Embolization Therapy: Principles and Clinical Applications, 1 Ed.

Intracranial Aneurysms

M. Imran Chaudry • Alejandro Spiotta • Raymond Turner • Harris Hawk • Jonathan R. Lena • Aquilla Turk

The International Symptomatic Aneurysm Trial (ISAT) and the Barrow Ruptured Aneurysm Trial (BRAT) firmly established endovascular therapy as a primary method for treating ruptured intracranial aneurysms. The development of new techniques has broadened the scope of practice to allow for the treatment of geometrically complex aneurysms.16 Critical advances in coil technology and the development of novel flexible guide and intermediate catheters providing improved device stability and deliverability, intracranial stents, as well as the introduction of balloon remodeling and flow-diverting stent technology have expanded the indications of endovascular therapy to both wide-necked and fusiform aneurysms. The adoption of these devices has contributed to a larger proportion of aneurysms treated by endovascular means.7

DEVICE DESCRIPTIONS

Distal Access Guide Catheters

Fundamental to any endovascular intervention is the need for stable access to the target lesion. Proximal vessel tortuosity may limit the ability to deliver the guide catheter distally in the vessel of interest, thereby resulting in long distances that the working microcatheter must cover before addressing the target lesion. If the microcatheter and wire travel over redundant segments of a vessel or multiple acute-angled turns, the microcatheter and wire may respond unpredictably when manipulated. Erratic behavior of the microcatheter or microwire may result in technical complications, for example, aneurysm perforation during access for coil embolization and suboptimal stent placement during unsheathing if the microcatheter sails in either direction. The development of neurospecific guiding catheters has resulted in various access devices that offer various advantages with regard to trackability, distal and proximal support, and improved distal access. There is considerable crossover in the design of intermediary catheters and newer generation neurospecific guide catheters. The Neuron 0.053-in and 0.070-in in guide catheters, the 0.088-in Neuron Max sheath (Penumbra, Inc., Alameda, California), as well as the Chaperon 0.071-in guide catheter (MicroVention, Tustin, California) are designed to provide distal guide catheter access, often to the cavernous segment of the internal carotid artery, providing a large stable conduit for intracranial procedures (Fig. 14.1).

These devices have been shown to be safer than traditional axial guide catheters while providing distal access, often obviating the need for an intermediate catheter. The goal is to place the diagnostic insert into the petrous segment over a 0.038-in hydrophilic guidewire (Glidewire; Terumo Interventional Systems, Somerset, New Jersey) and then advance the guide or sheath over the diagnostic insert into at least the petrous carotid. These larger guide catheters and sheath allow for multiple devices (either balloon and coiling microcatheter or stent delivery catheter and coiling microcatheter) to be deployed simultaneously. The use of larger sheaths may allow for three devices to be deployed simultaneously when coiling with the aid of two balloons, for example.

Microcatheters and Microwires

Endosaccular coil embolization relies on the ability to safely access the aneurysmal sac with a microcatheter that can house a coil. Access to the aneurysm is safest with the microcatheter tracking over a microguidewire. Catheter and microguidewire technology has not significantly changed since the introduction of the 0.0165-in SL-10 (Boston Scientific Corporation, Natick, Massachusetts) microcatheter. To date, the SL-10 remains our workhorse microcatheter as do the 0.014-in Transend Platinum (Stryker Corporation, Kalamazoo, Michigan) and Synchro-2 microwires (Boston Scientific Corporation, Natick, Massachusetts). These two wires deliver the adequate “softness” needed to negotiate tortuous anatomy without causing microperforations while providing sufficient support for over-the-wire microcatheter navigation. Note that intermittent reshaping of the microwire may be necessary during a procedure to navigate a patient’s specific anatomy. We have found that the SL-10 microcatheter tracks favorably over an 0.014-in microwire even in acutely angled vessels. Microcatheters are available in straight and preshaped angled or curved variations, allowing more versatility. Slightly stiffer microcatheters such as the Echelon 10 (Covidien, Irvine, California) maybe used when there is concern for catheter prolapse out of the target aneurysm or when more support for coiling is required. Once access to the aneurysm is obtained, these flexible microcatheters will respond to the stress applied to it by superimposed curves by adopting the parent vessel curvature, which leads to their stability at the aneurysm during coil deployment. The introduction of large-volume coils (Penumbra PC 400; Penumbra, Inc., Alameda, California) has required the introduction of larger 0.025-in coiling microcatheters (Penumbra PX400 and Penumbra SLIM) to allow delivery of these coils. Catheter technology has improved to make these larger and inherently stiffer catheters extremely navigable. However, the main issue with these larger catheters is catching on the lip of the aneurysm neck that may limit catheter access. This may be overcome by advancing the microwire well into the aneurysm, loading the microcatheter and spinning the wire so as to raise the microcatheter from the aneurysm neck. Care must be taken not to load the microcatheter to a degree where it jumps forward into the aneurysm.

Coil Technology

The introduction of coils into an aneurysm provides a thrombogenic mechanical barrier to aneurysmal inflow, which immediately protects the dome while promoting intra-aneurysmal progressive thrombosis and occlusion. The coils furthermore provide a biologic scaffold to promote endothelial growth across the aneurysm neck and vessel healing, resulting in complete exclusion of the aneurysm from the circulation. The initial experience with aneurysm coil embolization did not involve any adjunctive devices such as balloons or stents (“unassisted” coil embolization). As such, the only factors that could be modified by the operator to achieve a successful embolization were the position of the microcatheter relative to the aneurysm neck and dome as well as the size, length, and shape of the coil selected. The introduction of complex coils that could adopt various geometric shapes once deployed resulted in a greater number of aneurysm morphologies considered suitable for coil embolization. The first commercially available detachable coils8 were stiff by today’s standards. Although the duration required for detachment ranged between 10–45 minutes, the detachment mechanism allowed for controlled deployment, repositioning, and removal. This was a significant improvement over detachable balloons used for vessel sacrifice. However, coil distribution of this two-dimensional design (helix) did not consistently allow for good neck coverage. The introduction of coils that adopt an intrinsic three-dimensional (3-D) spherical shape once deployed revolutionized the approach to coil embolization. These would become known as framing coils, thereby creating a robust frame covering the neck and dome of an aneurysm (Fig. 14.2).

Subsequently, the frame is filled with softer (filling) coils in a “Russian doll” manner. This technique allows for a greater safety margin as the framing coil restricts outward movement of subsequent coils away from the dome and parent vessel and directs filling towards the center of the aneurysm sac. Smaller and softer coils with irregular breakpoints were then introduced to act as “finishing coils” to fill in irregularly shaped neck remnants. The material of the coil greatly affects how it will behave in vivo. Although platinum, which is an inert metal with material characteristics favorable for coil manufacturing, has emerged as the only material in clinical use, variations of coil composition have been introduced to impart additional biologic advantages. For example, a proinflammatory bioactive coil (Matrix; Boston Scientific Corporation, Natick, Massachusetts; Cerecyte; Micrus Endovascular Corporation, San Jose, California) may promote the wound healing cascade and cellular ingrowth into the coil mass and at the neck, whereas a gel–platinum hybrid coil (HydroCoil/HydroSoft; Terumo Interventional Systems, Somerset, New Jersey) that swells to a greater volume when in an aqueous solution such as blood may provide a higher packing density and thereby a lower recurrence rate. Recently, the Penumbra 400 (Penumbra, Inc., Alameda, California) represents another iteration of coil evolution. The Penumbra 400 has a much larger 0.020-in cross-sectional area, which is four times the cross-sectional area of a 0.010-in coil system. By using a nitinol core wire and an outer shell of platinum, the approach was to use a very high volume to length coil to rapidly fill aneurysms. Whatever coil system and strategy is employed, one factor remains constant: results from the Cerebral Aneurysm Rerupture After Treatment (CARAT) study9support aggressive coil embolization (packing density) as the likelihood of recurrence is related to the degree of initial occlusion.

Balloons

There are five commercially available neurovascular balloons. These are the HyperForm, HyperGlide (Covidien/EV3; Irvine, California), Scepter C, Scepter XC (Terumo/MicroVention, Inc., Tustin, California), and the Transform (Stryker Corporation, Kalamazoo, Michigan) balloons. The HyperGlide, Scepter C, and Transform balloons are compliant balloons intended for the treatment of sidewall aneurysms, whereas the HyperForm and Scepter XC are hypercompliant balloons intended for use in the treatment of wide-necked bifurcation aneurysms. These hypercompliant balloons tend to protrude well into the aneurysm neck and may be used to preserve vessels that arise within the neck of an aneurysm. To a large degree, we have found the compliance of the balloons to be somewhat similar and the balloons maybe used interchangeably. What sets the balloons apart is their ability to navigate tortuous, difficult anatomy as well as their stability at the aneurysm neck.

Stents

Currently, there are two commercially available nitinol self-expanding stents: an open-cell Neuroform stent (Stryker Corporation, Kalamazoo, Michigan) and a closed-cell Enterprise Vascular Reconstruction Device (VRD) (Cordis Corporation, Miami Lakes, Florida). Briefly, the open-cell design may have better wall apposition around sharp turns; however, it may create a shelflike extension into an aneurysm that arises around an acute bend or bifurcation (basilar apex). This shelf may be advantageous depending on its position but has the risk of coil loops prolapsing into the parent vessel. The closed-cell design of the Enterprise VRD may have suboptimal wall adherence around turns, but this can be reduced by more pushing of the stent as it is deployed rather than a true unsheathing. In theory, there is a lower chance of coil loops prolapsing into the parent vessel. On the other hand, newer, self-expanding braided stents are currently available as part of investigational device exemption (IDE) or 510(k) trials and should be commercially available within the next 2 to 3 years. Within the near future, we expect to see the commercial availability of braided stents such as the Low-Profile Visualized Intraluminal Support (LVIS) and LVIS Jr. (Terumo/MicroVention, Tustin, California). The advantage of these self-expanding braided stents is that there is better wall apposition around turns, and the braided structure allows for pore sized such that coil loop prolapse is highly unlikely.

Flow Diversion

Large and giant aneurysms and fusiform aneurysms remain a challenge to treat, whether from an endovascular or open standpoint. The Pipeline Embolization Device (PED) (Covidien/eV3, Irvine, California) is a novel flow-diverting stent that revolutionized the treatment paradigm for large and giant aneurysms from the petrous internal carotid artery to the ophthalmic segment. The PED is a high mesh braided stentlike device that allows for remodeling of the parent vessel wall and gradual occlusion of an aneurysm. The use of these devices may be technically less challenging than traditional treatments (open clipping, coiling, balloon, or stent coiling) of these aneurysms; however, the long-term durability and morbidity/mortality related to the use of these devices remain to be seen. Currently, there is a randomized study (LARGE Aneurysm Randomized Trial: Flow Diversion versus Traditional Endovascular Coiling Therapy) that looks to evaluate the treatment of large and giant aneurysms with flow diversion versus traditional coiling methods. We eagerly await these results.

TECHNIQUES

Unassisted Coiling

The ISAT firmly established endovascular therapy as the primary method for treating ruptured aneurysms. With the considerable advances in coil technology, endovascular therapy is becoming the accepted treatment for ruptured and unruptured aneurysms. The introduction and development of complex framing coils, filling coils, and finishing coils have made many aneurysms previously considered uncoilable amenable to endovascular therapy.

The goal of any “coiling” procedure is the complete occlusion of the target aneurysm and the prevention of aneurysm rupture. The ideal aneurysm for unassisted coiling is one with a favorable neck (<4 mm) or dome-to-neck ratio greater than 2:1. Small-necked aneurysms are much more amenable to primary coiling, using the shoulders of the aneurysm neck to buttress the coils and keep them within the aneurysm sac. In smaller aneurysms (3 to 10 mm), the catheter is ideally positioned at the neck or within the proximal one-third of the base. In larger aneurysms, an “around the world” technique maybe used in which the coiling microcatheter is brought into the aneurysm and the tip placed approximately three-quarters of the way around the aneurysm sac in such a manner that the catheter is essentially pointing back at the neck. This allows the catheter to gradually migrate back to the neck, preventing early kick out of the catheter. Although there are many techniques in framing, filling, and finishing, we tend to use the “Russian doll technique.” We frame with a framing coil with the goal of getting neck coverage and systematically stepping down in coil size to coil within the coil mass. Coil diameters are sized to the largest diameter in spherical aneurysms, and in irregular oblong or bilobed aneurysms, coil diameter size is often based on the average diameter ([Length × Width × Height]/3). Commonly, we will use multiple framing coils (decreasing in diameter and length) to frame and fill the aneurysm and subsequently switch to soft helical or complex finishing coils to pack both the aneurysm sac and neck. Our goal is always complete occlusion of the aneurysm (Fig. 14.3).

Dual Catheter Technique

The dual catheter technique was an earlier technique employed in the treatment of irregular wide-necked aneurysms before the availability of balloons and stents. It is still used occasionally in the setting of subarachnoid hemorrhage where stents (and antiplatelet therapy) is contraindicated and in tortuous small vessel anatomy where a balloon may not navigate. In this technique, two microcatheters are introduced into the aneurysm sac. The first is usually positioned at the neck through which a framing coil is delivered. The second catheter is placed into the aneurysm sac through which filling and finishing coils are introduced. The initial framing coil is not detached until the end in attempts to maintain its position and stability throughout the case. Commonly, the framing coil is undersized to prevent encroachment into the parent neck (Fig. 14.4).

Balloon Remodeling

The use of balloon remodeling, first described by Moret and colleagues10 in 1997, involves the temporary inflation of a balloon across the neck of an aneurysm, allowing for coil deployment into aneurysms with unfavorable neck-to-dome ratios.4 As coils are inserted, a stable 3-D coil structure forms, thereby holding the coil mass within the aneurysm in cases in which coil herniation into the parent vessel is a primary concern. An advantage of coil introduction with adjunctive balloon use is that the microcatheter is stabilized, preventing premature kickback and need to reaccess. However, there are two drawbacks: first, as the microcatheter is firmly pinned within the aneurysm, it prevents recoil when excessive pressure is applied on a deployed coil, thereby directing the pressure to the aneurysm dome, potentially contributing to perforation; and second, balloon inflation leads to cessation of antegrade flow, potentially risking ischemia. Balloon inflation leads to local anterograde flow arrest in the territory involved. The other well-described risks of balloon remodeling include perforator occlusion, parent vessel dissection or rupture, and promotion of thromboemboli.3,1113 The available evidence is conflicting with respect to use of balloon remodeling in aneurysm coil embolization and rates of ischemic complications, with some studies reporting a higher incidence4,12,1416 and others reporting an equal or decreased incidence compared to unassisted coiling.13,1720 Balloon inflation can be performed intermittently, allowing reperfusion of the distal vascular territory in addition to unconstrained manipulation of the microcatheter within the aneurysm itself, even after coiling has been initiated. Although there are risks to the use of balloons, the most dreaded is aneurysm perforation; the benefit of having a balloon ready and available to achieve immediate flow arrest and to continue coiling to aneurysm occlusion in a controlled fashion is a significant advantage. Balloon remodeling is a very useful adjunct in the hands of an experienced operator but should be employed cautiously in the uninitiated (Fig. 14.5).

Stent-Assisted Coiling

The technique of stent-assisted coiling in the clinical setting was first described in 1997.21 Soon after, the availability of new flexible, self-expanding intracranial stents allowed for increasing application of this technique and observation of its benefits. Stents have been quickly adopted as promising adjuncts with potential mechanical, hemodynamic, and biologic properties, imparting an advantage over coil embolization alone.22 Stent deployment provides mechanical support to prevent coil prolapse, and it may serve as a conduit to divert flow and provide a scaffold for endothelial growth and vessel healing.2224In addition, an implanted stent may incur subtle changes in the parent vessel–aneurysm geometry, imparting significant hemodynamic alterations which change the inflow substantially.

A stent may be deployed across the aneurysm neck followed by microcatheter selection of the aneurysm through the twines of the stent, or the aneurysm can be selected first with the microcatheter and the stent deployed across the neck and microcatheter (jailing technique). The jailing strategy has the advantage of affixing or “pinning” the microcatheter between the outer confines of the stent and the lining of the parent vessel. This achieves a more stable, although somewhat locked-in, microcatheter position within the aneurysm and minimizes the risk of premature kickback of the microcatheter out of the aneurysm during coil deployment. A second strategy is the “coil through,” in which a stent is first fully deployed across the aneurysm neck and then the aneurysm is catheterized by navigating through the tines of the stent. This method allows for relatively unrestricted movement of the microcatheter, allowing it to paint back and forth with the introduction of coils; however, at times, depending on anatomy, it may be difficult to traverse a newly deployed stent. The microcatheter may get caught up on the stent tines and there is risk of the stent migrating distally. Third, the “coil–stent” technique involves an unassisted coil embolization to completion, immediately followed by stent deployment, potentially to capitalize on the biologic benefit of vascular remodeling or to constrain a prolapsed coil loop. Last, the “balloon stent” method involves a stent placement after completion of a balloon-assisted embolization.

The advantage of employing a stent to bridge the neck of an aneurysm, as opposed to balloon remodeling, is that it does not involve flow arrest in the parent vessel. A disadvantage is that it requires permanent placement of the device and a minimum antiplatelet regimen of at least 3 months. Most aneurysms treated with stent-assisted coiling are geometrically complex and pose a technical challenge. Since the first clinical applications in the late 1990s, several studies have proven stent-assisted coiling to be a feasible, safe, and effective method of embolization2534 of aneurysms previously believed to be not amenable to coiling (Fig. 14.6).

Stent Reconstruction

Despite all these device advancements and the refinement of technical nuances by experienced operators, broad-necked aneurysms arising at bifurcations that incorporate the daughter vessel origins remain a formidable challenge to endovascular treatment. This is perhaps best exemplified by the difficulty in treating middle cerebral artery bifurcation aneurysms but also those at the basilar apex and carotid terminus. At vascular bifurcations, a stent can be used to stabilize a coil mass within an aneurysm while protecting the parent vessel and the daughter vessel at greatest risk. When the aneurysm neck incorporates the origins of both daughter vessels and there is a significant risk of coil herniation into either vessel, a single stent, even with balloon remodeling as an adjunct, may not be sufficient.

The “Y-stent” technique3540 involves the passage of a second stent through the interstices of the first deployed stent. Y-stent reconstruction enables the endovascular management of otherwise complex, wide-necked cerebral aneurysms by providing two critical functions: support for the coil mass and preservation of the daughter vessels. The open-cell design of the Neuroform stent as the initial placed stent allows this construct to be possible because the first stent deployed can expand at its interstices to accommodate the second self-expanding stent. Y-stent using a closed-cell design stent at the first stent, although technically feasible, results in undesirable synching of the second deployed stent because of its constrained interstices. The initial short- and midterm results using the Y-configuration technique are promising.39,40 Although many of the aneurysms displayed residual filling at initial treatment, some were found to have spontaneous thrombosis on angiographic follow-up. These results have been considered satisfactory because the technique addresses aneurysms for which there are otherwise no viable treatment options. However, there are several concerns regarding the long-term effects in patients harboring the Y-configured reconstruction. The longer term effects of having two overlapping stents in the distal basilar as well as the junction of the Y in which there is considerable intraluminal stent overlap not amenable to endothelization without the scaffolding provided by adjacent intima are unknown. In addition, this reconstruction is technically demanding. Navigating through the first stent with either a 0.021-in (closed-cell) or 0.027-in (open-cell) microcatheter to prepare to deliver the second stent of the construct can be difficult and result in stent migration. Initial microcatheter selection and reaccessing of the aneurysm during coiling following Y stenting can also pose a challenge. Indeed, there are many steps required to successfully achieve Y-stent reconstruction, each with possibility of technical complications.

Stent Delivery through Balloon Catheter

Balloon-remodeling and stent assistance techniques may be used in combination to capitalize on the benefits that each affords. This “balloon–stent” method involves stent placement after completion of a balloon-assisted embolization. The drawback to this sequential technique is that employing currently available stent delivery systems requires either a 0.021-in or a 0.027-in microcatheter system; the coil mass achieved during balloon remodeling must be crossed before stent deployment. This additional maneuver introduces the potential risk of coil disruption, especially when there is coil loop prolapse or herniation into the parent vessel, which may lead to thromboembolic or ischemic complications. In addition, this step may add fluoroscopy and procedure time, especially when access to the lesion is challenging.

We described the first report of a novel technique for “balloon stenting,” which incorporates the use of two novel devices.41 The Scepter C is a new temporary occlusion balloon system that has a dual coaxial lumen catheter attached to a low-inflation pressure compliant balloon. The design accommodates a steerable 0.014-in guidewire through a 0.0165-in inner lumen. The LVIS is a novel neurovascular self-expanding retrievable stent system which is composed of a single nitinol round braided wire and double helix tantalum strands in addition to radiopaque tantalum proximal and distal markers to assist full-length visualization. It is a compliant, closed-cell system which is retrievable up to 80% deployment and provides 15% surface area coverage. The commercially available LVIS stent is 0.021-in microcatheter compatible. However, the LVIS Jr. stent is 0.017-in microcatheter compatible, allowing it to be delivered by the Scepter C balloon catheter system. We have found this technique to be safe and feasible, reducing both the number of steps involved in this technique and the opportunities for mechanical coil-related complications.

Flow Diversion

Stents were recognized to impart flow diversion properties on aneurysm inflow, spurring the introduction of flow diversion stents. Flow-diverting stents are constructed of lower porosity with higher device surface area coverage at the aneurysm neck. By shunting flow preferentially down the parent vessel and away from the aneurysm, it promotes conditions leading to progressive aneurysm thrombosis and eventual vessel remodeling (Fig. 14.7).

Theoretically, even small-caliber perforating vessels, which are covered by the flow diverter, will remain patent due to the siphoning effect of the distal territory they irrigate. Aneurysms have no such downstream outflow and will thrombose. Flow diversion has been used effectively in the treatment of fusiform and giant aneurysms. Disadvantages include the inability to cross the stent with a microcatheter for treatment of recurrences, reports of perforator occlusions leading to strokes, as well as reported cases of delayed aneurysmal rupture and subacute and remote intracerebral hemorrhage.

Pushing the Envelope

Despite these technologic advances, broad-based aneurysms continue to pose a formidable challenge for endovascular treatment, which requires creative solutions.4146 As long as there are complex aneurysms that require treatment and highly skilled neurointerventionalists who are knowledgeable about the devices available and motivated to treat them, devices will be used in an off-label fashion in an attempt to address the unmet needs of adjuncts. Retrievable, closed-cell design stents can be partially deployed across an aneurysm neck and then recaptured following stent-assisted coil embolization, thereby incorporating the benefits of balloon remodeling without the drawbacks of parent vessel occlusion and without permanent stent implantation. A stent may also be deployed with its distal extent aimed at the aperture of the aneurysm to support a coil mass rather than across the neck along the long axis of the parent vessel, the so-called waffle cone technique.47,48 In the treatment of a fusiform aneurysm, stents can be deployed in parallel in the so-called double-barrel technique.47 Aneurysms incorporating two daughter vessels have been addressed, employing two simultaneously inflated balloons after selecting the aneurysm with a microcatheter (“kissing balloon” technique). Last, to promote thrombosis and occlusion of fusiform aneurysms, some operators advocate jailing a microcatheter with a flow-diverting stent to capture the benefits of flow diversion and coil embolization in one strategy.

CLINICAL APPLICATIONS

At our institution, we tend to use a fair amount of primary coiling and balloon remodeling. We prefer the use of the balloon as an adjunctive device over stents as balloons are temporary implants, obviating the need for long-term dual antiplatelet therapy. Also, in the setting of subarachnoid hemorrhage where antiplatelet therapy is contraindicated, balloons allow for the treatment of complex, wide-necked aneurysms without the use of stents. Ultimately, the choice of how to coil, balloon remodel, or perform a stent-assisted coiling is up to the primary operator. The risks/benefits of each technique must be weighed against not only the anatomy and geometry of the aneurysm but also the operator’s comfort level with each technique.

Preoperative Planning

Elective patients are pretreated with dual antiplatelet therapy regardless if stenting is planned to mitigate the risk of thromboembolic complications. Ideally, patients are given a 600 mg clopidogrel and 650 mg acetylsalicylic acid (ASA) load the night before a coiling procedure. Alternatively, a 5-day loading regiment may be used: 75 mg clopidogrel and 325 mg ASA daily starting 5 days before the procedure. For patients where a stent or endoluminal device is planned, clopidogrel and ASA response assays may be performed. At this time, a decision should be made regarding how to approach the aneurysm. Will primary coiling suffice? Will there be a need for an adjunctive device or will newer technologies such as flow-diverting stents or newer intrasaccular devices be used? These decisions will determine access devices and microcatheter selection on the day of operation.

We perform all embolization procedures under general anesthesia. All patients are systemically anticoagulated: Elective patients receive a bolus dose of 5,000 units of heparin, whereas subarachnoid hemorrhage patients receive 3,000 units bolus dose. After placement of the first coil, patients are titrated to an activated clotting time (ACT) of 2 to 2.5 times their ACT baseline.

Procedure

 1. Femoral access: Depending on the devices used, either a 6-Fr or 8-Fr sheath is placed in the groin.

 2. Guiding catheter: We commonly use the 0.070-in Neuron and 0.071-in Chaperon guiding catheters and the 0.088-in Neuron Max sheath. Our goal is safe distal access, ideally to at least the petrous segment of the internal carotid artery.

 3. Working views: Orthogonal views that demonstrate the aneurysm neck and dome are ideal. When balloon remodeling, views may be modified with the balloon inflated and the first coil partially deployed to achieve a “down the barrel” view and an orthogonal view that lays out the dome.

 4. Adjunctive device access: If an adjunctive device is used, it is advanced first before the coiling microcatheter across the aneurysm ostium.

 5. Coiling microcatheter access: The coiling microcatheter is advanced into the aneurysm sac.

 6. Control angiograms in working and anteroposterior (AP) and lateral projections are performed. Working to determine residual filling of aneurysm and AP and lateral to demonstrate patency of all vessels unchanged from the initial angiograms.

COMPLICATIONS

Potential complications can be divided into two main types: hemorrhagic and ischemic. Ischemic complications are more common and can be caused by vasospasm from guide catheter access, cessation of antegrade flow with use of a balloon catheter, and thromboembolic events from clot formation along the coil mass, which tends to occur when there is a large coil mass/parent vessel interface. Many of these issues can be avoided by preprocedure prophylactic antiplatelet therapy and systemic anticoagulation during the procedure. Hemorrhagic complications are uncommon but feared as they tend to result in major morbidity and mortality. Most commonly, this is a result of aneurysm perforation either from coil or microcatheter herniation through the wall of the aneurysm. Less common, microguidewire perforations can occur either during access of the parent vessel, distal wire access for balloons or other adjunctive devices, and wire perforation of the aneurysm dome.

TIPS AND TRICKS

REFERENCES

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