Technical aspects of combined intrasaccular and endoluminal flow diversion

Abstract

Introduction

The concurrent use of endoluminal flow diversion with coils is a viable option when treating complex or large aneurysms. Alternatives to coil embolization as an adjunctive treatment are currently limited. The Food and Drug Administration recently approved the Woven EndoBridge (WEB) device (Microvention, Aliso Viejo, California) as an intrasaccular flow diverter for wide-neck bifurcation aneurysms. We present the technical aspects of combined WEB device plus endoluminal flow diversion for the treatment of complex wide-necked intracranial aneurysms.

Methods

A retrospective chart review of all patients treated via intrasaccular flow diversion at a single institution over the last 12 months was performed.

Results

In total, seven patients underwent treatment of eight aneurysms via combined intrasaccular and endoluminal flow diversion. Of the seven patients, six were treated in a single setting. The most common aneurysm location was the posterior communicating artery. The majority of the aneurysms required steam shaping of the Via deployment catheter to place the WEB device orthogonally to the aneurysm dome. There were no complications.

Conclusions

We believe this is one of the first series reporting the combined use of the WEB device and endoluminal flow diversion for the treatment of intracranial aneurysms. This series demonstrates that the concurrent use of the WEB device with endoluminal flow diversion is safe for achieving immediate aneurysm treatment and may enhance the long-term durability in complex aneurysms.

Introduction

Endovascular treatment of wide-neck and/or bifurcation aneurysms continues to be a present-day challenge.^1–3 Treatment strategies such as flow diversion, stent-assisted coil embolization, and balloon remodeling have been described to bolster treatment durability and efficacy.

Endoluminal flow diversion is the endovascular treatment of choice for wide-neck non-bifurcation aneurysms, especially for those in the cavernous and supraclinoid internal carotid artery (ICA). Previous studies have suggested, however, that larger aneurysms—particularly those with vessels arising from the neck—may not be adequately cured with endoluminal flow diversion alone.^4,5 Large aneurysms treated with endoluminal flow diversion are at a higher risk of procedural and delayed complications, such as mural remodeling and rupture. Therefore, endoluminal flow diversion alone may not be favored; rather, adjuvant coil embolization for aneurysm stabilization should be considered. ⁶ Despite advances in coil embolization technology, wide-neck aneurysms—specifically those with significant branching vessels—remain difficult to coil, balloon remodel, or manage operatively.

Recently, the Food and Drug Administration approved the Woven EndoBridge (WEB) device (Microvention, Aliso Viejo, California) for the treatment of wide-neck bifurcation aneurysms. ⁷ The WEB device functions as an intrasaccular flow diverter.^8–10 Once deployed in an aneurysm, the tight-knit interlaced metal lattice of the WEB device provides flow diversion and is a substrate for neoendotheliazation. The WEB-IT trial showed adequate aneurysm occlusion in 84.6% of cases, with one case experiencing a major neurological morbidity. ¹⁰ These results are similar to the previously reported results of the WEBCAST and WEBCAST2 registries as well as the French Observatory.^9,11 More recent series have described “off label” use of the device to assist in the embolization of non-bifurcation aneurysms.^12,13

One strategy that has yet to be rigorously explored is the combined use of intrasaccular and endoluminal flow diversion for the treatment of complex aneurysms. Herein, we present our experience with the use of combined endoluminal and intrasaccular flow diversion of the treatment of intracranial aneurysms.

Methods

A retrospective chart review of all patients who underwent combined endoluminal and intrasaccular flow diversion for an intracranial aneurysm between January 1, 2019, and May 1, 2020, was performed. The Institutional Review Board approved this study as minimal risk, waiving informed consent. Endoluminal flow diversion was achieved either by the Pipeline Embolization Device (PED) (Medtronic, Minneapolis, Minnesota) or the Flow Reduction Endoluminal Device (FRED) (Microvention, Aliso Viejo, California). Intrasaccular flow diversion was achieved with the WEB device. Patients were selected for endovascular therapy based on their age, medical comorbidities, and aneurysm size, location, and morphology. Demographic information and radiographic data were collected. Aneurysm volume was calculated by an auto-segmentation software.

All patients were started on dual antiplatelet therapy prior to treatment. On the day of the surgery, patients were confirmed to be therapeutic on their antiplatelet agents by an aspirin response assay and a platelet P2Y12 reactivity assay. Patients were placed under general anesthesia for the duration of the procedure. At the time of groin puncture, patients were fully heparinzed with a goal activated clotting time of 2x baseline. The WEB device and endoluminal flow diverter were placed in succession through a triaxial system. Following the procedure, all patients underwent magnetic resonance imaging (MRI) and quantitative phase-contrast magnetic resonance angiography (MRA) to confirm patency of the flow diverter and assess for thromboembolic events or hemorrhage. Post procedure, patients underwent an MRI/MRA at three months, followed by an angiogram at six to nine months and at the one year mark.

Results

In total, eight aneurysms in seven patients were treated by the combined endoluminal and intrasaccular flow diversion. Six of the aneurysms were found during the work up of a headache or otherwise incidentally. One aneurysm presented with a thromboembolic event, with an acute thrombus found in the aneurysm at the time of presentation. Another was found in a patient with previous subarachnoid hemorrhage (SAH). The patient with SAH was treated initially with the WEB device at the time of rupture. One month later, follow-up cerebral angiography revealed that the aneurysm recanalized. Five of eight aneurysms originated from the posterior communicating artery or adjacent supraclinoid segment. The other three arose from the vertebrobasilar junction, superior hypophyseal artery, and ophthalmic artery. The average aneurysm volume was 0.447 mL. In total, seven out of eight aneurysms had large branches arising from the neck.

The most common intermediate catheter was the Sofia EX, which was used in six of the eight cases. Benchmark was used in the other two cases and guide catheter choice was variable (Table 1). When a PED was used, the Via 27 microcatheter was selected for its navigability; however, in the case of FRED, the Headway 27 was utilized. The benefit of the Via microcatheter is that it may be used to deploy both the PED and WEB devices. Seven aneurysms were treated with PED and one was treated with FRED. The majority of patients had a single endoluminal flow diverter deployed (Table 1). Six out of the eight cases required steam shaping of the Via delivery microcatheter to facilitate WEB deployment. WEB sizes can be found in Table 1; size was based on aneurysm volume, and maximum aneurysm diameter and length. Transverse size of the aneurysm is important, because the WEB device requires lateral compression to prevent device compaction. ¹⁴ It was found that sizing the device was based partially on aneurysm width, but ultimately on aneurysm volume, which achieved optimal device selection in the majority of cases. It may be appropriate to slightly oversize the WEB device in cases that the intent is to endoluminally remodel the aneurysm, as the radial force of the stent can be used to prevent herniation of the WEB.

Table 1.

Technical data.

Aneurysm location	Type of flow diverter	Number of flow diverters	web size	Intermediate catheter	Web catheter	Stent catheter	Guide Cath	Balloon
PCOMM	Pipeline	2	11x8	Benchmark	Via 33	Marksman	4F Fubuki	None
PCOMM	Pipeline	1	11x8	Sofia EX	Via 33	Via 27	6 F Neuronmax	None
PCOMM	Pipeline	1	8x4	Sofia EX	Via 21	Via 27	6 F ArrowFlex	None
PCOMM	Pipeline	1	7x4	Sofia EX	Via 21	Via 27	5 F Fubuki	None
PCOMM	Pipeline	1	6x8	Sofia EX	Via 21	Via 27	5 F Fubuki	None
Superior Hypophyseal	Pipeline	2	10x7	Sofia EX	Via 21	Via 27	5 F Fubuki	Scepter XC
Vertebrobasilar	Pipeline	1	7x3	Sofia EX	Via 27	Via 27	6 F Neuronmax	None
Ophthalmic	FRED	1	6x4	Benchmark	Via 27	Via 27	4 F Fubuki	NONE

Post treatment, significant contrast stagnation was immediately visible in all aneurysms after the placement of the WEB device and endoluminal flow diverter. Only one case’s initial size choice was found to be too large, requiring re-sizing of the WEB device. Another case required balloon angioplasty of the PED due to incomplete stent opening. No patients experienced periprocedural complications. Post-procedural MRA verified good flow distal to the stent in all cases. Post-embolization MRI was negative in six out of eight cases. The remaining two patients had small scattered diffusion weighted imaging (DWI) changes that were clinically silent. Follow up can be seen in Table 2 In total, six patients had at least one month of follow up and of those, two patients achieved complete aneurysm occlusion. The remaining four patients had a small-neck remnant. Of the three patients with longer follow up (eight to 10 months), two had complete aneurysm occlusion and one had a small-neck remnant.

Table 2.

Patient demographics and aneurysm morphology.

Age	Presentation	Aneurysm Location	Aneurysm height	aneurysm neck	aneurysm width	Aneurysm Volume	Neck vessel	Follow up	Angiographic outcome
64	Previous Rupture	PCOMM	11	7.5	10	916	Yes	1 month	near complete occlusion
63	Incidental	PCOMM	12	7.9	9	762	Yes	10 months	No residual, patent PCOMM
63	Incidental	PCOMM	9	7.8	8	NA	Yes	9 months	Small neck remnanet, patent PCOMM
72	Incidental	PCOMM	5.9	4.5	4.5	162	Yes	8 months	No residual, patent PCOMM
60	Thromboembolic event	PCOMM	12.6		8.4	473	Yes	Immediate	Significant stagnation
55	Incidental	Superior Hypophyseal	13.8	7.6	10	560	No	2 months	Neck remnant
77	Incidental	Vertebrobasilar	9	5.6	5.8	133	Yes	Immediate	Near complete occlusion
54	Incidental	Ophthalmic	9.6	5.4	5	124	Yes	1 month	Neck remnant, patent ophth

Case 1

A 60-year-old female was found to have bilateral intracranial aneurysms on non-contrast head computed tomography performed post-head trauma. Subsequent MRI/MRA revealed bilateral posterior communicating artery (PCOM) aneurysms. Digital subtraction angiography showed a 9 × 5 mm right PCOM aneurysm and 12 × 9 mm left PCOM artery aneurysm (Figures 1(a) and 2(a)). The patient underwent subsequent staged WEB device and PED embolization of the bilateral aneurysms described below. Both treatment sessions required steam shaping of the Via catheter for optimal WEB placement (Figure 1(b)).

Figure 1.

(a) Lateral diagnostic cerebral angiography with injection of the left internal carotid artery demonstrating a large PCOM aneurysm with fetal PCA, which is better seen in the magnified view in B. (b and c) Placement of the WEB device orthogonal to the aneurysm dome with a large curve on the Via catheter achieved by steam shaping. (d) Post-PED and WEB device placement showing near complete immediate occlusion with patent fetal PCA. (e) Three-dimensional post-embolization Dyna CTA demonstrating WEB apposition to the PED. (f) Long term follow up at 10 months with complete aneurysm occlusion and patent fetal PCA.

Figure 2.

(a) Lateral diagnostic angiography demonstrating a large PCOM aneurysm with fetal origin PCA with (b) demonstrating a magnified view post-WEB device placement. (c) Three-dimensional Dyna CTA showing the WEB device apposition to the PED and patient PED. (d) Nine month follow up showing small aneurysm residual with patient fetal PCA.

The left-sided aneurysm was treated first. A 11 × 8 WEB SL was deployed within the aneurysm and detached, followed by a single PED across the aneurysm neck. The Via microcatheter tip was steam shaped to achieve an orthogonal orientation within the aneurysm (Figure 1(c)) and the WEB device was deployed to prevent occlusion of the large PCOM. Repeat partial re-sheathing was preformed until the WEB device was situated in a position that was not obstructing the origin of the adjacent PCOM. Post-stenting angiography demonstrated significant contrast stagnation within the aneurysm and a patent PCOM with a well-opposed stent construct (Figure 1(d) and (e)). The right side was treated one month later in a similar fashion (Figure 2(b) and (c)). Follow-up angiography at nine and 10 months showed complete occlusion of the right-sided aneurysm with a small neck remnant on the left. Notably, endoluminal remodeling with the PED did not alter the robust filling of the PCOM bilaterally (Figures 1(f) and 2(d)).

Case 2

A 76-year-old male underwent diagnostic angiography for a right carotid occlusion and was found to have dysplasia of the vertebrobasilar junction. This dysplasia was found to enlarge into an aneurysm on follow-up imaging. The patient subsequently underwent treatment of this lesion. At the time of treatment, the aneurysm measured 9 × 5 mm and was closely associated with the right AICA-PICA complex (Figure 3(a) and (b)). The initial 7 × 4 WEB device was oversized and subsequently downsized (Figure 3(c)). A 7 × 3 WEB device was placed into the sac of the aneurysm, with a small portion protruding into the parent vessel (Figure 3(d)). A PED was subsequently placed over the aneurysm to ensure that the parent vessel was not compromised and to maintain a patent AICA-PICA complex on the right (Figure 3(e) to (g)). Of note, the PED did demonstrate incomplete apposition proximally without flow compromise or thrombus formation. The patient tolerated the procedure well without complications.

Figure 3.

(a and b) Three-dimensional and conventional angiography demonstrating a large basilar aneurysm closely associated with a large AICA-PICA branch. (c) The initial placement of an oversized WEB device with subsequent (d) placement of the appropriately-sized WEB device with minimal WEB protrusion into the parent basilar. (e) Post-WEB device placement angiography showing mild WEB protrusion into the parent basilar with (g) Post-PED placement showing no WEB protrusion with the PED adequately compressing the WEB device. (f) Three-dimensional Dyna CTA displaying good WEB and PED apposition with patent AICA PICA complex. No coverage of the AICA PICA neck with the WEB device.

Discussion

The WEB device has been recently approved for the treatment of wide-neck internal carotid artery, middle cerebral artery, basilar bifurcation, and anterior communicating artery bifurcation aneurysms. ⁷ It provides intrasaccular flow diversion with a high degree of metal coverage at the neck and the dome of the aneurysm, with the goal of neoendothelialization over the neck and durable occlusion of the aneurysm. The safety of the device alone has been previously described and is comparable to standard coil embolization, with most complications being thromboembolic in nature.^{8,10,11,15,16} Previous studies have demonstrated occlusion in approximately 85% of patients at one-year follow up, which is durable for up to at least three years.^9,11 However, the majority of published series to date have focused on its use at bifurcations, with few papers discussing its use in non-bifurcation aneurysms.^12,13

In contrast to the WEB device, endoluminal flow diverters provide an endoluminal scaffold for neoendothelialization over the entirety of the aneurysm neck. They have become a valuable endovascular treatment choice for wide-neck cavernous and supraclinoidal internal carotid artery aneurysms. However, their failure rates have been reported to be from 12– 20%, depending upon the size of the aneurysm and the presence of branch vessels at the aneurysm neck.^17,18 Furthermore, larger aneurysms are more likely to be associated with delayed complications, such as intracranial hemorrhage or aneurysm rupture. ⁵ This is thought to be, in part, due to mural destabilization. Adjuvant coil embolization has, therefore, been adopted in many centers for the treatment of larger aneurysms in conjunction with the placement of a flow diverting stent. ⁶

Here, we present our experience with the combined use of intrasaccular and endoluminal flow diversion on a series of challenging aneurysms. In total, seven patients with eight aneurysms were treated. All except one of the aneurysms were located on the supraclinoid internal carotid artery, with the other aneurysm located at the vertebrobasilar junction. There were no complications associated with treatment. Immediate post-embolization angiography demonstrated immediate contrast stagnation in all aneurysms.

To date, only three prior studies have mentioned the use of WEB device with a flow diverting stent and our study is the second series dedicated to the technical nuances.^12,13,19 We believe that endosaccular flow diversion may be a viable alternative to adjuvant coil embolization for large and wide necked aneurysms with significant branching vessels. Large branches arising from an aneurysm’s neck are known to potentially prevent complete aneurysm occlusion if flow diversion alone is utilized. ¹⁷ In this series, seven out of the eight aneurysms had major branch vessels associated with the aneurysm, which increased the importance of accurate deployment to avoid branch vessel occlusion. In our experience, compared to adjuvant coil embolization, endosaccular flow diversion can provide superior control when trying to maintain patency of a branching vessel. For the large aneurysms included in this series, multiple coils would be required for sufficient embolization as opposed to one WEB device. For this reason, the price is comparable between the two treatment strategies when treating large aneurysms. The use of the WEB device, as opposed to coils as an adjuvant to endoluminal flow diversion, provides the added benefit of decreased artifact and beam hardening compared to a coil mass, allowing for clearer post-embolization imaging, including during follow up. ²⁰

Technically, the deployment of the WEB device in non-bifurcation aneurysms is difficult. Because of its design, the WEB device should be deployed parallel to the axis of the aneurysm to achieve the greatest neck coverage. ¹⁴ The steep angulation at which non-bifurcation aneurysms arise from the parent vessel often increases the difficulty of achieving a stable orientation of the delivery microcatheter that is parallel to the aneurysm axis. Therefore, in all cases except one, the Via microcatheter required steam shaping to appropriately deploy the WEB device into the aneurysm. The WEB device often had to be deployed and recaptured multiple times within the aneurysm in order to ensure optimal placement. Furthermore, aneurysm volume should be considered in combination with the width to determine optimal WEB device sizing. Doing this will permit compression of the lateral wall of the WEB device, which will prevent long-term device compaction, although this may be mitigated by the concurrent deployment of an endoluminal flow diverter. This series is limited by its retrospective design, the variable follow-up times, the small number of patients, and the need for longer-term follow up.

In conclusion, our results demonstrate that aneurysm repair using combined intrasaccular and endoluminal flow diversion may result in early aneurysm occlusion, achieving similar vessel remodeling to surgical clip reconstruction. Nonetheless, combined intrasaccular and endoluminal flow diversion is technically feasible and appears safe based on this study.