Microsnare retrieval as a bail-out technique of Detached Woven EndoBridge device: Illustrative series

Abstract

Background

The Woven EndoBridge (WEB) device (MicroVention, Tustin, CA, USA) has an excellent safety profile. While major complications such as device malposition and migration are rare, they can have serious consequences if not addressed promptly. Our case series describes the safety and efficacy of Amplatz goose neck microsnare device (Medtronic in Irvine, CA, USA) in endovascular retrieval of a detached WEB device.

Methods

We retrospectively reviewed six consecutive patients who underwent endovascular WEB retrieval using Amplatz microsnare device between March 2012 and December 2022.

Results

All six WEB devices were successfully retrieved either directly from the aneurysm sac due to device malpositioning or from a distal branch following device migration. None of the patients experienced intra-operative aneurysm perforation, arterial dissection, or vasospasm attributable to the process of WEB extraction. Five out of six patients (83.3%) had a good functional outcome (mRS 0-1) upon discharge from the hospital and at 24 months.

Conclusion

Our experience suggests that detached WEB devices can be safely retrieved using an Amplatz microsnare. Apart from addressing device migration, direct removal of an undersized or malpositioned WEB from the aneurysm sac appears to be a safe option that can be considered when all other rescue techniques have been exhausted.

Introduction

The Woven EndoBridge (WEB) device is the first intrasaccular flow disrupting device specifically designed for endovascular treatment of wide-necked intracranial aneurysms. ¹ A recently published meta-analysis supports the long-term efficacy of the WEB system. ² While major complications such as malposition and migration of the WEB device are rare, it is crucial to establish effective rescue strategies to prevent potentially catastrophic outcomes. Although there have been a few documented cases of endovascular retrieval to address WEB distal migration,^3,4 no reports exist regarding extraction of a detached WEB device directly from the aneurysm sac. In this case series, we aim to present our own firsthand experience using the Amplatz goose neck microsnare as the last option to manage challenging post-WEB deployment complications.

Subjects and methods

We performed a retrospective analysis of patients with intracranial aneurysms treated with WEB embolization at our institution between March 2012 and December 2022. Ethics committee approval was not required for this study. All symptomatic complications related to the procedure (i.e. thromboembolic or hemorrhagic complications) were documented in patient electronic system. Pre-operative baseline imaging including unenhanced computed tomography (CT), magnetic resonance imaging (MRI) of the brain and CT intracranial angiography were recorded on picture archiving and communication system (PACS). Intra-operative aneurysm geomorphological features including aneurysm height, width, neck size, and presence of daughter sac were evaluated. WEB sizing was performed manually based on measurements derived from the three-dimensional (3D) reconstruction of the rotatory angiogram.

Technical details

The Amplatz goose neck microsnare is designed for manipulation and retrieval of intravascular foreign bodies. The device possesses a 90° angled gold-plated tungsten loop construction which provides good fluoroscopic visualization. The loop diameter ranges from 2 to 7 mm and can be deployed either with the supplied catheter or a standard 0.017–0.027” microcatheter. In our series, microsnares with 2 and 4 mm loop diameter were used for WEB extraction, depending on the device orientation in relation to the parent vessel.

When the long axis of the detached WEB remains aligned to the parent vessel, a 2mm microsnare is used to capture the proximal detachment marker by placing the snare loop around a small depression area located between the platinum marker and the body of the device. If the proximal marker is difficult to access due to device malrotation or misalignment, a 4mm microsnare is deployed directly around the body of the WEB instead. The delivery catheter is then advanced forward to close the snare loop. Once secured, a torque device is locked over the proximal shaft of the delivery wire, followed by gradual withdrawal of the entire system under fluoroscopic screening.

Results

Out of 319 WEB embolization cases performed over a 10-year period, 6 patients (1.9%) were identified who underwent WEB retrieval using the Amplatz microsnare. The average patient age was 45 ± 8.1 years (mean ± SD) with 1:1 male to female ratio. Among the six patients, five were admitted with acute subarachnoid haemorrhage (SAH). The target aneurysms were situated at the anterior communicating artery (ACOM) artery in two patients, the posterior communicating artery (PCOM) segment of the internal cerebral artery (ICA) in two patients, middle cerebral artery (MCA) bifurcation in one patient, and P1/P2 junction of the left posterior cerebral artery (PCA) in one patient. Details regarding the size and model of the WEB devices used can be found in Table 1. The devices were successfully retrieved in all six cases.

Table 1.

Baseline, treatment characteristics, and outcomes of patients who underwent WEB retrieval.

	Case 1	Case 2	Case 3	Case 4	Case 5	Case 6
Gender	Male	Male	Male	Female	Male	Female
Age group (years)	30–39	50–59	40–49	30–39	40–49	50–59
Rupture status	Grade 1 SAH	Grade 4 SAH	Grade 4 SAH	Grade 5 SAH	Unruptured	Grade 2 SAH
Aneurysm location	ACOM artery	PCOM segment of the left ICA	ACOM artery	P1/P2 junction of the left PCA	PCOM segment of the left ICA	Right MCA bifurcation
Vascular access	TFA	TFA	TRA	TFA	TFA	TRA
WEB size and model	4.5 × 2 mm SL 17	3 × 2 mm SL 17	5 × 3 mm SL 17	5 × 2 mm SL 17	9 mm SLS	4 × 3 mm SL 17
Indication for WEB retrieval	Device migration into the ipsilateral pericallosal artery	Device migration into the left MCA bifurcation	Malrotation of undersized device upon detachment	Deformed WEB caused by unanticipated catheter tip movement	Spontaneous device detachment with partial occlusion of the parent vessel	Side branch occlusion due to device protrusion
Loop diameter	4 mm	4 mm	2 mm	2 mm	4 mm	2 mm
Snare target	Body of the WEB device	Body of the WEB device	Proximal marker	Proximal marker	Proximal marker	Proximal marker
Microcatheter for microsnare delivery*	Headway 27	Prowler select plus	Headway 21	Headway 21	Prowler select plus	Headway 21
Retreatment of aneurysm	Coil embolization	Coil embolization	Replaced with a 6 × 3 mm WEB SL	Replaced with a 4 × 2 mm WEB SL	Replaced with an 8 mm WEB SLS	Coil embolization
Functional outcome (mRS)	1	1	0	0	0	4
24-month MRA follow up	1 mm neck remnant	Satisfactory occlusion	Satisfactory occlusion	Satisfactory occlusion	Satisfactory occlusion	Satisfactory occlusion

Microcatheters*—Headway 21, 27 (MicroVention, Tustin, California, USA), Prowler select plus (Codman Neurovascular, Raynham, MA, USA).

mRS: Modified Rankin Scale; SL: single lumen; TFA: transfemoral approach; TRA: transradial approach; WEB SL: Woven EndoBridge Single Layer; WEB SLS: Woven EndoBridge Single Layer Sphere.

The patients in this series were divided into two groups—Group 1 encountered distal WEB migration (cases 1 and 2), requiring extraction from a distal vessel to restore blood flow. Group 2 experienced WEB malpositioning, necessitating direct extraction from the aneurysm sac proper.

Group 1: Distal WEB migration

Shallow, broad-necked aneurysms are prone to WEB migration, a phenomenon that can impact both undersized and oversized WEB implants.

Case 1: WEB migration to pericallosal artery

Patient presented with acute SAH secondary to a shallow ruptured ACOM aneurysm. A 4.5 × 2 mm WEB Single Layer (WEB SL) was successfully deployed with evidence of contrast stasis inside the aneurysm sac. After 15 h, the patient developed new right lower limb weakness. CT angiogram confirmed distal migration of the device into the left pericallosal artery. The WEB device was retrieved with a 4mm microsnare. The ACOM aneurysm was secured with coils (Figure 1).

Figure 1.

Three-dimensional angiography shows ACOM aneurysm measuring 3.5 mm (width) × 3.1 mm (height) (A). A 4.5 × 2 WEB SL was deployed in the aneurysm dome with satisfactory contrast stagnation distally (B). Postprocedural CTA and DSA (C and D, respectively) demonstrated distal migration of WEB (dotted circle) into the pericallosal artery. Note ACOM aneurysm rendered unprotected (arrowhead) (C). A 4mm microsnare which was placed directly over the body of the implant, retrieving the device (E). Final angiography demonstrated patency of pericallosal artery (F). CTA: computed tomography angiogram; DSA: digital subtraction angiography; WEB SL: Woven EndoBridge Single Layer.

Case 2: WEB migration to MCA

Patient presented with a small blister-like ruptured left PCOM aneurysm with heavy blood load. A 3 × 2 mm WEB SL was deployed with the objective of circumventing the need for a remodeling stent following the initial unsuccessful attempt at balloon-assisted coil embolization. Upon detachment, the oversized implant spontaneously migrated into the left MCA bifurcation. It has also rotated inside the vessel lumen, with its axis positioned perpendicular to the parent vessel's axis, preventing direct access to the proximal marker. A 4mm microsnare was placed over the body of the device and successfully retrieved. The aneurysm was secured with a single coil (Figure 2).

Figure 2.

Three-dimensional angiography (A) and lateral projection DSA (B) demonstrated a 2 mm (width) × 3.1 mm (height) conical-shaped left PCOM aneurysm. A 3 × 2 WEB SL was deployed in the aneurysm sac with contrast stagnation distally (C). Following WEB migration to left MCA, a 4mm microsnare was placed over the body of the device and retrieved (D and E). Left PCOM aneurysm was treated with coils (F). WEB SL: Woven EndoBridge Single Layer.

Group 2: WEB malpositioning necessitating device extraction from the aneurysm sac

Following detachment, the placements of the WEB implants in this cohort were deemed suboptimal, posing a risk of inadequate aneurysm protection or an elevated potential for thromboembolic events. Subsequently, these WEB devices were extracted directly from the aneurysms using a microsnare after all other rescue options have been exhausted.

Case 3: Lateral rotation of WEB following detachment

Patient presented with a ruptured ACOM aneurysm which was initially treated with a 5 × 3 mm WEB SL. The undersized device was unstable and rotated laterally on its short axis after detachment, exposing a large section of the aneurysm's lumen to the bloodstream. The device was extracted using 2mm microsnare and replaced with a larger WEB, achieving a more stable fit (Figure 3).

Figure 3.

Three-dimensional angiography and DSA (A and B, respectively) demonstrating ACOM aneurysm measuring 4.8 mm (width) × 3.1 mm (height) with smaller lateral bleb (asterisk in A). A 5 Å∼ 3 mm WEB SL was deployed (C). The undersized device rotated laterally as indicated by proximal marker (white arrowhead) upon delivery wire withdrawal (D). A 2mm microsnare was placed at the WEB's proximal marker (black arrowhead), successfully retrieving the device. Note the elongation of WEB device during retrieval (E). The aneurysm was subsequently retreated with a larger WEB device (F). WEB SL: Woven EndoBridge Single Layer.

Case 4: Compression of WEB following detachment

Patient presented with a ruptured aneurysm located at the left P1–P2 junction. A 5 × 2 mm WEB SL was satisfactorily positioned within the aneurysm sac. However, due to the accumulation of excessive loading pressure in the catheter system, an unexpected abrupt forward movement of the delivery catheter occurred upon detachment. This resulted in significant compression of the WEB along its central axis, which was retrieved using 2mm microsnare and subsequently replaced with appropriately sized WEB device (Figure 4).

Figure 4.

Three-dimensional (3D) angiography (A) and frontal and lateral projection DSA (B and C) demonstrated a left P1/P2 junction aneurysm measuring 3.3 (width) × 5.7 mm (height). A 5 × 2 mm WEB device was taken to the aneurysm (no images available before detachment). On detachment, an unanticipated forward movement of the delivery catheter caused by excessive built-up loading pressure on the microcatheter led to compression of the WEB along its central axis (D). A 2 mm microsnare was placed at the WEB's proximal marker and withdrawn. Note how the device elongated and became partially collapsed when traction was applied to the proximal detachment marker (E and F). This was then replaced by a smaller 4 × 2 mm WEB SLS (G). A 24-month follow-up 3D MRA demonstrated satisfactory aneurysm occlusion (H). WEB SLS: Woven EndoBridge Single Layer Sphere.

Case 5: Spontaneous detachment of WEB due to excessive handling

Patient had initially been scheduled for elective flow diversion of a left PCOM aneurysm. However, the treatment plan was changed to WEB embolization after an exophytic growth in the epiglottic vallecula was discovered during endotracheal intubation to avoid the need for long-term dual antiplatelet therapy. An effort was made to deploy a 9 mm WEB Single Layer Sphere (WEB SLS). However, the deployment proved challenging, leading to multiple resheathing attempts. In the end, the WEB detached spontaneously, leaving the proximal portion of the implant outside the aneurysm neck (Figure 5). It was successfully retrieved using a 4mm microsnare and replaced with a smaller-sized WEB.

Figure 5.

Three-dimensional angiography (A) and lateral projection DSA (B) demonstrated 9.1 (height) × 8 mm (width) left PCOM aneurysm. A 9 mm WEB SLS spontaneously detached, leaving the proximal portion of the implant outside the aneurysm neck (C). A 4mm microsnare was placed at the WEB's proximal marker (white arrowhead in D) and withdrawn. Note the elongation of the body of the device during retrieval (D and E). An 8 mm WEB SLS was deployed in the aneurysm (F). WEB SLS: Woven EndoBridge Single Layer Sphere.

Case 6: Partial protrusion leading to clot formation on the WEB device

During WEB embolization of a ruptured right MCA bifurcation aneurysm, the patient developed intra-operative aneurysm rupture secondary to microcatheter injury. Hemostasis was promptly achieved by deploying a 4 × 3 mm device. A delayed angiography revealed thrombus formation around the base of the WEB. Severe perianeurysmal vasospasm rendered bail-out stenting unfeasible. The WEB device was cautiously removed from the aneurysm sac with a 2mm microsnare. No contrast extravasation was seen following WEB retrieval (Figure 6). The aneurysm was then secured with coils.

Figure 6.

Three-dimensional angiography and frontal projection DSA (A and B, respectively) demonstrated 3.3 mm (width) × 4.3 mm (height) MCA bifurcation aneurysm. Aneurysm rupture (asterisk in C) occurred during microcatheter cannulation. The aneurysm was promptly secured with a 4 × 3 WEB SL device. Delayed angiography revealed thrombus formation at the adjacent M2 MCA bifurcation (D) with absence of MCA branches (demonstrated by white arrowheads in B). A 2mm microsnare was used to retrieve WEB (E). No bleeding events were encountered following WEB retrieval (F). WEB SL: Woven EndoBridge Single Layer.

Treatment outcome

Half of the procedures involved the use of 2mm microsnares, while the other half utilized 4mm devices for retrieval. Among the cases, three aneurysms were retreated using appropriately sized WEB devices, while the remaining three underwent coil embolization.

There were no recorded instances of vasospasm, aneurysm perforation, or arterial dissection which can be directly attributable to the process of WEB extraction. Postembolization cross-sectional imaging in four patients with acute SAH demonstrated ischemic changes within territories distinct from that of the embolized aneurysms. Five out of six patients were reported to have a good functional outcome (mRS 0-1) by the time they were discharged from the hospital and at 24 months. One patient who suffered intra-operative microcatheter aneurysm rupture underwent clot evacuation postembolization and was subsequently discharged to a rehabilitation facility with left hemiplegia (mRS 4).

Five patients (83.3%) had complete aneurysm occlusion while one patient (16.7%) had a 1 mm neck remnant on subsequence imaging follow ups. The latter was coiled at a later stage.

Discussion

Distal migration of WEB is a rare phenomenon. Shallow wide-necked aneurysms appear to pose the greatest risk of such events. Several technical issues can also contribute to WEB migration—repetitive resheathing of the device may result in spontaneous detachment, while failure to recognize incomplete detachment can lead to unintentional withdrawal of the detached device into the parent vessel. In the event of WEB migration, it is crucial to promptly remove the migrated device to prevent permanent ischemic damage. ⁵ König et al. reported the first case of successful WEB retrieval using the alligator retrieval device in 2018. ² Several other endovascular devices ranging from aspiration catheters to stent retrievers have also been evaluated in some case reports.^6,7

At our institution, we favor the Amplatz goose neck microsnare for its suitability in navigating small and tortuous vessels, which may present challenges for aspiration catheters or stent retrievers. Radu et al. reported successful retrieval of a distally migrated WEB device using the microsnare technique following unsuccessful attempts with two different stent-retrievers and a 5Fr distal access catheter. ⁸ After evaluating the effectiveness of Amplatz microsnare on a porcine model, Simgen et al. recommend placing the snare loop directly around the first half of the WEB body. ⁹ In our own experience, we found that capturing the proximal marker offers a more secure method for WEB retrieval. The use of a 2mm microsnare is well suited for this purpose as the smaller loop diameter allows for easier capture of the device. In addition, withdrawing the microsnare after securing the proximal marker often leads to elongation of the body of the device, thereby reducing the risk of vascular injury in the process (Figure 5).

The use of microsnare as a salvage technique has been documented for correcting WEB malposition or deformation.^10,11 As of now, there are no published accounts detailing retrieval of a detached WEB directly from the aneurysm sac as an endovascular approach to address potential severe adverse events.

Thorough scrutinization of the device position and paying attention to the details before detachment may prevent undersizing or oversizing of the WEB implant. This, in turn, helps avoid the need for rescue procedures such as WEB retrieval. ¹² Incorrect sizing of the WEB device is a significant factor leading to unfavorable long-term outcomes and poses challenges in aneurysms treatment with WEB device. This challenge is particularly pronounced when the operator is in the early phase of the learning curve, increasing the risk of detaching a WEB implant only to discover the device is improperly sized. The ability to safely retrieve the detached device provides flexibility in salvaging situations where undersized devices may not offer adequate protection against future rupture.

A partially dislocated device can be manipulated using the delivery microcatheter ³ or a balloon catheter. If unsuccessful, bail-out stenting can be employed to restore normal blood flow. While these rescue strategies prove effective, there are potential drawbacks that could make these approaches less favorable. The use of antiplatelet therapy increases the risk of hemorrhagic complications in patients with acute SAH who may require cerebrospinal fluid (CSF) diversion or clot evacuation later. Moreover, undersized or malpositioned devices may not offer adequate protection against rebleed in acute SAH. Extracting the WEB device directly from the aneurysm eliminates the necessity for antiplatelet therapy and offers the operator the chance to explore alternative treatment approaches.

Conclusion

With increasing utilization of the WEB device for treating wide-necked aneurysms, understanding rescue strategies for managing severe adverse events becomes paramount. Our experience highlights that a WEB device can be safely and effectively retrieved using an Amplatz goose neck microsnare. Apart from addressing device migration, direct removal of a malpositioned WEB from the aneurysm sac appears to be a safe and effective option that can be considered when all other salvage techniques have been exhausted.

Abbreviations

WEB SL

Woven EndoBridge Single Layer

WEB SLS

Woven EndoBridge Single Layer Sphere