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Treatment of Visceral Artery Aneurysms Using Novel Neurointerventional Devices and Techniques
REVIEW ARTICLE
Treatment of Visceral Artery Aneurysms Using Novel Neurointerventional Devices and Techniques Timothy Eanna Murray, MB, MCh, MRCS, FFR, EBIR, Paul Brennan, MB, MSc, MRCPI, FRCR, FFR, Julian T. Maingard, MBBS, BBiomedSci, Ronil V. Chandra, MBBS, MMed, FRANZCR, CCINR, Dilly M. Little, MD, BSc, FRCS (Urol), D. Mark Brooks, MBBS, FRANZCR, CCINR, EBIR, Hong K. Kok, MB, BMedSci, MRCPI, MRCP(UK), FFR, FRCR, EBIR, Hamed Asadi, MD, PhD, FRANZCR, CCINR, EBIR, and Michael J. Lee, MB, MSc, FRCPI, FRCR, FFR, EBIR ABSTRACT The presence of branching vessels, a wide aneurysm neck, and/or fusiform morphology represents a challenge to conventional endovascular treatment of visceral artery aneurysms. A variety of techniques and devices have emerged for the treatment of intracranial aneurysms, in which more aggressive treatment algorithms aimed at smaller and morphologically diverse aneurysms have driven innovation. Here, modified neurointerventional techniques including the use of compliant balloons, scaffold- or stent-assisted coil embolization, and flow diversion are described in the treatment of visceral aneurysms. Neurointerventional devices and their mechanisms of action are described in the context of their application in the peripheral arterial system.
ABBREVIATIONS VAA ¼ visceral artery aneurysm, WEB ¼ Woven EndoBridge
From the Departments of Interventional Radiology (T.E.M., M.J.L.), Interventional Neuroradiology (P.B.), and Urology and Transplant Surgery (D.M.L.), Beaumont Hospital, Beaumont Road, Dublin, Ireland; Department of Interventional Radiology and Interventional Neuroradiology Unit (J.T.M., D.M.B., H.A.), Austin Health, Melbourne, Australia; School of Medicine, Faculty of Health (J.T.M., D.M.B., H.A.), Deakin University, Waurn Ponds, Australia; Interventional Neuroradiology Unit (R.V.C., H.A.), Monash Imaging, Monash Health, Melbourne, Australia; Interventional Radiology Service (H.K.K.), Northern Hospital Radiology, Melbourne, Australia; and Royal College of Surgeons in Ireland (M.J.L.), Dublin, Ireland. Received August 25, 2018; final revision received and accepted December 30, 2018. Address correspondence to T.E.M.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2019 J Vasc Interv Radiol 2019; 30:1407–1417 https://doi.org/10.1016/j.jvir.2018.12.733
Endovascular treatment of visceral artery aneurysms (VAAs) requires a tailored approach encompassing aneurysm morphology, arterial branching, vessel angulation, and multiplicity of aneurysms where present. Aneurysm exclusion with coils or covered stents is well described in the treatment of VAAs, but these techniques are limited in their applicability to certain aneurysm types (1). Fusiform aneurysm morphology can preclude coil embolization because an insufficient aneurysm neck prevents the creation of a stable coil ball (2). When branching vessels arise from a visceral aneurysm, the use of covered stents may be precluded as coverage of the branching arterial ostium risks infarction of the supplied parenchyma (3). Within the intracranial circulation, the criticality of maintaining branch vessel perfusion while excluding aneurysms has spurred the development of a variety of devices, to enable the endovascular treatment of aneurysms previously untreatable by an endovascular approach. Many of these neurointerventional devices are suitable for adoption in
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Figure 1. (a) Illustration of a microcatheter positioned within an intermediate-necked bifurcation aneurysm. A hypercompliant occlusion balloon is positioned across the aneurysm neck and inflated within the parent vessel, thereby remodeling the aneurysm neck to support coil embolization. In addition to using the side wall of the balloon, the toe (ie, distal curve) and heel (ie, proximal curve) can also be positioned as needed to conform to the anatomy of the aneurysm. (b, i) An 8-F sheath is positioned within the left renal artery. Angiogram confirms a relatively wide-necked saccular aneurysm. (b, ii) A microcatheter (arrowhead) is positioned within the aneurysm while a deflated hypercompliant balloon (arrow; Sceptre C; Microvention) is advanced across the aneurysm neck. (b, iii) The hypercompliant balloon is now inflated (arrow), and detachable coils are deployed within the aneurysm sac. (b, iv) Completion angiogram with the balloon deflated demonstrates satisfactory aneurysm occlusion with preserved patency of the parent vessel and distal branches. This case also appears in the report of Das et al (7).
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peripheral and visceral arteries, which may permit endovascular treatment of anatomically challenging and complex VAAs.
PREPROCEDURAL PREPARATION The need for preprocedural medication and maintenance of antiplatelet medication is device-specific. When stent implantation is planned, dual antiplatelet therapy is typically recommended within the neurovascular system. As is often the case, when primary stent deployment is not planned but “bailout” stent-assisted coil embolization may be required, dual antiplatelet coverage may still be prudent (4). Loading doses (300–325 mg aspirin and 300 mg clopidogrel) on the day of or before the procedure or low doses (75–100 mg aspirin and 75 mg clopidogrel) represent alternate dosing strategies. When a neurovascular device or technique is being considered, the interventionalist must ensure that an appropriate selection of hardware is in stock, including microcatheters and guide catheters, which may be devicespecific. Furthermore, many of these devices are available in a range of sizes, and selection requires a knowledge of the aneurysm anatomy, the size and length of arterial branches distal to the aneurysm (for delivery of microwires or other devices), and the landing zone requirements for device deployment.
BALLOON-ASSISTED ANEURYSM EXCLUSION Balloon-assisted aneurysm exclusion may be chosen when an aneurysm neck is believed to be sufficiently narrow to retain a formed coil ball, but initial formation of the coil ball is at risk of unsecured coil protrusion or migration (3). When a microcatheter has been positioned within the aneurysm sac, a parallel balloon catheter can be inflated within the parent vessel across the aneurysm neck to prevent coils prolapsing into the parent vessel lumen or embolizing. Sequential coil deployment and balloon deflation permits the interventionalist to assess for any coil protrusion, with the goal of achieving high-density coil packing without protrusion of the coil ball or individual coils into the parent vessel (Fig 1). Unlike noncompliant balloon catheters used for angioplasty, dedicated neurovascular hypercompliant balloons allow the balloon to grow and conform to the parent vessel across the aneurysm neck, the point of least resistance. This provides an optimal seal for coil embolization of the aneurysm, and successful visceral artery embolization with coils and liquid embolic agents has been reported in individual case reports and case series (3,5–7). Compliant balloon catheters designed for coil embolization of intracranial aneurysms include the Sceptre (Microvention, Aliso Viejo, California), HyperForm (Medtronic, Dublin, Ireland), TransForm (Stryker, Kalamazoo, Michigan), and ASCENT (DePuy Synthes, Raynham, Massachusetts) devices. Most of these devices work over a 0.010–0.014-inch guide wire platform.
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STENT- AND STENT SCAFFOLD– ASSISTED EMBOLIZATION The temporary nature of the occlusion balloon means that coils packed into the aneurysm may protrude back into the parent vessel following balloon deflation. Prolonged balloon deployment may also induce distal ischemia and thrombosis. Deployment of an uncovered stent within the parent vessel allows placement of a microcatheter into the aneurysm sac parallel to the stent or through the stent interstices (8). The stent struts act as a barrier to coil protrusion, and this technique is suited for cases such as saccular aneurysms in which the neck may be insufficiently narrow to prevent coil ball protrusion. The concept of balloon- and stentassisted coil embolization in the treatment of VAA is well described (8–11). This technique can be performed with conventional uncovered vascular stents, microcatheters, and coils. Inherent drawbacks to the insertion of permanent stents include the risk of in-stent stenosis and thrombosis, the requirement for prolonged antiplatelet therapy, and the risk of permanent maldeployment. Temporary stent scaffolds have been developed to offer the benefits of stent-assisted coil embolization without necessitating permanent stent deployment. The Comaneci “neck-bridging” device (Rapid Medical, Yokneam, Israel) is one such temporary scaffold (Fig 2). This device is delivered via a microcatheter, which is unsheathed to deploy a temporarily expandable wire mesh within the parent artery. When the device has been deployed, the aneurysm is coil-embolized via a second microcatheter, which can be placed parallel to the device into the aneurysm sac or directly through the interstices. When satisfactory coil packing has been obtained, the scaffold device is resheathed and removed (without the option for permanent deployment). The open mesh design permits continuous perfusion of the visceral parenchyma, in contrast to an inflated balloon catheter. A single case report (12) describes the use of this device in visceral arteries in the successful treatment of a bilobed renal artery aneurysm. More than 1 scaffold device can be used in the treatment of an aneurysm. In the case of an aneurysm at a bifurcation, 2 devices can be placed in a Y-configuration extending from the parent vessel into both branches, providing a barrier to coil protrusion into the parent vessel and both branch vessels. Two devices and a separate microcatheter for coil embolization can all be delivered through an 8-F guiding catheter or sheath, facilitating treatment through a single percutaneous access site (12). The length of the deployed Comaneci device is 32 mm, with a fully expanded diameter of 4.5 mm. The distal portion of the device tapers to a flexible tip to reduce vessel trauma. Traditional stent-assisted coil embolization relies on the radial force of the stent to prevent coil protrusion into the parent vessel lumen. The pCONUS stent (Phenox, Bochum, Germany) and the PulseRider stent (Pulsar Vascular, Los Gatos, California) are permanent stents specifically designed for bifurcation aneurysms. The uncovered pCONUS stent consists of a standard tubular design with a modification to the
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Figure 2. (a) Illustration of a microcatheter advanced into the bifurcation aneurysm sac. Two Comaneci stents are deployed in a Yconfiguration across the aneurysm neck, extending from the parent vessel into 2 branches on either side of the aneurysm. Coils are deployed into the aneurysm sac. (b) When satisfactory coil packing has been obtained, the microcatheter and Comaneci devices are removed, leaving only the coil ball in situ. (c, i) Angiogram of the right kidney demonstrates a bilobed aneurysm at a renal artery bifurcation. (c, ii) Microcatheters are separately positioned into both branches (arrows). (c, iii) Through each microcatheter, a Comaneci stent is deployed (arrowheads), facilitating coil embolization of the aneurysm while preventing coils from protruding into the respective vessels. (c, iv) Final angiogram following removal of the Comaneci stents confirms satisfactory aneurysm coil embolization, with no residual device within the parent vessels. This case also appears in the report of Maingard et al (12).
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Figure 3. (a) Magnified view of an unsheathed pCONUS stent. (b) Illustration of pCONUS device deployed with the distal stent within the aneurysm and the petals opening around the aneurysm neck to support coil deployment. A microcatheter passes through the stent lumen with its tip in the aneurysm for coil deployment. (c, i). Curved 6-F sheath positioned within the left main renal artery. Angiogram obtained via the sheath confirms a bifurcation aneurysm. A pCONUS device has been deployed with the petals (red in c, ii) expanded within the aneurysm sac and the stent portion (pink in c, ii) within the terminal main renal artery. (c, ii) Magnified annotated image illustrates the deployed petals spanning the neck of the aneurysm. (d) A second microcatheter is positioned through the stent portion of the pCONUS device and into the aneurysm sac to permit coil deployment. (e) Final angiogram demonstrates good coil packing within the aneurysm. The microcatheter used for coil deployment has therefore been withdrawn, and the pCONUS device remains in situ (partly obscured by the coil ball). (f) Corresponding graphical representation of the detached and deployed pCONUS device with the microcatheter removed following adequate coil packing of the aneurysm.
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Figure 4. (a) Illustration of a flow-diverter stent spanning a wide-necked bifurcation aneurysm involving a side-branch vessel. The tightly knit interstices of the flow diverter preserve laminar flow into the side-branch artery while increasing the turbulence of flow (and residency time of blood) within the aneurysm sac. (b) After several months, thrombosis occurs within the aneurysm sac, with the branch vessel preserved. (c, i) Angiogram obtained via a guide catheter within the proper hepatic artery demonstrates a saccular hepatic artery aneurysm with a calcified rim and eccentric thrombus with filling of the central aneurysm sac. (c, ii) A Surpass flow diverter (Stryker) is deployed within the parent vessel, spanning the aneurysm neck. (c, iii) Unsubtracted angiography following deployment of the flow diverter (dashed line) and (c, iv) corresponding subtracted angiography demonstrate persistent filling of the sac immediately after device deployment, an expected finding.
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Figure 5. Graphical representation of optimal flow-diversion thrombogenicity.
distal aperture, containing a number of petals (Fig 3). The stent is positioned with the distal aperture within the aneurysm sac, allowing these petals to unfold, buttressing the aneurysm neck. A separate microcatheter is then advanced through the stent, emerging through the distal stent aperture into the aneurysm to permit coil embolization. The stent is electrolytically deployed when coil deposition has been completed and the microcatheter is removed. The wide interstices of this uncovered stent permit continuous side-branch perfusion. To the authors’ knowledge, the peripheral deployment of a pCONUS device has not been previously reported, while the PulseRider stent has not been reported.
FLOW DIVERSION In comparison with conventional uncovered stents, flowdiverting stents have a larger metallic surface (accounting for 30%–35% of the total surface area) with tightly spaced nonocclusive interstices that permit neointimal hyperplasia across an aneurysm neck and occlude over a period of weeks to months (13,14). These have been developed to span the aneurysm, preserving laminar flow within the stent lumen but creating turbulent flow outside the stent, which increases the residency time of blood within the sac (15). This promotes gradual thrombosis and occlusion of the aneurysm sac over time. In cases in which branches arise from the aneurysm or parent vessel, laminar flow into these vessels through the stent interstices can persist despite ostial coverage (provided stent struts occlude less than 50% and a pressure gradient persists; Fig 4) (16). This offers several potential benefits; by avoiding the need to enter the aneurysm with a microcatheter, the risk of intraprocedural rupture is reduced. In addition, preservation of branch vessels reduces the risk of infarction, which has been demonstrated in the intracranial circulation (17). A variety of commercially available flow diverters have been developed for use in the carotid, vertebral and intracranial circulation, in a variety of lengths and with a variety of delivery systems. These vary in width of interstices or number of layers within the stent wall, with resulting variance in flow-diverting properties (18–21). These include neurovascular flow diverters such as the FRED device (Microvention), LEO device (Balt, Montmorency, France), Pipeline Embolization Device (Medtronic), and Surpass flow diverter (Stryker); carotid flow diverters such as the
Figure 6. Graphical representation of a Barrel vascular reconstruction device. The deployable stent contains a central bulge (or barrel) that can be aligned with an aneurysm neck. When the device has been deployed, this can permit coil deployment into the aneurysm sac, which is now supported, while protecting branch vessels.
Casper/Roadsaver device (Microvention); and largerdiameter peripheral flow-diverter designs such as the Cardiatis Multilayer Stent (Cardiatis, Isnes, Belgium). Many of these stents were specifically designed and sized for the intracranial internal carotid artery (diameter of 5 mm, matching that of many visceral arteries). Most flow-diverter platforms are also highly deliverable across tortuous anatomy, with less inherent rigidity than comparably sized covered stents. Successful deployment of a variety of flow diverters has been described in the treatment of VAAs, with more than 10 years of published experience (14,22–25). The largest prospective reistry to date contains 54 patients (23), demonstrating a 93.3% rate of aneurysm sac occlusion at 1 year in a heterogenous group of visceral and peripheral arterial aneurysms treated with flow-diverting stents. Primary stent patency rate was 86.9% at 1 year, with a sidebranch patency rate of 96.1% at 1 year. Size reduction at 1 year was demonstrated in 91.1% of all aneurysms (23). Dual antiplatelet therapy (long-term aspirin and addition of clopidogrel or ticagrelor for a period of 3–6 mo) is typically required with the use of flow-diverter stents to
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Figure 7. (a) Photograph of an eCLIPs detachable neck-bridging device, published with written permission from EVASC. (b) Graphical representation of the eCLIPs detachable neck-bridging device spanning a saccular bifurcation aneurysm. The dense rib structure of the flow-diverting leaf segment is positioned over the aneurysm neck and permits endothelialization over time. The less dense rib structure of the anchor segment provides stability.
prevent platelet-mediated stent thrombosis (14). Overly rapid clotting will result in thrombosis of the aneurysm, side branches, and even the stent itself, whereas ineffective clotting will result in continued patency of the aneurysm. Flow diverters can be used in combination with antiplatelet medication to obtain an effective balance between these competing outcomes (Fig 5). Although sac depressurization occurs early, complete aneurysm thrombosis is a slower process than stent-graft exclusion (20). Longer follow-up imaging intervals are therefore required to assess flowdiverter treatment adequacy. It is possible to see residual flow into the aneurysm on early angiographic or crosssectional imaging studies, which should not be mistaken for treatment failure (as would be the case with persistent flow in a conventional stent-graft procedure).
FUTURE PERSPECTIVES Stent-assisted embolization devices have been developed to incorporate a central bulge (or “barrel,” ie, Barrel Vascular Reconstruction Device; Medtronic; Fig 6). These aim to provide additional control when performing coil embolization of bifurcated aneurysms and branch vessel origins. Aligning the central barrel with the aneurysm neck provides a concave support along the aneurysm neck to enhance coil stability while also covering the branch vessel ostium to prevent coil entry (26). Although not reported in the peripheral vascular literature, such a design would offer potential applications in a subset of visceral aneurysm morphologies. A number of detachable neck-bridging devices have also been developed for deployment across an aneurysm neck to facilitate coil depolyment into the sac or flow diversion with eventual endothelization. These are available in a
Figure 8. Graphical representation of a deployed WEB device within a saccular bifurcation aneurysm.
variety of shapes and designs, such as the TriSpan device (Target Therapeutics/Boston Scientific, Fremont, California) and the newer eCLIPs device (EVASC; Vancouver, British Columbia, Canada; Fig 7). Deployment of the eCLIPs device has not been described in the treatment of VAAs, and a single case report (27) describes the use of a TriSpan device for the successful treatment of a renal artery aneurysm. The Woven EndoBridge (WEB) device (Sequent Medical/ Microvention, Aliso Viejo, California) is a self-expanding nitinol mesh with a structure analogous to the Type I AMPLATZER Vascular Plug (Fig 8). The WEB device is deployed within an aneurysm sac and expands to cover the neck of the aneurysm, resulting in blood-flow
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Table. Overview of Devices Available for Aneurysm Treatment Device Name
Length (mm)
Diameter (mm)
Relevant Diameter(s)
Manufacturer
Scepter
10–20
4
HyperForm
7–20
3–7
0.010-inch wire, Medtronic (http://www.medtronic.com/content/dam/medtronic2.2–3-F distal outer com/products/neurological/neurovascular-product-catalog.pdf)
TransForm
10–30
3–7
0.014-inch wire, 2.8-F distal outer
Stryker (https://www.stryker.com/us/en/neurovascular/products/ transform-occlusion-balloon-catheter.html)
ASCENT
7–15
4–6
0.014-inch wire, 2.9-F distal outer
DePuy Synthes (https://www.depuysynthes.com/hcp/codmanneuro/products/qs/ASCENT-Occlusion-Balloon-Cathet)
0.021-inch delivery catheter, inner
Rapid Medical (https://www.rapid-medical.com/comaneci)
Compliant balloons 0.0165-inch wire, 2.1-F distal outer
Microvention (https://microvention.com/emea/product/scepter)
Stent-assisted and stent scaffold devices Comaneci (including Petit and 17)
22–32
pCONUS (including pCONUS 1 and 2)
15–25
PulseRider
NA
0.5–4.5
Shaft, 3–4; 0.021-inch delivery crown, 5–15 catheter, inner
2.7–4.5
0.021-inch delivery catheter, inner
Phenox (http://www.phenox.net/products/pconus.html)
Pulsar Vascular (http://www.pulsarvascular.com/products/ pulserider)
Flow diverters FRED (including FRED Jr)
8/13– 2.5–5.5 (52.8% 2.1–2.7 F distal 39/45 porosity) delivery catheter, outer 13/9– 2.5–5.5 (83.9% 1.7–2.1 F distal 33/29 porosity) delivery catheter, outer
Microvention (https://microvention.com/emea/product/fred-family)
Pipeline
10–35
Medtronic (http://www.medtronic.com/us-en/healthcareprofessionals/products/neurological/hemorrhagic-stroke/ pipeline-flex.html)
Surpass Streamline
15–50
3–5 (70.0% porosity)
3.7 F distal delivery catheter, outer
Stryker (http://www.stryker.com/us/en/neurovascular/products/ surpass-streamline-flow-diverter.html))
LEO (including LEO Baby)
12–75
2–5.5 (83% porosity)
1.9–3.3 F distal delivery catheter, outer
BALT (http://www.balt.fr/en/technologie)
LVIS (including LVIS Jr)
2.5–5 (71.2% 3 F distal delivery porosity) catheter, outer
Microvention (https://microvention.com/emea/product/lvis-family)
Neck-bridging devices eCLIPs
NA
2–3.25 (30.0% 0.014 inch neck deployment wire coverage)
EVASC (https://www.evasc.com/features)
Woven EndoBridge devices WEB (including WEB SL and SLS)
2–9.6
3–11
0.017–0.033-inch delivery catheter, inner
Microvention (https://www.microvention.com/emea/product/webfamily)
NA ¼ not applicable.
disruption and eventual occlusion without the need for antiplatelet medication (28). Although this has not been reported in the peripheral circulation, this is effective for the treatment of intracranial wide-necked bifurcation aneurysms and may find use in analogous visceral aneurysms.
FOLLOW-UP OF VAAs TREATED WITH DEVICES In the intracranial circulation, there is considerable variation in posttreatment aneurysm follow-up protocols between treatment centers in terms of modality, frequency,
and overall duration (29). This is compounded by the range of devices available and their varying modes of action. Involvement of the interventional radiologist in the interpretation of follow-up imaging is essential. As the mechanism of action of devices such as flow diverters induces gradual occlusion, persistent flow does not necessarily equate to treatment failure. The persistence of flow within an aneurysm should be interpreted in the context of the technique employed (coil embolization vs flow diversion), duration since the initial procedure, current antiplatelet therapy, sac size, and branch vessel patency. Follow-up may also detect reperfusion of a previously occluded
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aneurysm, but this is uncommon, occurring in 2 of 45 endovascular-treated renal artery aneurysms (both within the first 2 mo) in 1 series (30). When successful aneurysm occlusion has occurred, the need for, or duration of, additional radiologic follow-up remains uncertain; however, the risk of delayed sac reperfusion and the need for repeat intervention may warrant long-term clinical and radiologic follow-up (31). A variety of challenges exist in the adaption of endovascular devices for peripheral aneurysm treatment. As these devices may be selectively approved for neurovascular deployment, the off-label nature of peripheral deployment may be restricted in certain jurisdictions. Initial use often necessitates the presence of a product representative or proctoring colleague, which introduces scheduling complexity. Device-compatible delivery catheters are typically neurointervention-specific and may be not be readily available in centers without onsite neurointerventional stock, requiring specific advance stocking. The nature of the devices often requires personalized ordering of single products, requiring accurate preprocedural measurements (Table). The costs of these devices can be significant, and several are manufactured by niche neurovascular companies with whom interventional radiology departments may not have supply relationships. Finally, previous studies have demonstrated a steep learning curve with the deployment of specific neurovascular devices (32). Although this is not necessarily generalizable to all classes of these devices, the infrequent deployment of any complex device in a multiple-catheter procedure is technically challenging, and a learning curve may be expected. Finally, many of these devices are relatively new, and there is a lack of evidence of their efficacy in the visceral arteries. Allowing for the low numbers of patients with such challenging aneurysms, and their heterogenous aneurysm anatomy, such evidence is likely to be confined to case reports and small series, and the peripheral adoption of these devices must acknowledge this ongoing clinical uncertainty. In conclusion, a variety of neurointerventional devices and techniques allow for the endovascular treatment of aneurysms that would be challenging or even untreatable with the use of standard endovascular exclusion techniques. The choice of device and technique is tailored to aneurysm morphology. The need for surgery, or for endovascular sacrificing of arterial branches and therefore organ function, can be mitigated by the use of these devices in selected patients.
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device developed for cerebral aneurysms: preliminary results. Ann Vasc Surg 2018; 53:272.e1–272.e9. 26. Gory B, Blanc R, Turjman F, Berge J, Piotin M. The Barrel vascular reconstruction device for endovascular coiling of wide-necked intracranial aneurysms: a multicenter, prospective, post-marketing study. J Neurointerv Surg 2018; 10:969–974. 27. Dib M, Sedat J, Raffaelli C, Petit I, Robertson WG, Jaeger P. Endovascular treatment of a wide-neck renal artery bifurcation aneurysm. J Vasc Interv Radiol 2003; 14:1461–1464. 28. Jia ZY, Shi HB, Miyachi S, Hwang SM, Sheen JJ, Song YS, et al. Development of new endovascular devices for aneurysm treatment. J Stroke 2018; 20:46–56.
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29. Gupta R, Griessenauer CJ, Adeeb N, et al. Evaluating imaging follow-up strategies and costs of unruptured intracranial aneurysms treated with endovascular techniques: a survey of academic neurovascular centers in the United States. World Neurosurg 2016; 94:360–367. 30. Li Z, Zhao Z, Qin F, et al. Outcomes of endovascular treatment and open repair for renal artery aneurysms: a single-center retrospective comparative analysis. J Vasc Interv Radiol 2018; 29:62–70. 31. Kok HK, Asadi H, Sheehan M, Given MF, Lee MJ. Systematic review and single-center experience for endovascular management of visceral and renal artery aneurysms. J Vasc Interv Radiol 2016; 27:1630–1641. 32. Chiu AH, Vries JD, O’Kelly CJ, et al. The second-generation eCLIPs Endovascular Clip System: initial experience. J Neurosurg 2018; 128:482–489.
Treatment of Visceral Artery Aneurysms Using Novel Neurointerventional Devices and Techniques Timothy Eanna Murray, MB, MCh, MRCS, FFR, EBIR, Paul Brennan, MB, MSc, MRCPI, FRCR, FFR, Julian T. Maingard, MBBS, BBiomedSci, Ronil V. Chandra, MBBS, MMed, FRANZCR, CCINR, Dilly M. Little, MD, BSc, FRCS (Urol), D. Mark Brooks, MBBS, FRANZCR, CCINR, EBIR, Hong K. Kok, MB, BMedSci, MRCPI, MRCP(UK), FFR, FRCR, EBIR, Hamed Asadi, MD, PhD, FRANZCR, CCINR, EBIR, and Michael J. Lee, MB, MSc, FRCPI, FRCR, FFR, EBIR ABSTRACT The presence of branching vessels, a wide aneurysm neck, and/or fusiform morphology represents a challenge to conventional endovascular treatment of visceral artery aneurysms. A variety of techniques and devices have emerged for the treatment of intracranial aneurysms, in which more aggressive treatment algorithms aimed at smaller and morphologically diverse aneurysms have driven innovation. Here, modified neurointerventional techniques including the use of compliant balloons, scaffold- or stent-assisted coil embolization, and flow diversion are described in the treatment of visceral aneurysms. Neurointerventional devices and their mechanisms of action are described in the context of their application in the peripheral arterial system.
ABBREVIATIONS VAA ¼ visceral artery aneurysm, WEB ¼ Woven EndoBridge
From the Departments of Interventional Radiology (T.E.M., M.J.L.), Interventional Neuroradiology (P.B.), and Urology and Transplant Surgery (D.M.L.), Beaumont Hospital, Beaumont Road, Dublin, Ireland; Department of Interventional Radiology and Interventional Neuroradiology Unit (J.T.M., D.M.B., H.A.), Austin Health, Melbourne, Australia; School of Medicine, Faculty of Health (J.T.M., D.M.B., H.A.), Deakin University, Waurn Ponds, Australia; Interventional Neuroradiology Unit (R.V.C., H.A.), Monash Imaging, Monash Health, Melbourne, Australia; Interventional Radiology Service (H.K.K.), Northern Hospital Radiology, Melbourne, Australia; and Royal College of Surgeons in Ireland (M.J.L.), Dublin, Ireland. Received August 25, 2018; final revision received and accepted December 30, 2018. Address correspondence to T.E.M.; E-mail: [email protected] None of the authors have identified a conflict of interest. © SIR, 2019 J Vasc Interv Radiol 2019; 30:1407–1417 https://doi.org/10.1016/j.jvir.2018.12.733
Endovascular treatment of visceral artery aneurysms (VAAs) requires a tailored approach encompassing aneurysm morphology, arterial branching, vessel angulation, and multiplicity of aneurysms where present. Aneurysm exclusion with coils or covered stents is well described in the treatment of VAAs, but these techniques are limited in their applicability to certain aneurysm types (1). Fusiform aneurysm morphology can preclude coil embolization because an insufficient aneurysm neck prevents the creation of a stable coil ball (2). When branching vessels arise from a visceral aneurysm, the use of covered stents may be precluded as coverage of the branching arterial ostium risks infarction of the supplied parenchyma (3). Within the intracranial circulation, the criticality of maintaining branch vessel perfusion while excluding aneurysms has spurred the development of a variety of devices, to enable the endovascular treatment of aneurysms previously untreatable by an endovascular approach. Many of these neurointerventional devices are suitable for adoption in
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Figure 1. (a) Illustration of a microcatheter positioned within an intermediate-necked bifurcation aneurysm. A hypercompliant occlusion balloon is positioned across the aneurysm neck and inflated within the parent vessel, thereby remodeling the aneurysm neck to support coil embolization. In addition to using the side wall of the balloon, the toe (ie, distal curve) and heel (ie, proximal curve) can also be positioned as needed to conform to the anatomy of the aneurysm. (b, i) An 8-F sheath is positioned within the left renal artery. Angiogram confirms a relatively wide-necked saccular aneurysm. (b, ii) A microcatheter (arrowhead) is positioned within the aneurysm while a deflated hypercompliant balloon (arrow; Sceptre C; Microvention) is advanced across the aneurysm neck. (b, iii) The hypercompliant balloon is now inflated (arrow), and detachable coils are deployed within the aneurysm sac. (b, iv) Completion angiogram with the balloon deflated demonstrates satisfactory aneurysm occlusion with preserved patency of the parent vessel and distal branches. This case also appears in the report of Das et al (7).
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peripheral and visceral arteries, which may permit endovascular treatment of anatomically challenging and complex VAAs.
PREPROCEDURAL PREPARATION The need for preprocedural medication and maintenance of antiplatelet medication is device-specific. When stent implantation is planned, dual antiplatelet therapy is typically recommended within the neurovascular system. As is often the case, when primary stent deployment is not planned but “bailout” stent-assisted coil embolization may be required, dual antiplatelet coverage may still be prudent (4). Loading doses (300–325 mg aspirin and 300 mg clopidogrel) on the day of or before the procedure or low doses (75–100 mg aspirin and 75 mg clopidogrel) represent alternate dosing strategies. When a neurovascular device or technique is being considered, the interventionalist must ensure that an appropriate selection of hardware is in stock, including microcatheters and guide catheters, which may be devicespecific. Furthermore, many of these devices are available in a range of sizes, and selection requires a knowledge of the aneurysm anatomy, the size and length of arterial branches distal to the aneurysm (for delivery of microwires or other devices), and the landing zone requirements for device deployment.
BALLOON-ASSISTED ANEURYSM EXCLUSION Balloon-assisted aneurysm exclusion may be chosen when an aneurysm neck is believed to be sufficiently narrow to retain a formed coil ball, but initial formation of the coil ball is at risk of unsecured coil protrusion or migration (3). When a microcatheter has been positioned within the aneurysm sac, a parallel balloon catheter can be inflated within the parent vessel across the aneurysm neck to prevent coils prolapsing into the parent vessel lumen or embolizing. Sequential coil deployment and balloon deflation permits the interventionalist to assess for any coil protrusion, with the goal of achieving high-density coil packing without protrusion of the coil ball or individual coils into the parent vessel (Fig 1). Unlike noncompliant balloon catheters used for angioplasty, dedicated neurovascular hypercompliant balloons allow the balloon to grow and conform to the parent vessel across the aneurysm neck, the point of least resistance. This provides an optimal seal for coil embolization of the aneurysm, and successful visceral artery embolization with coils and liquid embolic agents has been reported in individual case reports and case series (3,5–7). Compliant balloon catheters designed for coil embolization of intracranial aneurysms include the Sceptre (Microvention, Aliso Viejo, California), HyperForm (Medtronic, Dublin, Ireland), TransForm (Stryker, Kalamazoo, Michigan), and ASCENT (DePuy Synthes, Raynham, Massachusetts) devices. Most of these devices work over a 0.010–0.014-inch guide wire platform.
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STENT- AND STENT SCAFFOLD– ASSISTED EMBOLIZATION The temporary nature of the occlusion balloon means that coils packed into the aneurysm may protrude back into the parent vessel following balloon deflation. Prolonged balloon deployment may also induce distal ischemia and thrombosis. Deployment of an uncovered stent within the parent vessel allows placement of a microcatheter into the aneurysm sac parallel to the stent or through the stent interstices (8). The stent struts act as a barrier to coil protrusion, and this technique is suited for cases such as saccular aneurysms in which the neck may be insufficiently narrow to prevent coil ball protrusion. The concept of balloon- and stentassisted coil embolization in the treatment of VAA is well described (8–11). This technique can be performed with conventional uncovered vascular stents, microcatheters, and coils. Inherent drawbacks to the insertion of permanent stents include the risk of in-stent stenosis and thrombosis, the requirement for prolonged antiplatelet therapy, and the risk of permanent maldeployment. Temporary stent scaffolds have been developed to offer the benefits of stent-assisted coil embolization without necessitating permanent stent deployment. The Comaneci “neck-bridging” device (Rapid Medical, Yokneam, Israel) is one such temporary scaffold (Fig 2). This device is delivered via a microcatheter, which is unsheathed to deploy a temporarily expandable wire mesh within the parent artery. When the device has been deployed, the aneurysm is coil-embolized via a second microcatheter, which can be placed parallel to the device into the aneurysm sac or directly through the interstices. When satisfactory coil packing has been obtained, the scaffold device is resheathed and removed (without the option for permanent deployment). The open mesh design permits continuous perfusion of the visceral parenchyma, in contrast to an inflated balloon catheter. A single case report (12) describes the use of this device in visceral arteries in the successful treatment of a bilobed renal artery aneurysm. More than 1 scaffold device can be used in the treatment of an aneurysm. In the case of an aneurysm at a bifurcation, 2 devices can be placed in a Y-configuration extending from the parent vessel into both branches, providing a barrier to coil protrusion into the parent vessel and both branch vessels. Two devices and a separate microcatheter for coil embolization can all be delivered through an 8-F guiding catheter or sheath, facilitating treatment through a single percutaneous access site (12). The length of the deployed Comaneci device is 32 mm, with a fully expanded diameter of 4.5 mm. The distal portion of the device tapers to a flexible tip to reduce vessel trauma. Traditional stent-assisted coil embolization relies on the radial force of the stent to prevent coil protrusion into the parent vessel lumen. The pCONUS stent (Phenox, Bochum, Germany) and the PulseRider stent (Pulsar Vascular, Los Gatos, California) are permanent stents specifically designed for bifurcation aneurysms. The uncovered pCONUS stent consists of a standard tubular design with a modification to the
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Figure 2. (a) Illustration of a microcatheter advanced into the bifurcation aneurysm sac. Two Comaneci stents are deployed in a Yconfiguration across the aneurysm neck, extending from the parent vessel into 2 branches on either side of the aneurysm. Coils are deployed into the aneurysm sac. (b) When satisfactory coil packing has been obtained, the microcatheter and Comaneci devices are removed, leaving only the coil ball in situ. (c, i) Angiogram of the right kidney demonstrates a bilobed aneurysm at a renal artery bifurcation. (c, ii) Microcatheters are separately positioned into both branches (arrows). (c, iii) Through each microcatheter, a Comaneci stent is deployed (arrowheads), facilitating coil embolization of the aneurysm while preventing coils from protruding into the respective vessels. (c, iv) Final angiogram following removal of the Comaneci stents confirms satisfactory aneurysm coil embolization, with no residual device within the parent vessels. This case also appears in the report of Maingard et al (12).
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Figure 3. (a) Magnified view of an unsheathed pCONUS stent. (b) Illustration of pCONUS device deployed with the distal stent within the aneurysm and the petals opening around the aneurysm neck to support coil deployment. A microcatheter passes through the stent lumen with its tip in the aneurysm for coil deployment. (c, i). Curved 6-F sheath positioned within the left main renal artery. Angiogram obtained via the sheath confirms a bifurcation aneurysm. A pCONUS device has been deployed with the petals (red in c, ii) expanded within the aneurysm sac and the stent portion (pink in c, ii) within the terminal main renal artery. (c, ii) Magnified annotated image illustrates the deployed petals spanning the neck of the aneurysm. (d) A second microcatheter is positioned through the stent portion of the pCONUS device and into the aneurysm sac to permit coil deployment. (e) Final angiogram demonstrates good coil packing within the aneurysm. The microcatheter used for coil deployment has therefore been withdrawn, and the pCONUS device remains in situ (partly obscured by the coil ball). (f) Corresponding graphical representation of the detached and deployed pCONUS device with the microcatheter removed following adequate coil packing of the aneurysm.
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Figure 4. (a) Illustration of a flow-diverter stent spanning a wide-necked bifurcation aneurysm involving a side-branch vessel. The tightly knit interstices of the flow diverter preserve laminar flow into the side-branch artery while increasing the turbulence of flow (and residency time of blood) within the aneurysm sac. (b) After several months, thrombosis occurs within the aneurysm sac, with the branch vessel preserved. (c, i) Angiogram obtained via a guide catheter within the proper hepatic artery demonstrates a saccular hepatic artery aneurysm with a calcified rim and eccentric thrombus with filling of the central aneurysm sac. (c, ii) A Surpass flow diverter (Stryker) is deployed within the parent vessel, spanning the aneurysm neck. (c, iii) Unsubtracted angiography following deployment of the flow diverter (dashed line) and (c, iv) corresponding subtracted angiography demonstrate persistent filling of the sac immediately after device deployment, an expected finding.
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Figure 5. Graphical representation of optimal flow-diversion thrombogenicity.
distal aperture, containing a number of petals (Fig 3). The stent is positioned with the distal aperture within the aneurysm sac, allowing these petals to unfold, buttressing the aneurysm neck. A separate microcatheter is then advanced through the stent, emerging through the distal stent aperture into the aneurysm to permit coil embolization. The stent is electrolytically deployed when coil deposition has been completed and the microcatheter is removed. The wide interstices of this uncovered stent permit continuous side-branch perfusion. To the authors’ knowledge, the peripheral deployment of a pCONUS device has not been previously reported, while the PulseRider stent has not been reported.
FLOW DIVERSION In comparison with conventional uncovered stents, flowdiverting stents have a larger metallic surface (accounting for 30%–35% of the total surface area) with tightly spaced nonocclusive interstices that permit neointimal hyperplasia across an aneurysm neck and occlude over a period of weeks to months (13,14). These have been developed to span the aneurysm, preserving laminar flow within the stent lumen but creating turbulent flow outside the stent, which increases the residency time of blood within the sac (15). This promotes gradual thrombosis and occlusion of the aneurysm sac over time. In cases in which branches arise from the aneurysm or parent vessel, laminar flow into these vessels through the stent interstices can persist despite ostial coverage (provided stent struts occlude less than 50% and a pressure gradient persists; Fig 4) (16). This offers several potential benefits; by avoiding the need to enter the aneurysm with a microcatheter, the risk of intraprocedural rupture is reduced. In addition, preservation of branch vessels reduces the risk of infarction, which has been demonstrated in the intracranial circulation (17). A variety of commercially available flow diverters have been developed for use in the carotid, vertebral and intracranial circulation, in a variety of lengths and with a variety of delivery systems. These vary in width of interstices or number of layers within the stent wall, with resulting variance in flow-diverting properties (18–21). These include neurovascular flow diverters such as the FRED device (Microvention), LEO device (Balt, Montmorency, France), Pipeline Embolization Device (Medtronic), and Surpass flow diverter (Stryker); carotid flow diverters such as the
Figure 6. Graphical representation of a Barrel vascular reconstruction device. The deployable stent contains a central bulge (or barrel) that can be aligned with an aneurysm neck. When the device has been deployed, this can permit coil deployment into the aneurysm sac, which is now supported, while protecting branch vessels.
Casper/Roadsaver device (Microvention); and largerdiameter peripheral flow-diverter designs such as the Cardiatis Multilayer Stent (Cardiatis, Isnes, Belgium). Many of these stents were specifically designed and sized for the intracranial internal carotid artery (diameter of 5 mm, matching that of many visceral arteries). Most flow-diverter platforms are also highly deliverable across tortuous anatomy, with less inherent rigidity than comparably sized covered stents. Successful deployment of a variety of flow diverters has been described in the treatment of VAAs, with more than 10 years of published experience (14,22–25). The largest prospective reistry to date contains 54 patients (23), demonstrating a 93.3% rate of aneurysm sac occlusion at 1 year in a heterogenous group of visceral and peripheral arterial aneurysms treated with flow-diverting stents. Primary stent patency rate was 86.9% at 1 year, with a sidebranch patency rate of 96.1% at 1 year. Size reduction at 1 year was demonstrated in 91.1% of all aneurysms (23). Dual antiplatelet therapy (long-term aspirin and addition of clopidogrel or ticagrelor for a period of 3–6 mo) is typically required with the use of flow-diverter stents to
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Figure 7. (a) Photograph of an eCLIPs detachable neck-bridging device, published with written permission from EVASC. (b) Graphical representation of the eCLIPs detachable neck-bridging device spanning a saccular bifurcation aneurysm. The dense rib structure of the flow-diverting leaf segment is positioned over the aneurysm neck and permits endothelialization over time. The less dense rib structure of the anchor segment provides stability.
prevent platelet-mediated stent thrombosis (14). Overly rapid clotting will result in thrombosis of the aneurysm, side branches, and even the stent itself, whereas ineffective clotting will result in continued patency of the aneurysm. Flow diverters can be used in combination with antiplatelet medication to obtain an effective balance between these competing outcomes (Fig 5). Although sac depressurization occurs early, complete aneurysm thrombosis is a slower process than stent-graft exclusion (20). Longer follow-up imaging intervals are therefore required to assess flowdiverter treatment adequacy. It is possible to see residual flow into the aneurysm on early angiographic or crosssectional imaging studies, which should not be mistaken for treatment failure (as would be the case with persistent flow in a conventional stent-graft procedure).
FUTURE PERSPECTIVES Stent-assisted embolization devices have been developed to incorporate a central bulge (or “barrel,” ie, Barrel Vascular Reconstruction Device; Medtronic; Fig 6). These aim to provide additional control when performing coil embolization of bifurcated aneurysms and branch vessel origins. Aligning the central barrel with the aneurysm neck provides a concave support along the aneurysm neck to enhance coil stability while also covering the branch vessel ostium to prevent coil entry (26). Although not reported in the peripheral vascular literature, such a design would offer potential applications in a subset of visceral aneurysm morphologies. A number of detachable neck-bridging devices have also been developed for deployment across an aneurysm neck to facilitate coil depolyment into the sac or flow diversion with eventual endothelization. These are available in a
Figure 8. Graphical representation of a deployed WEB device within a saccular bifurcation aneurysm.
variety of shapes and designs, such as the TriSpan device (Target Therapeutics/Boston Scientific, Fremont, California) and the newer eCLIPs device (EVASC; Vancouver, British Columbia, Canada; Fig 7). Deployment of the eCLIPs device has not been described in the treatment of VAAs, and a single case report (27) describes the use of a TriSpan device for the successful treatment of a renal artery aneurysm. The Woven EndoBridge (WEB) device (Sequent Medical/ Microvention, Aliso Viejo, California) is a self-expanding nitinol mesh with a structure analogous to the Type I AMPLATZER Vascular Plug (Fig 8). The WEB device is deployed within an aneurysm sac and expands to cover the neck of the aneurysm, resulting in blood-flow
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Table. Overview of Devices Available for Aneurysm Treatment Device Name
Length (mm)
Diameter (mm)
Relevant Diameter(s)
Manufacturer
Scepter
10–20
4
HyperForm
7–20
3–7
0.010-inch wire, Medtronic (http://www.medtronic.com/content/dam/medtronic2.2–3-F distal outer com/products/neurological/neurovascular-product-catalog.pdf)
TransForm
10–30
3–7
0.014-inch wire, 2.8-F distal outer
Stryker (https://www.stryker.com/us/en/neurovascular/products/ transform-occlusion-balloon-catheter.html)
ASCENT
7–15
4–6
0.014-inch wire, 2.9-F distal outer
DePuy Synthes (https://www.depuysynthes.com/hcp/codmanneuro/products/qs/ASCENT-Occlusion-Balloon-Cathet)
0.021-inch delivery catheter, inner
Rapid Medical (https://www.rapid-medical.com/comaneci)
Compliant balloons 0.0165-inch wire, 2.1-F distal outer
Microvention (https://microvention.com/emea/product/scepter)
Stent-assisted and stent scaffold devices Comaneci (including Petit and 17)
22–32
pCONUS (including pCONUS 1 and 2)
15–25
PulseRider
NA
0.5–4.5
Shaft, 3–4; 0.021-inch delivery crown, 5–15 catheter, inner
2.7–4.5
0.021-inch delivery catheter, inner
Phenox (http://www.phenox.net/products/pconus.html)
Pulsar Vascular (http://www.pulsarvascular.com/products/ pulserider)
Flow diverters FRED (including FRED Jr)
8/13– 2.5–5.5 (52.8% 2.1–2.7 F distal 39/45 porosity) delivery catheter, outer 13/9– 2.5–5.5 (83.9% 1.7–2.1 F distal 33/29 porosity) delivery catheter, outer
Microvention (https://microvention.com/emea/product/fred-family)
Pipeline
10–35
Medtronic (http://www.medtronic.com/us-en/healthcareprofessionals/products/neurological/hemorrhagic-stroke/ pipeline-flex.html)
Surpass Streamline
15–50
3–5 (70.0% porosity)
3.7 F distal delivery catheter, outer
Stryker (http://www.stryker.com/us/en/neurovascular/products/ surpass-streamline-flow-diverter.html))
LEO (including LEO Baby)
12–75
2–5.5 (83% porosity)
1.9–3.3 F distal delivery catheter, outer
BALT (http://www.balt.fr/en/technologie)
LVIS (including LVIS Jr)
2.5–5 (71.2% 3 F distal delivery porosity) catheter, outer
Microvention (https://microvention.com/emea/product/lvis-family)
Neck-bridging devices eCLIPs
NA
2–3.25 (30.0% 0.014 inch neck deployment wire coverage)
EVASC (https://www.evasc.com/features)
Woven EndoBridge devices WEB (including WEB SL and SLS)
2–9.6
3–11
0.017–0.033-inch delivery catheter, inner
Microvention (https://www.microvention.com/emea/product/webfamily)
NA ¼ not applicable.
disruption and eventual occlusion without the need for antiplatelet medication (28). Although this has not been reported in the peripheral circulation, this is effective for the treatment of intracranial wide-necked bifurcation aneurysms and may find use in analogous visceral aneurysms.
FOLLOW-UP OF VAAs TREATED WITH DEVICES In the intracranial circulation, there is considerable variation in posttreatment aneurysm follow-up protocols between treatment centers in terms of modality, frequency,
and overall duration (29). This is compounded by the range of devices available and their varying modes of action. Involvement of the interventional radiologist in the interpretation of follow-up imaging is essential. As the mechanism of action of devices such as flow diverters induces gradual occlusion, persistent flow does not necessarily equate to treatment failure. The persistence of flow within an aneurysm should be interpreted in the context of the technique employed (coil embolization vs flow diversion), duration since the initial procedure, current antiplatelet therapy, sac size, and branch vessel patency. Follow-up may also detect reperfusion of a previously occluded
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aneurysm, but this is uncommon, occurring in 2 of 45 endovascular-treated renal artery aneurysms (both within the first 2 mo) in 1 series (30). When successful aneurysm occlusion has occurred, the need for, or duration of, additional radiologic follow-up remains uncertain; however, the risk of delayed sac reperfusion and the need for repeat intervention may warrant long-term clinical and radiologic follow-up (31). A variety of challenges exist in the adaption of endovascular devices for peripheral aneurysm treatment. As these devices may be selectively approved for neurovascular deployment, the off-label nature of peripheral deployment may be restricted in certain jurisdictions. Initial use often necessitates the presence of a product representative or proctoring colleague, which introduces scheduling complexity. Device-compatible delivery catheters are typically neurointervention-specific and may be not be readily available in centers without onsite neurointerventional stock, requiring specific advance stocking. The nature of the devices often requires personalized ordering of single products, requiring accurate preprocedural measurements (Table). The costs of these devices can be significant, and several are manufactured by niche neurovascular companies with whom interventional radiology departments may not have supply relationships. Finally, previous studies have demonstrated a steep learning curve with the deployment of specific neurovascular devices (32). Although this is not necessarily generalizable to all classes of these devices, the infrequent deployment of any complex device in a multiple-catheter procedure is technically challenging, and a learning curve may be expected. Finally, many of these devices are relatively new, and there is a lack of evidence of their efficacy in the visceral arteries. Allowing for the low numbers of patients with such challenging aneurysms, and their heterogenous aneurysm anatomy, such evidence is likely to be confined to case reports and small series, and the peripheral adoption of these devices must acknowledge this ongoing clinical uncertainty. In conclusion, a variety of neurointerventional devices and techniques allow for the endovascular treatment of aneurysms that would be challenging or even untreatable with the use of standard endovascular exclusion techniques. The choice of device and technique is tailored to aneurysm morphology. The need for surgery, or for endovascular sacrificing of arterial branches and therefore organ function, can be mitigated by the use of these devices in selected patients.
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