Optimal guiding catheter position during advancement of the guiding catheter into the carotid artery from the aortic arch via transfemoral approach

Abstract

Background

Guiding catheter (GC) advancement into the target carotid artery is a crucial step in neuroendovascular therapy. In difficult anatomies, alternative methods have been reported to overcome difficult carotid access for swift GC advancement. However, studies focusing on the positional relationship between the GC and inner catheter (IC) at the aortic arch are lacking.

Methods

We evaluated the impact of the positional relationship between the GC and IC on whether the GC position affects catheter support or system straightening. We retrospectively reviewed 89 patients who underwent neuroendovascular therapy. We assessed the time to carotid access across difficult arch anatomies. The GC position was divided into Position 1, descending aorta level; Position 2, aortic arch level; and Position 3, origin of the left common carotid artery or innominate artery. We also evaluated the GC support and straightening effects in an in vitro vascular model study.

Results

The coaxial catheter flexion angle at the aortic arch was significantly larger when the GC was set to Position 3 (p < 0.0001). A significantly shorter time to carotid access was observed with Positions 2 and 3 than with Position 1 in the difficult arch anatomy group. In the in vitro vascular model evaluation, the catheter support effect significantly increased as the GC position became closer to the IC tip (p < 0.0001) and straightening effect significantly increased as the GC moved to Position 2 from Position 1 (p < 0.0001).

Conclusion

During GC advancement, the GC positional relationship changed the support of the coaxial system with system straightening. The optimal GC position, Position 3, facilitated swift GC advancement.

Introduction

In neuroendovascular therapy, the transfemoral approach is the standard for guiding catheter (GC) advancement. The need for prompt achievement of target carotid access is well known. However, a tortuous anatomy, difficult aortic arch anatomy, and acute-angle takeoff of the target vessels from the aortic arch are challenging. The transfemoral approach is often technically difficult and time-consuming owing to the features of the implicated anatomy. Difficult anatomical characteristics cause GC advancement failure, leading to prolonged fluoroscopy and procedure times, perioperative ischemic events, and poor outcomes.^1–7

Alternative methods or strategies are required for the swift and glide advancement of the GC in difficult anatomies. Although several promising techniques, coaxial systems, and alternative approaches have been reported to overcome difficult carotid access,^8–13 few studies have focused on the positional relationship between the GC and inner catheter (IC) at the aortic arch during GC advancement into the targeted artery as a crucial step in neuroendovascular therapy. In difficult carotid access, even the guidewire may not be able to advance distally because of tortuosity of the carotid artery and aortic arch anatomy, ¹⁴ leading to the coaxial system sliding off into the ascending aorta. GC advancement is mostly based on interfacility, verbal transmission, and experience. Therefore, here, we evaluated the most appropriate setting to increase catheter support during GC navigation. We focused on the position of the GC while navigating the coaxial system to the target carotid artery from the aortic arch. We hypothesized that moving the GC with a stiffer shaft to the origin of the target vessel would provide better support for the prevention of the catheter sliding off and that this would allow swift coaxial system advancement into the target carotid vessel by straightening the system.

This study aimed to assess optimal guiding catheter positioning during the advancement of the coaxial system into the target vessels from the aortic arch to prevent the system from sliding off. We evaluated the impact of the positional relationship between the GC and IC in terms of whether the GC position affects catheter support during GC advancement in patients undergoing neuroendovascular therapy. Furthermore, we evaluated the GC support and straightening effects by changing the GC position in an experimental study using an in vitro vascular model.

Methods

All procedures performed in this report involving human participant were in accordance with the ethical standards of the institutional and/or national research committee (Saint Luke’s International Hospital, No. 21-R014) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All participants provided verbal informed consent to participate this research.

Patients

To study the impact of the GC position at the aortic arch during the advancement of the coaxial system into the target carotid artery, we retrospectively analyzed the maneuver of GC advancement in neuroendovascular therapy (Table 1 for eligible patients). This retrospective study included 89 consecutive patients who underwent neuroendovascular therapy for the anterior circulation in our institution between March 2021 and April 2022. Data were analyzed for patients for whom intraoperative fluoroscopy images, video records, and conventional digital subtraction angiography (DSA) results were available. Demographic data, baseline clinical status, and imaging results were also collected from the medical records. The diagnosis and detailed angioarchitecture were evaluated based on multimodal imaging, including DSA, 3D-rotational angiography, and 3D-computed tomography angiography. A biplane angiography system (Artis zee Q; Siemens Healthcare GmbH, Forchheim, Germany) was used for neurointerventional therapy. Difficult arch anatomy for guiding catheter advancement was defined as severe vessel tortuosity, type III aortic arch, bovine arch, left common carotid artery (CCA) takeoff angle ≥30° from the aortic arch, change requirement in the catheter system, and catheter sliding off during advancement.^{1–5,15–18} Patients treated with an access route other than the transfemoral approach were excluded.

Table 1.

Characteristics of the overall patients.

Variable	Value
No. of patients	89
Age (years)	66 (IQR 33–94)
Male/Female	36 (40.4%)/53 (59.6%)
Treatment
Carotid artery stenting	17 (19.1%)
Coil embolization	54 (60.6%)
Mechanical thrombectomy	14 (15.7%)
Flow diverter	1 (1.1%)
PTA	2 (2.2%)
WEB	1 (1.1%)
Side (Rt/Lt)	41 (46.1%)/48 (53.9%)
Anatomic features
Aortic arch type I	31 (35.9%)
II	27 (30.4%)
III	30 (33.7%)
Bovine arch	9 (10.1%)
Take off angle >30 (Lt. CCA)	13 (14.6%)
Difficult arch anatomy	37 (41.5%)
GC position
Position 1/2/3	49 (55.0%)/9 (10.1%)/31 (34.9%)
Flexion angle (degree)
Position 1	87.6 (IQR 41.9–152.1)
Pre-position 2/Position 2	49.6 (IQR 23.5–111.8)/87.4 (IQR 59–148.4)
Pre-position 3/Position 3	69.8 (IQR 25.6–145.9)/110.7 (IQR 49.7–165.7)

Values are expressed as median (IQR) for quantitative variables or as absolute numbers (percentages) for qualitative variables.

CCA, common carotid artery; GC, guiding catheter; IQR, interquartile range; Lt, left; PTA, percutaneous transluminal angioplasty; Rt, right; WEB, woven endobridge.

Guiding catheter advancement into the carotid artery

After groin puncture, a coaxial system composed of an IC, GC, and 0.035-inch guidewire was advanced to the aortic arch via the transfemoral approach. After inserting the IC into the target carotid origin from the aortic arch in the left anterior oblique view, the IC was guided distally along the guidewire, and the GC followed these to the target carotid artery. In patients in whom coaxial system insertion into the innominate artery or left CCA was difficult, changing to another catheter was considered. All procedures were performed by well-experienced interventional neuroradiologists (consulting specialists, board-certified members of the Japanese Society of Neuroendovascular Therapy [JSNET], and specialists of the JSNET). Appropriate coaxial system selection was decided by the operator as follows: IC, 5–6-Fr. JB2 or Simmons type; GC, 7–8-Fr. GC or 8–9-Fr. balloon-guiding catheter (BGT).

Measurement of time to carotid access and flexion angle of the coaxial system

The positional relationship between the IC and GC was studied when the GC was advanced from the aortic arch to the target carotid artery. During GC navigation, the GC position was divided into Position 1, descending aorta level (Figure 1(a)); Position 2, aortic arch level (Figure 1(b)); and Position 3, origin of the left CCA or innominate artery from the aorta (Figure 1(c)). The flexion angle (degree) of the coaxial catheter system at the aortic arch was measured (Figure 2). The time from insertion of the IC into the brachiocephalic trunk or left CCA at the aortic arch to successful GC advancement into the targeted CCA was defined as the time to carotid access(s). Patients were divided into two groups based on aortic arch anatomy (difficult arch anatomy or non-difficult arch anatomy). We statistically analyzed whether the GC position affected the measured variables based on the review results.

Figure 1.

Positional relationship between the GC and IC. (a–c) Schemes show the positional relationship between the GC and IC at the aortic arch: Position 1 (a), descending aorta level; Position 2 (b), aortic arch level; Position 3 (c), origin level of the left CCA or innominate artery from the aorta. CCA, common carotid artery; GC, guiding catheter; IC, inner catheter.

Figure 2.

Impact of the positional relationship between the GC and IC during coaxial system advancement into the target carotid artery from the aortic arch. Illustrative cases of the advancement of the GC using a JB2-type IC (a–c) and Simmons-type IC (d–f) over the guidewire. The flexion angle θ (degree) of the coaxial catheter system at the aortic arch is measured. After the target carotid artery is selected by the inner catheter, the guidewire is advanced distally to the carotid artery (a, d). The GC is advanced closer to the origin of the carotid artery for support and straightening of the system (b, e). The GC is advanced to the target carotid artery along the IC following IC advancement (c, f). The black arrowheads indicate the IC tip. The white arrowheads indicate the GC tip. CCA, common carotid artery; GC, guiding catheter; IC, inner catheter.

In vitro vascular model

The vascular dry model (Cerebrovascular smart model 3 in 1, Medtronic, Irvine, CA, USA) simulating a type III and bovine arch with tortuous left CCA was used in this experimental in vitro study (Figure 3(a) and (b)). The model was prepared by die-cutting a region from the aortic arch over the distal middle cerebral artery. Using this vascular model made from acrylic and polyacetal resin, we experimentally observed how coaxial system support varies with the position of the GC in the aortic arch.

Figure 3.

In vitro vascular model evaluation. (a) Blueprint of the vascular model. (b) Fluoroscopic image of the vascular model. (c) Schematic illustration of the in vitro evaluation. The retraction force until the coaxial system slides off to the ascending aorta is measured. (d–i) In vitro measurement of the flexion angle θ (degree) of the coaxial catheter system at the aortic arch. (d–f) Fluoroscopic images of the coaxial system using JB2-type IC in each GC position (Positions 1–3). (g–i) Fluoroscopic images of the coaxial system using Simmons-type IC in each GC position (Positions 1–3). The black arrowheads indicate the IC tip. The white arrowheads indicate the GC tip. GC, guiding catheter; IC, inner catheter.

In vitro analysis of coaxial catheter behavior

After manual guidance with the coaxial catheter system as a composite construct, the IC was inserted into the orifice of the left CCA. The most downward U-shaped part of the IC tip was connected to a digital force gauge (ZTS 50N, IMADA CO., LTD, Aichi, Japan) with a filament, and the IC was retracted continuously (5 mm/s) caudally in a straight line using a linear measurement stand (Figure 3(c)). The retraction force was monitored and recorded using Force Logger Ver. 2.10 (IMADA Co). The IC was retracted continuously until the system slid off to the ascending aorta. Sliding off was defined as when the inserted IC tip slid off beyond the origin of the left CCA. The following four combinations of the coaxial system were used for in vitro evaluation: 8-Fr. Fubuki GC (ASAHI INTECC CO., LTD, Aichi, Japan) with a 6-Fr. JB2 125 cm (HANACO MEDICAL Co, Saitama, Japan) or 6-Fr. Simmons type SY3 135 cm (HANACO MEDICAL CO.), 9-Fr. Branchor BGC 90 cm (ASAHI INTECC CO.) with a 6-Fr. JB2 or 6-Fr. SY3. A 0.035-inch Radifocus guidewire (180 cm; Terumo, Tokyo, Japan) was used in all procedures. All procedures were performed on the same day using the same model settings under similar room temperature, humidity, and weather conditions. The entire procedure was performed under fluoroscopy using an angiography suite (Artis Zee Q, Erlangen, Germany). The measurements were performed by an examiner who was blinded to the system settings.

The GC position was divided into (Figures 1 and 3(d)–(i)) Position 1, descending aorta level; Position 2, aortic arch level; and Position 3, origin of the left CCA from the aorta. In each GC position, the continuous retraction force (N) and flexion angles (degrees) of the coaxial systems at the aortic arch were measured. After zero calibration in each procedure, a continuous retraction force until sliding off was measured as an indicator of coaxial catheter support. The flexion angle was used as an indicator of the straightening effect. First, measurements were performed in three GC positions without a guidewire, and then measurements were performed at Position 3 with guidewire insertion. In addition, at Position 3, with guidewire insertion, the measurement was performed by inflating the balloon. Each procedure was repeated five times for each condition. Maximum retraction forces and flexion angles were employed in the analyses.

Statistical analysis

Continuous variables are expressed as median (IQR) or mean ± standard deviation, and categorical variables are expressed as numbers and percentages. When comparing the two groups, categorical variables were evaluated using Pearson’s chi-squared test, and continuous variables were evaluated using the Kruskal–Wallis or Student’s t-test.

One-way analysis of variance (ANOVA) was used to analyze the differences between one quantitative dependent variable and one categorical independent variable. Two-way ANOVA was used to estimate how a quantitative dependent variable changed according to the level of two categorical variables. Tukey’s honestly significant difference post-hoc test was performed following each ANOVA. The significance level was set at p < 0.05. All statistical analyses were performed using JMP Pro16 (SAS Institute, Cary, NC, USA).

Results

Fluoroscopic evaluation in the retrospective study of neuroendovascular therapy

Patient characteristics are summarized in Table 1. Of the 89 patients, difficult arch anatomy was observed in 37 (41.5%). There was no navigation failure of the coaxial system into the target carotid artery, but device change or coaxial system sliding off into the ascending aorta was observed in five patients (5.6%). The coaxial catheter flexion angle at the aortic arch was significantly larger when the GC position was set to Position 3 (p < 0.0001) but not when it was set to Position 2 (Figures 2 and 4(a), Table 1).

Figure 4.

Comparison of time to carotid access between difficult and non-difficult arch anatomies. (a) Flexion angle of the coaxial catheter system at the aortic arch in each GC position. The coaxial catheter flexion angle at the aortic arch is significantly larger by setting the GC position to Position 3. (b) Comparison of the time to carotid access between difficult and non-difficult arch anatomies. The time to carotid access is significantly longer in the difficult arch anatomy. (c) Comparison of the time to carotid access between the arch anatomy and GC position. (d) Comparison of the time to carotid access between IC types and GC positions in difficult arch anatomy. (e). Comparison of the time to carotid access between GC types and GC positions in difficult arch anatomy. ANOVA, analysis of variance; GC, guiding catheter; IC, inner catheter.

The results of the comparison between the difficult and non-difficult arch anatomies are summarized in Table 2. The median age was significantly higher in the difficult arch anatomy group (76 [IQR 51–94] vs 58.5 [IQR 33–85] years, p < 0.0001), and the median time to carotid access was significantly longer in the difficult arch anatomy than in the non-difficult arch anatomy group (155 [IQR 50–1303] vs 76.5 [IQR 30–191] s, p < 0.0001, Figure 4(b)). There was a significant difference in the GC positions (p < 0.001) during coaxial system advancement into the target carotid artery between the groups (Supplementary movies 1 and 2), and a trend was observed where Position 3 was used frequently during coaxial system advancement in the difficult arch anatomy group (Table 2): Position 1, 11 (29.7%) vs. 38 (73.0%); Position 2, 3 (8.1%) vs. 6 (11.5%); Position 3, 23 (62.2%) vs. 8 (15.3%). Two-way ANOVA for the time to carotid access between arch anatomy and GC position (Figure 4(c)) showed a significant difference in difficult arch anatomy (F [1,83] = 34.61, p < 0.0001), GC position (F [2,83] = 6.06, p = 0.0035), and interaction effects (F [2,83] = 5.45, p = 0.006). Post hoc tests showed that the time to carotid access was significantly shorter with Positions 2 and 3 than with Position 1 in the difficult arch anatomy group (Position 1 > Position 2 [p = 0.035], Position 1 > Position 3, [p = 0.0009]).

Table 2.

Comparison between difficult and non-difficult arch anatomies.

Variable	Difficult arch anatomy	Non-difficult arch anatomy	p-Value
No. of patients	37	52
Age (years)	76 (IQR 51–94)	58.5 (IQR 33–85)	<0.0001
Male/female	19 (51.3%)/18 (48.7%)	17 (32.6%)/35 (67.3%)	0.077
Guiding catheter position
Position 1	11 (29.7%)	38 (73.0%)	<0.0001
Position 2	3 (8.1%)	6 (11.5%)
Position 3	23 (62.2%)	8 (15.3%)
Time to carotid access (sec)	155 (IQR 50–1303)	76.5 (IQR 30–191)	<0.0001
Position 1	307 (IQR 94–1303)	79.5 (IQR 30–191)
Position 2	102 (IQR 60–126)	68 (IQR 44–127)
Position 3	125 (IQR 50–900)	70 (IQR 49–172)
Flexion angle (degree)	87.4 (IQR 41.9–144.8)	100.1 (IQR 42.6–165.7)	0.153
Position 1	76.1 (IQR 41.9–105.2)	92.0 (IQR 42.6–152.1)
Position 2	81.3 (IQR 63.5–87.4)	101.8 (IQR 59–148.4)
Position 3	102.5 (IQR 49.7–144.8)	120.8 (IQR 72.6–165.7)
Device change or catheter sliding off	5 (13.5%)	0 (0%)	0.006
Coaxial catheter system
Guiding catheter type			0.002
7-Fr	5 (13.5%)	17 (32.6%)
8-Fr	10 (27.0%)	24 (46.2%)
8-Fr. BGT	12 (32.4%)	7 (13.4%)
9-Fr. BGT	10 (27.0%)	4 (7.6%)
Inner catheter type			0.028
JB2	28 (75.6%)	48 (92.3%)
Simmons	9 (24.4%)	4 (7.7%)

Values are expressed as median (IQR) for quantitative variables or as absolute numbers (percentages) for qualitative variables.

BGC, balloon-guiding catheter; Fr, French; IQR, interquartile range.

For difficult arch anatomy, the two-way ANOVA for the time to carotid access between the IC and GC positions (Figure 4(d)) did not show a significant difference in IC type (F [1,31] = 1.81, p = 0.18), GC position (F [2,31] = 0.44, p = 0.64), and interaction effects (F [2,31] = 0.75, p = 0.47). Two-way ANOVA for the time to carotid access between the GC type and GC position (Figure 4(e)) showed a significant difference in the GC type (F [3,27] = 10.64, p < 0.0001) and interaction effects (F [4,27] = 6.52, p = 0.0008) but no significant difference in GC position (F [2,27] = 0.0076, p = 0.99). Post hoc tests showed that the time to carotid access was significantly longer with a 9-Fr. BGT than with an 8-Fr. BGT or 8-Fr. catheter in the GC at Position 1 (9-Fr. BGT>8-Fr. GC [p = 0.0039], 9-Fr. BGT>8-Fr. BGT [p = 0.0013]). Positions 2 and 3 led to a significantly shorter time to carotid access than Position 1 with 9-Fr. BGT use (Position 1 > Position 3 [p = 0.0001]; Position 1 > Position 2 [p = 0.0008]).

In vitro vascular model evaluation

In vitro vascular model evaluation was performed to assess coaxial system support during catheter advancement in difficult arch anatomy (Supplementary Figures 1 and 2). According to one-way ANOVA, the relationship between the GC position and retraction force significantly differed in all coaxial catheter systems (p < 0.0001, Figure 5(a)–(d), Supplementary Tables 1 and 2). According to the post hoc analysis, the retraction force increased significantly as the GC position became closer to the IC tip for all coaxial catheter systems (Position 1 < Position 2 < Position 3, Figure 5(a)–(d)). In all combinations, insertion of the guidewire into the IC significantly increased the retraction force (Position 3 < Position 3 + guidewire insertion, Figure 5(a)–(d)). There was no significant increase in retraction force with balloon inflation of the BGT (Figure 5(c) and (d)).

Figure 5.

Comparison of the retraction force and flexion angle in the in vitro vascular model. (a–d) Comparison of the retraction force until the coaxial system slides off into the ascending aorta between each coaxial system and GC position. (a: 8-Fr. GC + 6-Fr. JB2, b: 8-Fr. GC + 6-Fr. SY3, c: 9-Fr. BGC + 6-Fr. JB2, d: 9-Fr. BGC + 6-Fr. SY3). (e–h) Comparison of the flexion angle of the coaxial catheter system between each coaxial system and GC position (e: 8-Fr. GC + 6-Fr. JB2, f: 8-Fr. GC + 6-Fr. SY3, g: 9-Fr. BGC + 6-Fr. JB2, h: 9-Fr. BGC + 6-Fr. SY3). *p < 0.0001, **p < 0.001, ***p < 0.01, post hoc Tukey’s honestly significant difference test. Fr, French; BGC, balloon-guiding catheter; GC, guiding catheter; GW, guidewire; IC, inner catheter.

According to one-way ANOVA, the relationship between the GC position and the flexion angle of the coaxial system significantly differed in all coaxial catheter systems (p < 0.0001, Figure 5(e)–(h), Supplementary Tables 1 and 2). According to the post hoc analysis, there was a significant increase in the flexion angle with Position 2, Position 3, and Position 3 with guidewire insertion than with Position 1 in all coaxial catheter systems (Position 1 < Position 2, Position 1 < Position 3, Position 1 < Position 3 with guidewire insertion, p < 0.0001 for all, Figure 5(e)–(h)).

Discussion

In this study, we evaluated whether the positional relationship between the GC and IC would affect the support for GC advancement into the target carotid artery in neuroendovascular therapy. Difficult arch anatomy increases technical difficulty and prolongs procedure time for GC advancement into the target carotid artery. We found that moving the GC position closer to the origin of the target vessel from the aortic arch increased catheter support and coaxial catheter straightening at the arch. This study showed that increased catheter support and straightening of the coaxial system prevented the system from sliding off and led to rapid advancement. We also scientifically proved the mechanism in a vascular model and in an empirical clinical sense. The catheter support effect, expressed as retraction force, was found to significantly increase as the GC was moved closer to the IC tip. The coaxial catheter straightening effect, expressed as the flexion angle, was also found to significantly increase when the GC position became closer to the IC tip. Thus, the optimal GC position to advance the GC into the target carotid artery was Position 3, the origin of the left CCA or the innominate artery from the aortic arch. To our knowledge, no study directly comparing the impact of the GC position during system navigation has been reported. This technique facilitated the rapid advancement of the GC without delaying the procedure time.

A coaxial catheter system constructed with the IC, GC, and guidewire was used to decrease the gap between devices for smooth system advancement. By moving the GC position closer to the IC, the IC will have more support and the shaft of the coaxial system will be thicker, reducing the possibility that it will slide off into the ascending aorta. Another reason may be that the downward force vector on the coaxial catheter system at the aortic arch in difficult arch anatomy is mitigated by straightening the system. It has been reported that catheter advancement can be facilitated by using a stiffer guidewire for additional support,^19–21 and our vascular model study also showed that the retraction force until the system slides off increases with the insertion of a guidewire. Although the flexion angle was not significantly changed between Positions 3 and 3 with guidewire insertion, a straightening effect of stiffer guidewire insertion in Position 1 or 2 may be expected. The balloon inflation anchoring technique is known to be effective for difficult carotid access. ¹¹ However, no increase in support or straightening effect was observed with GC balloon inflation in our experimental study, possibly because there was no anchoring effect, as balloon inflation was performed in the aorta rather than in the target proximal left CCA, and there was no flow-assisted effect because of the dry vascular model without continuous flow. The retraction force significantly increased as the GC position was moved closer to the IC tip; however, the flexion angle was different. No significant change in the flexion angle was observed after Position 2, suggesting that there may be a limit to the straightening effect.

Advancement of a coaxial catheter system into the target carotid artery is a crucial step in neuroendovascular therapy. We often encounter difficult catheter access owing to anatomical factors via the transfemoral approach, leading to the catheter sliding off into the ascending aorta and requiring an alternative access route. In particular, in carotid artery stenting, mechanical thrombectomy, and treatments requiring a GC/BGC of ≥8 Fr. combined with a large-diameter distal access catheter, advancement of the coaxial system is often challenging when the aortic arch anatomy is difficult. The presence of an unfavorable aortic arch is associated with a prolonged procedure, increased radiation exposure, technical failure, and poor outcomes after carotid artery stenting and mechanical thrombectomy.^{1,4,5,7,15,18,22}

The anatomical characteristics of difficult carotid access through the transfemoral approach reportedly include marked arteriosclerosis, severe vessel tortuosity, type III aortic arch, bovine arch, an angle ≤30° between the left CCA and aortic arch, and the carotid artery originating from inferior to the lesser curvature of the aortic arch.^{1,3,4,6,14,15,17,18,23} In difficult arch anatomy, a steep angle formed between the proximal target carotid artery, and bifurcation from the arch must be passed with the GC to access the target carotid artery. In this study, patients who showed anatomical features of tortuosity, bovine aorta, and type III arch were considered to have difficult arch anatomy. In the vascular model analysis, we also used a mimic of bovine and type III arch with left CCA tortuosity. Vascular risk factors for difficult catheter access, hypertension, age >75 years, dyslipidemia, and left anterior circulation stroke have been reported in acute ischemic stroke. ² Old patients have a high incidence of vascular risk factors, leading to high prevalence of elongated and tortuous vessels, which often complicates catheter navigation to the target vessel and is time-consuming. ² Age was also an independent predictor of neurological complications and technical failure. ¹⁵ In our retrospective analysis, patient age was significantly higher in the difficult arch anatomy group.

Several alternative systems and useful techniques have been proposed to overcome carotid access difficulty, such as the carotid-compression technique, ⁸ pull-through technique using a goose-neck snare, ⁹ balloon-inflation anchoring technique, ¹¹ turn-over technique, ¹⁰ and triaxial coaxial system.^24,25 Finally, switching to other approaches, such as the trans-radial artery approach or direct carotid artery puncture access, can be considered.^12,13,26,27 Catheter system and puncture site changes and more complex methods using multiple devices are also markedly useful for overcoming the issue of difficult carotid access, but access route change from the trans-femoral approach requires delay until the restart of the puncture and multiple devices are costly. ¹² Therefore, before attempting a different method or catheter system, first becoming aware of the GC position, as in this study, may be a convenient solution. This method is also effective in cases of external carotid artery occlusion, severe CCA stenosis, and in-stent stenosis because it reduces the risk of the coaxial system sliding off when the guidewire or IC cannot be guided distally to a sufficient degree.^7,14,16,25

The present study had some limitations. First, given the retrospective design and relatively small sample size, there may exist potential selection bias. Therefore, the generalizability of the conclusions of this study may be limited. Furthermore, we did not evaluate any condition-related outcomes in this study. Some methodological limitations of our in vitro study should also be noted. We used an acrylic and polyacetal resin dry model without continuous flow, which differs from actual cerebral blood vessels with blood flow and elasticity. Further investigation is necessary to bring the accuracy closer to that in clinical practice. This study was limited to a transfemoral approach to the anterior circulation. Thus, different approach routes are worth investigating.

Conclusion

During GC advancement into the target carotid artery from the aorta, the GC positional relationship between the GC and IC changed the support of the coaxial system with system straightening. The optimal GC position facilitated swift GC advancement to the target vessel at Position 3, the origin of the target carotid artery from the aortic arch, with higher support and straightening effects. We obtained similar results in the vascular model. Before attempting a different method or catheter system, first becoming aware of the GC position may be a convenient solution for rapid advancement of the GC without delaying the procedure time.

Supplemental Material

Video 1.

Video 2.

ORCID iDs

Bikei Ryu https://orcid.org/0000-0003-0323-6628

Shogo Shima https://orcid.org/0000-0002-2128-5602

Shinsuke Sato https://orcid.org/0000-0003-2911-6755