Clinical safety and efficacy of stent-assisted coil embolization with ACCERO stent in cerebral aneurysm: Short-term follow-up and precaution for use

Young Ha Kim; Chang Hyeun Kim; Sang Weon Lee; Chi Hyung Lee; Su Hun Lee; Jun Seok Lee; Soon Ki Sung; Dong Wuk Son

doi:10.7461/jcen.2025.E2025.02.002

J Cerebrovasc Endovasc Neurosurg > Epub ahead of print

Kim, Kim, Lee, Lee, Lee, Lee, Sung, and Son: Clinical safety and efficacy of stent-assisted coil embolization with ACCERO stent in cerebral aneurysm: Short-term follow-up and precaution for use

Clinical Article

Journal of Cerebrovascular and Endovascular Neurosurgery 2025;jcen.2025.E2025.02.002.

Published online: February 24, 2025

DOI: https://doi.org/10.7461/jcen.2025.E2025.02.002

Clinical safety and efficacy of stent-assisted coil embolization with ACCERO stent in cerebral aneurysm: Short-term follow-up and precaution for use

Young Ha Kim^1,^2,³, Chang Hyeun Kim^1,^2,³

, Sang Weon Lee^1,^2,³, Chi Hyung Lee^1,^2,³, Su Hun Lee^1,^2,³, Jun Seok Lee^1,^2,³, Soon Ki Sung^1,^2,³, Dong Wuk Son^1,^2,³

¹Department of Neurosurgery, Pusan National University Yangsan Hospital, Yangsna, Korea

²Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea

³Department of Neurosurgery, School of Medicine, Pusan National University, Yangsan, Korea

Correspondence to Chang Hyeun Kim Department of Neurosurgery, Pusan National University Yangsan Hospital 20 Geumo-Ro, Mulgeum-eup, Yangsan-si, Gyeongsangnam-do 50612, Korea Tel +82-55-360-2126 Fax +82-55-360-2156 E-mail mole83@daum.net

Received February 2, 2025 Revised February 12, 2025 Accepted February 17, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective

Stent-assisted coil embolization (SAC) is an effective method of treating intracranial aneurysms. The aim of the study was to assess the safety and efficacy of the new ACCERO stent for the treatment of cerebral aneurysms.

Methods

It was a retrospective, single-center study. Nine ruptured and 41 unruptured cerebral aneurysms were treated using the ACCERO stent between February 2021 and December 2023. Patient demographics, aneurysm characteristics, procedural parameters, grade of occlusion, complications, and clinical outcomes were analyzed. Follow-up was conducted with magnetic resonance angiography (MRA) or Digital subtraction angiography (DSA) was performed 6 to 12 months after the procedure.

Results

The ACCERO stent deployment was attempted in 51 cases, with replacement by the Neuroform Atlas stent in 1 case. Successful stent deployment was achieved in 50 cases, and appropriate wall apposition to the parent artery. The average clinical follow-up period was 17.1 months. Intimal hyperplasia was observed in 1 case, but no other clinical complications related to the stent occurred. Favorable clinical outcomes were observed in 92% of patients (46/50), including those with subarachnoid hemorrhage. Immediate favorable angiographic outcomes and complete occlusion were achieved in 90% (45/50) and 74% (37/50) of cases, respectively. Among the 45 patients who had imaging follow-up, favorable angiographic outcomes and complete occlusion were observed in 93.3% (43/45) and 82.2% (37/45) of cases, respectively.

Conclusions

The ACCERO stent is a braided-type stent that requires more attention than stents, such as the Neuroform Atlas or Enterprise stents. However, since the struts of the stent are fully visible, it can be more useful in treating challenging aneurysms once the user becomes familiar with its use.

Keywords: ACCERO stent, Stent-assisted coil embolization, Intracranial aneurysm

INTRODUCTION

In the treatment of cerebral aneurysm, stent-assisted coil embolization (SAC) is a commonly used method for treating complex or wide neck aneurysms [1,8]. As the detection and treatment of cerebral aneurysms increase, endovascular treatment is becoming more common, and thus SAC is also being performed more frequently. Although new devices such as flow diverters and flow disruptors have been introduced and used recently, stents are still an important device in the treatment of cerebral aneurysms [29].

SAC was first introduced by Higashide et al. in the 1990s [12], and has since been continuously used for endovascular treatment. Implantation of a stent offers several advantages, such as preventing coil protrusion into the parent vessel and the ability to increase the coil packing density, ultimately aiming to enhance the safety of the procedure and improve the long-term stability of coil occlusion in cerebral aneurysms [5,24]. With the innovative development of technology, a low-profile stent is being developed. The Neuroform Atlas (Stryker Neurovascular, Fremont, California, USA) stent and LVIS Jr. (MicroVention-TERUMO, Tustin, California, USA) stent are deliverable through micro-catheters with an internal diameter of 0.0165-0.017 inches. In particular, the Neuroform Atlas stent demonstrates excellent wall apposition stent performance with a mixed cell configuration of close-cell type and open-cell type. However, Neuroform Atlas stent, made of nitinol, is not easily visualized on fluoroscopic angiography equipment, so the full extent of conventional intracranial stent cannot be seen in real-time during deployment [16].

The ACCERO stent (Acandis GmbH, Pforzheim, Germany) is a self-expandable, low-profile, braided stent [23]. The device is characterized by complete contour visibility due to drawn-filled tubes (DFTs) consisting of an inner platinum wire and an outer nitinol wire. The ACCERO stent is a new stent, specifically designed for SAC, which has recently been introduced to the market. The aim of this study was to investigate the peri-procedural feasibility and safety of this new device for the treatment of intracranial aneurysms.

MATERIALS AND METHODS

Patient population

We retrospectively analyzed electronic medical records (EMR) and picture archiving and communication system (PACS) data from 50 patients with intracranial aneurysms treated at our institution using the ACCERO stent (Acandis GnbH, Pforzheim, Germany) between January 2021 and December 2023. Patients with both unruptured and ruptured aneurysms were included.

Additionally, data on technical aspects of the procedure (i,e., jailing, semi-jailing or trans-strut technique), angiographic outcomes (Raymond-Roy occlusion classification, RROC) and periprocedural complications (i,e., cerebral infarction, procedure-related hemorrhage, etc.), including information related to aneurysms (location, size, prior treatment, and dome-neck ratio), were collected. Clinical and radiological follow-up data were also included. In-stent stenosis was defined as a 10% or greater narrowing of the vessel after the procedure. Angiographic results were independently adjudicated by two neurovascular specialists.

Operator and procedural information

The operator first used the ACCERO stent three years after independently performing the procedure. During these three years, the operator completed approximately 450 endovascular surgeries. Prior to using the ACCERO stent, the operator had used the Neuroform Atlas stent, Enterprise (Codmann Neurovascular, Miami Lakes, FL, USA) and LVIS stent in about 250 cases of stent-assisted coil embolization.

Patients with unruptured aneurysms were pre-medicated with dual antiplatelet therapy (acetylsalicylic acid 100 mg daily and clopidogrel 75 mg daily) for at least 7 days. P2Y12 reaction units were analyzed using the Verify Now Assay prior to the procedure. If the P2Y12 reaction value was 240 or higher, the patient was considered non-responder to clopidogrel. For these patients, clopidogrel was either switched to or supplemented with cilostazol after the procedure to prevent thromboembolic events. During the procedure, 3,000 IU of heparin was administered (depending on the patient’s body weight, 50 IU/kg). If the procedure lasted more than 1 hour, an additional 1,000 IU of heparin was given every hour.

In patients with ruptured aneurysms who presented to the hospital due to subarachnoid hemorrhage, if stent deployment was expected, acetylsalicylic acid 300 mg and clopidogrel 300 mg were loaded. In cases where stent deployment was not expected but performed, glycoprotein IIb/IIIa inhibitor tirofiban (Aggrastat, Merck & Co, Kenilworth, NJ, USA) was administered intravenously. All such patients received maintenance infusions of tirofiban (0.1 µg/kg/min intravenously for 24 hours) [28]. Heparin was administered according to body weight after coil embolization of the rupture point of the aneurysm (50 IU/kg).

All procedures were performed under general anesthesia and via femoral artery access with systemic heparinization. The flush system contained 5,000 IU of heparin per liter.

Clinical and angiographic outcomes

Clinical outcomes were assessed by the physician using the modified Rankin Scale (mRS). According to the mRS, a favorable outcome was defined as a score of 0-2, and an unfavorable outcome was defined as a score of 3-6. Patients with ruptured aneurysms were assessed using the mRS at discharge and during follow-up at the outpatient department.

Angiographic outcomes were evaluated 6 months to 1 year after the procedure using digital subtraction angiography (DSA) or contrast-enhanced MRA. The outcomes were assessed by two experienced neuro-radiologists, each of whom independently performed neuro-interventions. Occlusion of the aneurysm was assessed based on the guidelines of the Raymond-Roy Occlusion Classification (RROC): class I (complete obliteration), class II (residual neck), and class III (residual sac). Recanalization was defined as minor recanalization when class I changed to class II, and major recanalization when class I or II changed to class III.

Clinical safety and efficacy

Regarding safety, the primary endpoint was defined as the rate of patients with favorable clinical outcomes (mRS ≤2). Regarding efficacy, the angiographic outcome was the proportion of patients with RROC class I and II in the most recent follow-up records. Secondary endpoints included procedure- or device-related complications and unexpected additional procedures. Procedure-related complications included aneurysm rupture during the procedure, thromboembolic events, and dissection. Device-related problems included “hook-in” issues and inadequate wall apposition.

RESULTS

Characteristics of patients and aneurysms

SAC using the ACCERO stent was performed on 51 cerebral aneurysms in 50 patients between July 2021 and February 2024. In one patient, the ACCERO stent was not properly deployed on the parent artery wall during deployment, so it was re-sheathed and replaced with a Neuroform Atlas stent. Therefore, ACCERO stent was used in 50 aneurysms. Nine cases were ruptured cerebral aneurysms, and 41 cases were unruptured cerebral aneurysms. In one case, a ruptured dissecting aneurysm of the ICA where the tiny aneurysm could not be selected was treated by adding two ACCERO stents. Table 1 presents the baseline patient characteristics. The mean patient age was 58.060±11.42 years (range, 37-85), and 39 patients (78%) were female.

Except for two dissecting aneurysms, 48 were saccular aneurysms: thirty-three (66%) were located in the ICA, eleven (22%) were in the ACA, two (4%) were in the MCA and four (8%) were in the posterior circulation. Forty were sidewall aneurysms, and 10 were bifurcation aneurysms. The mean aneurysm size was 4.79 mm (range, 1-20). The mean dome-neck ratio was 1.5.

Clinical and angiographic outcomes

Of the 50 cases in which stent deployment was successful, 18 were performed using the jailing technique and 32 were performed using the semi-jailing technique. No cases of stent migration or inadequate wall apposition were observed. Among 41 unruptured cases, one case experienced a rupture during the procedure. Some coils leaked out of the aneurysm sac while filling, but enough coils were packed, allowing the procedure to be completed without any particular problems. The patient also did not experience any particular problems. There were no cases of thromboembolic events during the treatment of unruptured cerebral aneurysms. In 41 unruptured cases, the mRS was 0 before the procedure and remained 0. The immediate complete occlusion rate (RROC class I) was achieved in 32 cases (78%), RROC class II in 6 cases (14.6%) and RROC class III in 3 cases (7.3%).

In 9 cases or ruptured cases, the Hunt-Hess Grade (H-H grade) was I in 1 patient, II in 4, III in 1, and IV in 3. Of these, all three grade IV patients died. Thrombus occurred within the ACCERO stent during the procedure in 1 case (Fig. 1). Tirofiban was used to dissolve the thrombus, but cerebral infarction occurred in the ipsilateral ACA territory. The patient recovered to the extent of being able to self-care, but neurologic deficits remained. The remaining 5 patients recovered without any significant problems. The immediate complete occlusion rate (RROC 1 class I) was achieved in 5 cases (55.5%), RROC class II in 2 cases (22.2%), and RROC class III in 2 cases (22.2%).

Clinical and angiographic follow-up after procedure

Clinically, 46 patients were available for follow-up, and the average follow-up period was 17.1 months. Except for one case of cerebral infarction, all 45 patients had an mRS score of 0 and were available for outpatient follow-up. One patient refused imaging follow-up, and the first imaging follow-up was performed 6 to 12 months after the procedure in the remaining 45 patients. On average, imaging was performed at 7.6 months, and 2 cases required retreatment, which involved additional coils. The results of the angiographic outcomes are presented in Table 2.

Intimal hyperplasia was confirmed in one case on imaging at 6 months. Although improvement in the stenotic lesion was observed during additional imaging follow-up, complete recovery was not achieved (Fig. 2). This patient was maintained on a mono antiplatelet agent to prevent delayed thromboembolic event. Except for this case, dual antiplatelet agents were used for 6 months, and all antiplatelet agents were discontinued after 1 year. There were no cases of thromboembolic events after discontinuation of antiplatelet agents.

DISCUSSION

Recently, neuro-endovascular therapy has become established as the first-line treatment for most cerebral aneurysms, replacing surgical clipping [22,27]. In particular, the introduction of specially designed self-expandable stents for intracranial use has significantly expanded the spectrum of endovascular therapy in cerebral aneurysms. Although no randomized clinical trial has been carried out yet, many case series and meta-analyses indicate that SAC provides more durable results than simple coiling [13,14]. Since the Neuroform stent was reported in 2002 [11], various stents have been developed and introduced. Open cell type stents have the advantage of good wall apposition to the parent artery, but have the disadvantage of coil loops protruding and migration [3]. Additionally, it must be noted that re-sheathing is not possible. On the other hand, close-cell type stents with laser cuts have the disadvantage of ovalizing or kinking at tight curves [18]. Braided-type stents, which were developed later than nitinol stents, have shown good clinical results with high metal coverage and improved flexibility [10,20]. However, in some sections of the stent, incomplete expansion may occur in tortuous parent vessels, so caution is required, and the operator’s attention and high level of technical expertise are essential to achieve good wall apposition [7,19].

To our knowledge, this study reports the largest number of cases among studies on the ACCERO stent. We would like to focus on the advantages and disadvantages of the ACCERO stent as experienced at our institution. Compared to existing braided-type stent, the ACCERO stent is particularly attractive due to its full fluoroscopic visibility and mid-marker. Since the entire stent body is visible, it is possible to confirm whether the aneurysm neck is properly covered during coil packing. There were no cases of coil prolapse into the parent artery in our cases. The mid-marker is also very helpful in predicting the total length of the stent within the parent artery. This marker provided a useful reference point during deployment, ensuring optimal stent placement. The ACCERO stent demonstrates strong opening ability due to its improved radial force compared to the previous braided-type stent due to DFT technology [9]. In our results, there were no cases in which distal opening was a problem. Additionally, since the cells that make up the ACCERO stent are much smaller than those of the Neuroform Atlas stent, there is no need to worry about treating small aneurysms. In our experience, the ACCERO stent was able to be used without concern in the treatment of a tiny ruptured aneurysm (Fig. 3).

However, despite these advantages, the ACCERO stent has some weaknesses. The ACCERO stent is equipped with a transport wire (TW) that enables re-sheathing and holds the stent in the microcatheter. If interference (hook-in) occurs due to misalignment of the proximal end of the stent and the TW, the entire stent may be dragged down or deformed, requiring the operator’s attention. A well-organized paper on problems related to hook-in should be reviewed by the operator before the procedure [17]. Compared to the previous braided-type stent, the ACCERO stent has the advantage of easier stent opening and improved radial force, which enhances wall apposition. However, this can cause the parent artery to straighten its curve, making the roadmap prepared during the procedure unreliable, therefore, caution is required (Fig. 4).

Since the ACCERO stent is a braided-type stent, the cell size is variable. This allows the trans-strut technique to be used, but it may be difficult to re-select the stent in areas, with a tortuous parent artery. In areas where the parent artery is severely curved, the semi-jail technique is safer. Sufficient filling of the aneurysm sac, followed by removal of coil microcatheter, and then deploying the stent, improves the wall apposition. There was one case in which the stent and the coil microcatheter competed within the parent artery, disrupting the wall apposition and neck coverage of the stent, leading to the retrieval of the stent (Fig. 5).

In our study, no case of stent-related thromboembolic event or neurological problem occurred during the follow-up period. Clinical safety was demonstrated in unruptured patients. Favorable clinical outcomes were observed in 92% of patients (46/50), including patients with subarachnoid hemorrhage. This result is satisfactory compared to other reports on the clinical safety of Neuroform Atlas [16,25]. In our study, immediate favorable angiographic outcomes and complete occlusion were observed in 90% (45/50) and 74% (37/50) of cases, respectively. In the imaging follow-up performed 6 months later, favorable angiographic results were observed in 93.3% (43/45) and complete occlusion was observed in 82.2% (37/45). Our results are quite satisfactory when compared with the Neuroform Atlas stent, which reported favorable angiographic outcomes of 69.2% to 84% [2,15,16,26].

A braided-type stent comparable to the ACCERO stent is the LVIS EVO stent. This stent was also introduced to the market relatively recently and is being used more actively. According to the results of treating 118 aneurysms with the LVIS EVO, the complete occlusion rate for 86 aneurysms that were available for imaging follow-up was reported to be 79.1% at 6 months and 82.2% at 12 to 18 months [21]. These results are similar to those of our study. The ACCERO and EVO stents are compatible with smaller microcatheter (0.017 inches). Both stents are made of drawn-filled tube (DFT) wires, which consist of a nitinol outer material and a platinum core. However, the metal coverage of the ACCERO stent is 15~20%, while that of the LVIS EVO stent is slightly higher at 17~28% [6]. High metal coverage may have the effect of flow diversion, but it may also induce thrombosis within the stent or parent vessel [21].

No coil prolapse was observed in our study. This may be explained by higher density of the stent struts and smaller cell and better retention of coils. Therefore, braided ACCERO stents may reduce complications associated with SAC. In our study, intimal hyperplasia occurred in one case, while another report on the ACCERO stent showed mild intimal hyperplasia in 20% (6/30), but no specific treatment was needed [4]. Intimal hyperplasia can lead to delayed thromboembolic complications after SAC, so caution is required.

This study has limitations as it is a single-center retrospective design study. Another limitation is the small number of patients included. Additionally, our study did not perform statistical analysis to compare the safety and efficacy of the ACCERO stent with other stents. However, this study is considered valuable, as it examines the safety and efficacy of the less commonly used ACCERO stent.

CONCLUSIONS

SAC using the ACCERO stent, a new braided-type stent, is clinically safe and effective. The entire stent is visible during the procedure, and the middle marker facilitates stent deployment. The higher density of the struts is particularly effective in treating very small aneurysms. However, the operator requires a higher level of skill and attention when using this stent. When the advantages and disadvantages of ACCERO stent are well understood, it serves as a valuable alternative for treating cerebral aneurysms.

ACKNOWLEDGEMENTS

This work was supported by a 2-year Research Grant of Pusan National University.

NOTES

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Fig. 1.

(A) A 55-year-old female patient, with subarachnoid hemorrhage observed on brain CT. (B) Embolization using the ACCERO stent was performed for ruptured ACoA aneurysm, and thrombus was observed in the proximal part of the stent (red arrow). (C) Intra-arterial tirofiban was used several times. (D) Ipsilateral ACA blood flow was significantly reduced due to thrombus. CT, computed tomography; AcoA, anterior communicating artery; ACA, anterior cerebral artery

Fig. 2.

(A) Embolization was performed using the ACCERO stent for an ophthalmic artery aneurysm. (B) MRA performed 6 months later showed a decrease in blood flow in the ipsilateral internal carotid artery. (C) Intimal hyperplasia within the ACCERO stent was observed using DSA. (D) MRA performed one year later confirmed the recovery of blood flow in the ipsilateral internal carotid artery. MRA, magnetic resonance angiography; DSA, digital subtraction angiography

Fig. 3.

(A) A very tiny ruptured anterior choroidal aneurysm was identified. (B, C) The ACCERO stent is a braided-type stent with a high strut density, which allowed for the safe treatment of very small coils. The coil used was a Target Helical 1×1 coil.”

Fig. 4.

(A) Treatment using the ACCERO stent was planned for the superior hypophyseal artery aneurysm. (B) When the ACCERO stent was deployed, the curvature of the parent artery straightened, causing a mismatch with the prepared road map. (C, D) The overall shape of the stent is clearly visible, with good wall apposition, and the aneurysm appears to be well occluded.

Fig. 5.

(A) Treatment using the ACCERO stent was planned for the paraclinoid aneurysm. (B) The ACCERO stent and the coil microcatheter competed within the parent artery, disrupting the wall apposition and neck coverage of the stent. (C) It was successfully treated by replacing the Neuroform Atlas with the ACCERO stent.

Table 1.

Baseline characteristics of patients treated with ACCERO stent

Characteristic	Total	Unruptured	Ruptured
No. of cases	50	41	9
Mean age ± SD, yrs	58.06 ± 11.42	59.07 ± 10.67	53.44 ± 13.42
Females, n (%)	39 (78%)	32 (78.0%)	7 (77.8%)
HTN, n (%)	17 (34%)	14 (34.1%)	3 (33.3%)
DM, n (%)	5 (10%)	4 (9.8%)	1 (11.1%)
Dyslipidemia, n (%)	20 (40%)	18 (43.9%)	2 (22.2%)
Coronary disease, n (%)	5 (10%)	5 (12.2%)	0
Stroke, n (%)	4 (8%)	4 (9.8%)	0
Alcohol, n (%)	4 (8%)	2	2 (22.2%)
Smoking, n (%)	4 (8%)	4 (9.8%)	0
Aneurysm type, total, n	50	41	9
Saccular	48	41	7
Fusiform	2		2
Aneurysm location, n (%)
ICA	33 (66%)	29 (70.7%)	4 (44.4%)
ACA	11 (22%)	8 (19.5%)	3 (33.3%)
MCA	2 (4%)	2 (4.9%)	0
Posterior circulation	4 (8%)	2 (4.9%)	2 (22.2%)
Aneurysm configuration
Side wall aneurysm, n (%)	40 (80%)	33 (80.5%)	7 (77.8%)
Bifurcation aneurysm, n (%)	10 (20%)	8 (19.5%)	2 (22.2%)
Atherosclerosis, n (%)	6 (12%)	5 (12.2%)	1 (11.1%)
Procedure, n			9
Single stent	49	41	8
Double stenting	1		1
Aneurysm size (mm)±SD	4.79 (1~20) ± 3.14	4.39 (1.5~10.6) ± 1.73	6.96 (1~20) ± 6.55
Dome/Neck ratio	1.5	1.44	1.86

SD, standard deviation; n, number; HTN, hypertension; DM, diabetes mellitus; ICA, internal carotid artery; ACA, anterior cerebral artery; MCA, middle cerebral artery

Table 2.

Initial and follow-up angiographic outcomes

		Follow-up result			FU loss
		Class I	Class II	Class III	FU loss
Initial result	Class I: 37	29	4		4
	Class II: 8	5	2		1
	Class III: 5	3		2
Total	50	37	6	2	5

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