Article Text

Original research
The Barrel stent: new treatment option for stent-assisted coiling of wide-necked bifurcation aneurysms—results of a single-center study
  1. Ruben Mühl-Benninghaus,
  2. Andreas Simgen,
  3. Wolfgang Reith,
  4. Umut Yilmaz
  1. Department of Neuroradiology, Saarland University Hospital, Homburg/Saar, Germany
  1. Correspondence to Dr Ruben Mühl-Benninghaus, Department of Neuroradiology, Saarland University Hospital, Kirrberger Straße, Homburg 66421, Germany; ruben.mbe{at}gmail.com

Abstract

Purpose The Barrel stent is a laser cut stent designed for stent-assisted coil embolization of wide-necked bifurcation or branch aneurysms with a single device, with the purpose of lowering the metal-to-artery ratio and its inherent risk of thromboembolic complications of multiple stents. We report our early experiences with this device in 17 patients in this retrospective single-center analysis.

Materials and methods 17 consecutive patients who underwent stent-assisted coil embolization of wide-necked bifurcation aneurysms with the Barrel stent were retrospectively identified. We analyzed the feasibility of successful deployment and post-treatment angiographic results. Adverse events, clinical outcome, and angiographic follow-up results were also analyzed.

Results Aneurysms were located in the internal carotid artery (n=3), the middle cerebral artery (n=9), the anterior communicating artery (n=3), and the basilar artery (n=2). In the immediate post-treatment angiography, adequate occlusion (neck remnant or total occlusion) was observed in 16/17 (94.1%) of aneurysms. One patient experienced a transient ischemic attack. No permanent neurologic deficits were observed. 13/17 (76.5%) patients underwent short-term follow-up angiography after 3 months, all of which showed adequate occlusion of the aneurysm.

Conclusions In this small retrospective single-center analysis we show that stent-assisted coiling with the Barrel stent is a safe and effective option for the endovascular treatment of intracranial wide-necked bifurcation aneurysms.

  • Aneurysm
  • Angioplasty
  • Coil
  • Device
  • Stent

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Introduction

In recent years technical developments have substantially increased the options for the endovascular treatment of intracranial aneurysms, providing more alternatives to surgical clipping even in complex cases.1–3 However, standard coiling is not applicable to the treatment of aneurysms with unfavorable anatomy (wide-necked, bifurcation or fusiform aneurysm). Several endovascular techniques other than standard coiling—for example, stent-assisted coiling, balloon-assisted coiling, flow diversion, and flow disruption—have therefore been developed.4 ,5

The long-term results of standard coiling studies show a relatively higher percentage of incomplete occlusion and recanalization in large and wide-necked aneurysms.6 Wide-necked bifurcation aneurysms represent a particularly difficult subset to treat endovascularly. To achieve long-term occlusion of aneurysms, very complex and challenging techniques such as double balloon remodeling or stent-assisted coil embolization with double-stent deployment are often needed.5 ,7–9

The Barrel stent (Barrel Vascular Remodeling Device (VRD) system; Medtronic, Minneapolis, Minnesota, USA) obtained CE marking for the European Union in December 2013. The device is a self-expandable laser-cut stent developed with a bulged center section.

It is designed to treat wide-necked bifurcation or branch aneurysms without the use of a second stent and, as a consequence, to lower the metal-to-artery ratio and its inherent risk of thromboembolic complications of multiple stents.10 In this study we report on our initial single-center experiences of aneurysms treated with the Barrel stent.

Materials and methods

Seventeen consecutive patients (12 women) of mean age 58.4±12.2 years with wide-necked bifurcation aneurysms (mean dome-to-neck ratio <1.3) treated with the Barrel stent in our department between April 2015 and January 2016 were retrospectively identified. The Barrel stent was used when sufficient coverage of a wide-necked bifurcation aneurysm could not be expected by classical stent-assisted coiling.

Treatment of aneurysms with the Barrel stent was performed analogous to stent-assisted coiling. The Barrel stent is a laser-cut closed-cell microstent that has a unique design with a bulged center section for better coverage of the aneurysm neck to support coiling (figure 1). It has one spiral strut construction proximal and one distal of the center section for the purpose of preventing kinking. The device has 12 platinum markers: one longer marker at the proximal tip, one proximal and distal center marker, six markers at the center section, and three distal tip markers. The Barrel stent is mounted on a 180 cm nitinol pusher wire (0.016 inch) and delivered through a 0.021 inch microcatheter, and is up to three times resheathable over its full length due to its electrolytic detachment system, according to the specifications of the manufacturer. The devices are labeled for deployment in arteries with diameters between 2 and 4 mm and have useable lengths from 20 mm to 22 mm, depending on the size of the bulged center section diameter and length. The diameters currently available are from 5 mm to 7.5 mm with center section length from 5 mm to 8 mm.

Figure 1

Silicon model of a wide-necked bifurcation aneurysm treated with the Barrel vascular remodeling device (VRD) device. The bulged center section of the stent provides complete neck coverage. (Figure provided with permission from Medtronic, Minneapolis, Minnesota, USA).

For planning the placement of the stent, the efferent vessel was chosen so that as much of the aneurysm neck as possible could be covered by the central part of the stent. To determine the appropriate size of the device, bifurcation spans were measured according to the manufacturer's instructions. Therefore, measurement of a diagonal line from the distal shoulder of the aneurysm neck to the opposite wall of the parent vessel was made (figure 2).

Figure 2

Schematic illustration of stent-assisted treatment of wide-necked bifurcation aneurysms. (A) Use of standard stent device. A large part of the aneurysm neck is not covered. (B) Principle of the Barrel stent device with its bulged center section covering a greater part of the aneurysm neck. (C) Bifurcation span length (S) for determination of the appropriate size of the device.

Every procedure was performed under general anesthesia via the femoral approach. Double antiplatelet therapy was given before and heparin during the procedure as in standard stent-assisted coiling treatment. Platelet function testing was not performed. After the procedure, dual antiplatelet therapy (clopidogrel 75 mg/day and aspirin 100 mg/day) was administered for 3 months and aspirin 100 mg/day thereafter.

The endovascular procedures were performed by using a biplane angiographic system (Artis Q Biplane, Siemens, Erlangen, Germany). A 5–6 F guide catheter was positioned into the carotid or vertebral artery. A microcatheter (Rebar18; Medtronic) for stent delivery was positioned at least 10 mm past the aneurysm neck. The distal center section markers were positioned just past the distal shoulder of the aneurysm. The stent was unsheathed until the detachment zone was outside the microcatheter by slowly withdrawing the microcatheter while the pusher was held in place. If the six center section marker bands did not open, the stent was slowly pushed or pulled for adequate expansion and neck coverage. A control angiogram was obtained to check the correct position of the device. The device was in the correct position when the bulged center section marker bands extended into the aneurysm neck (figure 3). After electrolytic detachment of the Barrel stent, a coiling microcatheter was guided through the stent interstices and positioned inside the aneurysm sac. Jailing was not performed.

Figure 3

Unruptured aneurysm of the middle cerebral artery (MCA) (case example not included in this study). Oblique views of peri-procedural angiography. (A) Complete expansion of the Barrel stent center section marker extending into the aneurysm and showing complete neck coverage. The distal stent markers are located in the inferior M2 segment of the MCA. (B) Final result after coil implantation showing complete occlusion (Raymond–Roy occlusion classification 1, RROC1).

Angiographic results were categorized according to the revised Raymond–Roy Occlusion Classification (RROC) into one of the following groups: complete occlusion (RROC1), remnant neck (RROC2), or residual aneurysm (RROC3) by two raters in consensus.

At our institution, follow-up after stent-assisted coiling is routinely performed 3–4 months after the procedure by digital subtraction angiography (DSA).

Results

All 17 treated aneurysms were unruptured. Patient demographics and aneurysm features including location, size, neck dimension, and procedural details are shown in table 1.

Table 1

Patient and aneurysm characteristics

No aneurysm was thrombosed. The neck size was <4 mm in eight aneurysms (47%) and ≥4 mm in nine aneurysms (53.0%). The dome-to-neck ratio was <2.0 in all aneurysms with a mean value of <1.3.

Deployment of the stent and herniation of its center section was achieved in all cases. No kinking of the stent occurred. Treatment was successfully performed in 16 of 17 (94.1%) aneurysms. The cause of failure of the one case (5.9%) was the lack of access to the aneurysm with the microcather resulting in a residual aneurysm (RROC3). In this case, coiling was performed 3 months later resulting in total occlusion of the aneurysm. Complete occlusion (RROC1) was achieved in 11/17 cases (64.7%) (figure 4) and a residual neck (RROC2) remained in 5/17 cases (29.4%) (figure 5). No cases of stent migration or stent thrombosis occurred. No treatment-related mortality was observed. Treatment morbidity was encountered in one patient (5.8%) who developed a transient mild hemiparesis of the right arm after the procedure which resolved within 24 hours. Diffusion-weighted MRI showed no diffusion restriction after 1 hour and 24 hours after symptom onset. To date, 3–4 month short-term follow-up angiography is available in 13/17 patients (76.5%). One patient with incomplete occlusion (RROC2) showed complete occlusion at short-term follow-up resulting in a complete occlusion rate (RROC1) of 84.6% (11/13). A residual neck (RROC2) remained in 2/13 cases (15.3%).

Figure 4

Unruptured aneurysm of the basilar bifurcation (patient 14). (A) Anterior and (B) lateral views of pre-interventional angiography show the shape of a saccular wide-necked aneurysm harbored between the posterior cerebral arteries. (C) Anterior and (D) lateral views of post-procedural angiography show complete occlusion (Raymond–Roy occlusion classification 1, RROC1) of the aneurysm after coil implantation.

Figure 5

Unruptured aneurysm of the middle cerebral artery (patient 13). (A) Oblique view of pre-procedural angiography shows a lobulated saccular bifurcation aneurysm with a wide neck. (B) Oblique view of post-procedural angiography shows incomplete occlusion (Raymond–Roy occlusion classification 2, RROC 2) of the aneurysm after coil implantation.

Discussion

Stent-assisted coiling provides higher rates of complete occlusion and low rates of recurrence in long-term follow-up studies compared with conventional coiling.11–13 However, treatment of wide-necked bifurcation and fusiform aneurysms still remains challenging14–17

This retrospective analysis was made to evaluate the safety and efficacy of the Barrel stent. The advantage of widening or barreling of microstents for shortening the neck in the treatment of wide-necked bifurcation aneurysms has been reported for braided self-expandable stents.18–20 The Barrel stent is a laser-cut self-expandable stent designed with a pre-existing enlarged barrel-like center section. This structural feature of the device can help to reduce potential stent migration during the procedure.

The Barrel stent is used when sufficient coverage of a wide-necked bifurcation aneurysm could not be expected by classical stent-assisted coiling (figure 1). Its advantages over X- and Y-stenting techniques are a lower metal-to-artery ratio and simpler handling requiring a single microcatheter and allowing repositioning due to its complete resheathability.

On post-procedural DSA, adequate occlusion (neck remnant or total occlusion) was observed in 94.1%. These findings are similar to the initial French Barrel Registry trial study by Piotin et al 21 and to other clinical trial studies.7 ,9 The complication rate of 5.8% in this study was acceptably low and did not lead to a permanent neurologic deficit in any case. X- and Y-stenting techniques have been described for the treatment of such aneurysms.7 ,9 ,22 Studies using the X- or Y-stenting technique have reported complication rates of up to 10%.9 ,23 In addition, Möhlenbruch et al 23 observed partial stent thrombosis in 14% of the procedures in their study of 22 patients. No case of stent thrombosis occurred in our analysis. This might be explained by the fact that the X- or Y-stenting techniques require the use of at least two stents and therefore more thrombogenic material.

Other new devices have been designed for the same purpose of using one single device in wide-necked bifurcation aneurysms, including pCONus (phenox, Bochum, Germany) and Pulse rider (Pulsar Vascular, San Jose, California, USA). The pCONus is an intra-aneurysmal device and the Pulse rider is an extra-aneurysmal device. Gao et al 24 reported greater remodeling of the bifurcation angle and a decrease in the effective aneurysm neck in the treatment of bifurcation aneurysms with stent-assisted coiling. This effect is not expected from either device. Perez et al 25 described the intended use of the pCONus as being similar to the ‘waffle cone technique’. It has been suggested that the waffle cone technique might influence unfavorable blood flow patterns by directing the blood stream toward the aneurysm instead of diverting it away.26 However, in a study of the hemodynamics of intra-aneurysmal devices it has been shown that pCONus causes no adverse increase in aneurysmal blood flow.27

The use of the jailing technique of the coiling catheter is not recommended with the Barrel stent. Jailing the coiling catheter will reduce the bifurcation span and thus limit herniation and expansion of the barrel section of the device. This may represent a limitation of the technique. However, if jailing is requested, the manufacturer recommends the selection of a smaller device model.

A potential advantage is the fact that the device is mounted on a nitinol pusher wire and its detachment system is electrolytic, so the Barrel stent is full-length resheathable.

According to the manufacturer's instructions, the spiral strut construction at the proximal and distal center section was designed to prevent kinking of the device. In our series we did not observe any kinking of the stent, but we were not able to prove this fact.

With multiple stent markers the Barrel stent is in its total length well trackable. For those using the device for the first time, a total number of 12 stent markers can be confusing and affect the overview.

Our study has some limitations including the lack of systematic follow-ups due to its retrospective design. Another limitation is the small number of patients, but it was important to have a preliminary evaluation of this new endovascular approach that was performed analogous to the widely used stent-assisted coiling technique. Third, completion of short-term, mid-term, and long-term follow-up is needed to evaluate the efficacy of this treatment in terms of aneurysm recanalization and recurrence rate relative to double stent-assisted coiling or use of other new devices such as intrasaccular flow-disrupting devices.

Conclusion

In this retrospective analysis we report that stent-assisted coiling with the Barrel stent is a feasible, safe, and efficient method for embolization of intracranial wide-necked bifurcation aneurysms. Its unique bulged center section offers the possibility for better neck coverage than a conventional intracranial stent in the treatment of such aneuryms, and thereby it can be an alternative to complex techniques like double stenting or balloon-assisted remodeling. Further studies should be conducted to evaluate the mid-term and long-term efficacy and clinical utility of this new device.

References

Supplementary materials

  • Abstract in Deutsch

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Footnotes

  • Contributors RM-B: Substantial contributions to the conception, design, analysis and interpretation of data for the work; drafting the work and revising it critically for important intellectual content of the work. RM-B, AS, WR and UY: final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AS: substantial contributions to the design of the work and acquisition of data for the work. AS, WR and UY: revising the work critically for important intellectual content. WR: substantial contributions to the acquisition and interpretation of data for the work. UY: substantial contributions to the design of the work and acquisition and analysis of data for the work.

  • Competing interests None declared.

  • Ethics approval Ethics approval was obtained from Ethik-Kommission der Ärztekammer des Saarlandes.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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