pCONUS 2 and pCONUS 2-HPC for the treatment of wide-necked intracranial aneurysms: Periprocedural, 6-month, and early 2-year follow-up outcomes

Abstract

Background/Purpose

pCONUS 2 and pCONUS 2-HPC are novel neck-bridging devices designed to support endovascular coil occlusion of wide-necked intracranial bifurcation aneurysms. This study summarises periprocedural outcomes, 6-month, and early 2-year follow-up results following its introduction in an interventional neuroradiology centre.

Materials/Methods

This prospective, single-arm study assessed 20 aneurysms treated over a 40 month time period from time of procedure to 2 years post-procedure. Data collected included patient demographics, aneurysm features, and intraprocedural, 6-month, and 2-year post-procedural complications and angiographic features.

Results

The mean age of the cohort was 59+-SD 7.7 years. 16 unruptured aneurysms were treated (pCONUS 2 13/16, pCONUS 2-HPC 3/16) and 4 ruptured aneurysms were treated with pCONUS 2-HPC. Unruptured cases received dual antiplatelet therapy pre- and post-procedure while ruptured cases received single antiplatelet therapy. 9/20 aneurysms were located at the MCA bifurcation and 7/20 at the basilar tip. The remaining 4 aneurysms were at various bifurcations in the anterior circulation. 11/20 were small (<10mm) and 9/20 were large (10–25mm). There was one periprocedural complication: a retroperitoneal bleed. There were no post-procedural intracranial complications or at 6-months follow-up. At 6 months, satisfactory occlusion was achieved in 94% of cases (15/16). There was one delayed death at 2-year follow-up from an unrelated cause.

Conclusion

pCONUS 2 and pCONUS 2-HPC have excellent short and medium-term safety profiles and clinical outcomes with no procedure-related mortality or morbidity and good occlusion rates at 6-month follow-up. The use of pCONUS 2-HPC with single antiplatelet therapy is feasible and did not cause any complications.

Introduction

The pCONUS 2 and the pCONUS 2-HPC (Phenox, Germany) are novel bifurcation aneurysm implants designed for the treatment of wide-necked aneurysms. They are the second generation of the pCONUS family of devices, which are neck-bridging devices designed to provide support for intrasaccular coils and prevent coils extruding into the parent vessel. ¹

They innovate on the previous pCONUS devices by increasing the number of wire petals in the crown of the device from four to six, increasing stability of the implant, and shortening the length of the device shaft. This allows the pCONUS 2 devices to be used in cases where there is a larger angle between the parent vessel and the aneurysm. ²

To date there is minimal evidence in the literature regarding the efficacy of pCONUS 2 and pCONUS 2-HPC, particularly beyond a medium-term timeframe. This case series aims to present further data reporting on the medium-term efficacy of the pCONUS-2 devices, and also provide 2-year follow-up data beyond what is currently extant in the literature.

Materials and methods

Study design and participants

This prospective study reviewed data in all patients (n = 20) with wide-necked aneurysms who underwent assisted coil embolisation with the pCONUS 2 or pCONUS 2-HPC bifurcation aneurysm implant over a 40-month time period, between November 2017 and February 2021, at a tertiary centre for interventional neuroradiology.

The inclusion criteria were:

• Wide-necked unruptured aneurysm

• Aspect ratio < 1.6

• Dome-to-neck ratio < 2

• Neck length >4 mm

• Age > 18

All patients provided informed consent and the use of the pCONUS 2 or pCONUS 2-HPC device was at the discretion of the operator.

Pre-operative assessment

All patients underwent a pre-operative assessment consisting of neurological examination, routine blood tests, and imaging. 19 patients being treated for the first time underwent a CT angiogram, while 1 patient being treated for a recurrence had a MR angiogram. Pre-operative catheter angiography was not performed as CT and MR angiography provided sufficient information for aneurysm and device sizing. Aneurysm dimensions were measured by a single interventional neuroradiology consultant using reformatted angiography images. All procedures were conducted using an Artis Zee Biplane system (Siemens Healthineers, Germany).

Device characteristics & sizing

The pCONUS 2 and pCONUS 2-HPC have a CE mark but have not received Food and Drug Administration approval in the United States as of March 2021. ³ The devices are self-expanding, tubular vascular implants for supporting the coil occlusion of wide-necked intracranial bifurcation aneurysms. They consist of a shaft and a crown. The shaft is a self-expanding microstent 15 mm in length, designed to anchor the implant in the proximal intracranial vessel. The distal end of the implant features petal-like loops which together form a crown-like contact surface. These petals fold together when the device is in a compressed state. After the microcatheter is placed in the middle of the aneurysm, the petals are gently deployed and expand radially to create a crown. The crown is gradually pulled back towards the neck to allow for good apposition to the side wall of the aneurysm at its neck. This provides a scaffold for wide-necked aneurysms to be safely coiled with high packing density without risking coil protrusion into the parent vessel and possible occlusion of local side branches. ²

The pCONUS 2 iterates on its predecessor in multiple ways (Figure 1): there are 6 petals in the crown instead of 4, providing increased implant stability. The radiopaque markers on the crown are longer than previously and there is an additional marker at the junction between the crown and shaft, increasing visibility of all components of the device and resulting in improved positioning. The petals now converge into a single proximal wire providing the ability to bend up to 90°, facilitating treatment of aneurysms situated at an abrupt angle to the parent vessel. The pCONUS 2 also has design alterations aimed at reducing thrombogenicity: it has a shorter proximal stent component with less metal in the parent vessel and its metal to artery surface ratio improves on its predecessor’s ratio of approximately 5%.^2,4,5 The HPC variant of the device has a hydrophilic polymer coating that mimics the glycocalyx therefore reducing CD61+ve platelet aggregation and clot formation.^6,7

Figure 1.

Digital renderings of the pCONUS and pCONUS 2 implants. Multiple design changes to the shaft and crown in pCONUS 2 can be appreciated, including more metal within the crown, an increased number and length of radiopaque markers, convergence of the crown to a single wire, and reduced shaft volume and surface area. Digital renderings CC Phenox GmbH 2017.

Figure 2.

Townes (a) and lateral (b) projections of a wide-necked basilar tip aneurysm that incorporates the origin of the left posterior cerebral artery. A pCONUS 2 device was deployed covering the neck of the aneurysm and the aneurysm was subsequently coiled. Post-coiling Townes (c) and lateral (d) projections show aneurysm occlusion with a small neck remnant maintained to preserve patency the left posterior cerebral artery.

Figure 3.

Frontal (a) and lateral (b) projections of a wide-necked left middle cerebral artery bifurcation aneurysm. This aneurysm was subsequently coiled following the insertion of a pCONUS 2 device. Post-coiling frontal (c) and lateral (d) projections show the crown of the pCONUS device holding the coils in situ within the aneurysm. Black arrowhead: Proximal marker of jailed coiling microcatheter. White arrow: Distal tip of 0.021" microcatheter. White arrowhead: Proximal marker of pCONUS 2 device.

The pCONUS 2 and pCONUS 2-HPC are supplied in multiple sizes to aid fit in a variety of aneurysm sizes. All device sizes of pCONUS 2 can be deployed in a 0.021" microcatheter, such as the Prowler Select Plus (Johnson and Johnson, USA) and Via 21 (Sequent Medical, USA). The sizing options range from a crown diameter of 5mm to 15mm. The shaft length and diameter remain constant at 15mm and 4mm respectively to accommodate most intracranial aneurysm locations. ⁴

Device sizing was assessed by the operator prior to deployment using advanced 3D reconstruction software available in the angiosuite. The device was usually oversized at the neck to ensure ample opposition to the side walls at this location. The marker at the junction between the crown and shaft was located outside the aneurysm to achieve a flat dome configuration.

Treatment description

All 16 elective patients received dual antiplatelet therapy (DAPT) the night before the procedure. There were two regimens used for pre-procedure DAPT: the first 3 cases received PO doses of aspirin 300 mg and prasugrel 30 mg or 60 mg 5 days prior to treatment, followed by daily 75 mg aspirin PO and 5 or 10 mg prasugrel until the day of the procedure. The dose of prasugrel was 30 mg and 5 mg if bodyweight was below 75 kg and 60 mg and 10 mg if above 75 kg. This regimen was subsequently altered due to proctoring recommendations and the remaining 13 cases received PO doses of aspirin 300 mg and clopidogrel 600 mg the night prior to treatment.

All 4 acute cases were treated with the pCONUS 2-HPC. These cases all received single antiplatelet therapy (SAPT) on the morning of the procedure. This was either PO prasugrel 30 mg or 60 mg with the dose based on bodyweight as described above.

The VerifyNow P2Y12 assay (Werfen, Spain) was used to confirm an adequate response to DAPT immediately prior to commencement of the procedure. There were no P2Y12 antagonist poor or non-responders in the cohort. If there had been, the procedure would have been abandoned in elective patient P2Y12 antagonist non-responders and the post-procedure regimen would have been altered for elective patient P2Y12 antagonist poor responders. In acute cases, the procedure would have continued as the benefits of treatment outweighed the risks.

All procedures were carried out under general anaesthesia. Arterial access was established via ultrasound guided common femoral artery puncture in all cases. Radial access was not attempted for any cases. After the establishment of arterial access, intravenous heparin was administered. The dose of heparin was titrated to achieve an activated clotting time of 1.5x to 2x the patient’s baseline. Activated clotting times were measured at regular intervals during the procedure with additional heparin boluses administered as required to maintain an optimal level of anticoagulation.

Two techniques were used to perform coiling:

1. Dual microcatheter jailing technique: A 0.017" coiling microcatheter and 0.021" microcatheter for device deployment were initially placed in the aneurysmal sac. The pCONUS 2 device was then deployed, jailing the coiling microcatheter outside the stent and passing through the crown. pCONUS 2 position was then checked using cone beam CT (Dyna-CT, Siemens) and the aneurysm was coiled.

2. Sequential microcatheter technique: A 0.021" microcatheter for device deployment was first placed in the aneurysmal sac. pCONUS 2 was then deployed and satisfactory positioning confirmed using cone beam CT (Dyna-CT, Siemens). A 0.017" coiling microcatheter was then passed through the stent portion of the device, entering the centre of the crown to achieve a favourable central location of the microcatheter tip. The aneurysm was then coiled.

Once coiling was deemed satisfactory, the device was electrolytically detached at its base via commercially available detachment devices and detachment cables. Complete separation sometimes required up to two electrical cycles lasting two minutes each to complete. Please see Figures 2 and 3 for sample images from two procedures in the case series.

Following treatment, all elective patients were placed on a post-procedure DAPT regimen. For the first 3 patients, who all received the pCONUS 2, this comprised lifelong PO aspirin 75 mg and prasugrel 5 mg or 10 mg for 5 months. The dose of prasugrel was 5 mg if bodyweight was below 75 kg and 10 mg if above 75 kg. The post-procedure DAPT regimen was adapted in line with the pre-procedure DAPT regimen for the remaining 13 patients. 10 of these patients, who were treated with the pCONUS 2, received lifelong PO aspirin 75 mg and clopidogrel 75 mg for 5 months. 3 elective patients received the pCONUS 2-HPC and had a post-procedure DAPT regimen of PO aspirin 75 mg for 12 months and PO clopidogrel 75 mg for 5 months.

The acute patients were commenced on a lifelong SAPT regimen of PO prasugrel 5 mg or 10 mg, again based on bodyweight.

Follow-up assessments

Patients had immediate periprocedural monitoring and follow-up MR angiography at 6 months and 2 years after the procedure. Images were assessed for degree of aneurysm occlusion using the Modified Raymond-Roy Classification (MRRC) ⁸ by the treating neurointerventionalist.

Study endpoints

The primary end-point of the study was 2 years post-procedure. The secondary end-point was an unacceptable rate of mortality or stroke, intraprocedural complications, or serious adverse events within the cohort within the study timeframe. Study investigators were required to report all mortalities, intraprocedural complications, and serious adverse events.

Statistical analysis

Data were analysed via an intention-to-treat approach. Discrete variables were summarised using frequency and percentage calculations; whilst continuous variables were analysed using frequency, mean, standard deviation, median, and minimum & maximum values as deemed appropriate. Statistical analysis was performed using Microsoft Excel (Microsoft, USA).

Results

16 patients with unruptured aneurysms and 4 patients with ruptured aneurysms were treated. The mean age of the cohort was 59 +-SD 7.7 years, and 15 patients were female (M:F ratio of 1:3).

The mean aneurysm width (W) and height (H) was 10.1 mm and 8.4 mm respectively. The mean aneurysm neck size (N) was 7.4 mm. The average dome-to-neck ratio (W/N) was 1.4 and the average aspect ratio (H/N) was 1.2.

In the 16 patients with unruptured aneurysms, 13 received the pCONUS 2 and 3 received the pCONUS 2-HPC. The choice of device was based on availability. 10 were located in the anterior circulation (7 at the middle cerebral artery (MCA) bifurcation, 2 at the internal cerebral artery (ICA) terminus, and one at the origin of the anterior communicating artery) and 6 were at the basilar tip.

All 4 ruptured aneurysms were treated with the pCONUS 2-HPC. Two aneurysms were located at the basilar tip – one of these was a recurrence which had previously been coiled with balloon assistance. The remaining aneurysms were located at the MCA bifurcation and within the pericallosal artery.

Peri-procedural complications

There were no peri-procedural intracranial complications. There was no mortality or strokes in the cohort. There was a post-procedural groin haematoma with extension into the retroperitoneal space in an elective patient with an anterior communicating artery aneurysm. The aneurysm had been coiled uneventfully. The patient became hypotensive five minutes post-procedure and clinical examination showed a large swelling over the access site. The patient’s 8 French Angio-Seal (Terumo, Japan) was noted to be correctly placed but oozing was observed around the puncture site, likely secondary to their pre-procedure DAPT and intra-procedural heparin dose, which had totalled 8000 units. The patient underwent surgical repair and received a blood transfusion and reversal of heparinisation with protamine. The patient made a full recovery and was neurologically intact throughout the event. A CT head performed next day did not reveal any new ischaemic change in the brain.

6-months follow-up results

16 patients have undergone 6-months follow-up via Time of Flight MRA: 15 elective cases and 1 acute case (Table 1). Satisfactory occlusion (MRRC of I or II) has been achieved in 15/16 cases (94%). The unsatisfactory outcome is in the acutely treated recurrent basilar tip aneurysm. This aneurysm had been treated with pCONUS 2-HPC and SAPT, and had deteriorated in radiological appearance from an MRRC of II to IIIb. This aneurysm has been subsequently re-coiled. Within the 15 satisfactory cases, two have deteriorated from a post-procedural MRRC of I to II at 6 months. The remainder have shown no change from their post-procedural appearances. The clinical outcome of all cases has also been satisfactory with stable modified Rankin scores for all patients. ⁹ There was no recorded clinical deterioration at 6 months follow-up (Table 2). 4 aneurysms (3 acute cases and 1 elective case) have not had 6-month follow-up due to delays caused by the COVID-19 pandemic.

Table 1.

MRA follow-up results.

Aneurysm location	Immediate post-procedural MRRC	6-M post-procedural MRRC	2-Y post-procedural MMRC	Additional information
Acute cases
Basilar tip	I	Awaiting	Awaiting	HPC used
Basilar tip	II	IIIB	Awaiting	Recurrent aneurysm HPC used Subsequently re-coiled
MCA bifurcation	I	Awaiting	Awaiting	HPC used
Pericallosal artery	IIIa	Awaiting	Awaiting	HPC used
Elective cases
ACom	I	I	I
Basilar tip	I	I	I
Basilar tip	I	I	II
Basilar tip	II	II	IIIb
Basilar tip	I	I	Awaiting
Basilar tip	I	I	Awaiting
Basilar tip	II	II	Awaiting	HPC used
ICA terminus	I	I	I
ICA terminus	I	I	Awaiting
MCA bifurcation	I	I	I
MCA bifurcation	I	I	Awaiting
MCA bifurcation	I	I	Deceased	Non-device related cause of death
MCA bifurcation	I	II	Awaiting
MCA bifurcation	I	II	Awaiting
MCA bifurcation	II	II	Awaiting	HPC used
MCA bifurcation	II	Awaiting	Awaiting	HPC used

Table 2.

Clinical outcomes at 6 months post-procedure.

	mRS pre-procedure	mRS at 6 months
19 patients	0	0
1 patient (previous subarachnoid haemorrhage from ICA terminus aneurysm)	1	1

Early 2-year follow-up results

2-year follow-up was available for 6 elective patients. 5 continue to have satisfactory occlusion, while 1 has had a recurrence of a basilar tip aneurysm. This patient was treated with the pCONUS 2 and had DAPT. They had a peri-procedural MRRC of II. This was unchanged at 6-months, but at 2 years the aneurysm had recurred and there was contrast along the aneurysm wall, corresponding to an MRRC of IIIb. The patient remains asymptomatic and due to their co-morbidities and patient preference, there is no current plan for retreatment.

There was a single delayed death. This was not a device related complication. This occurred in a patient with a 12 mm × 9 mm left MCA wide-necked aneurysm with a neck measuring 9 mm. At 17 months post-procedure they suffered an extensive left corpus striatum bleed with intraventricular extension and subarachnoid haemorrhage. At the time of death, their post-procedure anticoagulation regime consisted of daily aspirin 75 mg PO. 6-month MRA follow up of this patient had showed complete aneurysm occlusion (MRRC of 1). The pattern of bleeding was consistent with a hypertensive intracerebral haemorrhage rather than aneurysmal bleeding due to its classical location and the focus of bleeding being distant from the patient’s treated aneurysm. The patient died before angiographic imaging could be undertaken.

Discussion

Endovascular treatment options for intracranial aneurysms have expanded in recent decades since the seminal ISAT trial demonstrated endovascular coiling was a superior treatment option to traditional neurosurgical clipping in the treatment of unruptured aneurysms. ¹⁰ Despite this, wide-necked aneurysms, defined as a neck of >4 mm and a dome to neck ratio of <2, ¹¹ have consistently provided challenging to treat via coil occlusion due to a lack of coil stability. ⁶ Surgical clipping remains an attractive treatment option in this field, ¹² and various endovascular devices and techniques have also been designed and described to meet the unique needs of treatment for these aneurysms. These include flow disrupting devices, balloon-assisted coiling, stent-assisted coiling, flow diverting stents, and neck-bridging devices. ¹³

The most established of these options has been to coil under balloon assistance when possible and rely on a Y-stenting approach. Various Y-stenting techniques and stent types have been described. These include crossing and kissing stent configurations, and various combinations of open and closed-cell stents. Examples of the most commonly used stents include the open-celled Neuroform stent (Stryker Neurovascular, USA) and the closed-cell Enterprise stent (Johnson & Johnson, USA). Allowing for the heterogeneity in Y-stenting approaches, a 2019 meta-analysis found an overall treatment-related complication rate of 8.9%, with permanent morbidity of 2.4% and mortality of 1.1%. This meta-analysis found treatment with the Enterprise stent was associated with a 6.5% complication rate and treatment with the Neuroform stent was 14%. ¹⁴ New devices for Y-stenting continue to be developed, including the open-celled Accero (Acandis, Germany) and LVIS EVO (Microvention, USA) stents. Early data regarding these devices is promising though complication rates remain similar to previous devices.^15,16

Intrasaccular flow disruptor devices, such as the Woven EndoBridge device (Sequent Medical, USA) and Cerus Contour (Cerus Endovascular, USA), have established themselves as a safe alternative approach for wide-necked aneurysms in recent years, and do not necessarily require a dual antiplatelet regimen.^17,18 However, the largest WEB device is 11 x 9 mm wide and so the device is only suitable to treat aneurysms up to 10 mm unless using a specialised corking technique to coil distally to the WEB device. This is a complex procedure that is not extensively used in clinical practice. ¹⁹ In addition, the largest WEB requires a large 0.033” microcatheter, such as a VIA 33 (Sequent Medical, USA), which limits the range of aneurysms that can be treated and increases the difficulty of accessing aneurysms and heightens the risk of complications. Furthermore, it is accepted in the field that the WEB device does not work well for multilobulated complex aneurysms. It should be noted the Contour device avoids the WEB device’s sizing issues by simplifying sizing to only require consideration of neck size and widest diameter, as opposed to aneurysm morphology in addition to these dimensions. There is currently very limited data regarding the efficacy of this device and further results are awaited with interest.^18,20

Neck-bridging devices are a further group of novel devices which includes the pCONUS family and competitors such as the eCLIPs device (Evasc Medical Systems Corp, Canada) and PulseRider (Pulsar Vascular, USA). ²¹ These devices offer an alternative method of treatment for wide-necked aneurysms specifically located at vessel bifurcations by providing a scaffold for coil placement. Despite their common goal, these devices have notable variations in their design. For example, the eCLIPS device has two limbs and is anchored in a distal vessel, ²¹ whilst the Neqstent Coil Assisted Flow Diverter has no stent component at all. ²² There are also varying approaches for filling the aneurysm after deployment of the device, such as reports of neck-bridging devices being used in conjunction with intrasaccular flow diverters as opposed to coils. ²³ Further intriguing developments in the treatment of wide-necked aneurysms include the use of hybrid devices such as the Medina embolization device, which combines the morphologies of coils and intrasaccular flow disrupters into a single instrument.^24,25

Both dual microcatheter jailing and sequential microcatheter techniques were used to perform pCONUS 2 assisted coiling in this dataset. The dual microcatheter technique with a jailed coiling microcatheter provides the option of repositioning the crown of the pCONUS 2 device during coiling if the petals move to an unfavourable position. This manoeuvre is not possible in the sequential microcatheter technique after detachment of the first framing coil as the coiling microcatheter is inside the pCONUS 2 device. If repositioning of the crown of the pCONUS 2 device is necessary during the sequential technique, both the coil and coiling microcatheter have to be retracted outside the device or otherwise there is a risk of coil migration into the parent vessel and side branches, increasing the risk of stroke during the procedure. The authors are also aware some centres perform a two stage procedure: the pCONUS 2 device is deployed during an initial procedure and the aneurysm is subsequently coiled after a brief interval, ranging from a week to a month. Proponents of this technique suggest this provides time for the vessel wall and the aneurysm neck to fully adapt to the device, facilitating tighter coiling packing and so enhancing coil embolisation.

The original pCONUS has been demonstrated to have good short-term ²⁶ and medium term ²⁷ outcomes across multiple studies in various centres. ²⁸ However, data regarding the efficacy of pCONUS 2 is limited. A 12 patient case series from Argentina showed encouraging immediate angiographic results and some incomplete evidence of satisfactory post-procedural results at 6 months ²⁹ while there is a case report of pCONUS 2 being successfully deployed at an Italian neurointerventional centre, though this lacks any follow-up data. ³⁰

This study of 20 patients with 6 month and limited 2 year follow up is among the largest case series on the pCONUS 2 to date. It suggests it is a safe and efficacious device with no device-related periprocedural complications, and 6-month follow-up results showed satisfactory occlusion in 94% of the assessed aneurysms. These findings are comparable with medium term results of other neck-bridging devices: for example, De Vries et al. report acceptable MRRCs in 20 of 21 patients (95%) treated with eCLIPS ²¹ while the ANSWER trial reports 29 of 33 patients (88%) treated with PulseRadar had acceptable Raymond-Roy scores. ³¹ Further follow-up data from this pCONUS 2 cohort is awaited with keen interest to observe if long-term outcomes are also comparable.

In this study, there were no device-related complications at any timepoint. This compares favourably to the previously noted 8.9% treatment-related complication rate for Y-stenting. ¹⁴ The study size is too small to draw any conclusions from this finding, but neck-bridging devices such as the pCONUS 2 may offer a number of possible advantages: firstly, the pCONUS 2 is deployable through smaller 0.021” microcatheters such as the Prowler Select Plus (Johnson and Johnson, USA), Rebar 18 (Medtronic, USA), or VIA 21 (Sequent Medical, USA), improving access in tortuous intracranial vessels. The pCONUS 2 device is also available up to 15 mm in crown diameter, meaning aneurysms up to 14 mm neck width can be coiled with pCONUS 2 device assistance. As it is a neck-bridging device, the size of the aneurysm itself and its morphology is not significant when using the pCONUS 2 device, making treatment of large or giant multi-lobulated wide necked aneurysms possible. There is also less metal within the parent vessel compared to Y-stenting approaches and the original pCONUS device, which may reduce the risk of thromboembolic complications to below the complication rate of Y-stenting. When correctly sized, the crown of the pCONUS 2 device achieves a flat dome configuration, optimising neck coverage, with its proximal marker in the parent vessel. If the device is oversized, the crown of the device forms a champagne glass configuration at the neck, leaving neck remnants on either side, risking neck recurrence at follow-up.

Within the dataset, there was a single periprocedural complication. This was not intracranial in location and was associated with a high load of anticoagulation as opposed to any device-related factor. During the follow-up period, there has been a single non-device related death. This was an intracranial haemorrhage 17 months post- procedure and occurred at a location distant from the implanted pCONUS 2 device. It was thought to be caused by malignant hypertension as the patient was found to have a significantly raised blood pressure on presentation and the haemorrhage’s location was typical of hypertensive bleeds. It should be noted there is a possibility the patient’s antiplatelet regime contributed to their terminal event. At the time of death, the patient was on lifelong daily aspirin 75 mg PO and there is a known association between low dose aspirin and intracerebral haemorrhage, though this link was found to be non-significant in a 2019 meta-analysis of 10 trials involving 55,260 patients (relative risk of 1.23; 0.98 – 1.54 95% confidence interval). ³² As the patient presented to a district general hospital and had not been reviewed by our tertiary centre since their 6-month imaging almost a year previously, details regarding their recent health and medication compliance at time of death are minimal. Given this paucity of data, the possibility that their antiplatelet medication exacerbated their terminal event can neither be confirmed nor excluded, though the patient’s hypertension and the haemorrhage’s location suggests that the role played by aspirin, if any, was secondary to hypertension.

The pCONUS 2-HPC’s predecessor, the pCONUS-HPC, has been shown to reduce device thrombogenicity in vitro ³³ and its 30- and 180-day biocompatibility is similar to its uncoated counterpart in vivo. ³⁴ There is a comprehensive body of evidence demonstrating the antithrombogenic properties, safety, and feasibility of the hydrophilic polymer coating when applied to other devices, such as the p48 and p64 flow diverters (Phenox, Germany). These extend from in vitro models^35,36 and in vivo biocompatibility studies^37,38 to early clinical experiences which are especially exciting as they all demonstrate the viability of SAPT with devices utilising HPC.^39–41 There is limited clinical data regarding the pCONUS-HPC, though it has been successfully used in the treatment of ruptured aneurysms with SAPT. ⁶ The evidence within the literature regarding its successor is minimal – this study addresses this gap. 7 patients received the pCONUS 2-HPC in this study: 3 elective patients and 4 acute patients. The elective patients all received DAPT while the acute patients all received SAPT. None of the 7 patients experienced periprocedural complications. 3 pCONUS 2-HPC cases have undergone 6 month follow-up (1 acute, 2 elective). The acute case has had a deterioration in aneurysm appearance from an MRRC of II to IIIb but there has been no reported clinical deterioration and no other reported complications in any of the remaining patients, and these findings, particularly in relation to the 4 acute patients who received SAPT, are encouraging. While the small sample size and limited medium-term nature of the data means no conclusions can be made, the combination of a proven low thrombogenicity device ² and SAPT would be an attractive option for reducing bleeding risk compared to DAPT, and these early findings indicate SAPT is a feasible treatment option in combination with pCONUS 2-HPC. This is an exciting area of interventional neuroradiology, as evidenced by a recent international DELPHI consensus study which concluded that while a DAPT approach was currently favoured due to familiarity, there was an appetite for more and better data on differing antiplatelet approaches, including SAPT. ⁴²

It should be noted that the limited 2-year data available at time of publication shows aneurysm recurrence in 1 of the 6 patients assessed. Further data regarding the performance of the remainder of the patients within the case series is required before any conclusions can be made. This study has significant limitations. It is a single-armed study with a small sample size, limiting the scope and power of the conclusions that can be drawn from the findings. In addition, analysis was conducted by the treating interventionalist and the possibility of bias must therefore be acknowledged.

Conclusion

The pCONUS-2 and the pCONUS-2-HPC have excellent safety profiles and clinical outcomes periprocedurally, at 6-months, and at 2-years follow-up. There was no procedure-related mortality or morbidity in this cohort with good occlusion rates at 6 months follow-up. The use of the pCONUS 2-HPC with single antiplatelet therapy is feasible and did not cause any complications.