Pipeline embolization device versus Neuroform Atlas stent in the treatment of distal anterior circulation aneurysms: a retrospective cohort study

Introduction

Distal anterior circulation aneurysms (DACAs) are a common type of intracranial aneurysm located at the terminal segment of the internal carotid artery (ICA). They typically include aneurysms of the middle cerebral artery (MCA), anterior cerebral artery (ACA), anterior communicating artery (ACoA), and posterior communicating artery (PCoA) (1,2). The endovascular treatment of DACAs can be challenging due to the technical difficulties of distal navigation, and the small size, delicate structure, and tortuosity of the arteries, as well as the frequent involvement of bifurcation branches and perforators (3,4). Recent studies report that a flow diverter (FD) can be used to treat DACAs, such as the pipeline embolization device (PED) (Covidien Neurovascular, Medtronic Inc, Dublin, Ireland). As an important tool in the management of aneurysms, the PED provides scaffolding for endoluminal vascular reconstruction, and diverts blood flow in the parent artery, thereby promoting aneurysm thrombosis, and eliminating the need to use microcatheters or microwires to enter the fragile aneurysm sac (2,5). However, the PED was initially designed with a larger and stiffer delivery system, and a narrow range of available device diameters to treat large and giant aneurysms located on the petrous and superior hypophyseal segments of the ICA. The high metal density coverage of PED also increases the potential risk of occlusion of the covered artery. Therefore, treating the smaller, more distal, and tortuous vascular segments of DACAs as safely and effectively as those of proximal ICA aneurysms remains a challenge.

Conventional stent-assisted coiling (SAC) is another well-established endovascular approach for the treatment of intracranial aneurysms, and some small-sized stents have emerged, offering improved navigability and conformability in the treatment of DACAs. The Neuroform Atlas Stent System (Stryker Neurovascular, Kalamazoo, MI, USA) is a new-generation conventional mini-stent with a self-expanding hybrid cell design and a smaller delivery system (via a 0.0165-inch inner diameter microcatheter), which has enhanced stent conformability, coil support, deliverability, and deployment accuracy. However, direct comparisons between SAC and FDs for the treatment of DACAs are lacking. Meanwhile, the hospital costs associated with different devices are gaining increasing attention.

This study presented the combined experience of two neurosurgical centers in the treatment of 114 consecutive DACAs. It aimed to evaluate the effectiveness of two currently popular treatment options (PED and Atlas SAC) for DACAs, placing more focus on clinical and angiographic outcomes, as well as hospital costs. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2946/rc).

Methods

Study design and patient enrollment

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Medical Ethics Committee of Beijing Tiantan Hospital (Approval No. KY 2018-098-02), and informed consent was provided by all participants. All participating hospitals/institutions were informed of and agreed to the study.

This study consecutively enrolled 2,743 patients with unruptured intracranial aneurysms treated with either the PED or Atlas SAC at two neurosurgical centers (Beijing Tiantan Hospital and Peking University International Hospital) from January 2018 to December 2022. Patients were included in the study if they met the following inclusion criteria: (I) were aged 18–80 years; (II) had an unruptured aneurysm; (III) had an aneurysm located at or beyond the MCA, ACA, ACoA, or PCoA as confirmed by digital subtraction angiography (DSA); and (IV) had received a PED or Atlas SAC to treat the target aneurysm. Patients were excluded from the study if they met any of the following exclusion criteria: (I) had a fusiform or dissecting aneurysm; (II) had an arteriovenous malformation, moyamoya disease, or fistula; (III) had undergone a single stent implantation procedure to treat more than one aneurysm; and/or (IV) had not undergone follow-up angiography.

Ultimately, a total of 112 patients with 114 unruptured DACAs were included in this study. The patients were divided into two groups (the Atlas group and the PED group) based on their device type and were subsequently compared.

Antiplatelet therapy and procedure details

All the patients received dual antiplatelet therapy (aspirin 100 mg daily and clopidogrel 75 mg daily) for at least 5 days before the procedure (6). All the patients received the platelet functional test (via turbidimetric light transmittance aggregometry). If the maximal platelet aggregation response exceeded 50% to adenosine diphosphate and 20% to arachidonic acid, the patients received a modified dual antiplatelet therapy regimen consisting of aspirin (100 mg daily) and ticagrelor (90 mg twice daily) (6). After the procedure, the same dual antiplatelet therapy was continued for 6 months, after which it was switched to aspirin monotherapy. Aspirin was prescribed for 1 year to patients who received the Atlas SAC and for life in those who received the PED.

For the endovascular procedure, all the patients in the cohort were placed under general anesthesia and received systemic heparinization during the procedure. Each target aneurysm was accessed using a standard transfemoral arterial approach. The treatment strategy, including PED implantation or Atlas SAC, was determined by the interventional physician. Three-dimensional DSA was performed in every interventional surgery to identify the optimal working projection. For aneurysms treated by Atlas SAC, the stent length was chosen according to the aneurysm neck size to cover the distal and proximal limits of the neck by at least 3 mm. The stents were delivered via SL-10 microcatheters (Stryker Neurovascular, Fremont, USA), and adjunctive coiling was commonly performed to achieve dense coil packing for the target aneurysms. Two Atlas stents were used if bifurcation aneurysms involve multiple branches, and Y-configuration stents were used to ensure branching artery patency (7). For aneurysms treated using the PED, the device was delivered through a Marksman or Phenom-27 microcatheter (Medtronic, Minneapolis, Minnesota, USA). Adjunctive coiling was considered if the following was observed: (I) an unstable aneurysm prone to rupture (i.e., an irregular shape or daughter blebs); or (II) a persistent jet sign at the aneurysmal neck on immediate postoperative DSA, indicating a high risk of postoperative hemorrhage. Meanwhile, if a single PED did not fully cover the aneurysm neck, two or more PEDs were deployed in a bridging configuration (8).

Data collection

The following data were collected: (I) demographic data, including age, sex, alcohol drinking, smoking habit, and comorbidities such as hypertension, diabetes, dyslipidemia and intracranial atherosclerotic stenosis (ICAS), and symptomatic aneurysms; (II) aneurysm data, including the maximum diameter, neck size, parent artery diameter, and the presence of an incorporated branch (i.e., a notable artery arising from the aneurysm wall) (9); (III) procedural details, including the device type, adjuvant coiling, stent adjustment (assisted by balloon or stent re-sheathing). and procedure duration time; (IV) total in-hospital costs; and (V) angiographic and clinical outcomes at discharge and follow-up. In this cohort, multiple treated aneurysms were considered separate cases if each hospitalization involved only one procedure targeting a single aneurysm. As for the follow-up strategy, we conventionally scheduled clinical and angiographic follow-up at 6, 12, and 24 months for patients after discharge. It was recommended that all patients attend at least one of these time points, and DSA was considered the optimum imaging examination for the first follow-up. For patients with completely occluded aneurysms confirmed by a DSA, annual magnetic resonance angiography (MRA) or computed tomography angiography (CTA) follow-up was recommended.

The angiographic outcomes included aneurysm occlusion status, recanalization, and the patency of parent and branch arteries, which were assessed both postoperatively and at follow-up. In the PED group, aneurysm occlusion was evaluated using the O’Kelly-Marotta grading scale, with grade D indicating complete occlusion, and grades A, B, and C indicating incomplete occlusion (10). In the Atlas SAC group, aneurysm occlusion was evaluated using the modified Raymond-Roy classification, where class I indicated complete occlusion, and classes II and III indicated incomplete occlusion. Aneurysm recanalization was defined as a worsening of the O’Kelly-Marotta or modified Raymond-Roy classification grade on follow-up angiography. Artery stenosis was defined as a ≥50% obstruction of the maximum vessel caliber.

Patients who developed neurological deficits after the procedure underwent computed tomography (CT) or magnetic resonance imaging examination to determine the underlying cause. The clinical outcomes were stratified into the perioperative period or follow-up period, and recorded separately as follows: (I) neurological complications, including any procedure-related hemorrhage, infarction, severe neurological deficits, or death; (II) ischemic complications, including treatment-related cerebral ischemic events, such as postoperative transient ischemic attacks, cerebral infarctions, and in-stent thrombosis; and (III) hemorrhagic complications, including delayed rupture of target aneurysms and distal intraparenchymal hemorrhage after the procedure. Neurological functional status was assessed using the modified Rankin scale (mRS). A favorable outcome was defined as an mRS score of 0–2, while an unfavorable outcome was defined as an mRS score of 3–6. Both the angiographic and clinical results were independently determined by two neuro-interventionalists.

Statistical analysis

The statistical analyses were conducted using SPSS software (version 26.0, IBM SPSS Statistics for Windows, IBM Corp., Armonk, NY). The continuous variables are expressed as the mean ± standard deviation (SD), or the median with the interquartile range (IQR), while the categorical variables are presented as the number with the percentage. The unpaired t-test and Mann-Whitney U test were used to assess differences in the continuous variables, and the chi-square test or Fisher’s exact test were applied to analyze the categorical variables. A multivariable logistic regression model was employed to evaluate risk factors for incompletely occluded aneurysms, with odds ratios (ORs) and 95% confidence intervals (CIs) reported. The variables included in the model comprised clinically relevant factors and those with a P value <0.1 in the univariate analysis. P values <0.05 were considered statistically significant.

Results

Baseline characteristics

A total of 112 patients with 114 aneurysms were included in the study. Of the aneurysms, 51 were treated with a PED and 63 were treated with an Atlas SAC. The mean age of the patients was 55.8±12.1 years, and 70 (61.4%) were female. Of the patients, 21 (18.4%) had a history of smoking, and 8 (7.0%) had a history of alcohol abuse. In terms of comorbidities, 10 (8.8%) patients had hypertension, 14 (12.3%) had diabetes, 16 (14.0%) had dyslipidemia, and 6 (5.3%) had ICAS. Among the 64 symptomatic patients, 40 (35.1%) presented with dizziness or headache, and 24 exhibited cranial nerve dysfunction. Three (2.6%) patients presented with an mRS score of >2 at admission. In terms of aneurysm location, 42 (36.8%) were located in the ACoA, 30 (26.3%) in the MCA, 24 (21.1%) in the ACA, and 18 (15.8%) in the PCoA. The mean maximum aneurysm diameter was 5.9±2.3 mm, and the mean neck size was 4.5±1.9 mm. The baseline characteristics of the patients in the PED and Altas groups are shown in Table 1.

Procedure details

Compared with the PED group, the Atlas group had a lower stent adjustment rate [0% (0/63) vs. 7.8% (4/51), P=0.037]. In the PED group, 20 (39.2%) patients received adjunctive coiling, while in the Atlas group, all patients received adjunctive coiling (P<0.001). Four (6.3%) patients in the Atlas group were treated with Y-stent technology, while no patients in the PED group were treated with multiple devices (P=0.127). The immediate aneurysm occlusion rate was higher in the Atlas group than the PED group [88.9% (56/63) vs. 25.3% (12/51), P<0.001]. The procedure time was shorter in the PED group than the Atlas group (132.2±32.3 vs. 147.6±45.5 minutes, P=0.047) (Table 2).

Outcomes and total cost

During the postoperative hospitalization, 6 (11.7%) patients in the PED group and 5 (7.9%) patients in the Atlas group experienced complications; however, there was no statistically significant difference between the two groups in terms of the postoperative complications (P=0.537). Specifically, 2 (3.9%) patients in the PED group and 1 (1.6%) patient in the Atlas group suffered from hemorrhages; while 4 (7.8%) patients in the PED group and 4 (6.3%) patients in the Atlas group suffered from ischemic events. At discharge, there was no statistically significant difference between the two groups in terms of the unfavorable neurological functional outcomes (Atlas 3.2% vs. PED 7.8%, P=0.491).

At the last follow-up, the two groups had similar rates of complete aneurysm occlusion (Atlas 85.7% vs. PED 84.9%, P=0.69). The PED group had a longer angiographic follow-up time than the Atlas group [8.0 (6.0–12.0) vs. 12.0 (8.0–14.0) months, P=0.03]. Although the aneurysm recanalization rate was numerically higher in the Atlas group (4.8% vs. 0%), this difference did not reach statistical significance (P=0.252). Similarly, the incidences of in-stent stenosis (13.7% vs. 4.8%, P=0.108) and branch artery occlusion (5.9% vs. 1.6%, P=0.323) were numerically higher in the PED group, but this difference did not reach statistical significance. Representative cases of Atlas SAC illustrating the procedure and effectiveness assessment are shown in Figure 1.

Figure 1 Surgical and follow-up angiography of an MCA aneurysm treated with Atlas SAC. (A,B) Preoperative DSA images in the anterior and lateral positions showed an aneurysm (as indicated by the white arrows) on the MCA. (C,D) Atlas stent (as indicated by the white arrows) and adjunctive coils immediately after the procedure on DSA in the anterior and lateral positions. (E,F) Complete aneurysm occlusion was evident at 8 months after the procedure on DSA in the anterior and lateral positions (as indicated by the white arrows). DSA, digital subtraction angiography; MCA, middle cerebral artery; SAC, stent-assisted coiling.

During the follow-up period, 4 (7.8%) patients in the PED group and 3 (4.8%) patients in the Atlas group developed new complications (P=0.198). In the PED group, 3 (5.9%) patients suffered from ischemic events and 1 (1.6%) patient suffered from a hemorrhage. In the Atlas group, all 3 (4.8%) suffered from ischemic events. At the last follow-up, the proportion of patients with favorable neurological outcomes was similar between the two groups (96.8% vs. 96.1%, P>0.99). Representative cases of the PED illustrating the procedure and effectiveness assessment are shown in Figure 2.

Figure 2 Surgical and follow-up angiography of an ACA aneurysm treated with PED. (A) Preoperative three-dimensional DSA revealed an aneurysm (as indicated by the white arrow) on the ACA. (B,C) Preoperative DSA images in the anterior and lateral views (as indicated by the white arrows). (D) DSA images of the deployed PED (as indicated by the white arrows) and adjunctive coils immediately after the procedure. (E,F) DSA images of the anterior and lateral views revealed complete aneurysm occlusion 12 months post-procedure (as indicated by the white arrows). ACA, anterior cerebral artery; DSA, digital subtraction angiography; PED, pipeline embolization device.

The hospitalization costs were significantly lower in the Atlas group than the PED group ($27,950.8±6,795.5 vs. $37,436.5±6,208.6, P<0.001).

Predictive factors for incomplete aneurysm occlusion

In the univariate logistic regression, hypertension (P=0.016) and the presence of an incorporated branch (P<0.001) were found to be associated with incomplete aneurysm occlusion. In the final multivariable logistic regression model, the presence of an incorporated branch (OR =10.263, 95% CI: 2.516–41.854, P=0.001) was an independent risk factor for incomplete aneurysm occlusion (Table 3).

The complete occlusion rate for aneurysms with incorporated branches was 68.4% (26/38), which was significantly lower than that for aneurysms without incorporated branches (94.7%, P<0.001). In the subgroup analysis of 38 of 114 (33.3%) aneurysms with an incorporated branch, 24 were treated by Atlas SAC and 14 were treated by PED. For these aneurysms, there was no statistically significant difference in the complete occlusion outcomes between the Atlas and PED groups (66.67% vs. 71.43%, P=1.00). The 4 aneurysms treated with Y-configuration Atlas stents were all occluded at follow-up.

Discussion

DACAs are common sites of intracranial aneurysms, and the debate continues as to the most effective treatment approach for DACAs. The off-label use of FDs, such as PEDs, has shown acceptable outcomes, making PEDs a feasible choice at these locations (8,11). Traditional SAC is also a first-line treatment for DACAs. Additionally, with the availability of new-generation stents, such as the Atlas, the safety and effectiveness of SAC have improved (7,12). Previous studies have examined the use of different endovascular therapies for DACAs; however, only a few studies have compared the PED and Atlas. Further, to date, reports on the hospitalization costs of DACAs are limited. In our two-center retrospective cohort, we found that both the PED and SAC were safe and effective in the treatment of DACAs. However, the two devices had different advantages; for example, the Atlas had cost-saving advantages, while the PED had a reduced procedure time. Notably, the presence of an incorporated branch is an independent factor associated with persistent unoccluded aneurysms for DACAs.

Technical success was achieved in all the Atlas stents in this cohort. Similarly, in a single-center cohort of 36 patients with 29 DACAs, Ulfert et al. reported a technical success rate of 100% (7). In a cohort of 182 patients from 25 centers with wide-neck anterior circulation aneurysms, of which 56.5% were DACAs, Zaidat et al. reported procedural success in all patients (13). Jankowitz et al. conducted the Atlas Investigational Device Exemption (IDE) clinical trial in which 30 patients from eight centers achieved 100% technical success (14). Like previous reports, we found that the Atlas stent was efficacious in the treatment of DACAs. Notably, Y-SAC with Atlas was applied in four bifurcation aneurysms that were all occluded at follow-up. Thus, the Y-stent technique is efficacious and effective in the treatment of DACAs with an incorporated branch. In a study of 30 bifurcation aneurysms treated by Y-SAC with Atlas, Aydin et al. reported that 93.3% of aneurysms achieved complete occlusion (15).

The stent adjustment rate of the PED was 7.8%, which was significantly higher than that of the Atlas (0%). This discrepancy was largely due to the device design characteristics: the Neuroform Atlas stent cannot be re-sheathed or repositioned once deployed. Additionally, the Atlas stent was deployed through SL-10 microcatheters, which have a lower inner diameter (0.0165–0.0170 inches) and are more suitable for the small and tortuous parent artery of DACAs (14). These features minimize the need for adjunctive maneuvers such as balloon angioplasty or stent repositioning. Conversely, the Marksman or Phenom-27 microcatheter, which has an inner diameter of 0.027 inches, may sometimes have navigability and conformability difficulties in tortuous and narrow parent arteries. As reported in previous studies, stent adjustment during PED procedures is not uncommon. In post-market multicenter retrospective research on the embolization of intracranial aneurysms with PEDs in China (PLUS), 68 of 1,322 devices were deployed after adjustment (16). Our results showed that the ideal deployment for PED was more challenging than that for Atlas; however, Atlas had advantages in deliverability and deployment accuracy at the DACA sites. Further, the procedure time of Atlas was longer than that of PED (132.2±32.3 vs. 147.6±45.5 minutes, P=0.047), as it appears that the dense-packing of coiling during Atlas SAC takes more time (7).

In our series, PED treatment follow-up was longer than Atlas treatment follow-up [12.0 (6.0–14.0) vs. 8.0 (6.0–12.0) months, P=0.03]. There could be a number of reasons for this finding. First, the majority of aneurysms treated by Atlas SAC were occluded at the first follow-up, reducing the patients’ willingness to attend longer-term follow-ups. Second, aneurysm occlusion led by PED is a gradual process (10). Thus, prudently, it was recommended that patients in the PED group attend more follow-ups after the procedure. Third, patients who have confirmed complete aneurysm occlusion after a DSA follow-up (which occurred more frequently and quickly in the Atlas group) could undergo follow-up head CTA and MRA scans at our institution or other medical imaging centers, but no imaging follow-up data for the latter were available at our institution.

At the last follow-up, although the difference was not statistically significant, PED had a slightly better occlusion rate than Atlas (88.2% vs. 85.7%, P=0.69). Several studies have examined the off-label use of PEDs in DACAs, and shown their effectiveness in occluding aneurysms. Primiani et al. conducted a 6-month multiple-center study, and reported an occlusion rate of 83% for 65 DACAs treated by PED (4). Michelozzi et al. examined flow diversion for aneurysms beyond the circle of Willis, and reported a complete occlusion rate of 82.1% (17). Saleme et al. examined 32 patients with 37 DACAs treated by PEDs with and without adjunctive coiling, and reported that at the 18-month follow-up, the aneurysm occlusion rate was 97.3% (18). Thus, all the above-mentioned studies showed that when properly planned, the PED is safe and effective in the treatment of DACAs. Similarly, several published studies have shown that Atlas is safe and effective in the treatment of DACAs. For example, Zaidat et al. reported that the occlusion rate of DACAs treated by Atlas was 84.7% (13). While Lefevre et al. reported an adequate occlusion rate of 98.9% for all types of intracranial aneurysms at 1-year follow-up (12). Our findings on the use of Atlas for site-specific DACAs are consistent with those of previous studies. Further, our results show that Atlas and the off-label use of PEDs are both safe and effective in the treatment of DACAs.

The total complication rate of the Atlas group was slightly lower than that of the PED group (12.7% vs. 19.6%, P=0.31), and a favorable neurological functional outcome was slightly higher in the Atlas group than the PED group (favorable outcome, 93.7% vs. 88.2%, P=0.49), but the difference was not statistically significant. As described above in our series, it may be that Atlas requires less stent adjustment than PED. As reported, stent adjustment may be a negative predictor of clinical outcomes (16). Once again, we emphasize the deployment advantages of Atlas for the treatment of DACAs at special sites. Further, the relatively lower metal surface coverage of the Atlas compared to that of the PED may also contribute to a reduced risk of ischemic events. In the PED group, the neurological functional outcome rate accorded with that of previous studies. For example, Gawlitza et al. examined flow diversion treatment in 18 MCA aneurysms, and reported symptomatic ischemic events in 3 patients (17.6%), all of which were resolved within 24 hours (19). In Atallah et al.’s study of 437 patients, 23 DACAs were treated by PED, and 22 (95.7%) had good clinical outcomes (mRS ≤2) (5). Primiani et al. reported that of 60 patients with aneurysms located on A2, M2, P2, and beyond, 57 (95.0%) had good clinical outcomes at the 3-month follow-up (4). Cagnazzo et al. reported that of 17 patients with DACAs treated by flow diversion, 16 (94.1%) had good clinical outcomes at the last follow-up (mean duration: 14 months) (20).

The favorable neurological functional outcome rate in the Atlas group also reflected that reported in previous studies. In IDE research, 25 patients, 13 of whom had DACAs, had mRS scores of 0 or 1 (14). In Hanel et al.’s study of 35 MCA aneurysms treated by Atlas, 27 patients had mRS scores ≤2 (27/32, 84.4%) at the 1-year follow-up (21) (the data of three patients were missing). Notably, while not statistically significant, the PED group in the present study exhibited a trend toward higher rates of in-stent stenosis (13.7% vs. 4.8%) and branch artery occlusion (5.9% vs. 1.6%) at the last follow-up. These findings may have implications for long-term arterial patency, and highlight the need for further research.

According to the multivariate analysis, the independent predictor of persistent unoccluded aneurysms was the presence of an incorporated branch (OR =10.26, 95% CI: 2.516–41.854, P=0.001). Thus, it was more difficult to achieve complete occlusion in the DACAs with incorporated branches than in the DACAs without incorporated branches (68.4% vs. 94.7%, P<0.001). This result reflects previous findings. De Leacy et al. reported a series of 72 bifurcation aneurysms on MCA treated by coiling. Among those, 71.7% had Raymond-Roy class I occlusion at 1 year, and no significant difference was found between the unassisted, stent-assisted, and balloon-assisted methods (22). Michelozzi et al. reported 28 complex bifurcation aneurysms beyond the Willis circle treated by flow diversion. In their series, 22 (78.6%) aneurysms were completely occluded, 5 (17.9%) were stable, and 1 (3.6%) recurred (17). Chiu et al. examined 119 aneurysms treated by PEDS, and reported that an incorporated vessel was a significant factor for no occlusion at the 6-month and 1-year follow-up time points. Chiu et al. speculated that an incorporated branch may decrease the slow, turbulent flow achieved in flow diversion, reducing the efficacy of clot formation in the cavity (9). This explanation may also apply to Atlas SAC, and may explain why there were statistically significant differences between the PED and Atlas DACA patients with incorporated branches (Atlas vs. PED, 16/24 66.6% vs. 10/14 71.4%, P=1.00). However, DACAs with incorporated branches are challenging to treat. The Y-stent technique is recommended when it is feasible (in our series, the 4 cases treated with Y-stent-assisted coiling with Atlas were all occluded). Alternatively, other endovascular approaches such as the Woven EndoBridge may be appropriate for bifurcation aneurysms.

Our results showed that the cost of the PED was significantly higher than that of the Atlas. Recent studies have reported on the cost advantages of Atlas (23), and we found no change in the trend of cost effectiveness in the treatment of DACAs. Subsequent costs included the costs of imaging follow-up, antiplatelet drugs, and rehabilitation for patients with unfavorable functional outcomes. The costs of DSA, CTA, and MRA at our center are $1,100 (range: $900–1,300), $200, and $150, respectively. The costs of drugs are cheap and fixed (< $100/month). Due to its lower immediate occlusion rate (25.3% vs. 88.9% for Atlas, P<0.001) and the gradual occlusion mechanism, patients who received the PED treatment had a longer follow-up period than those who received the Atlas treatment. Thus, theoretically, the patients in the PED group may have higher costs for imaging follow-up and antiplatelet drugs. Based on the equivalent unfavorable functional outcomes at discharge, the few patients with disabilities had roughly similar rehabilitation costs. Thus, overall, Atlas had an economic advantage in the treatment of DACAs located at special sites.

Limitations

This study had several limitations. First, this was a non-randomized retrospective observational series; thus, unmeasured confounding factors might have affected the final results. Second, the cost analysis of this study only included the costs of the initial hospitalization, imaging follow-up, and antiplatelet drugs; however, the rehabilitation costs for patients with unfavorable functional outcomes were not recorded in detail. Third, due to the low incidence of incomplete occlusion events, effective subgroup analyses within each treatment group (e.g., identifying predictors of incomplete occlusion separately in the PED and Atlas groups) could not be performed, which might limit the provision of treatment-specific guidance. Finally, prospective research with a large number of random samples and long-term follow-up is still required to verify our conclusions.

Conclusions

The new-generation SAC and PED are safe and effective in the treatment of DACAs. There were no statistically significant differences in the clinical and radiological outcomes between the two groups. The Atlas stents showed an advantage in deliverability and deployment accuracy; however, the procedure duration of SAC was significantly longer than that of the PED. The economic cost of the PED was significantly higher than that of the SAC. The multivariate analysis showed that the presence of an incorporated branch was an independent factor for incomplete DACA occlusion. Thus, proper planning that considers all factors is required to balance the treatment outcomes, procedure duration, and cost effectiveness.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2946/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2946/dss

Funding: This study was supported by grants from the Beijing Municipal Public Welfare Development and Reform Pilot Project for Medical Research Institutes (grant No. JYY2023-5), China Postdoctoral Science Foundation (grant No. 2024M75178), and Postdoctoral Fellowship Program of CPSF (grant No. GZC20241099).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2024-2946/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Medical Ethics Committee of Beijing Tiantan Hospital (approval No. KY 2018-098-02) and informed consent was provided by all participants. All participating hospitals/institutions were informed and agreed the study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Hanel RA, Cortez GM, Jankowitz BT, Sauvageau E, Aghaebrahim A, Lin E, Jadhav AP, Gross B, Khaldi A, Gupta R, Frei D, Loy D, Price LL, Hetts SW, Zaidat OO. ATLAS Investigators. Anterior circulation location-specific results for stent-assisted coiling - carotid versus distal aneurysms: 1-year outcomes from the Neuroform Atlas Stent Pivotal Trial. J Neurointerv Surg 2024;16:1125-30. [Crossref] [PubMed]
2. Luo B, Kang H, Zhang H, Li T, Liu J, Song D, Zhao Y, Guan S, Maimaitili A, Wang Y, Feng W, Wang Y, Wan J, Mao G, Shi H, Yang X. Pipeline Embolization device for intracranial aneurysms in a large Chinese cohort: factors related to aneurysm occlusion. Ther Adv Neurol Disord 2020;13:1756286420967828. [Crossref] [PubMed]
3. Ma C, Zhu H, Liang S, Liang F, Sun J, Zhang Y, Jiang C. Comparison of Pipeline Embolization Device and Traditional Endovascular Therapeutic Approaches in Distal Cerebral Circulation Aneurysms Using Propensity Score Matching Analysis. Front Neurol 2022;13:755122. [Crossref] [PubMed]
4. Primiani CT, Ren Z, Kan P, Hanel R, Pereira VM, Lui WM, et al. A2, M2, P2 aneurysms and beyond: results of treatment with pipeline embolization device in 65 patients. J Neurointerv Surg 2019;11:903-7. [Crossref] [PubMed]
5. Atallah E, Saad H, Mouchtouris N, Bekelis K, Walker J, Chalouhi N, Tjoumakaris S, Smith M, Rosenwasser RH, Zarzour H, Herial N, Feghali J, Gooch MR, Missios S, Sweid A, Jabbour P. Pipeline for Distal Cerebral Circulation Aneurysms. Neurosurgery 2019;85:E477-84. [Crossref] [PubMed]
6. Li W, Zhu W, Wang A, Zhang G, Zhang Y, Wang K, Zhang Y, Wang C, Zhang L, Zhao H, Wang P, Chen K, Liu J, Yang X. Effect of Adjusted Antiplatelet Therapy on Preventing Ischemic Events After Stenting for Intracranial Aneurysms. Stroke 2021;52:3815-25. [Crossref] [PubMed]
7. Ulfert C, Pham M, Sonnberger M, Amaya F, Trenkler J, Bendszus M, Möhlenbruch MA. The Neuroform Atlas stent to assist coil embolization of intracranial aneurysms: a multicentre experience. J Neurointerv Surg 2018;10:1192-6. [Crossref] [PubMed]
8. Martínez-Galdámez M, Romance A, Vega P, Vega A, Caniego JL, Paul L, Linfante I, Dabus G. Pipeline endovascular device for the treatment of intracranial aneurysms at the level of the circle of Willis and beyond: multicenter experience. J Neurointerv Surg 2015;7:816-23. [Crossref] [PubMed]
9. Chiu AH, Cheung AK, Wenderoth JD, De Villiers L, Rice H, Phatouros CC, Singh TP, Phillips TJ, McAuliffe W. Long-Term Follow-Up Results following Elective Treatment of Unruptured Intracranial Aneurysms with the Pipeline Embolization Device. AJNR Am J Neuroradiol 2015;36:1728-34. [Crossref] [PubMed]
10. O'kelly CJ, Krings T, Fiorella D, Marotta TR. A novel grading scale for the angiographic assessment of intracranial aneurysms treated using flow diverting stents. Interv Neuroradiol 2010;16:133-7. [Crossref] [PubMed]
11. Cagnazzo F, Perrini P, Dargazanli C, Lefevre PH, Gascou G, Morganti R, di Carlo D, Derraz I, Riquelme C, Bonafe A, Costalat V. Treatment of Unruptured Distal Anterior Circulation Aneurysms with Flow-Diverter Stents: A Meta-Analysis. AJNR Am J Neuroradiol 2019;40:687-93. [Crossref] [PubMed]
12. Lefevre PH, Schramm P, Kemmling A, Barreau X, Marnat G, Piotin M, Berlis A, Wanke I, Bonafe A, Houdart E. ATLAS EU PMCF Investigators. Multi-centric European post-market follow-up study of the Neuroform Atlas Stent System: primary results. J Neurointerv Surg 2022;14:694-8. [Crossref] [PubMed]
13. Zaidat OO, Hanel RA, Sauvageau EA, Aghaebrahim A, Lin E, Jadhav AP, Jovin TG, Khaldi A, Gupta RG, Johnson A, Frei D, Loy D, Malek A, Toth G, Siddiqui A, Reavey-Cantwell J, Thomas A, Hetts SW, Jankowitz BT. ATLAS Investigators. Pivotal Trial of the Neuroform Atlas Stent for Treatment of Anterior Circulation Aneurysms: One-Year Outcomes. Stroke 2020;51:2087-94. [Crossref] [PubMed]
14. Jankowitz BT, Hanel R, Jadhav AP, Loy DN, Frei D, Siddiqui AH, Puri AS, Khaldi A, Turk AS, Malek AM, Sauvageau E, Hetts SW, Zaidat OO. Neuroform Atlas Stent System for the treatment of intracranial aneurysm: primary results of the Atlas Humanitarian Device Exemption cohort. J Neurointerv Surg 2019;11:801-6. [Crossref] [PubMed]
15. Aydin K, Balci S, Sencer S, Barburoglu M, Umutlu MR, Arat A. Y-Stent-Assisted Coiling With Low-Profile Neuroform Atlas Stents for Endovascular Treatment of Wide-Necked Complex Intracranial Bifurcation Aneurysms. Neurosurgery 2020;87:744-53. [Crossref] [PubMed]
16. Kang H, Zhou Y, Luo B, Lv N, Zhang H, Li T, Song D, Zhao Y, Guan S, Maimaitili A, Wang Y, Feng W, Wang Y, Wan J, Mao G, Shi H, Yang X, Liu J. Pipeline Embolization Device for Intracranial Aneurysms in a Large Chinese Cohort: Complication Risk Factor Analysis. Neurotherapeutics 2021;18:1198-206. [Crossref] [PubMed]
17. Michelozzi C, Darcourt J, Guenego A, Januel AC, Tall P, Gawlitza M, Bonneville F, Cognard C. Flow diversion treatment of complex bifurcation aneurysms beyond the circle of Willis: complications, aneurysm sac occlusion, reabsorption, recurrence, and jailed branch modification at follow-up. J Neurosurg 2019;131:1751-62. [Crossref] [PubMed]
18. Saleme S, Iosif C, Ponomarjova S, Mendes G, Camilleri Y, Caire F, Boncoeur MP, Mounayer C. Flow-diverting stents for intracranial bifurcation aneurysm treatment. Neurosurgery 2014;75:623-31; quiz 631. [Crossref] [PubMed]
19. Gawlitza M, Januel AC, Tall P, Bonneville F, Cognard C. Flow diversion treatment of complex bifurcation aneurysms beyond the circle of Willis: a single-center series with special emphasis on covered cortical branches and perforating arteries. J Neurointerv Surg 2016;8:481-7. [Crossref] [PubMed]
20. Cagnazzo F, Cappucci M, Dargazanli C, Lefevre PH, Gascou G, Riquelme C, Bonafe A, Costalat V. Treatment of Distal Anterior Cerebral Artery Aneurysms with Flow-Diverter Stents: A Single-Center Experience. AJNR Am J Neuroradiol 2018;39:1100-6. [Crossref] [PubMed]
21. Hanel RA, Yoon N, Sauvageau E, Aghaebrahim A, Lin E, Jadhav AP, Jovin TG, Khaldi A, Gupta RG, Johnson A, Frei D, Loy D, Malek A, Toth G, Siddiqui A, Reavey-Cantwell J, Thomas A, Hetts SW, Jankowitz BT, Zaidat OO. Neuroform Atlas Stent for Treatment of Middle Cerebral Artery Aneurysms: 1-Year Outcomes From Neuroform Atlas Stent Pivotal Trial. Neurosurgery 2021;89:102-8. [Crossref] [PubMed]
22. De Leacy R, Bageac DV, Siddiqui N, Bellon RJ, Park MS, Schirmer CM, Woodward KB, Zaidat OO, Spiotta AM. Safety and Long-Term Efficacy Outcomes for Endovascular Treatment of Wide-Neck Bifurcation Aneurysms of the Middle Cerebral Artery: Insights From the SMART Registry. Front Neurol 2022;13:830296. [Crossref] [PubMed]
23. Wang C, Dong L, Liu J, Zhang Y, Wang K, Liu P, Yang X, Lv M, Zhang Y. Pipeline embolization device versus Atlas stent assisted coiling for intracranial aneurysm treatment: a retrospective, propensity score matched study with a focus on midterm outcomes and hospital costs. J Neurointerv Surg 2024;16:379-84. [Crossref] [PubMed]