Intra-cranial aneurysm treatment with contour or WEB – a single center comparison of intervention times and learning curves

Abstract

Background and purpose

Treating aneurysms with intra-saccular flow disruption is a feasible alternative to coil-embolization. Besides the established WEB device, the novel Contour Neurovascular System has emerged as a potentially easier alternative regarding sizing and deployment. We report the learning curve experienced at our center from the first 48 patients treated with Contour and compared it with 48 consecutive WEB cases.

Methods

Both groups were compared concerning intervention time, sizing failures leading to device changes and radiation dose. Additionally, we analyzed potential learning effects by comparing the first 24 Contour cases with our last 24 Contour cases and WEB cases respectively.

Results

Patient demographics, acute vs. incidental cases and aneurysm localization were comparable in both groups. The deployment time was faster in our 48 Contour cases (median: 22.0 ± 17.0 min), than in the WEB group (median: 27.5 ± 24.0 min). Total intervention time was similar for Contour (median: 68.0 ± 46.9 min) and WEB cases (median: 69.0 ± 38.0 min). Device implantation times in our WEB cases were slightly shorter in the later cases (median: 25.5 ± 24.1 min) than in the earlier (median: 28.0 ± 24.4 min) cases. In the Contour cohort, deployment times were similar for the first 24 cases (median: 22.0 ± 14.5 min) and the final 24 (median: 22.0 ± 19.4 min). Radiation dose was lower in the Contour group (1469.0 ± 1718 mGy*cm² vs. 1788.0 ± 1506 mGy*cm² using the WEB device). Less intra-procedural device changes were performed in the Contour cohort (6 of 48 cases, 12.5%), than in the WEB group (8 of 48 cases, 16.7%).

Conclusion

Aneurysm occlusion times and consequently radiation doses, as well as the amount of device changes were lower in the Contour group. Occlusion times did not differ in the first and last 24 Contour cases, leading to the assumption that the handling of Contour does not require extended training. A short training effect in occlusion times was noted, however, between the first and last WEB cases as shorter procedure times were seen in the latter cases.

Background and purpose

Treating aneurysms with intra-saccular flow disruption is an established method and is proven to be an appropriate alternative to coil-embolization and flow-diverting stents with good results concerning safety of use and aneurysm occlusion rates.^1,2 Possible advantages of intra-saccular devices over coil-embolization and flow-diverting stents could be the ability to treat wide-necked aneurysms without the assistance of a balloon or stent and potentially removing the requirement for dual antiplatelet therapy as well as avoiding affection of the parent vessel. Besides the established WEB-device (Woven EndoBridge, Microvention, Aliso Viejo, California, USA), the novel Contour Neurovascular System (Cerus Endovascular, Fremont, CA, USA) has emerged as an alternative, being potentially easier to size and deploy. ³ Moreover, aneurysm treatment through WEB or Contour is potentially less elaborated and faster than coiling because of the single-implant aspect of both devices. There is already profound data available for WEB, as a safe device with good occlusion rates.^4,5 The Contour device has been made available as an alternative to WEB for several years since 2020. It is designed for the embolization of wide-necked aneurysms and promotes flow disruption within the aneurysm. ⁶ When the Contour is deployed, it adapts to the aneurysm wall and provides flow diversion by forming a new vessel bifurcation due to its’ convex shape within the parent artery as well as intrasaccular flow disruption. After deployment, flow arrest in the aneurysm dome enables thrombus formation. ⁷ Since only the neck is treated, the aneurysmal sac morphology and height do not play an important role in the choice of the correct Contour size. Since the WEB device is available in various sizes and two different shapes, this is possibly an advantage of the Contour as the device may be easier to size, since there are only five available dimensions which cover the vast majority of aneurysm sizes (Table 1).

Table 1.

CONTOUR sizing chart.

Product Code	Microcatheter	Diameter (mm)	Aneurysm Neck (mm)	Aneurysm Width (mm)
CNS21005-15	0.021″	5.0	2.0–3.0	2.0–3.5
CNS21007-15	0.021″	7.0	3.0–5.0	3.0–5.5
CNS21009-15	0.021″	9.0	4.0–6.0	5.0–7.5
CNS011-15	0.027″	11.0	5.0–8.0	7.0–8.5
CNS014-15	0.027″	14.0	7.0–10.0	8.0–10.5

In this study, we retrospectively compared early and later Contour cases from our department with a matched group of early and later WEB cases concerning procedure time and radiation doses.

Methods

Data collection

We included all cases performed up to the time of this study where a Contour was used as a single implant without additional devices. We reviewed our earliest and more recently performed WEB cases and selected interventions with similar criteria, matched for localization and presence of a rupture. Patient demographics and aneurysm characteristics are listed in Table 2.

Table 2.

Demographic data.

Characteristics of 48 patients treated with CONTOUR
Age, mean (range)	58 ± 12.5 years (31–88 years)
Sex Radiation dose Mean intervention time	36 female (75%), 12 male (25%) 1469.0 ± 1718 mGy*cm2 68.0 ± 46.9 min
Clinical setting	33 incidental findings (69%), 15 acute bleedings (31%)
	Anterior circulation (n = 39)	Posterior circulation (n = 9)
Incidental (n = 33)	28/39 (72%)	5/9 (56%)
Acute SAH (n = 15)	11/39 (28%)	4/9 (44%)
Characteristics of 48 patients treated with WEB
Age, mean (range)	63.5 ± 10.7 years (32–82 years)
Sex Radiation dose Mean intervention time	32 female (66%), 16 male (34%) 1788.0 ± 1506 mGy*cm2 69.0 ± 38.0 min
Clinical setting	33 incidental findings (69%), 15 acute bleedings (31%)
	Anterior circulation (n = 39)	Posterior circulation (n = 9)
Incidental (n = 33)	28/39 (72%)	5/9 (56%)
Acute SAH (n = 15)	11/39 (28%)	4/9 (44%)

Primary endpoints

As endpoints we defined the total intervention time, the deployment time, sizing failures leading to device changes and radiation dose. Additionally, we analyzed potential learning effects within our two cohorts. The time between the first and the last image of an intervention, including angiography of other vessels and treatments of further pathologies, were defined as the total intervention time. The deployment time was defined as the time between the DSA run of the working projection and the first DSA after the detachment of the device.

Learning curves were analyzed by comparing the deployment times of the first 24 and the last 24 cases in both groups respectively. Information about radiation dose was collected for the complete intervention only.

Statistical analysis

Statistical analysis was performed with Microsoft Excel 2021 and Jamovi (Version 1.6), (The jamovi project (2021)). Intervention times were compared using student’s t-test.

Endovascular treatment

Aneurysm occlusion in both acute and elective settings was performed under general anaesthesia via trans-femoral arterial access in a bi-planar angio-suite (Allura Xper FD20/10, Philipps). Triaxial access was employed both for WEB and Contour cases. A long sheath was regularly placed in the corresponding vessel at the skull base (ICA or vertebral artery) and an intermediate catheter was positioned intracranially, through which the 3D angiography is carried out. Device sizing was based on a cone beam CT-scan with multiplanar reconstruction, following the official recommendations of the manufacturer. Additionally, the 3D imaging allows the definition of the working projections. Based on the roadmap of the working projection with the maximum magnification, the microcatheter was introduced and positioned inside the aneurysm under fluoroscopy. Subsequently, the device was inserted through a micro-catheter. Prior to detachment, device position and its effect on the parent vessel were evaluated through a control angiogram. The detachment was then accomplished under direct fluoroscopic visualization. Another DSA with large magnification aiming at the aneurysm allows the evaluation of a possible parent vessel compromise and the stasis within the aneurysm. Finally, a DSA run of the complete vascular territory ruled out complications such as embolism or perfusion delay due to stenosis.

Results

Patient demographics, acute vs. incidental cases, and aneurysm location were comparable in both groups. Total intervention time for Contour averaged out at median: 68.0 ± 46.9 min and for WEB 69.0 ± 38.0 min. Radiation dose was lower in the Contour group (1469.0 ± 1718 mGy*cm² vs. 1788.0 ± 1506 mGy*cm² using WEB). The deployment time was shorter in the 48 CONTOUR cases (median: 22.0 ± 17.0 min), than in the WEB group (median: 27.5 ± 24.0 min, p: 0.312) (see Table 3). In our WEB group we observed a small training effect regarding deployment times, which were slightly faster in the latter cases (median: 25.5 ± 24.1 min) than in the first 24 (median: 28.0 ± 24.4 min, p: 0.758) (see Table 4). We didn’t observe a time reduction between initial (median: 22.0 ± 14.5 min) and final 24 (median: 22.0 ± 19.4 min, p: 0.557) cases in the Contour cohort. In the Contour group, at least one intra-procedural device change was performed in 6 of 48 cases (12,5%), in the WEB group at least one change of device was necessary in 8 of 48 cases (16,7%).

Table 3.

Deployment times (min), 48 cases.

Table 4.

Learning curves, CONTOUR, and WEB.

Table 5.

WEB SL sizing chart.

Smallest Aneurysm Height (mm)
9.5–10.4											SL 11 × 9
8.5–9.4										SL 10 × 8	SL 11 × 8
7.5–8.4									SL 9 × 7	SL 10 × 7	SL 11 × 7
6.5–7.4								SL 8 × 6	SL 9 × 6	SL 10 × 6	SL 11 × 6
5.5–6.4							SL 7 × 5	SL 8 × 5	SL 9 × 5	SL 10 × 5
4.5–5.4						SL 6 × 4	SL 7 × 4	SL 8 × 4	SL 9 × 4
3.5–4.4			SL 4 × 3	SL 4.5 × 3	SL 5 × 3	SL 6 × 3	SL 7 × 3	SL 8 × 3
2.5–3.4	SL 3 × 2	SL 3.5 × 2	SL 4 × 2	SL 4.5 × 2	SL 5 × 2
	2.0–2.6	2.7–3.1	3.2–3.6	3.7–4.1	4.2–4.6	4.7–5.5	5.6–6.5	6.6–7.4	7.5–8.3	8.4–9.2	9.3–10.0
Average Aneurysm Width (mm)
Delivery Catheter	Via 17					Via 17& Via 21		Via 27		Via 33

Discussion

In this retrospective and single-center analysis, we compared procedure times and learning effects of intra-cranial aneurysms treated with the novel Contour device and the more established WEB device. Despite the fact of having less experience with the Contour device, procedures were carried out slightly faster and consecutively required less radiation. We found no significant learning effect between our early and later Contour procedures regards intervention times, whereas a small effect was detected for the WEB group.

Table 6.

WEB SLS sizing chart.

Smallest Aneurysm Height (mm)
10.6								SLS 11
9.6							SLS 10
8.6						SLS 9
7.6					SLS 8
6.6				SLS 7
5.6			SLS 6
4.6		SLS 5
3.6	SLS 4
	3–3.7	3.8–4.6	4.7–5.5	5.6–6.5	6.6–7.4	7.5–8.3	8.4–9.2	9.3–10.0
Average Aneurysm Width (mm)
Delivery Catheter	Via 17		Via 17 & Via 21		Via 27		Via 33

The Contour Neurovascular System is a promising device for intra-saccular flow disruption in wide-necked intra-cranial aneurysms. A major difference to the established WEB-device is the fact that aneurysmal dome height and morphology do not play a crucial role in selection of the right device size since Contour aims at the aneurysm neck only. Preliminary reports have already supported the safety and efficacy of the Contour.^3,8

The WEB device is an established tool for the intra-saccular treatment of wide-necked bifurcation aneurysms by causing neck flow disruption. Different from intra-luminal devices such as flow-diverting stents, no permanent anti-platelet therapy is necessary after implantation. The WEB is placed inside the aneurysm sac and promotes thrombus formation within the aneurysm. For a satisfactory sizing, not only the aneurysmal width but also its height must be taken into account. Therefore, 37 different sizes are available to cover aneurysm sizes up to approximately 10.6 in diameter (Microvention) (Table 5, Table 6) . The peri-procedural safety of the WEB device has been previously described. ⁹ Moreover, the 1-year results of the CLARYS study document no re-bleeding in 60 patients treated with WEB in acutely ruptured aneurysms. ¹⁰

In this study, we explored the intervention times in both acute and elective settings for Contour device implantation and compared them with a similar WEB cohort. A similar analysis analyzing treatment times was performed by Forbrig et al. by comparing aneurysm treatments through WEB, coil embolization and flow-diverting stents. In conclusion, fluoroscopy time was fastest for WEB, followed by flow-diverting stents and coil embolization. Combined techniques were associated with the longest fluoroscopy times. ¹¹

We also compared procedure times of WEB and Contour cases. To avoid confounding such as angiography of additional vessels or treatment of other pathologies in the same session, we defined the deployment time as explained above. We summarized time effects of micro-catheter navigation and device implantation only. Overall, the Contour procedures were faster. As a possible explanation, we assume that the treatment of the neck only is potentially faster than a treatment of the whole aneurysm sac. Secondary modulation or repositioning of the device as well as device changes due to incorrect sizing is less likely to be necessary. Correspondingly, device sizes had to be changed in 6 of 48 cases of the Contour group versus 8 of 48 cases in the WEB group.

We evaluated the learning effect as a difference in median deployment times between the early and the latter half of cases in each group. No learning effect was found in the Contour group. A possible explanation is that the implantation of a Contour device is generally straightforward and can be achieved adequately with only moderate experience. On the other hand, we assume, that the learning effect we found in our WEB group can be related to the fact, that the implantation process requires greater experience. A possible bias for this finding is that our use of the WEB device over several years has helped to train us using intrasaccular flow disruptors in general.

An advantage of our study design is the good comparability between the groups, because all procedures were performed in the same center, by the same interventionists, with a standardized catheter-setup and on the same machines.

Limitations

This single-center retrospective study has several limitations, such as the limited number of cases. In such a small group, the total intervention time is susceptible to confounding factors such as additional angiography of other vascular territories and the treatment of other pathologies in the same session. Moreover, it must be noted that the interventionists already have many years of experience with the implantation of WEB devices. This contributed to our hands-on experience and to standardize aneurysm occlusion procedures before using Contour as an alternative to intra-saccular flow disruption.

Conclusion

The implantation of the Contour device seems to be easy to learn, is slightly faster compared with the WEB device and is consecutively associated with less radiation exposure. For future studies, a prospective collection of a larger number of cases derived from multiple centers and long-term follow-up data should be relevant to assess this novel modality in the treatment of wide-necked aneurysms. We are aware that our findings do not have any impact on the efficacy and durability of the treatment methods. Nonetheless, we assume that shorter intervention times correlate with less procedural complications and that the simplicity of these techniques, indicated by the learning curves, is especially interesting for interventionists with a more modest experience or a smaller caseload.