neck of the aneurysm, a microstent deployed across the neck of the aneurysm, or the deposit of GDCs into the aneurysm allowed faster and more complete filling of the aneurysm with Onyx. However, these protection devices did not totally preclude intractable migration of Onyx into the parent artery (migration rate, 9-33%). CONCLUSION: Although complete occlusion of experimental aneurysms with Onyx is feasible using protective devices, migration of the liquid embolic agent into the parent artery or intracranially remains a difficult challenge. Further experimental studies need to be performed to master this technique and to select those aneurysms that can be safely treated in clinical practice.     

Embolization of peripheral vascular malformations with ethylene vinyl alcohol copolymer (Onyx)

PURPOSE: To demonstrate the feasibility and preliminary efficacy of endovascular embolization of peripheral congenital vascular malformations (VMs) with use of a nonadhesive liquid embolic agent, Onyx. MATERIALS AND METHODS: Nine patients with a mean age of 20.8 years had local low-flow (n = 4), local high-flow (n = 3), or diffuse high-flow (n = 2) VMs located in the upper or lower extremities. In all patients, endovascular embolization was performed via the superselective catheterization of arterial feeders of VMs with use of microcatheters in a coaxial technique. A total of 15 embolization procedures were performed with Onyx, which was composed of 6%, 8%, or 20% ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide. RESULTS: In two of four patients with local low-flow VMs, the lesions were embolized completely. In the other two patients with local low-flow VMs, embolizations were incomplete. The remaining five high-flow lesions of local (n = 3) or diffuse (n = 2) types were also embolized incompletely. In all patients with local low-flow VMs and in one patient with a local high-flow VM, clinical signs and symptoms were resolved significantly. Other patients did show clinical benefit from embolization to varying degrees. CONCLUSION: In our experience in a limited number of cases, Onyx promises and provides important advantages over conventional embolic agents in the endovascular transcatheter embolization of congenital peripheral VMs. However, as with other embolic agents, it is far from perfect.     

Endovascular Embolization of Visceral Artery Aneurysms with Ethylene-vinyl Alcohol (Onyx): A Case Series

We report the application of the liquid embolic agent ethylene-vinyl alcohol (Onyx; MicroTherapeutics, Irvine, CA, USA) in the management of visceral artery aneurysms. The technique and indications for using Onyx are discussed with emphasis on the management of wide-necked aneurysms and maintenance of patency of the parent vessel. None of the cases was considered suitable for stent-grafting or embolization with conventional agents. Two aneurysms of the renal artery bifurcation and one aneurysm of the inferior pancreaticoduodenal artery were treated. Following treatment there was complete exclusion of all aneurysms. There was no evidence of end-organ infarction. Follow-up with intervals up to 6 months has shown sustained aneurysm exclusion. Onyx is known to be effective in the management of intracranial aneurysms. Our experience demonstrates the efficacy and applicability of the use of Onyx in the treatment of complex visceral artery aneurysms.     

Curative embolization of cerebral arteriovenous malformations (AVMs) with Onyx in 101 patients

INTRODUCTION: Onyx has emerged in the recent years as a new embolic material. We present our experience with Onyx in the curative embolization of brain cerebral arteriovenous malformations (AVMs). METHODS: We retrospectively reviewed the files of all patients that we had treated with Onyx embolic material for a brain AVM during the last 4 years. We identified 101 patients who underwent a total of 219 sessions of embolization. RESULTS: The treatment has been concluded in 52 patients; in this group, total occlusion was obtained in 28 (53.9%) patients and near-total occlusion was obtained in 18 (34.6%). The respective figures based on the 101 patients of the study cohort are 28/101 (27.7%) and 18/101 (17.8%). More embolization sessions are to be carried out on the remaining 49 patients. There were three deaths, and eight patients had permanent neurological deficits with a resulting morbidity of 8% and mortality of 3%. CONCLUSION: High rates of total or near-total occlusion of brain AVMs can be achieved with multiple sessions of Onyx embolization with acceptable morbidity and mortality.     

A new liquid embolic material for liver tumors

Purpose: To evaluate the feasibility of a new liquid embolic material, Onyx, for treating liver tumors.Material and Methods: Onyx is a mixture of 6% (w/v) ethylene-vinyl-alcohol copolymer dissolved in anhydrous dimethyl sulfoxide (DMSO) with 28% (w/v) tantalum powder. In addition to 6% Onyx, we also tried 4%, 2% and 1% solutions, prepared by adjusting the amount of DMSO. We used 15 white rabbits with liver tumors created by percutaneous injection of VX2 tumor cells. In 4 groups with 3 rabbits in each, the liver arteries were embolized with 6%, 4%, 2% and 1% Onyx, respectively, and in 3 rabbits DMSO alone was injected. The injections were performed just proximal to the bifurcation of the proper hepatic artery, followed by celiac arteriography. Post mortem, the livers were examined by soft-tissue radiography, and liver-tissue section microscopy.Results: The maximum number of arterial branching points passed by embolic material in either the right or left hepatic arteries was 11, 15 and 16, for 6%, 4% and 2% Onyx, respectively, but was non-measurable for 1% Onyx. Minimum diameters of arteries reached by 6%, 4%, 2% and 1% Onyx in tumorous areas were 40 μm, 35 μm, 20 μm and 10 μm, respectively, and in non-tumorous areas 35 μm, 5 μm, 5 μm and 5 μm, respectively.Conclusion: This study suggests that Onyx may be feasible for treatment of hepatic tumors.     

The treatment of a dural carotid cavernous fistula (CCF) using Onyx via a transorbital approach: a technical note

We report the successful case of embolisation of a Barrow D (White et al. in Am J Neuroradiol 28:1415–1417, 2007) dural carotid cavernous fistula (CCF) with bilateral external carotid artery and internal carotid arterial supply, using a direct percutaneous transorbital approach with the embolic agent Onyx. In particular, we highlight the properties of Onyx which make it suitable to treat the multi-compartmental nature of CCFs. The patient developed transient complications which may be related to the volume of embolic agent used, and we discuss this point further. This is still a developing technique, and we present our case as a technical note to aid those contemplating embolisation via a transorbital approach with Onyx.     

Endovascular Balloon-Assisted Embolization of High-Flow Peripheral Vascular Lesions Using Dual-Lumen Coaxial Balloon Microcatheter and Onyx: Initial Experience

Balloon-assisted embolization performed by delivering Onyx ethylene vinyl alcohol copolymer through a dual-lumen coaxial balloon microcatheter is a new technique for the management of peripheral vascular lesions. This technique does not require an initial reflux of Onyx to form around the tip of the microcatheter before antegrade flow of Onyx can commence. In a series of four patients who were treated with the use of this technique, the absence of significant reflux of Onyx was noted, as were excellent navigability and easy retrieval of the balloon microcatheter. However, in one patient, there was inadvertent adverse embolization of a digital artery, which was not caused by reflux of Onyx but could still be related to balloon inflation.     

Complex Renal Artery Aneurysms: Liquids or Coils?

Although renal aneurysms are considered uncommon lesions, they are being disclosed more often with the increasing use of noninvasive imaging diagnostic methods. As the natural history is poorly defined, criteria for treatment are still controversial. Because it is less invasive, the endovascular treatment of renal artery aneurysms has become preferable to surgery, over recent years. The development of microcatheter-guidewire systems and new embolic materials, primarily used in interventional neuroradiolgy, enables a superselective embolization, even in complex lesions. We describe our experience in 11 complex renal artery aneurysms, using platinum detachable coils, liquid embolic agents (glue and Onyx), and remodeling technique, according to the lesion architecture and topographic classification. Complete durable occlusion was obtained in all cases, with only two minor complications. If an appropriated strategy is done and the tools are available, the endovascular approach currently is the first treatment option for renal artery aneurysms.     

Flüssigembolisate – Onyx als Problemlöser

Clinical/methodical issue

Liquid embolic agents are used for permanent occlusion of capillaries but optimal administration properties are lacking.

Standard radiological methods

The lack of visualization by fluoroscopy and the risk of serious complications are disadvantages of conventional embolic agents, such as ethanol and Histoacryl.

Methodical innovations

Onyx is a liquid embolic agent consisting of ethylene vinyl alcohol copolymer dissolved in various concentrations of dimethyl sulfoxide (DMSO) and suspended micronized tantalum powder to provide contrast for fluoroscopy.

Performance

The physicochemical characteristics of Onyx allow controlled application, forming a defined cast and permanent occlusion. Disadvantages are the high costs. Furthermore, the solvent DMSO requires special catheter material and causes pain during Onyx application.

Achievements

Onyx has been primarily used for interventional neuroradiological treatment but peripheral applications are becoming increasingly more common.

Practical recommendations

Currently, Onyx is mainly used for embolotherapy of endoleaks after endovascular aortic aneurysm repair, for treatment of acute arterial bleeding and for treatment of arteriovenous malformations.     

Late angiographic and clinical follow-up results of 100 consecutive aneurysms treated with Onyx reconstruction: largest single-center experience

We present the long-term clinical and angiographic follow-up results of 100 consecutive intracranial aneurysms treated with Onyx liquid embolic system (MTI, Irvine, Calif.), either alone or combined with an adjunctive stent, in a single center. A total of 100 aneurysms in 94 patients were treated with endosaccular Onyx packing. Intracranial stenting was used adjunctively in 25 aneurysms including 19 during initial treatment and 6 during retreatment. All aneurysms except two were located in the internal carotid artery. Of the 100 aneurysms, 35 were giant or large/wide-necked, and 65 were small. Follow-up angiography was performed in all 91 surviving patients (96 aneurysms) at 3 and/or 6 months. Follow-up angiography was performed at 1, 2, 3, 4 and 5 years in 90, 41, 26, 6 and 2 patients, respectively. Overall, aneurysm recanalization was observed in 12 of 96 aneurysms with follow-up angiography (12.5%). All 12 were large or giant aneurysms, resulting in a 36% recanalization rate in the large and giant aneurysm group. One aneurysm out of 25 treated with the combination of a stent and Onyx showed recanalization. There was also no recanalization in the follow-up of small internal carotid artery aneurysms treated with balloon assistance only. At final follow-up, procedure- or device-related permanent neurological morbidity was present in eight patients (8.3%). There were two procedure-related and one disease-related (subarachnoid hemorrhage) deaths (mortality 3.2%). Delayed spontaneous asymptomatic occlusion of the parent vessel occurred in two patients, detected on routine follow-up. Onyx provides durable aneurysm occlusion with parent artery reconstruction resulting in perfectly stable 1-year to 5-year follow-up angiography both in small aneurysms treated with balloon assistance only (0% recanalization rate) and large or giant aneurysms treated with stent and Onyx combination (4% recanalization rate). Endosaccular Onyx packing with balloon assistance may not be adequate for stable long-term results in those with a large or giant aneurysm. However, the recanalization rate of 36% in these aneurysms is better than the reported results with other techniques, i.e., coils with or without adjunctive bare stents.     

Transarterial Embolization of Type II Endoleaks after EVAR: The Role of Ethylene Vinyl Alcohol Copolymer (Onyx)

Purpose

To determine the feasibility and efficacy of transarterial endoleak embolization using the liquid embolic agent ethylene vinyl alcohol copolymer (Onyx).

Methods

Over a 7-year period eleven patients (6 women, 5 men; mean age 68 years, range 37–83 years) underwent transarterial embolization of a type II endoleak after endovascular aortic aneurysm repair using the liquid embolic agent Onyx. Two patients (18 %) had a simple type II endoleak with only one artery in communication with the aneurysm sac, whereas 9 patients (82 %) had a complex type II endoleak with multiple communicating vessels. We retrospectively analyzed the technical and clinical success of transarterial type II endoleak embolization with Onyx. Complete embolization of the nidus was defined as technical success. Embolization was considered clinically successful when volume of the aneurysm sac was stable or decreased on follow-up CT scans.

Result

Mean follow-up time was 26.0 (range 6–50) months. Clinical success was achieved in 8 of 11 patients (73 %). Transarterial nidus embolization with Onyx was technically successful in 6 of 11 patients (55 %). In three cases the nidus was embolized without direct catheterization from a more distal access through the network of collateral vessels.

Conclusion

Onyx is a favorable embolic agent for transarterial endoleak embolization. To achieve the best clinical results, complete occlusion of the nidus is mandatory.     

Embolization of profunda femoris artery branch pseudoaneurysms with ethylene vinyl alcohol copolymer (onyx)

This report describes the use of a new embolic agent, Onyx, which is composed of ethylene vinyl alcohol copolymer dissolved in 8% dimethyl sulfoxide, in the endovascular transcatheter embolization of traumatic profunda femoris artery branch pseudoaneurysms in three cases. Two of the cases involved massive thigh swelling after penetrating injury and the other involved massive hemorrhage at the site of a surgical fixator pin. Diagnostic angiography revealed pseudoaneurysm formation of the profunda femoris artery branches in all cases. Immediate control angiography after the embolization procedures demonstrated complete closure of the pseudoaneurysms. During the follow-up period there was no recurrent bleeding. The advantages of Onyx over conventional liquid embolic agents and coils are discussed.     

Treatment and follow-up of 22 unruptured wide-necked intracranial aneurysms of the internal carotid artery with Onyx HD 500

BACKGROUND AND PURPOSE: The purpose of this study was to demonstrate endovascular treatment of wide-necked aneurysms of the internal carotid artery with the liquid embolic agent Onyx HD 500. METHODS: Twenty-two wide-necked, large or giant aneurysms of the internal carotid artery (ICA) were treated in 22 patients with Onyx HD 500 (15 ophthalmic, 1 clinoid, and 6 cavernous aneurysms). Sixteen patients were asymptomatic, and mass effect of the aneuryms caused cranial nerve palsy in 6. Seven aneurysms showed regrowth after prior endovascular coiling. RESULTS: Postinterventional angiography demonstrated total occlusion in 18 aneurysms, and a small remnant was left in 4. Clinical and angiographic follow-up data are available in 19 patients (average follow-up, 13 months; range, 5-36 months). Total occlusion was demonstrated in 17 aneurysms (91%), and a partial recanalization was seen in 2. There were 2 ICA occlusions and 1 ICA stenosis. Clinical follow-up demonstrated a transient ischemic attack in 1 patient; 2 with cranial nerve palsy were unchanged, and 2 showed improved symptoms compared with the findings before treatment. The remaining 14 patients were clinically asymptomatic. There was no permanent severe morbidity and no mortality at follow-up. CONCLUSION: The endovascular treatment of wide-necked, large or giant ICA aneurysms with Onyx HD 500 is a treatment option in these selected cases. The benefit is a primary high and stable occlusion rate and good clinical outcome. ICA occlusion caused by Onyx migration in the parent artery is a typical problem, with a benign clinical course in this series.     

Dural arteriovenous fistula of the anterior fossa treated with the Onyx liquid embolic system and the Sonic microcatheter

We report an association of new technologies (the Onyx liquid embolic system and the Sonic microcatheter) for transarterial embolization through the anterior branch of the middle meningeal artery of a dural arteriovenous fistula (DAVF) of the anterior fossa. The place of endovascular treatment in anterior fossa DAVFs is reviewed, and its clinical implications discussed in light of the case of a patient whose management was modified by this association of new technologies.     

Bivalirudin as an anticoagulation agent: safety and efficacy in peripheral interventions

PURPOSE: Traditionally, unfractionated heparin is used to prevent thrombotic complications in peripheral interventions. The purpose of this study is to evaluate the use of bivalirudin as the anticoagulant agent for peripheral interventions. MATERIALS AND METHODS: A retrospective analysis of 108 patients who underwent 110 peripheral interventions between January 2002 and January 2004 and received bivalirudin as the sole anticoagulation agent was conducted at Baptist Cardiac and Vascular Institute. Interventions were performed in the following areas: iliac, femoropopliteal, and distal (n = 55), carotid (n = 31), vertebral (n = 1), renal (n = 14), aorta (n = 7), and subclavian (n = 2). The following procedural and clinical endpoints were examined: death, requirement of urgent surgery or surgery during the same admission, urgent percutaneous revascularization in the same treated vessel, thrombotic or embolic events, bleeding events, and groin complications. RESULTS: A total of 266 lesions were dilated in 185 arteries. There were no procedural mortalities, procedural success was 99.1%, and the complication rate was 3.6%. There was one embolic stroke (0.9%), one thrombosis (0.9%), and two groin hematomas (1.8%). No patient required urgent surgery or reintervention in the same treated vessel. No complications were noted at 7 days after the procedure. There were two interventions by postprocedure day 30: toe amputation and groin debridement. CONCLUSION: Bivalirudin is a safe alternative to unfractionated heparin as the anticoagulation agent in peripheral interventions. This study shows that the complication profile is comparable to other bivalirudin studies. Bivalirudin is effective, easy to use, and is associated with few bleeding complications.     

Stent placement versus percutaneous transluminal angioplasty of human carotid arteries in cadavers in situ: distal embolization and findings at intravascular US, MR imaging and histopathologic analysis.

PURPOSE: To compare endovascular stent placement with percutaneous transluminal angioplasty (PTA) of carotid arteries with respect to distal embolization and findings at intravascular ultrasonography (US), magnetic resonance (MR) imaging, and histopathologic analysis. MATERIALS AND METHODS: PTA was performed in situ in one carotid artery, and stent placement was performed in the other, in ten cadavers (age range, 57-82 years; mean age, 68 years) with severe atherosclerosis by using fluoroscopic and intravascular US guidance. The carotid artery was connected to a pressurized tubing system in which a pulsatile pump circulated water. The effluent water was collected during the interventions, and after filtration and staining, the embolic material was analyzed histologically. After the interventions, the arteries were excised and 1.5-T spin-echo MR imaging was performed. RESULTS: No difference in severity of distal embolization during stent placement versus during PTA was found. The embolic particles were composed mainly of intimal strips and cellular constituents of the atherosclerotic plaques. MR imaging accurately depicted postinterventional changes, and the findings correlated closely with those of intravascular US and histopathologic analysis. CONCLUSION: Although stent placement and PTA were associated with equal distal embolization, the smooth surface and fully patent arterial lumen depicted at intravascular US and MR imaging postinterventionally may indicate that stent placement is preferable to PTA.     

Transarterial Onyx Embolization of Cranial Dural Arteriovenous Fistulas: Long-Term Follow-Up

BACKGROUND AND PURPOSE:Endovascular therapy with liquid embolic agents is a common treatment strategy for cranial dural arteriovenous fistulas. This study evaluated the long-term effectiveness of transarterial Onyx as the single embolic agent for curative embolization of noncavernous cranial dural arteriovenous fistulas.MATERIALS AND METHODS:We performed a retrospective review of 40 consecutive patients with 41 cranial dural arteriovenous fistulas treated between March 2006 and June 2012 by using transarterial Onyx embolization with intent to cure. The mean age was 57 years; one-third presented with intracranial hemorrhage. Most (85%) had cortical venous drainage. Once angiographic cure was achieved, long-term treatment effectiveness was assessed with DSA and clinical follow-up.RESULTS:Forty-nine embolization sessions were performed; 85% of cranial dural arteriovenous fistulas were treated in a single session. The immediate angiographic cure rate was 95%. The permanent neurologic complication rate was 2% (mild facial palsy). Thirty-five of the 38 patients with initial cure underwent short-term follow-up DSA (median, 4 months). The short-term recurrence rate was only 6% (2/35). All patients with occlusion at short-term DSA undergoing long-term DSA (median, 28 months) had durable occlusion. No patient with long-term clinical follow-up (total, 117 patient-years; median, 45 months) experienced hemorrhage.CONCLUSIONS:Transarterial embolization with Onyx as the single embolic agent results in durable long-term cure of noncavernous cranial dural arteriovenous fistulas. Recurrence rates are low on short-term follow-up, and all patients with angiographic occlusion on short-term DSA follow-up have experienced a durable long-term cure. Thus, angiographic cure should be defined at short-term follow-up angiography instead of at the end of the final embolization session. Finally, long-term DSA follow-up may not be necessary if occlusion is demonstrated on short-term angiographic follow-up.

Endovascular therapy is commonly used for the treatment of noncavernous cranial dural arteriovenous fistulas (cDAVFs). Cyanoacrylates, ethyl alcohol, coils, and particles can be used alone or in combination via transarterial, transvenous, or occasionally direct percutaneous treatment routes. There is no US Food and Drug Administration–approved liquid embolic agent for the treatment of cDAVFs. The ethylene-vinyl alcohol copolymer liquid embolic system (Onyx; Covidien, Irvine, California) is FDA-approved for the presurgical embolization of brain arteriovenous malformations. Since Onyx has become available, transarterial embolization of cDAVFs by using Onyx as the sole endovascular embolic agent has become our preferred treatment strategy. This endovascular treatment approach represents an “off-label” use of the Onyx liquid embolic system.The immediate occlusion rate in large cohort studies of patients treated with transarterial Onyx embolization ranges from 62% to 92%, and short-term durable occlusion has been demonstrated.^1–4 We have previously reported our short-term experience using Onyx in these patients⁵ and have compared the success of this technique with embolization using n-butyl cyanoacrylate.⁶ However, there currently remain no published data on the long-term effectiveness for embolization of cDAVFs by using Onyx, to our knowledge. Here we report our long-term angiographic occlusion rate and clinical follow-up in a cohort of noncavernous cranial DAVFs that were treated by using transarterial Onyx embolization with the intention of complete cure.     

Liquid Embolic Agents for Endovascular Embolization: Evaluation of an Established (Onyx) and a Novel (PHIL) Embolic Agent in an In Vitro AVM Model

BACKGROUND AND PURPOSE:Embolization plays a key role in the treatment of arteriovenous malformations. The aim of this study was to evaluate an established (Onyx) and a novel (precipitating hydrophobic injectable liquid [PHIL]) liquid embolic agent in an in vitro AVM model.MATERIALS AND METHODS:An AVM model was integrated into a circuit system. The artificial nidus (subdivided into 28 honeycomb-like sections) was embolized with Onyx 18 (group Onyx; n = 8) or PHIL 25 (group PHIL; n = 8) with different pause times between the injections (30 and 60 seconds, n = 4 per study group) by using a 1.3F microcatheter. Procedure times, number of injections, embolization success (defined as the number of filled sections of the artificial nidus), volume of embolic agent, and frequency and extent of reflux and draining vein embolization were assessed.RESULTS:Embolization success was comparable between Onyx and PHIL. Shorter pause times resulted in a significantly higher embolization success for PHIL (median embolization score, 28 versus 18; P = .011). Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization (median volume per section of the artificial nidus, 15.5 versus 3.6 μL; P < .001).CONCLUSIONS:While the embolization success was comparable for Onyx and PHIL, pause time had a considerable effect on the embolization success in an in vitro AVM model. Compared with Onyx, lower volumes of PHIL were required for the same extent of embolization.

Arteriovenous malformations are complex vascular structures composed of feeding arteries, an intervening network of small pathologic blood vessels (the so-called nidus), and draining veins. The lack of an intervening capillary bed allows high-flow arteriovenous shunting of blood. While AVMs can occur throughout the entire body, cerebral AVMs are of particular relevance due to their ability to cause impairing neurologic symptoms and their considerable risk of hemorrhage.¹Alone or in combination with microneurosurgery and stereotactic radiation therapy, embolization plays an important role in the management of cerebral AVMs.² The aim of AVM embolization is complete filling of the nidus, while unwanted reflux into the feeding arteries should be minimized and premature embolization of the draining veins should be avoided.³A wide variety of embolic agents has been and is currently used for embolization of AVMs. At present, the liquid embolic agents (LEAs) ethylene-vinyl alcohol copolymer (EVOH) and n-butyl cyanoacrylate are used most frequently.⁴ Although the embolization results have improved since the introduction of EVOH-based LEAs with rates of complete obliteration ranging from 16% to 100%, the success rate of AVM embolization, especially for complex AVMs, is not yet satisfying.^2,3 Currently, new LEAs are being introduced to improve embolization features, such as embolization efficacy, intraprocedural handling, and control. Furthermore, their use should improve fluoroscopic visibility and reduce artifacts in postinterventional imaging.The aim of this study was to evaluate an established EVOH-based embolic agent and a novel copolymer-based embolic agent in an in vitro AVM model.     

Embolization of high-flow craniofacial vascular malformations with onyx

BACKGROUND AND PURPOSE: Various techniques and materials have been used for the endovascular treatment of craniofacial high-flow arteriovenous vascular malformations, because their rarity precludes standardization of their treatment. The aim of this retrospective review is to assess Onyx as the primary embolic agent in the treatment of these vascular malformations. MATERIALS AND METHODS: Six patients with arteriovenous fistulas and 3 with arteriovenous malformations (AVMs) of the head and neck region were treated with intra-arterial (IA)/direct percutaneous injections of Onyx. Adjunctive maneuvers used during embolization included external compression of the arterial feeders or venous outflow (6 patients), balloon assist (4 patients), and direct embolization of the draining vein remote to the fistula site (1 patient). n-butyl-2-cyanoacrylate (n-BCA) was used in addition to Onyx for rapid induction of thrombosis in a large venous pouch (1 patient) and for cost containment purposes (1 patient). Four patients were treated surgically after the embolization. RESULTS: There were no neurologic complications secondary to the embolization procedure. The arteriovenous shunt was eliminated in all of the fistulous lesions and 2 of the 3 AVMs. The embolization was incomplete in 1 patient with a large AVM who declined further endovascular or surgical procedures. Untoward events included 2 instances of catheter entrapment (of 9 IA injections), blackish skin discoloration necessitating surgical revision in 1 patient, and difficulty of balloon deflation/wire withdrawal during a balloon-assisted embolization. CONCLUSION: Onyx appears to be a safe and effective liquid embolic agent for use in the treatment of craniofacial high-flow vascular malformations with distinct advantages and disadvantages compared with n-BCA.     

Experimental studies of segmental hepatic artery embolization with a super absorbent embolic agent

Super absorbent (Sumikagel) is a unique polymer mainly composed of polysodium acrylate (PSA). When PSA contacts water, it absorbs water and swells in a few seconds. This new embolic material suspended in Lipiodol (Lp-PSA), was used for hepatic artery embolization in five dogs. The purpose of this study is to examine the necrotizing effect of the new embolic material on segmental hepatic artery embolization. Gross liver examination demonstrated congestion and segmental infarction within the embolized area, and microscopically focal necrosis of liver parenchyma was observed. Segmental hepatic artery embolization with Lp-PSA should be an effective method of hepatic tumor embolization.