Abstract
Background
Balloon and stent-assisted coiling of aneurysms have increased the number of aneurysms available for endovascular treatment. Newer devices that allow flow within the parent vessel but coverage at the neck have recently entered the market. The Cascade is a new non-occlusive fully retrievable neck-bridging support device that has been designed to provide temporary support during coil embolisation of intracranial aneurysms.
Methods
Using a silicone aneurysm model three different aneurysms were catheterised with the coiling microcatheter placed in three different positions within each aneurysm – at the neck, centrally, and looped within the aneurysm. Multiple different coils were then deployed within each aneurysm with the Cascade device deployed across the neck to provide protection. In total 480 attempted coilings were performed. Aneurysm flow was used to calculate the change in intra-aneurysmal flow with the Cascade device deployed across the neck of the aneurysm.
Results
We did not observe a single episode of coil protrusion through the Cascade mesh nor did we observe any coil protrusion into the parent vessel when the Cascade was deployed across the neck. There was an average flow velocity reduction of 23% with the Cascade device deployed across the neck of the aneurysm.
Conclusion
The Cascade device offers robust protection of the aneurysmal neck and parent vessel as well as inducing significant intra-aneurysmal flow velocity reduction.
Keywords: Cascade, aneurysm, aneurysm flow
Introduction
Since the publication of the pivotal International subarachnoid aneurysm trial study1 coil embolisation and endovascular approaches to intracranial aneurysms are widely considered the gold standard of treatment, at least from the perspective of morbidity and mortality, around the world. Despite the widespread technical advances with regards to microcatheters, coils and microwires certain challenges remain. In particular, aneurysms with wide necks, or unfavourable aspect ratios typically defined as >4 or <1.4 mm, respectively, remain a challenge. In the elective setting, stent-assisted coiling or flow diversion is viable option; however, the need for anti-platelet medication may increase the risk in patients with acutely ruptured aneurysms.2,3 Despite these concerns numerous studies using stents and flow diverters in the acute setting have been reported.4–9 Balloon-assisted coiling has been widely adopted as a technique to negate the potential complications of stent-assisted coiling in the acute scenario.
Although balloons should be considered essential tools in the armamentarium of the interventionists they are not without their limitations, one of which includes the temporary cessation of anterograde blood flow with potential drops in cerebral perfusion.10–12
Devices that offer the ability to temporarily cover the neck of the aneurysm but without impeding flow in the parent artery have been developed and may offer certain advantages over balloons.13–17 One potential complication of these devices is the potential for coils to become entangled with the braids of the device and for this complication to go unrecognised with the potential that a coil can become dislodged from the aneurysm during deflation and removal of the device.
The Cascade™ Non-Occlusive Remodeling Net (Perflow Medical, Israel) is a next-generation temporary bridging device. Here we describe our in vitro tests performed to determine whether coil prolapse and entanglement was possible when using this device.
Materials and methods
Cascade device
The Cascade is a new non-occlusive fully retrievable neck-bridging support device that has been designed to provide temporary support during coil embolisation of intracranial aneurysms. The device received CE mark in late 2018.
The Cascade is constructed from 42 braided nitinol and platinum wires that form a compliant net-like structure (Figure 1). The platinum wires enable good visualisation of the device. The design is akin to that of a flow diverter and the average pore size is <0.3 mm2. There is a short, flexible distal wire, and radio-opaque markers are positioned at the proximal and distal ends of the braided parts of the device. The proximal handle allows controlled ‘inflation’ and ‘deflation’ of the braided net (Figure 2). The device is delivered through a 0.021in. microcatheter and is available in two diameter sizes and four models:
M – recommended for vessel diameters of 2–4 mm
L – recommended for vessel diameters of 4–6 mm
M Agile – a shorter version of the Cascade M
L Agile – a shorter version of the Cascade L
Figure 1.
The Cascade is constructed from 42 nitinol and platinum wires that form a controllable braided net allowing for excellent visualisation and good apposition to the parent vessel.
Figure 2.
The different parts of the Cascade. A – handle, B – actuation shaft, C – proximal marker, D – distal marker, E – braided net, F – distal wire tip.
The device is delivered in collapsed form via the microcatheter and subsequently inflated and deflated via the handle. The control handle has two modes – auto-lock (ratchet) mode for stepwise radial expansion and continuous mode for smoother and more gradual expansion that can also provide tactile feedback (Figure 3). The device can be fully deployed or partially deployed (Figure 4). Additionally, the device can be made to bulge into the aneurysm if needed in order to protect branches close to the neck of the aneurysm.
Figure 3.
The handle of the Cascade allows controlled inflation of the device and has two modes – auto-lock (ratchet) mode for stepwise radial expansion and continuous mode for smoother and more gradual expansion that can also provide tactile feedback. The design allows easy operation with one hand which allows the positioning of the device to be maintained with the other hand as per standard endovascular practice.
Figure 4.
The Cascade device can be partially deployed ((a) and (c)) or completely unsheathed ((b) and (d)) depending on the anatomy.
Aneurysm model
Procedural setup
Models were connected via silicone tubing to a non-pulsatile flow pump (Aqua One Maxi 101). Fluid was heated to 37.0°C by a thermostat-controlled heating element. To approximate the viscosity of blood at this temperature, the system was filled with a mixture of 45% glycerol and 55% water and a small amount of liquid soap was added to reduce friction. All angiographic imaging was performed on an Allura Xper FD 20/15 biplane system (Philips Healthcare, Best, The Netherlands).
Aneurysm models
Model aneurysms (H + N-S-A-001-cust+, Elastrat) were treated by a single interventional neuroradiologist with six years of experience but with no clinical experience of using the Cascade device. Access was obtained via an 8Fr AXS Infinity guide catheter (Stryker Neurovascular, Kalamazoo, MI). Access to the distal vasculature and for deployment of the Cascade was performed using a 0.021 in. microcatheter (Rebar 18, Medtronic, Dublin, Ireland). Each aneurysm was catheterised using an SL10 microcatheter (Stryker Neurovascular) with 45° tip shape. Coil sizes were based on standard techniques after rotational angiography.
For each aneurysm the coiling microcatheter was placed in three locations:
The approximate midpoint of the aneurysm to replicate the typical location of the microcatheter tip during a standard coiling procedure.
At the very neck of the aneurysm – to replicate an unstable position.
Looped within the aneurysm and pointing directly at the neck so that coil protrusion risk could be maximised (Figure 5).
Figure 5.
Schematic representation of the different microcatheter position within the aneurysms ((a) to (c)), with corresponding photographs ((d) to (f)), and angiograms ((g) to (i)) – white arrows point to microcatheter tip position. The different microcatheter positions were used in order to test the effectiveness of the Cascade at preventing coil protrusion in the standard coiling position ((a), (d) and (g)) as well the extreme example demonstrated in (c), (f) and (i).
After each coil deployment the Cascade was deflated to assess coil prolapse. For each aneurysm the procedure was repeated 20 times. Several different coils, including Axium (Medtronic), Target XL Soft (Stryker Neurovascular), Barricade (Balt, Montmorency, France) and Kaneka ED10 (Kaneka, Kanagawa, Japan) were tested to determine the efficacy of the Cascade at preventing coil protrusion when using coils from different manufacturers. For the sidewall aneurysms, the Cascade device was placed in the parent artery. For the bifurcation aneurysm, the device was placed in a single branch and inflated so that it ‘bulged’ across the neck of the aneurysm. This particular aneurysm was the largest of the three aneurysms tested and had a wide neck (7.8 mm; Figure 6). The coiling microcatheter was positioned in three different locations as described above.
Figure 6.
Single images taken from the rotational angiogram used to determine the size of the aneurysm with the superior solid (white arrow) and inferior (dashed white arrow) daughter branches visible ((a) and (b)). The cascade device was placed into the superior branch and then bulged across the neck of the aneurysm as one may do with a microballoon. A photograph of the coiling microcatheter at the neck of the aneurysm is also shown ((c)).
Across the three aneurysms, and with the microcatheter in three different positions within each aneurysm, this resulted in 480 attempted coilings.
The characteristics of the aneurysms are detailed in Table 1 in addition to the coils and the Cascade device that were tested.
Table 1.
Characteristics of each model aneurysm, coils used, and number of attempted coil placements for each coil for each aneurysm with the coiling microcatheter in each position (neck, mid aneurysm, and looped).
| Aneurysm No. | Aneurysm characteristics |
Coils tested | Cascade device | Total no. of coilings attempted per coil | |
|---|---|---|---|---|---|
| Aneurysm location | Size (mm) | ||||
| 1 | Outer curve | 14 × 15 | Barricade 14 × 47 | Cascade L | 60 |
| Kaneka ED 16 × 20 | 60 | ||||
| 2 | Side wall | 10 × 9.5 | Stryker Target XL 360 Soft 10 × 40 | Cascade M | 60 |
| Axium Prime 10 × 30 | 60 | ||||
| Kaneka ED 10 × 30 | 60 | ||||
| 3 | Bifurcation | 13 × 15 | Baricade 14 × 47 | Cascade M | 60 |
| Axium Prime 14 × 30 | 60 | ||||
| Target XL 360 Soft 12 × 45 | 60 |
In addition, for the largest aneurysm, aneurysm flow high-frequency digital subtraction angiography (HF-DSA, Philips Healthcare) was performed.
Imaging
Three-dimensional rotational angiography was obtained using a 4s rotational acquisition, 220° rotation, 116 single frames at a frame rate of 29/s, 22 cm detector field of view, 512 acquisition matrix.
Aneurysm flow
Aneurysm flow HF-DSA was obtained using a 19-cm field of view at 60 frames per second for 420 total frames. For aneurysm flow assessment, 3 mL of contrast (Imeron 300, Bracco Imaging Deutschland GmbH, Konstanz, Germany) were injected by a coupled power injector with a flow of 1 mL/s via the 6F guide. The catheter tip was positioned proximal to the aneurysm so that it was just within the field of view. A working projection that clearly demonstrated the aneurysm, the aneurysmal neck and the parent vessel, whilst avoiding vascular overlap in the feeding artery, was selected.18
Image reconstruction and analysis
Processing of the aneurysm flow HF DSA imaging was done automatically. The arterial segment used for the flow calculation was selected automatically by the software according to the method previously described by Pereira et al.9 The Mean Aneurysmal Flow Amplitude (MAFA) ratio represents the ratio of intra-aneurysmal flow velocity after and before deployment of the Cascade. In addition to the MAFA ratio, we also calculated the flow velocity reduction (FVR).19
Results
Coil protrusion
We did not observe a single episode of coil protrusion through the Cascade mesh nor did we observe any coil protrusion into the parent vessel when the Cascade was deployed across the neck of the sidewall aneurysms. Similarly, when the device was positioned in one of the branches of the bifurcation aneurysm we did not see any instances of coil herniation/protrusion through the device into the parent artery or either of the branches.
The different position of the coiling microcatheter did not affect the likelihood of coil protrusion into the Cascade (Figures 7 and 8). Stable coil ball masses could be easily formed with no/minimal movement of the coil ball mass seen after deflation of the device.
Figure 7.
With the coiling catheter looped and pointing directly at the parent vessel and Cascade device the coil (Target XL Soft 10 × 40) can be seen to bounce off the device (Figure 6(a) and (b)). Similarly, with the microcatheter in the more traditional position the coil can still be seen to bounce off the Cascade device and not penetrate the Cascade mesh nor enter the parent vessel (Figure 6(c) and (d))
Figure 8.
With the coiling microcatheter looped and pointing directly at the neck and parent vessel lumen, as well as the Cascade device, an Axium 10 × 30 coil can be seen bouncing off the device (Figure 7(a) and (b)). A stable coil ball mass could be made with the device inflated (Figure 7(c)) that did not change configuration after deflation of the device (Figure 7(d)). The coil immediately entered the parent vessel with the microcatheter in this position (Figure 7(e)).
In addition to the protection of the parent vessel offered by the Cascade, we also noticed that the microcatheter could be easily manipulated during coiling if needed. Although the aim of these tests was to assess protection of the parent vessel this ease of manipulation of the microcatheter during coil placement could prove useful in vivo. Similarly, we also noticed that the catheter tip, when position in the usual coiling position, moved and ‘painted’ as would often be expected with coiling without adjunctive devices.
Aneurysm flow
The average MAFA ratio was 0.77 (n = 3), which resulted in a FVR of 23%. Figure 8 shows an ‘averaged’ image from the aneurysm flow with reduction in velocity and intra-aneurysmal flow after inflation of the Cascade across the neck of the aneurysm (Figure 9(b)) compared to without the device in situ (Figure 9(a)).
Figure 9.
Averaged aneurysm flow images without the Cascade device in situ (Figure 8(a)) and with the device inflated across the aneurysm neck (Figure 8(b)) showing an overall decrease in intra-aneurysmal flow velocity and greater flow within the parent vessel with inflation of the Cascade.
Discussion
The results of our in vitro tests show that prolapse and/or entanglement of coils through the Cascade device is extremely unlikely and was not seen for either the sidewall or bifurcation aneurysms tested. Even under extreme circumstances when the microcatheter was pointing directly at the neck of the aneurysm and the Cascade device there was no evidence of either entanglement or prolapse.
To date there are two publications regarding the Cascade device. Sirakov et al.20 recently published their early clinical experience with the device. In total, 12 patients with aneurysmal subarachnoid haemorrhage underwent coil embolisation with adjunctive use of the Cascade. In all cases, the device was chosen based on morphological features that would have deemed unassisted coiling challenging or impossible including aspect ratio of ≤1.2. The majority of cases were performed via a right radial approach (9/12, 75%) with the remaining cases performed via the right common femoral artery. In all cases, either a Headway 21 (Microvention, Tustin, CA) or Rebar 18 were tracked into the parent vessel distal to the aneurysm neck following which the aneurysm itself was catheterised using an Echelon 10 microcatheter (Medtronic). After catheterisation, the Cascade device was inflated across the neck of the aneurysm and the Echelon microcatheter jailed. In selected cases, the authors reported over-expanding the device in order to achieve the desired effect. The device was deflated before detachment of the initial framing coil to ensure a stable coil position within the aneurysm and no evidence of prolapse into the parent artery. The average aneurysm dome size was 5.75 mm (range 3–9.1 mm), median neck size 3.55 mm (2.3–7.9 mm). The authors report complete aneurysm exclusion (Raymond Roy classification I) in 75% of cases with intentional neck remnant in the remaining 25%. None of the patients received oral anti-platelets prior to the procedure nor did they receive intravenous anti-platelet medication during the procedure. There was no evidence of thrombus formation on the device nor of distal embolism. Furthermore, there was no evidence of device related spasm, perforation or coil entanglement. Tomasello et al.21 recently published their multicentre retrospective analysis of 15 patients (11 female) with average age 58 ± 13 years. The majority of the aneurysms were unruptured (n = 10) and 13 aneurysms were located in the anterior circulation. The average aneurysm dome height was 6.27 ± 2.33 mm with average neck width 3.64 ± 1.19 mm. Eleven aneurysms had an aspect ratio ≤2, two of which had an aspect ratio of 0.8. The mean number of coils inserted was 5 ± 2 and the mean Cascade usage was 30 ± 14 min. In total 11 aneurysms achieve modified Raymond-Roy occlusion (mRRC) grade 1 (73.3%) and 4 aneurysms (26.7%) were mRRC II. Delayed angiographic follow-up < 6 months was available in seven patients, six of whom remained mRRC I but in one patient a neck recanalisation was seen (mRRC II). In terms of complications, there were no coil herniations or entanglements seen. There were no thromboembolic complications although pre-operative anti-platelets were used in all the patients with unruptured aneurysms pre-procedurally and in three patients with ruptured aneurysms. None of the patients received long-term post-procedural anti-platelet medication.
Although only a small number of cases were included in these studies the results are consistent with our in vitro tests and support the idea that the dense neck coverage seen with the Cascade limits the chance of coil protrusion or entanglement. Coil protrusion is more likely to occur with similar devices with fewer braided wires and larger pores. Sirakov et al. also noted significant contrast stagnation after device inflation. The most plausible reason for this is the densely braided 42 wires simulate a flow diverter. In our aneurysm flow assessment, we saw a FVR of approximately 23% after inflation of the device. We believe that this flow stagnation may promote intra-aneurysmal thrombosis particularly in the presence of coils. Additionally, it may offer some protection if intra-operative aneurysm rupture occurs although certainly not to the same degree that an occlusive balloon would afford. The inability to enable flow arrest has been raised as a concern for similar devices previously. Certainly our results do not demonstrate complete flow arrest as would be possible with a balloon and it is hypothetical as to whether the degree of flow diversion offered by the device would be beneficial in the event of a rupture. Whilst the Cascade could not completely arrest flow we believe that, based on our in vitro test, the chances of coil entanglement with the device are very low. As such, in the case of aneurysm rupture, rapid coiling could be performed without the need for deflation of the device after each deployment.
Similarly, given the existing clinical data regarding the Cascade there does not appear to be a need for intra-procedural anti-platelet medication which may also offer advantages especially if the aneurysm was to rupture during the procedure.
Our study has several limitations including the limited number and limited morphologies of the aneurysms available on the model. Aneurysm models with more unfavourable aspect ratios and wider necks would be preferable to test the ability to form stable coil ball masses; however, this may not be a necessity when testing coil penetration through the braids of the Cascade which was the primary aim of our study. Similarly, replicating the study with an even greater variety of coils would provide more certainty that likelihood of coil penetration is low. Finally, although the FVR in this simulation may theoretically offer some protection in the setting of acute aneurysm rupture without being able to replicate an actual ‘rupture’ we are unable to truly test this hypothesis in vitro.
Conclusion
The Cascade device offers robust protection of the aneurysmal neck and parent vessel as well as inducing significant intra-aneurysmal FVR.
Authors’ contributions
P Bhogal involved in manuscript preparation, study design, concept; K Wong: manuscript and image preparation; HLD Makalanda: manuscript review.
Declaration of conflicting interests
The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Pervinder Bhogal has a consulting and proctoring agreement with phenox.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
ORCID iD
References
- 1.Molyneux AJ, Kerr RSC, Yu L-M, et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 2005; 366: 809–817. [DOI] [PubMed] [Google Scholar]
- 2.Bodily KD, Cloft HJ, Lanzino G, et al. Stent-assisted coiling in acutely ruptured intracranial aneurysms: a qualitative, systematic review of the literature. AJNR Am J Neuroradiol 2011; 32: 1232–1236. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Murchison AG, Young V, Djurdjevic T, et al. Stent placement in patients with acute subarachnoid haemorrhage: when is it justified? Neuroradiology 2018; 60: 735–744. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Bhogal P, Brouwer PA, Söderqvist ÅK, et al. Patients with subarachnoid haemorrhage from vertebrobasilar dissection: treatment with stent-in-stent technique. Neuroradiology 2015; 57: 605–614. [DOI] [PubMed] [Google Scholar]
- 5.Pérez MA, Bhogal P, Moreno RM, et al. Use of the pCONus as an adjunct to coil embolization of acutely ruptured aneurysms. J Neurointerventional Surg 2017; 9: 39–44. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.AlMatter M, Aguilar Pérez M, Hellstern V, et al. Flow diversion for treatment of acutely ruptured intracranial aneurysms. Clin Neuroradiol Epub ahead of print 4 November 2019. DOI: 10.1007/s00062-019-00846-5. [DOI] [PMC free article] [PubMed]
- 7.Bhogal P, Henkes E, Schob S, et al. The use of flow diverters to treat small (≤5 mm) ruptured, saccular aneurysms. Surg Neurol Int 2018; 9: 216. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Aydin K, Arat A, Sencer S, et al. Treatment of ruptured blood blister-like aneurysms with flow diverter SILK stents. J Neurointerventional Surg 2015; 7: 202–209. [DOI] [PubMed] [Google Scholar]
- 9.Mokin M, Chinea A, Primiani CT, et al. Treatment of blood blister aneurysms of the internal carotid artery with flow diversion. J NeuroInterventional Surg Epub ahead of print 24 February 2018. DOI: 10.1136/neurintsurg-2017-013701. [DOI] [PubMed]
- 10.Pereira VM, Bonnefous O, Ouared R, et al. A DSA-based method using contrast-motion estimation for the assessment of the intra-aneurysmal flow changes induced by flow-diverter stents. AJNR Am J Neuroradiol 2013; 34(4): 808–815. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Spiotta AM, Bhalla T, Hussain MS, et al. An analysis of inflation times during balloon-assisted aneurysm coil embolization and ischemic complications. Stroke 2011; 42: 1051–1055. [DOI] [PubMed] [Google Scholar]
- 12.Sluzewski M, van Rooij WJ, Beute GN, et al. Balloon-assisted coil embolization of intracranial aneurysms: incidence, complications, and angiography results. J Neurosurg 2006; 105: 396–399. [DOI] [PubMed] [Google Scholar]
- 13.Fischer S, Weber A, Carolus A, et al. Coiling of wide-necked carotid artery aneurysms assisted by a temporary bridging device (Comaneci): preliminary experience. J Neurointerventional Surg 2017; 9: 1039–1097. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Gupta R, Kolodgie FD, Virmani R, et al. Comaneci neck bridging device for the treatment of cerebral aneurysms. J Neurointerventional Surg 2016; 8: 181–185. [DOI] [PubMed] [Google Scholar]
- 15.Lawson ALD, Chandran A, Puthuran M, et al. Initial experience of coiling cerebral aneurysms using the new Comaneci device. J Neurointerventional Surg 2016; 8: e32. [DOI] [PubMed] [Google Scholar]
- 16.Sirakov S, Sirakov A, Hristov H, et al. Early experience with a temporary bridging device (Comaneci) in the endovascular treatment of ruptured wide neck aneurysms. J Neurointerventional Surg 2018; 10: 978–982. [DOI] [PubMed] [Google Scholar]
- 17.Sirakov SS, Sirakov A, Hristov H, et al. Coiling of ruptured, wide-necked basilar tip aneurysm using double Comaneci technique. BMJ Case Rep Epub ahead of print 18 May 2018. DOI: 10.1136/bcr-2017-222703. [DOI] [PMC free article] [PubMed]
- 18.Cebral JR, Mut F, Chung BJ, et al. Understanding angiography-based aneurysm flow fields through comparison with computational fluid dynamics. AJNR Am J Neuroradiol 2017; 38: 1180–1186. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Frölich AM, Nawka MT, Ernst M, et al. Intra-aneurysmal flow disruption after implantation of the Medina® Embolization Device depends on aneurysm neck coverage. PloS One 2018; 13: e0191975. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Sirakov S, Sirakov A, Minkin K, et al. Early clinical experience with Cascade: a novel temporary neck bridging device for embolization of intracranial aneurysms. J Neurointerventional Surg. Epub ahead of print 21 September 2019. DOI: 10.1136/neurintsurg-2019-015338. [DOI] [PubMed] [Google Scholar]
- 21.Tomasello A, Hernandez D, Gramegna LL, et al. Early experience with a novel net temporary bridging device (Cascade) to assist endovascular coil embolization of intracranial aneurysms. J Neurosurg Epub ahead of print 24 January 2020. 1–9. DOI: 10.3171/2019.11.JNS192477. [DOI] [PubMed]