The selection of an appropriate guiding catheter that can provide not only sufficient supportability for working devices, but also sufficient distal navigability is essential to ensure procedural success in endovascular procedures. In the past, placing guiding catheters in the common or proximal internal carotid artery (ICA) had to be accomplished using rigid and thick guiding catheters that lacked sufficient distal navigability and had the potential risk of inducing carotid artery injury, such as dissection or vasospasm.14) With the continuous improvement of materials, various attempts have been made to develop a system where guiding catheters can be localized closer to the lesion with good supportability and safety.1)7)8)15) The practical usefulness of new devices, such as intermediate catheters, has been proven in several studies.3)4)13)14) However, these intermediate guiding systems require co-axial double guiding or exchange techniques for positioning guiding catheters. A newly-designed guiding catheter, the ENVOY 6F distal access (DA) guiding catheter (Codman Neuro, Raynham, MA), is expected to have high distal navigability and sufficient supportability, without requiring co-axial double guiding or exchange for accurate positioning. We evaluated the distal navigability, supportability, and safety of the ENVOY 6F DA guiding catheter with no co-axial guiding system for the endovascular coiling of anterior circulating cerebral aneurysms.

The baseline characteristics of the patients are described in Table 1. The median age was 63 (range: 25–84) years. There were 72 women (73.47%), and 61 (62.24%) patients had unruptured aneurysms.

The ENVOY 6F DA guiding catheter was successfully placed in the internal carotid artery on the side of the lesion without failure. Among the 98 cases, the co-axial technique was required in 20 cases (20.4%). The 125-cm angiocatheter used in the co-axial system included the VTK (16 cases), Headhunter (two cases), and Bern (two cases) catheters.

The initial location of the guiding catheter tip prior to coil embolization and final location of the guiding catheter tip after coil embolization were described in Table 2. The guiding catheter moved proximally from the initial position in 25 cases (25.51%).

Procedure-related complications during the positioning of the guiding catheter were identified in nine cases (9.18%) and all involved vasospasm that showed spontaneous improvement in blood flow, exhibiting no vascular abnormal findings on delayed follow-up angiography (Table 3). Therefore, there was no procedural symptomatic morbidity.

The immediate post-procedural radiological outcomes are described in Table 1. Twenty-two cases (22.45%) showed complete occlusion, 67 (68.37%) showed remnant neck, and eight (8.16%) showed remnant sac, according to the modified RROC during immediate post-procedural angiography.10) In one case, coil embolization failed. In this case, during coil embolization, the coil and coil delivery microcatheter were not separated. While trying to separate the coil and microcatheter, they simultaneously exited the aneurysm, and a thrombus was formed inside the sac. However, in that case, the guiding catheter was well placed.

An ideal guiding catheter system should have sufficient navigability to be placed as close as possible to the target lesion to reduce the working length of the microcatheter or microwire without procedural complications. It should also have sufficient supportability to allow use of the device.3)4) However, designing a guiding catheter system that has good navigability and supportability would be difficult because good navigability requires device softness and might conflict with good supportability that requires device stiffness.9) Conventionally, to achieve proper levels of supporting power and navigability, we have used numerous techniques, such as a “buddy” wire, co-axial double guiding catheters, or changing of the access route.1)2)8)11)12)15)16) These techniques require many devices and additional procedural steps and involve a high risk of complications, such as vasospasm, artery wall dissection, air embolism, and embolic infarction.8)

Unlike previous guiding catheters, the ENVOY 6F DA guiding catheter has an 8-cm distal flexible segment that can likely improve distal navigability in more tortuous vessels. The co-axial technique using the 125-cm angiocatheter for placing the guiding catheter was used in 20 cases (20.4%). This may be attributed to the flexibility of the distal segment of the ENVOY 6F DA guiding catheter, which renders it less stable while navigating the guidewire into the carotid artery because of the angle between the aortic arch and the right brachiocephalic trunk or left CCA. Therefore, in the lesions with acute angles between the aortic arch and the right brachiocephalic trunk or left CCA, the co-axial technique with an additional catheter should be considered for using the ENVOY 6F DA guiding catheter.

In our series, positioning of the ENVOY 6F DA guiding catheter involved the distal cervical ICA (cervical ICA C3, n=62 (63.3%)) and petrous ICA (n=12, 12.2%) (Fig. 2). This result signifies that the navigability of the ENVOY 6F DA guiding catheter is superior to that of traditional guiding catheters but inferior to that of other new generated intermediate catheters, such as SOFIA (Soft torqueable catheter Optimized for Intracranial Access, MicroVention Inc, Tustin, CA) and Catalyst (Stryker Neurovascular, Fremont, CA).12) Accordingly, in tortuous vasculatures that have a redundant working length, an intermediate catheter rather than the ENVOY 6F DA guiding catheter would be better for distal navigability.

Differences between the initial and final location of the guiding catheter tip, reflecting the supportability of the guiding catheter, were noted in 25 cases (25.5%). This may be attributable to inevitable decrease in supporting forces due to structural differences.5) In this regard, the authors' experience shows that the more complicated the procedure is, for example, as the number of devices used increases, the more the guiding catheter is draw back during the procedure due to this lack of support.

Based on our results, the distal navigability of the ENVOY 6F DA guiding catheter without a co-axial guiding system will be superior to that of traditional guiding system but inferior to that of newly-designed intermediate catheters. The supportability of the ENVOY 6F DA guiding catheter without a co-axial guiding system will be superior to that of intermediate catheters but inferior to that of traditional guiding catheters. However, an intermediate catheter will generally use a co-axial guiding system to overcome the insufficient supportability of intermediate catheters. Therefore, the ENVOY DA 6F guiding catheter without a co-axial system will not be considered practically useful for all cases of anterior circulation aneurysms. To prevent or overcome the insufficient supportability of the ENVOY DA 6F guiding catheter, a co-axial guiding catheter system will be considered in tortuous vasculatures.

This study has some limitations. This was a single-center retrospective study, and it is possible that there was selection bias with regard to the included cases, although we enrolled consecutive patients. Moreover, we attempted to control other variables that could possibly affect the outcome of the procedure, such as tortuosity of the ICA. However, other factors remain that could have possibly affected the outcome, such as operator-related differences. Therefore, to overcome these limitations, additional prospective, multicenter studies are needed.

In our series, the ENVOY 6F DA guiding catheter had relatively sufficient distal navigability without symptomatic procedural complications. However, changes in catheter position after endovascular coiling denoted that supportability was insufficient.