TransForm occlusion balloon catheter

The TransForm occlusion balloon catheter (Stryker Neurovascular, Fremont, California, USA) is the latest innovation of balloon microcatheter design. It is a single lumen balloon catheter using 0.014-inch microguidewires with compliant and super compliant versions.17 The device has a micromachined hypotube design with multiple slits to allow rapid inflation and deflation of the balloon catheter, increased visibility and reduced procedural times.8 In an early clinical experience and retrospective review of 23 ruptured and unruptured aneurysms treated with the TransForm, the authors report complete aneurysm occlusion (Raymond Roy Classification (RRC), RRC I) in 78% (18/23) of aneurysms and residual neck in 22% (5/23) of aneurysms (RRC II) in post-treatment angiography. No serious complications were observed, and no follow-up data were reported.17

In a prospective multicentre trial published in 2018, the authors enrolled 81 patients undergoing TransForm balloon-assisted coil embolisation for treatment of ruptured and unruptured aneurysms. Of the aneurysm characteristics reported, 50% (36/72) were bifurcation aneurysms and 82% (59/72) were located in the anterior circulation. Complete occlusion (RRC I) was observed in 69.4% (50/72) of cases, residual neck (RRC II) in 25% (18/72) and residual aneurysm (RRC III) in 5.6% (4/72). In 4.9% (4/81) of subjects, thrombus formation occurred and led to thromboembolic events in 2.5% (2/81). However, no thromboembolic infarctions or serious complications occurred.8

Scepter

Scepter (Microvention, Irvine, California, USA) is a coaxial dual lumen compliant balloon catheter using 0.014 inch microguidewires.8 This device was approved by the FDA in 2012. The Scepter balloon has a compliant version for sidewall aneurysms providing minimal slipping and longitudinal coverage called Scepter-C, and a supercompliant version that conforms to bifurcation aneurysms called the Scepter-XC.16 The double lumen design of the Scepter balloons provides a unique advantage of the ability to deploy a low profile stent in the event of coil loop prolapse.

HyperForm and HyperGlide

The HyperForm and HyperGlide balloon catheters are single lumen compliant balloons using 0.010 inch microguidewires.8 The HyperGlide is primarily used for balloon remodelling of wide-neck sidewall aneurysms, especially those located in the internal carotid and vertebral arteries. The HyperGlide is oblong, while the HyperForm is round and more compliant. The HyperForm can conform to complex bifurcation aneurysms and protect branches originating from and adjacent to the aneurysm neck. The more compliant HyperForm is preferred for wide-neck aneurysm as well as small arteries, such as posterior inferior cerebellar artery, posterior cerebral artery and anterior communicating artery. The 0.010-inch microwire requirement limits the easy of use and navigability for the HyperFrom and HyperGlide balloons.16

Ascent balloon

The Ascent occlusion balloon catheter (Micrus Endovascular Corp, San Jose, California, USA) uses a 0.014-inch microguidewire and has compliant and supercomplaint versions. The device was approved by the FDA for neurovasculature and peripheral use in 2008. These were an older generation balloon design and are no longer routinely used.

PulseRider

The PulseRider Aneurysm Neck Reconstruction Device (Pulsar Vascular, Inc, Los Gatos, California, USA) comes in two shapes: T or Y, both of which are made of nitinol (nickel titanium) with 8 mm and 10 mm wide arches. It was first approved for use in the USA by the Food and Drug Administration (FDA) on 19 June 2017.21 Prior to approval, the Adjunctive Neurovascular Support of Wide-neck Aneurysm Embolization and Reconstruction (ANSWER) Trial examined its use in the treatment of 34 aneurysms. Of the 34 treated aneurysms, 82.4% showed immediate Raymond I or II occlusion, and at 6-month follow-up, the rate increased to 87.9%, thus supporting the use of the PulseRider device.22 Notably, Aguilar-Salinas and colleagues systematically reviewed the use of PulseRider device in bifurcation aneurysms, across three studies conducted throughout Europe and the USA. A total of 63 aneurysms were treated and although it seems ‘safe and probably effective’ for treating intracranial bifurcation aneurysms, a bigger sample size is needed to support this statement.23 More recently, Srinivasan et al 24 reported early postmarket results across 13 centres in the USA for the treatment of 54 aneurysms. Both clinical and radiographic outcomes were comparable with early studies with technical success in 52 cases (96.2%), major complications in three cases and immediate Raymond I or II occlusion in 69.1%. Follow-up angiography at 3 or 6 months was only available in 28 patients, and in these cases, observed Raymond I or II occlusion was 92.7%. Further long-term outcomes with the use of PulseRider device and additional experiences in off-label indications are still needed.

Low-profile Visualised Intraluminal Support (LVIS) and LVIS Jr

The LVIS and LVIS Jr stents are hybrid braided and closed-cell nitinol stents approved for treating wide-neck aneurysms by the FDA on 30 May 2018.25 The LVIS is delivered through a larger microcatheter (0.021″ inner diameter), while the LVIS Jr is delivered through a smaller microcatheter (0.017″ inner diameter).26 The use of a smaller microcatheter with LVIS Jr allows easier access to smaller vessels with a more tortuous path. In 2018, a multicentre retrospective analysis was conducted at seven medical centres (six in the USA and one in Croatia) to investigate the technical and clinical outcome in LVIS Jr assisted coiling for the treatment of wide-neck aneurysms. The authors used the LVIS Jr in Y-stent configuration to treat 30 wide-neck bifurcation aneurysms (24 unruptured) in 30 patients. The use of LVIS Jr device resulted in immediate complete obliteration of aneurysm in 26 patients out of 30 (89.6%). At a mean follow-up of 5.2 months, 23 patients out of 26 (96%) had complete occlusion. This study supports the use of Y-stenting with the LVIS Jr device to assist in endovascular coiling of bifurcated, wide-neck cerebral aneurysms.27

Several other important studies evaluating the safety and effectiveness of the LVIS have since been published. A pivotal, prospective, multicentre trial for LVIS published its final results in 2019. The study enrolled 153 patients with wide-neck cerebral aneurysms from 21 US institutions. Complete occlusion was observed in 79.1% (110/139) after 12 month angiography, while 90% or greater occlusion was observed in 95% (132/139). Adverse effects (stroke or death) was observed in 5.2% (8/153).28 In a single-centre retrospective study comparing 229 patients treated with three different types of stents, the authors found that a higher degree of complete occlusion was observed for patients receiving LVIS and LVIS Jr devices (49/60, 81.7%), compared with those receiving the laser-cut open design stent and laser-cut closed design stent, during follow-up angiography at least 6 months after treatment; however, the authors do report that intraprocedural complications were higher for patients in the LVIS group (7/69, 10.1%).29 A multicentre retrospective study with 659 patients published in 2019 shows a statistically significant difference (p=0.004) in complete occlusion for 84% of patients receiving LVIS stent (251/299) compared with 78% of those receiving Neuroform stent (117/150) and 67% of those Enterprise stent (83/123). The complete occlusion was determined from follow-up angiography, occurring an average of 10.5 months after treatment.30

Neuroform Atlas Stent System

Neuroform Atlas Stent System is the newest vascular reconstruction device, approved by the FDA on 16 May 2019 (Stryker Neurovascular). It is a nitinol self-expanding stent redesigned from the previous Neuroform stent system by incorporating a hybrid closed cell and open cell design aimed to assist wide-neck aneurysm endovascular coiling. It is one of the most commonly used vascular reconstruction device (VRD) for stent-assisted coiling techniques with its ease of use through a smaller microcatheter (0.017″ inner diameter) delivery. The Atlas Investigational Device Exemption (IDE) Trial was conducted at eight US centres to investigate the usefulness of Neuroform Atlas Stent System. Data from 27 patients were available at 12-month follow-up and 92.6% (25/27) achieved complete occlusion. One patient suffered from stroke but recovered fully. The authors supported the use of the Neuroform Atlas Stent System in the treatment of cerebral aneurysms.31

In a prospective study of 55 bifurcation aneurysms, Ciccio et al 32 employed a double-stent technique in Y and X configurations with the Neuroform Atlas stent. The majority of cerebral aneurysms achieved complete occlusion (n=33; 60%), while the remaining ones had either incomplete occlusion (n=14; 25.4%) or neck remnant (n=8; 14.5%). Digital subtraction angiography (DSA) between 1 year and 3 years (mean=16 months) showed that follow-up data were available for 38 aneurysms in which 87% (n=33) were completely occluded, 5% (n=2) were incompletely occluded and 8% (n=3) had a neck remnant. The procedural complication rate was 12.7%, which was considered high; therefore, the authors cautioned the use of double stent-assisted coiling.32

Barrel VRD

The Barrel VRD (Medtronic/Covidien, Irvine, CA, USA) is a novel, fully retrievable, self-expanding, laser cut, nitinol stent designed as an adjunctive treatment for endovascular coiling of wide-neck bifurcation aneurysms.33 The unique feature of the Barrel VRD is its bulged centre, which allows greater aneurysm neck coverage with a single implant, as opposed to a double stent implant. It is delivered through a 0.021-inch inner diameter microcatheter. Although it has received CE approval for use in Europe, the Barrel VRD has not obtained FDA approval for US market use.

In a prospective, multicentre trial, Gory et al 33 enrolled 20 patients with wide-neck bifurcation aneurysms, 19 of which were ultimately treated with Barrel VRD as an adjunct to coil embolisation. At 12-month angiographic follow-up, 63% (12/19) of patients experienced complete occlusion, while 79% (15/19) with neck remnant or complete occlusion were considered successfully treated. The authors reported a 5.3% (1/19 patients) rate of neurological complication. In a later study, Kabbasch et al 34 published a two-centre retrospective analysis of 21 patients with wide-neck bifurcation aneurysms undergoing Barrel VRD stent-assisted endovascular coiling. The authors report that 90% (19/21) of patients experienced immediate complete occlusion. Of the patients available for short-term and midterm follow-up, 95% (19/20) experienced complete occlusion (median follow-up 282 days, range: 17–591 days). Two patients experienced in-stent thrombus formation and one patient experienced in-stent stenosis; however, these complications were medically resolved. These results support a satisfactory safety profile.34 Despite the initial experiences, the Barrel VRD has not gained wide adoption.

Comaneci

On 7 May 2019, FDA approved the use of Comaneci device as a Temporary Coil Embolization Assist Device (Rapid Medical, Israel) to assist with coiling wide-neck aneurysms. The Comaneci device comes in three different sizes: (1) Comaneci is 32 mm in net length and expands to 4.5 mm in diameter; (2) Comaneci Petit is 24 mm in net length and expands to 3.5 mm; and (3) Comaneci 17 is 22 mm in net length and expands to 3.0 mm.35 Sirakov et al 36 2018 described their experience with Comaneci in treating ruptured wide-neck aneurysms. Complete occlusion was achieved in 86% (25/29) of the patients, and only one patient had possibly procedure-related complications, thus supporting the use of Comaneci in treating ruptured aneurysms. Additionally, Sirakov et al described the use of two Comaneci devices in a challenging case: a bifurcated, wide-necked and ruptured aneurysm located at the basilar artery. The use of two Comaneci devices allowed the endovascular coiling to be successfully deployed and stabilised inside the aneurysm. The patient had a full recovery and no neurological deficit. Based on the DSA at 3 and 12 months of follow-up, aneurysm recurrence was not observed, indicating that the aneurysm was obliterated, along with patent bilateral posterior cerebral arteries . This case report demonstrated the advantage and the potential of using multiple Comaneci devices to manage similar complex anatomical configuration.37 Experience with the Comaneci devices remains few and limited at this time.

Cascade Non-Occlusive Remodeling Net

Cascade (Perflow Medical, Netanya, Israel) is a novel, retrievable, neck-bridging device designed to assist in coil embolisation of cerebral aneurysms. Cascade, like other neck-bridging devices, may serve as an alternative to balloon-assisted techniques, with the added advantage of providing patency of the parent vessel during coil delivery, thus reducing risk of complications associated with ischaemia. Sirakov et al report an early 2019 clinical experience using Cascade with coil embolisation for treatment for 12 ruptured wide-neck aneurysms. Complete occlusion was observed in 75% (9/12) patients, and no patients received antiplatelet therapy. No technical or clinical complications were observed during treatment; however, the study did not report follow-up data. The Cascade is similar to Comaneci (see section dedicated to Comaneci); however, Cascade is compatible with a smaller 0.017 microcatheter better suited for more tortuous vessels. Cascade features denser net and deflected shape during expansion unlike Comaneci. Sirakov et al 12 report less coil entanglement and better compliance with parent vessel during expansion with Cascade compared with Comaneci. The authors acknowledge several limitations of their study, such as the small sample size and lack of long-term follow-up. The higher rate of complications for patients undergoing endovascular coiling for wide-neck aneurysms remains an important issue, and early data for the use of the novel non-occlusive Cascade device appear promising and warrant further safety and efficacy studies.

The pCONus is a laser-cut, self-expanding, nitinol stent with a distal crown and four petals that are deployed into the aneurysm sac. It is compatible with 0.021-inch diameter microcatheters. This device is currently approved for use in Europe but not in the USA by the FDA.38 39 The distal portion of stent consists of six polyamide fibres that cross and provide additional support to the coil ball in the aneurysm. The proximal extra aneurysmal portion consists of segmental radiopaque markers made of platinum-iridium wire that is released into the parent vessel to aid accurate positioning of the stent. In a recent meta-analysis and systematic review of 203 cerebral aneurysms treated with pCONus devices, it was found that the technical success rate was 100%, technical complication rate was 0%, complete occlusion rate was 60%, retreatment rate was 14%, morbidity rate was 7% and mortality rate was 0%.40

The second-generation device, pCONus 2, has two additional petals and a distal crown with a central spur. The design allows the crown to articulate providing additional flexibility, especially for aneurysms with high angulation between parent vessel and aneurysm. Centrally, the pCONus 2 has greater metal coverage to decrease the risk of coil prolapse. An early clinical experience with pCONus 2 involving 12 patients in the anterior and posterior circulations has been published. In this retrospective analysis, the authors report 92% (11/12) aneurysms with a modified RRC I (complete occlusion) and 8% (1/12) aneurysm with a modified RRC II after immediate angiography posttreatment. In angiographic follow-up (mean=4.6 months, range=3–6 months), adequate aneurysm occlusion was observed in 83% (5/6) and aneurysm recanalisation in 17% (1/6). The use of pCONus 2 did not result in any haemorrhagic complications or death.39

The pCANvas is the third-generation device to its predecessors, pCONus 1 and pCONus 2, used to treat wide-neck intracranial aneurysms (Phenox, Bochum, Germany). This device is also only currently approved for use in Europe but not in the USA by the FDA. The pCANvas consists of a detachable, laser-cut, neck bridging stent shaft with a distal crown of petals covered in a biocompatible membrane that inhibits blood flow into the aneurysm and prevents coil displacement into parent artery. A novel feature of pCANvas is its four radio-opaque markers on the distal crown allowing accurate deployment at the aneurysm neck. Lylyk et al 13 in 2019 published the earliest clinical data on the use of pCANvas. In a retrospective analysis of prospectively collected data, the authors included 17 patients treated for intracranial aneurysms with the pCANvas alone. The device was deployed without intraoperative complications. At early follow-up (median=6.1 months, range=3–10 months), five aneurysms were completely occluded (RRC I) and 11 were completely filled (RRC III). Seven patients were retreated with endovascular coiling because the pCANvas device as a singular treatment failed to occlude the aneurysm. Fourteen patients were available for midterm follow-up (median=18.2 months, range=7–38 months): 57% (8/14) aneurysms were completely occluded (RRC I), 21% (3/14) aneurysms were completely filled (RRC III) and 21% (3/14) aneurysms had neck remnants (RRC II). The authors conclude the pCANvas appears safe, and they recommend that the device be used as an adjunctive device to coiling.

eCLIPS

The second-generation eCLIPS is a novel self-expanding, fully retrievable, nitinol, stent-like device with flow diverter properties and the successor to the original eCLIPS device first described in 2008. This device is only currently approved for use in Europe but not in the USA by the FDA. Unlike its predecessor, the second-generation eCLIPS is not balloon mounted and its non-circumferential design prevents jailing of branch or parent vessels. The device has a leaf segment that diverts blood flow away from the aneurysm and acts as a scaffold for neointimal hyperplasia to cover the aneurysm neck. An initial clinical experience with the second-generation eCLIPS was published in 2018, describing a multicentre analysis of 33 patients with bifurcation aneurysms, mostly at the basilar tip, receiving eCLIPS implantation. The device was successfully deployed in 76% (25/33) patients, and coils were added during device implantation in all but two patients. The authors attribute the unsuccessful deployments to the learning curve associated with the new device, as the device was successfully implanted in all patients included in the study following the first year of use. Regarding safety, the authors report two ischaemic complications and two asymptomatic thrombotic events. Eighty-one per cent (17/21) of patients demonstrated complete occlusion or residual neck at angiographic follow-up (mean=8 months, range=3–18 months). Of these 21 patients, 42.9% of patients had an improvement in RRC grade at follow-up.41 The European eCLIPS Safety, Feasibility, and Efficacy study is an ongoing multicentre prospective study that should help determine the utility of eCLIPS for the treatment of cerebral bifurcation aneurysms (ClinicalTrials.gov).

3D printed vascular models

3D printing of artificial vascular models for pretreatment simulation holds promise for guiding the treatment of intracranial aneurysms, particularly those that are more challenging to treat. These silicone vascular replicas can be made for less than US$2 and in 24 hours using a desktop 3D printer costing approximately $1300. Data from CT, magnetic resonance angiography or rotational angiography can be used to generate a printable vascular model tailored to a patient’s unique anatomy, then further processed with the addition of a liquid silicon coat, smoothing out of the artificial vessels, and attachment to peristaltic pump to allow simulation with endovascular devices.45 In a case report involving two patients, Kaneko et al 46 designed and printed patient-specific hollow vascular models to determine the optimal endovascular treatment for more challenging to treat aneurysms. The first case was a wide-neck A3 aneurysm, pretreatment simulation led the authors to use the Neuroform ATLAS stent over the LVIS Jr stent based on degree of stent herniation into the aneurysmal sac. The second case was a wide-neck basilar-superior cerebellar artery aneurysm where Neuroform ATLAS was chosen over LVIS Jr based on superior coil embolidation stability using Neuroform Atlas during pretreatment simulation. In this small number of patients, simulation accurately predicted the outcome of the procedure and aided in deciding which stent would likely be more effective for each specific patient based on degree of side branch protection, coil embolisation stability and degree of stent expansion. The authors note a few limitations in their study, namely the challenge in replicating vascular elasticity in their printed silicon vascular models, which are more fixed and inelastic compared with human vessels. Nonetheless, these results are promising and additional studies with a greater sample size appear to be warranted to assess the utility of using personalised 3D-printed vascular models for preprocedural simulation of endovascular coiling.