29 Aneurysm Embolization with Liquid Embolic Agents
Introduction
Liquid embolic agents include nonadhesive Onyx (ethylene vinyl alcohol copolymer (Medtronic), adhesive N-butyl-2-cyanoacrylate (NBCA) (Trufill, DePuy Synthes), and precipitating hydrophobic injectable liquid (PHIL) (MicroVention), which is new to the market. Endovascular aneurysm obliteration with liquid agents is largely reserved for very distal and/or infectious aneurysms. Because of infectious etiologies, mycotic aneurysms arise largely in the distal middle cerebral artery (MCA) and anterior cerebral artery (ACA) territories. Mycotic or infectious aneurysms have a high propensity for rupture and are prone to multiplicity; however, they are usually small in size and can be fusiform. Conventional treatment has consisted of lengthy antibiotic regimens with surveillance via serial computed tomography angiography (CTA) or digital subtraction angiography (DSA) imaging. However, recent studies have shown hemorrhage rates of 60% in patients with mycotic aneurysms, with 57% of these patients having infarcts. Moreover, a study from 2018 reported that only 25% of mycotic aneurysms regressed after antibiotic treatment at a median of 36 days and 36% of mycotic aneurysms enlarged or duplicated. The conclusions of these studies have led authors to suggest surgical or endovascular treatment of these lesions up front, especially when they are > 6 mm. Typically, treatment options are dictated by presentation, with large hemorrhages or surrounding abscesses needing evacuation. Given the friable nature of the vessel wall because of a full mural infection, hybrid approaches can be useful with coil embolization performed in the endovascular suite followed by surgical evacuation of the space-occupying lesion. More proximal fusiform lesions will require clip reconstruction versus a trapping and bypass procedure. Because these patients are typically very ill and have usually undergone open heart surgery for valve replacement, endovascular options are very appealing. A meta-analysis of endovascular treatment 86 mycotic aneurysms noted 95.3% occlusion rates, 7.9% recurrence rates, and 5.8% rehemorrhage rates. Good (modified Rankin Scale score < 2) long-term neurological outcomes were noted in 68%, with 12.6% procedure-related morbidity rates.
Intranidal aneurysms are another aneurysm still treated by liquid embolic agents. The presence of an intranidal aneurysm greatly increases the risk of arteriovenous malformation (AVM) rupture. One study revealed that 12% of AVMs had intranidal lesions.
Indications
Liquid embolic agents are ideal for dealing with aneurysms located in distal noneloquent territories such as those found with mycotic aneurysms of the MCA or ACA territories. In addition, these agents can be used to secure head and neck pseudoaneurysms causing epistaxis or oropharyngeal hemorrhage. Last, liquid embolic agents can be used to secure feeding arterial pedicle aneurysms of AVMs, as well as intranidal aneurysms.
Neuroendovascular Anatomy
Because mycotic aneurysms are predominately found in distal cerebral locations that necessitate long reaches with the microcatheter, it is important to assess the patient’s anatomy for tortuosity and stenosis with diagnostic angiography. The presence of a type 3 aortic arch can necessitate alternative access routes. Because these lesions are typically very friable and can circumferentially involve the vessel, soft wires must be used to decrease the risk of vessel perforation. Eloquent lesions, such as those found in the left-sided opercular vessels (M3 segment of the MCA) or motor area (M4 and M5 MCA segments, can present challenging clinical decisions. Prior to any vessel embolization in these regions, superselective Wada testing with amobarbital (Amytal) and lidocaine or a balloon test occlusion (BTO) should be performed. Distal access catheters (DACs, Stryker) are very useful for these long reaches into the distal cerebral circulation.
Perioperative Medication
Systemic heparinization is administered with target activated coagulation time values of 200–250 s. Amobarbital (Amytal) and lidocaine are administered during Wada testing.
Specific Techniques and Key Steps
If possible, access is obtained by way of a femoral arteriotomy. A transitional 6 French (F) dilator is utilized once the position of the microwire is deemed appropriate in relation to the femoral head by way of fluoroscopy imaging. A 6–8F femoral sheath is placed depending on biaxial or triaxial needs for vessel tortuosity.
The guide catheter with copilot valve is placed in the internal carotid artery or vertebral artery depending on the aneurysm location.
Initial digitally subtracted runs are performed in anteroposterior and lateral views ( Fig. 29.1–29.4, Video 29.1–29.4 ). Oblique magnified working views are also obtained; rotational 3D runs can greatly help with this.
Given the distal mycotic aneurysm locations, triaxial systems are utilized for more support ( Video 29.1–29.4 ).
The microwire–microcatheter assembly can be utilized to help navigate the intermediate catheter to the desired location, typically the A1 segment of the ACA or the M1 segment of the MCA.
The intermediate catheter (DAC or Sofia, MicroVention) is advanced into the M2 MCA segment or A2 or A3 ACA segment over the microwire.
If Onyx is selected as the embolic agent, a dimethylsulfoxide (DMSO)-compatible microcatheter is advanced as close as possible to the aneurysm ( Fig. 29.1–29.4, Video 29.1–29.4 ). If the lesion is in an eloquent location, a superselective awake Wada test with amobarbital and lidocaine should be performed. Preservative-free lidocaine (30 mg) is injected, followed by amobarbital (75 mg) via the microcatheter. Each medication is injected solely and slowly (30–60 s). A neurological examination is performed to assess for speech or motor deficits.
If embolization is desired, DMSO must be injected at a rate of 0.1 mL/minute to fill the microcatheter dead space, followed by Onyx 18 or 34, which is injected at the same rate. A blank roadmap technique should be utilized ( Fig 29.1–29.4, Video 29.1–29.4 ). If using NBCA, the catheter must be removed within seconds after embolization, and the correct viscosity obtained with a mixture of NBCA and lipiodol. A 5% dextrose solution is used to flush the ionic contrast material prior to injecting NBCA.
Final runs are taken postembolization. If the Onyx has refluxed and the catheter is stuck, the DAC can sometimes provide countertraction; or a detachable tip microcatheter can be used in these distal locations.
Device Selection
The following are common set-ups and devices used for liquid embolic embolization of distal mycotic aneurysms.
6–8F sheath.
90-to 100-cm-long 6F guide catheter (Neuron or Neuron MAX 90-cm guide catheter, Penumbra; Envoy, Synthes; or Benchmark 0.071-inch guide catheter, Penumbra).
0.044- to 0.058-inch intermediate catheter (Sofia, MicroVention; DAC, Navien, Medtronic; Catalyst 5, Stryker).
DMSO-compatible 0.016-inch microcatheter (e.g., Headway Duo, MicroVention; SL-10, Stryker; or detachable tip microcatheter, Apollo, Medtronic).
0.014-inch microwire (Synchro 2, Stryker).
If BTO is desired (selective), use a 4 × 10 mm Scepter XC balloon catheter (MicroVention) in larger MCA vessels and inject Onyx via the dual-lumen Scepter XC microcatheter, but keep in mind that this product is stiffer than a Headway Duo.
DMSO, sterile 1 mL syringes (Onyx package), and Medallion syringe (Merit Medical) for microinjection or superselective Wada test.
Preservative-free lidocaine and amobarbital.
Onyx 18 or 34.
Continuous heparinized flush.
Pearls
If a conservative approach is utilized for mycotic aneurysms, serial CTA or DSA images must be obtained weekly or biweekly to monitor lesion growth.
Coiling, stent coiling, and flow diversion have been described with some success for mycotic aneurysms requiring parent vessel preservation in patients too ill for open cranial repair. However, the use of a stent or flow-diversion device is not the first-line option.
Endovascular therapy is no longer the second option for mycotic aneurysms but represents a valid, safe, first therapeutic option ( Fig. 29.1–29.4, Video 29.1–29.4 ).
After embolization, repeat angiograms (CTA or DSA) are necessary to ensure no recurrence; magnetic resonance imaging (MRI) is also valuable given that mycotic aneurysms can be associated with abscesses and infarcts. Prior to treatment, baseline MRI is obtained to establish whether the targeted area is already infarcted.
If the superselective Wada test is positive, alternative treatment options with vessel preservation should be strongly considered.
The presence of a mycotic aneurysm is not a contraindication for heart valve repair.
Case Overview: CASE 29.1 Mycotic Middle Cerebral Artery Aneurysm: Liquid Embolic Agent (n-BCA)
A 60-year-old female with multiple intracranial aneurysms presented with a ruptured pericallosal artery aneurysm that was treated endovascularly. Her hospital stay was complicated with bacteremia and sepsis. Neurologically, the patient recovered completely. After several weeks in the hospital, a routine computed tomography revealed a new small left middle cerebral artery (MCA) hyperdensity.
Computed tomography (CT) angiogram demonstrated a de novo left MCA aneurysm that was not present on previous imaging.
Procedure
The patient underwent endovascular treatment of mycotic left distal MCA aneurysm with liquid embolic agent N-butyl cyanoacrylate (n-BCA). The procedure was performed under conscious sedation and through a right femoral artery approach. 4,500 units of heparin were given to obtain an activated clotting time of more than 250.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
