Mechanical Thrombectomy for Medium Vessel Occlusion with Extracranial Vessel Tortuosity Using Quadruple Coaxial System: A Case Series

Abstract

Objective: Medium vessel occlusions (MeVOs) during acute ischemic stroke present challenges due to their distal occlusion sites. Furthermore, MeVO cases with tortuous extracranial vessels are complex, and effective management techniques are lacking. This study reports the utility of combining a 6-French distal access catheter with a low-profile aspiration catheter, guiding catheter, and microcatheter to establish a quadruple coaxial system for treating MeVOs with tortuous extracranial vessels.

Methods: We retrospectively reviewed data from mechanical thrombectomy cases with MeVO at our institution between March 2022 and February 2024. A total of 81 patients were enrolled, and 5 patients were treated using the quadruple coaxial system. The primary efficacy outcome was the first pass effect (FPE), and the rate of successful recanalization, determined by the expanded thrombolysis in cerebral infarction (eTICI 2b/3) at the end of treatment. The safety assessment included hemorrhagic and procedure-related complications.

Results: Of the 81 enrolled patients, 5 patients were treated using the quadruple coaxial system. Three men and 2 women, with a mean age of 77 years, were included in this study. The median baseline National Institutes of Health Stroke Scale score was 10 points, and a tissue plasminogen activator was administered to 2 patients. Four patients had M2 occlusions, and 1 patient had a P2 occlusion. In 4 cases, the guiding system could not be advanced distally because of extracranial vessel tortuosity. The quadruple coaxial system achieved a significantly higher rate of FPE (80% vs. 30%; P = 0.0401) than the standard coaxial system, with no postoperative intracerebral hemorrhage or procedure-related complications.

Conclusion: The quadruple coaxial system is a valuable approach for treating MeVOs with severe extracranial vessel tortuosity. This system offers a reliable and safe treatment modality when a guiding system cannot be advanced distally.

Introduction

Mechanical thrombectomy is a key therapeutic intervention for acute ischemic stroke. Approximately one-third of such cases are classified as a medium vessel occlusion (MeVO).¹⁾ The efficacy of mechanical thrombectomy for MeVO has been reported,²⁾ especially regarding the first pass effect (FPE). Achieving complete recanalization, as measured by the expanded thrombolysis in cerebral infarction (eTICI 2c/3) with a single pass, is a significant predictor of favorable outcomes for MeVO.³⁾ Effective reperfusion is needed for MeVO treatment; however, mechanical thrombectomy for MeVO can pose challenges and lead to complications because of the distal occlusion site, complex vascular structure, and narrow vessel diameter.^4,5) Thus, safe and accurate treatment techniques are essential for MeVOs to allow precise catheter control and support during intervention. Navigation of the guiding catheter as distally as possible plays a pivotal role in reducing these risks⁶⁾; however, in Asian populations, extracranial vessels tend to be tortuous, and distal navigation of the guiding catheter is often impeded.^7,8) Recently, there has been a surge in the utilization of distal access catheters (DACs), which are characterized by flexible, soft-tipped designs that offer exceptional transversability even in highly tortuous arteries.^9,10) The use of DACs has been established in the endovascular treatment of intracranial aneurysms with difficult access; however, the efficacy of DACs in MeVO cases with tortuous extracranial vessels remains unclear.¹¹⁾ Given the feasibility of inserting smaller aspiration catheters into 6-French (6-F) DACs, this study aimed to report on the efficacy of combining a 6-F DAC with a low-profile aspiration catheter, guiding catheter, and microcatheter to establish a quadruple coaxial system for treating MeVOs with tortuous extracranial arteries.

Materials and Methods

Study design

We retrospectively reviewed cases of MeVO that underwent mechanical thrombectomy at our institution between March 2022 and February 2024. This study was approved by the Institutional Ethics Committee (approval number 24040901), and informed consent was obtained through an opt-out process. MeVO was defined as occlusion in the M2-3, P2-3, and A2-3 segments.¹²⁾ Patients with secondary MeVO, tandem lesions, intracranial atherosclerotic disease, or interrupted treatments were excluded. Among 81 cases of MeVO, 5 were treated using the quadruple coaxial system, and 76 were treated using the standard coaxial system. All patients were preoperatively evaluated for vascular occlusion using MRA or CTA. Early ischemic changes were assessed using non-contrast CT or diffusion-weighted imaging and evaluated by the Alberta Stroke Program Early CT Score (ASPECTS; range: 0–10). Early ischemic changes in the posterior circulation were scored using posterior circulation-ASPECTS (range: 0–10).¹³⁾ Segments of the internal carotid artery (ICA) were classified by Fischer’s classification. All procedures were performed under local anesthesia, with femoral artery access as the initial approach. Recanalization status was evaluated using the eTICI scale.¹⁴⁾ Intracranial hemorrhage (ICH) was assessed using the Heidelberg bleeding score¹⁵⁾ based on the CT findings of the following day. Symptomatic ICH (sICH) was defined as ICH associated with more than a 4-point increase in the National Institutes of Health Stroke Scale (NIHSS) score.

Quadruple coaxial system

For the quadruple coaxial system, we used SOFIASELECT 6F (MicroVention, Aliso Viejo, CA, USA) or AXS Vecta 71 (Stryker Neurovascular, Fremont, CA, USA) as a 6-F DAC; AXS Vecta 46 (Stryker Neurovascular) or 3MAX (Penumbra, Alameda, CA, USA) as a low-profile aspiration catheter; and microcatheters including Phenom 21 160 cm (Medtronic, Minneapolis, MN, USA), Trevotrak 21 162 cm (Stryker Neurovascular), or Trevo Pro 14 157 cm (Stryker Neurovascular). For the guiding catheter, either an 8-F balloon guiding catheter (BGC) or a 6-F guiding sheath (GS) with an inner diameter >0.087 inch was used. The quadruple coaxial system is shown in Fig. 1. The operator decided on the device selection and technique. After the guiding catheter was navigated into the common carotid artery or ICA, the decision to use the quadruple coaxial system was made based on vessel tortuosity. If there was no resistance or delay of flow, the 6-F DAC was advanced as distally as possible. During thrombus retrieval, the stent retriever was withdrawn into the 6-F DAC, with simultaneous manual suction from the DAC using syringes. When using a BGC, the balloon was inflated during retrieval.

Fig. 1 Quadruple coaxial system. Configuration of the quadruple coaxial system (A). Proximal side of the system (B). GC, 6-F DAC, low-profile AC, and MC are shown on the left. Distal side of the system (C). GC, 6-F DAC, low-profile AC, and MC are shown on the left. AC, aspiration catheter; DAC, distal access catheter; GC, guiding catheter; MC, microcatheter

Data collection

Patient characteristics, NIHSS scores, use of tissue plasminogen activator (tPA), catheter positions, treatment methods, total number of passes, and the processing time from puncture to successful reperfusion (eTICI score of 2b/3) were reviewed. The primary efficacy outcomes were the rate of FPE, achievement of complete recanalization (eTICI 2c/3) with a single pass, and successful recanalization (eTICI 2b/3) at the end of treatment. The safety assessment included the rates of hemorrhagic and procedure-related complications.

Statistical analysis

All statistical analyses were conducted using JMP Pro 12 (SAS Institute, Cary, NC, USA). Qualitative variables are presented as frequency and percentage, and quantitative variables are summarized as median with interquartile range (IQR). Qualitative and quantitative variables were analyzed using Fisher’s exact test and the Mann–Whitney U-test, respectively. All reported P-values were 2-tailed, and statistical significance was set at P <0.05.

Results

Patient characteristics

Table 1 shows the baseline characteristics of the enrolled patients. Five patients were treated using the quadruple coaxial system. Three patients were men and 2 were women, with a mean age of 77 ± 13 years. The baseline NIHSS score was 10 points (IQR, 6–12 points), and tPA was administered to 2 patients. M2 occlusion was present in 4 cases, whereas P2 occlusion was observed in 1 case. There were no significant differences in baseline characteristics between the group treated with the quadruple coaxial system and the group treated with the standard system.

Table 1 Baseline characteristics of the 2 groups

Characteristic	Quadruple coaxial (n = 5)	Standard coaxial (n = 76)	P value
Mean age ± SD (years)	77 ± 13	78 ± 9	0.95
Male	3 (60)	49 (65)	>0.999
NIHSS score	10 (6–12)	13 (6–23)	0.984
ASPECTS	10 (9–10)	9 (8–10)	0.269
IV-tPA	2 (40)	33 (43)	>0.999
Hypertension	3 (60)	38 (51)	>0.999
Dyslipidemia	1 (20)	13 (17)	>0.999
Diabetes	1 (20)	15 (20)	>0.999
Atrial fibrillation	3 (60)	27 (36)	0.354
Previous stroke/TIA	2 (40)	9 (12)	0.134
Occlusion site
M2	4 (80)	64 (85)	>0.999
M3	0 (0)	5 (7)	>0.999
A2	0 (0)	4 (5)	>0.999
A3	0 (0)	0 (0)
P2	1 (20)	3 (4)	0.229
P3	0 (0)	0 (0)
Time intervals
Onset-to-door time (min)	120 (67–120)	92 (49–238)	0.694
Door-to-puncture time (min)	44 (39–45)	45 (36.5–55)	0.743

Values are median (interquartile range), number of patients (%), or as otherwise indicated.

ASPECTS, Alberta Stroke Program Early CT Score; IV-tPA, intravenous tissue plasminogen activator; NIHSS, National Institutes of Health Stroke Scale; SD, standard deviation; TIA, transient ischemic attack

Outcomes

The details and outcomes of the patients treated with the quadruple coaxial system are shown in Table 2. In 4 cases (Cases #1–4), the guiding catheter could not be advanced distal to the cervical portion because of the tortuosity of the extracranial vessels (Fig. 2). In 4 cases, we were able to navigate the 6-F DAC intradurally (Cases #1–4). In 1 case, owing to atherosclerotic changes in the cavernous ICA, we could not advance the 6-F DAC over the carotid siphon (Case #5). Contact aspiration was performed in 4 cases, and the combined technique was performed in 1 case, resulting in successful reperfusion (eTICI 2b/3) in all cases. FPE was observed in 4 cases. The median puncture-to-recanalization time was 38 min (IQR, 28–74 min). Postoperative ICH was not observed in any case, and complications associated with treatment, including vascular dissection and spasms, were absent. Table 3 shows the clinical outcomes in the quadruple coaxial system group and the standard coaxial group. The quadruple coaxial group achieved a significantly higher rate of FPE (80% vs. 30%; P = 0.0401). There were no significant differences in the rates of successful recanalization (eTICI 2b/3) at the end of treatment. In terms of safety outcomes, subarachnoid hemorrhage was absent in the quadruple coaxial group but was observed in 19 patients (25%) in the standard coaxial group (P = 0.586). The incidence of any sICH and procedure-related complications did not differ between the 2 groups. Graphical views of a representative case during treatment are shown in Fig. 3.

Table 2 Details and outcomes of the cases treated using the quadruple coaxial system

Case	#1	#2	#3	#4	#5
Age (years)	88	55	86	82	74
Sex	Female	Male	Male	Female	Male
Premorbid mRS	4	0	2	0	2
Baseline NIHSS score	28	6	10	5	12
Occlusion site	Lt.M2 inf	Lt.P2	Rt.M2 sup	Lt.M2 sup	Rt.M2 sup
ASPECTS	5 (CT)	9 (DWI)†	6 (DWI)	9 (DWI)	9 (DWI)
IV-tPA	No	Yes	No	No	Yes
BGC/GS	8-F Emboguard 95 cm	6-F Fubuki XF GS 90 cm	8-F Optimo flex 90 cm	8-F Optimo flex 90 cm	8-F Emboguard 95 cm
BGC/GS placement	ICA orifice	VA orifice	ICA cervical portion	CCA (ICA–ECA bifurcation)	ICA pre-petrous portion
6-F DAC	SOFIASELECT 6F 125 cm	SOFIASELECT 6F 125 cm	AXS Vecta 71 125 cm	SOFIASELECT 6F 125 cm	SOFIASELECT 6F 115 cm
6-F DAC placement	ICA C2–3	V3–4	ICA C1–2	ICA C1–2	ICA C4–5
Low-profile AC	AXS Vecta 46	AXS Vecta 46	AXS Vecta 46	3MAX	AXS Vecta 46, 3MAX
Technique	1. Combined with Tron Fx 4 × 20 mm	1. CA	1. CA	1. CA	1. CA (AXS Vecta 46) 2. CA (3MAX)
Number of passes	1	1	1	1	2
P-to-R time (min)	74	28	21	38	80
Final eTICI	3	3	3	3	2b67
ICH	No	No	No	No	No
Other complication	No	No	No	No	No
90 days mRS	4	0	2	0	4

^†ASPECTS was scored by pc-ASPECTS.

3MAX, Penumbra, Alameda, CA, USA; AC, aspiration catheter; 6-F Fubuki XF GS 90 cm, ASAHI INTECC, Aichi, Japan; 8-F Emboguard 95 cm, CERENOVUS, Johnson & Johnson Medical Devices, Irvine, CA, USA; 8-F Optimo flex 90 cm, Tokai Medical Products, Aichi, Japan; ASPECTS, Alberta Stroke Program Early CT Score; AXS Vecta 46, Stryker Neurovascular, Fremont, CA, USA; AXS Vecta 71, Stryker Neurovascular; BGC, balloon guiding catheter; CA, contact aspiration; CCA, common carotid artery; DAC, distal access catheter; DWI, diffusion-weighted imaging; ECA, external carotid artery; eTICI, expanded thrombolysis in cerebral infarction; GS, guiding sheath; ICA, internal carotid artery; ICH, intracerebral hemorrhage; inf, inferior trunk; IV-tPA, intravenous tissue plasminogen activator; Lt., left; mRS, modified Rankin Scale; NIHSS, National Institutes of Health Stroke Scale; P-to-R, puncture-to-recanalization; Rt., right; SOFIASELECT 6F, MicroVention, Aliso Viejo, CA, USA; sup, superior trunk; Tron Fx 4 × 20 mm, Terumo, Tokyo, Japan; VA, vertebral artery

Fig. 2 Images of extracranial vessel tortuosity. Anterior–posterior angiography of Case #1 shows notable extracranial vessel tortuosity (A). Owing to the tortuosity, the BGC is positioned at the left ICA orifice (arrowhead, A). A kinky right VA orifice is observed on the initial angiography of Case #2 (B). Owing to this kink, it was difficult for the guiding sheath to advance distally (arrowhead, B). Lateral angiography of Case #3 shows a narrow-angle cervical ICA, in which the surgeon was unable to navigate the BGC distally (arrowhead, C). A curved ICA is observed in the cervical portion on the initial angiography of Case #4 (D). BGC, balloon guiding catheter; ICA, internal carotid artery; VA, vertebral artery

Table 3 Clinical outcomes of the 2 groups

	Quadruple coaxial (n = 5)	Standard coaxial (n = 76)	P value
Procedural outcomes
First-line strategy
Combined	1 (20)	40 (47)	0.201
CA	4 (80)	36 (52)	0.201
Reperfusion
FPE	4 (80)	23 (30)	0.0401
Final eTICI score 2b/2c/3	5 (100)	65 (85)	>0.999
Final eTICI score 2c/3	4 (80)	40 (47)	0.369
Final eTICI score 3	4 (80)	31 (41)	0.16
Number of passes	1 (1)	1 (1–2)	0.293
P-to-R time (min)	38 (28–74)	50 (32–69)	0.658
Clinical outcomes
90 days mRS 0–2	3 (60)	37 (49)	0.675
Mortality	0 (0)	5 (7)	>0.999
Safety outcomes
Any ICH	0 (0)	19 (25)	0.586
SAH	0 (0)	17 (22)	0.578
sICH	0 (0)	1 (1)	>0.999
Procedure-related complication	0 (0)	2 (3)	>0.999

Values are median (interquartile range), number of patients (%), or as otherwise indicated.

CA, contact aspiration; eTICI, expanded thrombolysis in cerebral infarction; FPE, first pass effect; ICH, intracerebral hemorrhage; mRS, modified Rankin Scale; P-to-R, puncture-to-recanalization; SAH, subarachnoid hemorrhage; sICH, symptomatic intracerebral hemorrhage

Fig. 3 Treatment images of Case #4. MRA reveals tortuous extracranial vessels (A). Anterior–posterior (B) and lateral (C) views of the left M2 superior trunk occlusion. A curved ICA is observed in the cervical portion. Because of the tortuosity, the BGC was positioned at the CCA just proximal to the ICA–ECA bifurcation (arrowhead, E). The 6-F DAC was advanced and positioned in the ICA C2–3 portion (arrow, D, E). From the 6-F DAC, a coaxial microcatheter with a low-profile aspiration catheter was advanced to the occlusion site. Contact aspiration was performed with a low-profile aspiration catheter, and it was retrieved into the 6-F DAC. The red thrombus was retrieved (F). Final anterior–posterior (G) and lateral (H) angiography show eTICI 3 recanalization without any findings of vessel dissection or vasospasm. BGC, balloon guiding catheter; CCA, common carotid artery; DAC, distal access catheter; ECA, external carotid artery; eTICI, expanded thrombolysis in cerebral infarction; ICA, internal carotid artery

Discussion

Herein, we report the efficacy of the quadruple coaxial system for MeVO cases with extracranial vessel tortuosity. The FPE and recanalization rates of this system remained favorable even in tortuous extracranial vessels, ensuring safe treatment for all cases and establishing it as an additional therapeutic option. The main advantage of this approach lies in treating MeVOs with low-profile aspiration catheters, while using the 6-F DAC as an intermediate catheter in situations where distally advancing the guiding system is difficult because of severe extracranial vessel tortuosity. Jeong et al. reported that the distal location of the BGC was independently associated with a successful recanalization rate.⁶⁾ However, attempting to advance a large guiding catheter into tortuous vessels may induce iatrogenic dissection or severe spasm, leading to treatment interruption. The DACs used in this study are recognized for their flexibility, allowing smooth advancement even in tortuous vessels.^9,10) Placing DACs between the guiding catheter and treatment devices reduces vascular friction resistance, improves maneuverability within the intracranial space, and enhances device support.¹⁶⁾

In mechanical thrombectomy for MeVO, the combined technique with a smaller aspiration catheter demonstrated a higher recanalization rate, FPE rate, and a lower incidence of sICH than the single use of a stent retriever.^17–19) Direct aspiration with a low-profile aspiration catheter in MeVO has also been reported to be effective and safe.²⁰⁾ When employing a combined technique or contact aspiration with smaller aspiration catheters for MeVO treatment, tortuous extracranial vessels may destabilize microcatheter control if the treatment devices are too far from the guiding system, which correlates with failed recanalization or hemorrhagic complications.¹¹⁾ Using a 6-F DAC as an additional platform makes the smaller treatment system easier to control, especially where tortuosity is present. In our study, the quadruple system was associated with a successful recanalization rate and FPE without ICH, suggesting a precise and safe method for mechanical thrombectomy in MeVOs with severe extracranial vessel tortuosity.

Another advantage of the quadruple system is the potential to prevent distal emboli via flow control from the 6-F DAC. Continuous suction from the aspiration catheter in the combined technique has reportedly decreased emboli in new regions.²¹⁾ Similarly, our technique incorporated manual continuous suction from the 6-F DAC, which was not associated with any distal emboli. Nogueira et al. have reported the potential of controlling collateral flow via the anterior and posterior communicating arteries by applying continuous suction from a large-bore intracranial catheter placed at the M1 segment.²²⁾ Depending on the case, inducing the 6-F DAC distally to the ICA terminus may help prevent distal emboli.

Finally, this technique appears to contribute to reducing hemorrhagic complications through vessel shift mitigation. The high risk of intracranial hemorrhage due to vessel stretching in cases of severe extracranial vessel tortuosity in MeVO has been reported.²³⁾ Inducing an aspiration catheter near the stent retriever is used to avoid the stretching of vessels.²⁴⁾ The aspiration catheter with proximal balloon technique, in which the stent retriever is completely withdrawn into the aspiration catheter, has been reported to result in fewer hemorrhagic complications.²⁵⁾ In our study, bringing the 6-F DAC as close as possible to the occlusion site may have reduced vessel shift and lowered hemorrhagic complications.

One important technical aspect of this technique is the presence of atherosclerotic changes in the intracranial vessels, which can prevent advancement of the 6-F DAC at the distal site, as in Case #5. The mean (± standard deviation) diameters of intracranial vessels have been reported as 3.95 ± 0.56 mm for the supraclinoid segment of the ICA,²⁶⁾ 2.2 ± 0.2 mm for the M1 proximal segment,²⁷⁾ and 3.9 ± 0.8 mm for the intradural entry of the vertebral artery.²⁸⁾ The outer diameters of the 6-F DACs used in this study (SOFIASELECT 6F at 2.1 mm [MicroVention], AXS Vecta 71 at 2.08 mm [Stryker Neurovascular]) suggest that advancement up to the proximal M1 segment and V4 may be feasible. However, atherosclerotic changes may lead to the formation of ledges or narrowing of the vessel diameter, making catheter advancement more difficult. Steam shaping the tip of the DAC²⁹⁾ or using delivery assist catheters³⁰⁾ could be solutions to avoid ledges. Thus, assessing the atherosclerotic changes of intracranial vessels based on pretreatment MRA or CTA is important in determining the treatment strategy.

The limitations of this study include its single-center, retrospective design, as well as its small sample size. Further prospective studies with larger patient cohorts are required to assess the efficacy of this technique.

Conclusion

The quadruple coaxial system, combining a 6-F DAC with a low-profile aspiration catheter along with a guiding catheter and microcatheter, appears to be a valuable additional option for MeVOs with severe extracranial vessel tortuosity. In cases where the guiding system cannot adequately advance distally, this approach may offer a reliable and safe treatment modality.

Disclosure Statement

The authors declare that they have no conflicts of interest.

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