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Abstract
Background An intermediate catheter (IMC) can improve the maneuverability and stability of the microcatheter.
Objective To investigate the efficacy and safety of using an IMC in triaxial systems for coil embolization of unruptured cerebral aneurysms (UCAs).
Methods A total of 2430 consecutive saccular UCAs (2259 patients) that underwent initial coil embolization at three institutions between November 2003 and May 2023 were retrospectively reviewed. Patients were classified into two groups: with IMC (IMC(+)) and without IMC (IMC(−)). To investigate whether IMC use increased the rate of complete occlusion and the packing density, a propensity score-matched analysis was used to control for clinical, anatomical, and procedural features.
Results Ultimately, 595 (24.5%) coil embolization used an IMC. Propensity score matching was successful for 424 paired IMC(+) and IMC(−) aneurysms. Compared with the IMC(−) group, the IMC(+) group had significantly higher rate of Raymond-Roy Occlusion Classification class 1 immediately after treatment (30.0% vs 20.8%, P=0.003) and at 6 months (28.8% vs 20.0%, P=0.004) and a higher volume embolization ratio (27.2% (SD 6.5%) vs 25.9% (SD 6.2%), P=0.003). Re-treatment rates were not significantly different between the two groups (0.7% vs 0.2%, P=0.624). No significant differences in the incidences of ischemic and hemorrhagic complications and IMC-related parent artery dissection were found between the two groups.
Conclusion Use of IMCs in triaxial systems can provide effective and safe support in coil embolization of UCAs because complete occlusion and dense coil packing can be achieved without increased complications.
- Aneurysm
- Angiography
- Catheter
- Coil
- Intervention
Data availability statement
Data are available upon reasonable request.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Improving the maneuverability and stability of the microcatheter is essential for successful coil embolization of cerebral aneurysms. Guiding the intermediate catheter to a more distal artery can improve the maneuverability and stability of the microcatheter.
WHAT THIS STUDY ADDS
The present study showed the efficacy and safety of the intermediate catheter in a triaxial system for coil embolization of unruptured cerebral aneurysms. The intermediate catheter achieved complete occlusion and dense coil packing without increased complications.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
Intermediate catheters may be encouraged in coil embolization of unruptured cerebral aneurysms to achieve complete occlusion and dense coil packing; their adoption might reduce the risk of aneurysm recanalization after treatment.
Introduction
Successful coil embolization of cerebral aneurysms depends on placing the microcatheter platform as close to the target aneurysm as possible to improve maneuverability and stability. However, conventional guiding catheters have difficulty in navigating into tortuous vessels en route to aneurysms, such as the siphon portion of the internal carotid artery (ICA) or the vertebral artery (VA) V3 segment—that is, the atlantic, extradural segment, and are limited to guiding to the proximal portion of the ICA or the VA.
Recent advances in endovascular devices have allowed the use of intermediate catheters (IMCs) for coil embolization of cerebral aneurysms. These catheters are designed to provide ideal tracking and a stable platform in tortuous vessels by combining a bendable distal tip with a supportive proximal shaft. These features allow the IMC to be guided to more distal arteries compared with guiding catheters, which improves the maneuverability and stability of the microcatheter.1–6 This could lead to higher rates of complete occlusion and higher packing density. However, research on the efficacy and safety of IMCs has been limited to a small number of case reports and case series.1–6 In this study, the efficacy and safety of IMCs in triaxial systems (guiding catheter, IMC, and microcatheter) for coil embolization of unruptured cerebral aneurysms (UCAs) were investigated.
Methods
Study population
A total of 3092 consecutive endovascular treatments for UCAs performed at our institution and two affiliated institutions (Kashiwa Hospital, Katsushika Medical Center) between November 2003 and May 2023 were retrospectively reviewed. Patients with dissecting aneurysms (n=56), fusiform aneurysms (n=54), pseudoaneurysms (n=5), and common carotid aneurysm (n=1) were excluded. In addition, patients with re-treated aneurysms (n=366), aneurysms treated with flow diversion (n=76), parent artery occlusion (n=16), and Woven EndoBridge (n=1) were also excluded because of the difficulty in accurately assessing post-embolization status. Subsequently, patients lost to follow-up at 6 months including, transfer to another hospital (n=37), missing data (n=34), no postoperative visit (n=13), and death from causes other than UCAs or treatment (n=3) were excluded. Ultimately, 2430 initial coil embolizations of saccular UCAs in 2259 patients with 6-month follow-up were included in the present study (figure 1). The patients were then classified into two groups: with IMC (IMC(+)) and without IMC (IMC(−)).
Flowchart of saccular UCA selection for initial coil embolization, and subsequent classification by use of an intermediate catheter. A total of 3092 consecutive endovascular treatments for UCAs performed at three institutions between November 2003 and May 2023 were retrospectively reviewed. Patients with dissecting aneurysms (n=56), fusiform aneurysms (n=54), pseudoaneurysms (n=5), and common carotid aneurysm (n=1) were excluded. In addition, patients with re-treated aneurysms (n=366), aneurysms treated with flow diversion (n=76), parent artery occlusion (n=16), and Woven EndoBridge (n=1) were also excluded because of the difficulty in accurately assessing post-embolization status. Subsequently, patients lost to follow-up at 6 months including, transfer to another hospital (n=37), missing data (n=34), no postoperative visit (n=13), and death from causes other than UCAs or treatment (n=3) were excluded. Ultimately, 2430 initial coil embolizations of saccular UCAs in 2259 patients with 6 month follow-up were included in the present study. The patients were then classified into two groups: with intermediate catheter (IMC(+)) and without intermediate catheter (IMC(−)). UCA, unruptured cerebral aneurysm.
At the participating centers in the present study, based on the results of previous studies,7–9 treatment for prophylactic rupture was indicated for UCAs with a maximum diameter larger than 5 mm, regardless of the aneurysm’s location. For aneurysms smaller than 5 mm, treatment was indicated only if the patient had a high degree of anxiety,10 a family history of cerebral aneurysms,11 an irregularly shaped aneurysm,9 an enlarged aneurysm,12 or a history of subarachnoid hemorrhage.7
Data collection
The following data were obtained by retrospectively reviewing the medical records and radiological data of these patients: age, sex, medical history, family history of cerebral aneurysms, smoking and drinking history, aneurysm characteristics, intermediate catheter used, endovascular technique (balloon-assisted, stent-assisted), type of coils (bioactive coils,13 hydrogel coils,14 or large coils with a primary diameter of 0.014 inches or larger15), period of treatment (early: 2003–2013, late: 2014–2023), embolization result, and complications. All aneurysms were analyzed for morphology using rotational angiography with three-dimensional image reconstruction (The Jikei University Hospital: Artis Q Biplane, Siemens Healthcare GmbH, Forchheim, Germany; Kashiwa Hospital: Artis zee BA Twin Large Display. Siemens AG, Forchheim, Germany; Katsushika Medical Center: Allura Clarity FD20/10, Philips Healthcare, Amsterdam, Netherlands). Based on three-dimensional rotational angiographic images, aneurysm size and volume were measured more objectively using NeuroVision software (Cybernet Systems, Tokyo, Japan), which enables automatic measurement by simply placing markers on the aneurysm and parent artery.16
Definition of intermediate catheter
An IMC was defined as a catheter introduced in coaxial fashion with a guiding catheter to improve the maneuverability and stability of the microcatheter. The IMCs used in the present study included Tactics (Technorat Corporation, Aichi, Japan), Guidepost (Tokai Medical Products, Aichi, Japan), Cerulean (Medikit Co. Ltd., Tokyo, Japan), DAC (Stryker Neurovascular, Kalamazoo, Michigan, USA), Asahi Fubuki (Asahi Intecc, Aichi, Japan), AXS Vecta (Stryker Neurovascular), Sofia (MicroVention Terumo, Tustin, California, USA), Tracker (Target Terapeutics, San Jose, California, USA), and Navien (Medtronic, Irvine, California, USA).
Endovascular treatment
All coil embolizations were conducted under general anesthesia in a standardized manner and were accomplished by, or under the supervision of, a board-certified interventional neurosurgeon.
All patients undertook oral antiplatelet regimens of 100 mg aspirin alone or 100 mg aspirin and 75 mg clopidogrel (or 3.75 mg prasugrel) per day, 1 to 4 weeks prior to endovascular treatment.
After puncturing the access site, 4000–5000 U of heparin were given intravenously via bolus infusion, and then 1000–2000 U of heparin were administered intermittently to sustain an activated clotting time more than twice the patient’s baseline level throughout the treatment period.
Endovascular treatment was typically performed as follows:
The femoral artery was the access site, and for an anterior circulation aneurysm, an 8 French (Fr) or 9Fr guiding catheter with a balloon or a 6Fr guiding sheath was directed into the cervical portion of the ICA. On the other hand, for a posterior circulation aneurysm, a 5Fr or 6Fr guiding sheath was navigated into the V1 or V2 segment of the VA. The use of an IMC was left to the discretion of the operator, but it was used more frequently in cases where the vessel leading to the aneurysm had a tortuous pathway. The microcatheter mainly selected was the Excelsior SL10 (Stryker Neurovascular), and it was guided into the aneurysm over a microguidewire (Asahi Chikai (Asahi Intecc) or Synchro (Stryker Neurovascular)). The coils used were left to the discretion of the operator. Adjunctive techniques including balloon-assisted, double-catheter, or stent-assisted technique were used for wide-necked aneurysms (neck size >4 mm or dome-to-neck ratio <2).
Evaluation of embolization results and outcomes
The primary outcome of the present study was the Raymond-Roy Occlusion Classification (RROC) scores at 6 months. The secondary outcomes included RROC scores immediately after treatment, packing density, and re-treatment rate.
The RROC was graded as follows: class 1, complete occlusion; class 2, residual neck; and class 3, residual aneurysm.17 RROC scores at 6 months was assessed with digital subtraction angiography (DSA) or MR angiography, and RROC score immediately after treatment was evaluated with DSA. The packing density was represented as volume embolization ratio (VER) and calculated as VER (%) = (volume of coils for embolization)/(volume of aneurysm) × 100. At the end of the endovascular procedures, VER was calculated by entering the inserted coils into the NeuroVision software. Re-treatment was performed if follow-up DSA or MR angiography confirmed an increase in the RROC scores from 1 to 3, 2 to 3, or a 3 with an increase in the Meyers scale.18 Re-treatment rates within 6 months after embolization were assessed.
Complications
Complications were divided into ischemic complications, hemorrhagic complications, and IMC-related parent artery dissection. Symptomatic complications were classified as a worsening of the modified Rankin Scale score by ≥1 point compared with the preoperative score. The present study complied with the principles outlined in the Declaration of Helsinki. The institutional review board of the participating institutions waived the need for informed consent because of the retrospective design.
Statistical analyses
Baseline characteristics of the IMC(+) and IMC(−) groups were compared using Fisher’s exact test for categorical variables and the unpaired t-test for continuous variables. A 1:1 propensity score matching with the nearest neighbor method, without replacement and with a caliper width of 0.20, to match groups according to the following covariates: age, sex, hypertension, diabetes mellitus, dyslipidemia, prior stroke, family history of cerebral aneurysms, smoking history, drinking history, maximum size of aneurysm, neck size, bleb formation, multiple aneurysms, aneurysm location, use of balloon assistance, use of stent assistance, use of bioactive coil, use of hydrogel coil, use of large coil, and period of treatment. R and R Commander-based Easy R (EZR) software (Saitama Medical Center, Jichi Medical School, Saitama, Japan) was used for all statistical analyses.19 A value of P<0.05 was considered significant.
Results
Clinical features
Of the 2430 UCAs that underwent coil embolization, IMCs were used in 595 (24.5%) (figure 1). Their clinical features are presented in table 1. Compared with the IMC(−) group, patients in the IMC(+) group were significantly older (63.1 (SD 12.1) years of age vs 59.4 (SD 11.6) years of age, P<0.001) and had a lower percentage of women (69.4% vs 76.1%, P=0.001). The IMC(+) group had a higher percentage of patients with diabetes mellitus (8.1% vs 5.5%, P=0.030), dyslipidemia (33.3% vs 18.7%, P<0.001), and a history of drinking (36.8% vs 19.4%, P<0.001) than the IMC(−) group.
Clinical, anatomical, and procedural features and outcomes between patients with and without an intermediate catheter for coiled unruptured cerebral aneurysms before and after propensity score matching
Anatomical and procedural features
Anatomical and procedural features are shown in table 1. Maximal aneurysm size (5.9 (SD 2.6) mm vs 6.7 (SD 3.2) mm, P<0.001) was significantly smaller in the IMC(+) group than in the IMC(−) group. The IMC(+) group had a significantly higher percentage of aneurysms with bleb formation (31.3% vs 22.7%, P<0.001) and anterior circulation aneurysms (91.9% vs 88.4%, P=0.015) compared with the IMC(−) group. There was no significant difference in neck size of aneurysms between the two groups.
Balloon-assisted coiling was significantly less frequently performed in the IMC(+) group than in the IMC(−) group (8.4% vs 17.8%, P<0.001), on the other hand, stent-assisted coiling was significantly more frequently applied in the IMC(+) group than in the IMC(−) group (51.8% vs 21.4%, P<0.001). Regarding the type of coils, bioactive coils were all the Matrix2 (Stryker Neurovascular), hydrogel coils were all the HydroCoil Embolic System (MicroVention Terumo), and large coils with a primary diameter of 0.014 inches or larger were all the Target XL (Stryker Neurovascular). Bioactive coils were used significantly less frequently in the IMC(+) group than in the IMC(−) group (8.1% vs 51.8%, P<0.001), while hydrogel coils (5.2% vs 0.2%, P<0.001) and large coils (16.1% vs 6.4%, P<0.001) were used significantly more frequently in the IMC(+) group than in the IMC(−) group.
The IMC(+) and IMC(−) groups were embolized for 48 (8.1%) and 842 (45.9%) in the early period (2003–2013) and 547 (91.9%) and 993 (54.1%) in the late period (2014–2023), respectively (table 1). The IMC(+) group had a significantly higher percentage treated in the late period compared with the IMC(−) group (P<0.001).
Types and sizes of IMCs
The IMC used for coil embolization was the Tactics in most cases (270/595; 45.4%), followed by the Guidepost in 128 cases (21.5%), Cerulean in 76 cases (12.8%), DAC in 35 cases (5.9%), Asahi Fubuki in 25 cases (4.2%), AXS Vecta in 24 cases (4.0%), Sofia in 23 cases (3.9%), Tracker in 8 cases (1.3%), and Navien in 6 cases (1.0%) (table 2). IMC size was 3.2 to 3.9Fr in 411 (69.1%, the most frequent), 4.0 to 4.7Fr in 74 (12.4%), 5.0 to 5.2Fr in 8 (1.3%), and 6.0 to 6.3Fr in 102 (17.1%) (table 2).
Summary of intermediate catheter types and sizes
Outcomes and complications
Distributions of RROC scores immediately after treatment in the IMC(+) and IMC(−) groups were 191 (32.1%) and 329 (17.9%) for class 1, 332 (55.8%) and 1278 (69.6%) for class 2, and 72 (12.1%) and 228 (12.4%) for class 3, respectively (table 1). The IMC(+) group showed a significantly higher percentage of RROC class 1 immediately after treatment than the IMC(−) group (32.1% vs 17.9%, P<0.001). In addition, the VER was significantly higher in the IMC(+) group than in the IMC(−) group (28.4% (SD 6.9%) vs 25.1% (SD 5.5%), P<0.001). There were no significant differences between the two groups in the incidence of ischemic and hemorrhagic complications and IMC-related parent artery dissection (table 1).
Distributions of RROC scores at 6 months in the IMC(+) and IMC(−) groups were 184 (30.9%) and 313 (17.1%) for class 1, 327 (55.0%) and 1178 (64.2%) for class 2, and 84 (14.1%) and 344 (18.7%) for class 3, respectively (table 1). The IMC(+) group showed a significantly higher percentage of RROC class 1 at 6 months than the IMC(−) group (30.9% vs 17.1%, P<0.001). Re-treatment rates were not significantly different between the two groups.
Outcomes between the groups with and without IMC after propensity score matching
Propensity score matching was successful for 424 paired IMC(+) and IMC(−) aneurysms (table 1). After matching for clinical, anatomical, and procedural features, the primary and secondary outcomes for the IMC(+) and IMC(−) groups were compared. On the primary outcome, the RROC scores at 6 months, the IMC(+) group still achieved a significantly higher percentage of RROC class 1 than the IMC(−) group (28.8% vs 20.0%, P=0.003). On the secondary outcomes including RROC scores immediately after treatment, packing density, and re-treatment rate, the IMC(+) group still had a significantly higher percentage of RROC class 1 immediately after treatment (30.0% vs 20.8%, P=0.002) and VER (27.2% (SD 6.5%) vs 25.9% (SD 6.2%), P=0.003) than the IMC(−) group. Re-treatment rates remained not significantly different between the two groups.
Discussion
The present study revealed that use of IMC significantly increased the complete occlusion rate and packing density for coil embolization of UCAs. Previous studies have shown the usefulness of the adjunctive techniques and the different types of coils as methods to increase the rate of complete occlusion and packing density. Regarding adjunctive techniques, the use of a remodeling balloon in endovascular treatment of ruptured cerebral aneurysms indicated a statistically significant relationship with complete occlusion of the aneurysm (P=0.012).20 Coil embolization with a stent for intracranial aneurysms had a significantly higher rate of complete occlusion than without a stent (62.7% vs 48.9%, P=0.003).21
As for the type of coils, Murayama et al experienced that embolization with the Matrix coils (Stryker Neurovascular), which have a platinum core covered with a bioactive, bioabsorbable polymer (polyglycolic acid/lactide), has a lower packing density than embolization with the Guglielmi detachable coils (Stryker Neurovascular) due to the relative increase in friction associated with coil delivery.13 In the Hydrogel Endovascular Aneurysm Treatment Trial (HEAT), a randomized controlled trial, compared with bare platinum coils, the HydroCoil Embolic System (MicroVention Terumo), which consists of a platinum core with integrated hydrogel, had significantly lower rates of initial complete occlusion (17.8% vs 28.3%, P=0.003) and higher average packing density (32.5% (SD 14.8%) vs 24.7% (SD 10.2%), P<0.001).14 For large coils, aneurysms embolized with 14-coil Target XL (Stryker Neurovascular) with a primary diameter of 0.014 inches had a significantly higher mean VER at the end of the procedure than aneurysms embolized with a 10-coil with a primary diameter of 0.010 inches (14 coil: 36.8% (SD 7.8%) vs 10 coil: 32.0% (SD 6.5%), P=0.03).15
Even after adjusting for such confounding factors with propensity score matching, the present study revealed that the use of an IMC in a triaxial system for coil embolization of UCAs can increase the percent of complete occlusion immediately after treatment and 6 months after treatment and achieve dense coil packing. Furthermore, an IMC did not increase postoperative ischemic and hemorrhagic complications and IMC-related parent artery dissection.
Benefits of IMC
The IMC can be guided to an artery more distal than the guiding catheter, which might contribute to the maneuverability and stability of microcatheters. Regarding maneuverability, positioning the IMC close to the target aneurysm allows for safe one-to-one manipulation of the microguidewire and microcatheter. As for stability, IMCs can also prevent proximal migration of the guiding catheter due to tension and redundancy that might occur in the tortuous cranial vasculature, thereby precluding the microcatheter from slipping off.4
By improving maneuverability and stability, IMCs might enable effective endovascular coil embolization for UCAs.1 6 Hauck et al successfully achieved 80% complete occlusion (n=12/15) and 20% near complete occlusion (n=3/15) in coil embolization of difficult-to-access aneurysms using IMCs with 3.9Fr or 4.3Fr outer diameters.1 Matsushige et al described their experience treating 35 anterior circulation aneurysms with a 3.4Fr IMC. They showed that the VER was significantly higher in the IMC group than in the non-IMC group (34.0% vs 28.7%, P=0.003), without increasing hemorrhagic and symptomatic ischemic complications.6 On the other hand, they failed to find a significant difference between the two groups for achieving RROC class 1 (P=0.23),6 but this was due to the small number of cases and the lack of statistical power.
The decision to use an IMC at our institutions was left to the discretion of the endovascular surgeons, but atherosclerotic changes in the target vessel that might have affected the maneuverability and stability of the microcatheter might have motivated the endovascular surgeons to use an IMC. In fact, the present study in univariate analysis found that patient age, the rate of drinking history, and the rate of conditions such as diabetes mellitus and dyslipidemia, related to atherosclerotic changes,22 were significantly higher in the group with an IMC than in the group without. In the present study, even after adjusting for such factors with propensity score matching, IMCs in triaxial systems in coil embolization for UCAs significantly increased both the rate of complete occlusion and the VER in the analysis of a larger number of cases. The ideal coil embolization for prevention of recanalization involves achievement of both complete occlusion and dense coil packing.23 IMCs should be used in coil embolization for UCAs because both complete embolization and dense coil packing can be feasible with their use.
Complete occlusion and recanalization
Complete occlusion can significantly reduce the risk of recanalization in coil embolization of cerebral aneurysms.24 On the other hand, a residual neck and incomplete occlusion may be risk factors for recanalization following coil embolization.24–26 Lecler et al noted that RROC class 2 or a residual neck (relative risk, 4.16; 99% CI 2.12 to 8.14) was a risk factor for recurrence in prospective studies.26 Incomplete occlusion can cause recanalization by changing hemodynamics and enhancing wall shear stress in the aneurysmal dome.24 Raymond et al found recanalization in 33.6% after initial coil embolization of 353 aneurysms, indicating that RROC class 3, or incomplete occlusion, was a risk factor for recanalization.25 In the present study, the rate of achieving complete occlusion was significantly higher with than without IMCs. In addition, the rate of aneurysms that maintained complete occlusion 6 months after treatment was significantly higher with than without IMCs. Use of IMCs in triaxial systems may be a better option for achieving complete occlusion and preventing recanalization in coil embolization of UCAs.
VER and recanalization
Recanalized aneurysms can rupture,25 27 so avoiding recanalization is very important. A lower VER has previously been observed to be an independent risk factor for recanalization.28 29 If the VER exceeds 20–25%, the risk of recanalization is significantly lower.28 29 Therefore, a higher VER is essential to prevent recanalization during coil embolization of UCAs. In the present study, the propensity score-matched analysis revealed that VER was significantly higher with an IMC than without. Consequently, the rate of complete occlusion at 6 months was also significantly higher with an IMC than without. The use of IMCs in triaxial systems can be a key strategy to achieving a higher VER and preventing recanalization during coil embolization of UCAs.
Limitations
There are several limitations to the present study. First, the observation period was approximately 20 years. The improvements in endovascular devices made during the long observation period in coil embolization for UCAs might have affected the outcomes of the present study. More operable IMCs were invented more recently,1 3 4 6 and in the present study, the group with an IMC was treated significantly more frequently in the late period (2014–2023) than the group without an IMC. However, the two groups were compared by propensity score matching adjusted for the adjunctive techniques (balloon-assisted20 and stent-assisted21), the type of coils (bioactive coils,13 hydrogel coils,14 and large coils15), and the period of treatment (early: 2003–2013, late: 2014–2023), which might affect the rate of complete occlusion, packing density, and re-treatment rate in coil embolization for UCAs.
Second, the disadvantage of using IMCs is that they require a coaxial catheter system with additional flush lines, which is more complicated to handle and involves additional cost. In particular, the addition of a coaxial catheter system can be a risk for potential thrombotic complications. However, in the present study, use of IMCs in triaxial systems did not increase the risk of ischemic complications.
Third, this study excluded recanalized aneurysms because of the difficulty in accurately measuring the volume and VER of such aneurysms. Certainly, re-treated aneurysms might have a lower rate of complete embolization, and the exclusion of those aneurysms might be a selection bias. However, recanalized aneurysms are more likely to recanalize even with dense coil packing,30 so the importance of achieving a higher VER might be comparatively low.
Fourth, regarding the re-treatment rate, no significant difference was found between the two groups in the present study. This might be due to the short observation period of 6 months. Longer follow-up might show that the use of an IMC reduces the rate of re-treatment because recanalization, which is an indication for re-treatment, is a time-dependent process.25
Finally, although the present study was multicenter and included a large number of aneurysms, a certain number of patients were lost to follow-up due to the retrospective nature of the study. However, because patients who were lost to follow-up represented only 3.5% (87/2517) of the total study population, their statistical impact may be negligible. In the future, this study should be validated by a prospective cohort study in a multicenter setting with no subjects who were lost to follow-up. Despite these limitations, the present study showed that use of IMCs in triaxial systems was significantly associated with complete occlusion and dense coil packing in coil embolization of UCAs.
Conclusions
Use of IMCs in triaxial systems can provide effective and safe support in coil embolization of UCAs because complete occlusion and dense coil packing can be achieved without increased complications.
Data availability statement
Data are available upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and was approved by the ethics committee of The Jikei University School of Medicine (ethics committee approval ID: 29-228(8844)). Owing to the retrospective nature of the present study, the need for patient consent was waived by the institutional ethics committee.
References
Footnotes
Contributors MF and TI contributed to the study design. MF, TI, KA, RT, and YM contributed to data collection and data validation. All authors contributed to endovascular treatment. MF prepared the manuscript. MF, TI, KA, RT, TT, and YM contributed to data analysis and critically revised the manuscript. All authors read the final manuscript and approved its submission to the journal. YM is responsible for the overall content as the guarantor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.