Telescope-Assisted Combined Thrombectomy (TACT-MeVO) for M2 Occlusion: A Technical Note and Initial Experience

Abstract

Objective

This study aimed to describe telescope-assisted combined thrombectomy for medium vessel occlusion (TACT-MeVO) in patients with M2 occlusion and report our initial experience.

Methods

We retrospectively reviewed 52 thrombectomy procedures in 51 patients with M2 occlusion between May 2015 and April 2026: 45 historical-protocol and 7 TACT-MeVO procedures. In TACT-MeVO, a small-bore aspiration catheter and stent retriever are withdrawn together into a large-bore M1 aspiration catheter. Outcomes and between-group P values were exploratory and descriptive; the study was not powered to test superiority.

Results

TACT-MeVO was first-line in all 7 procedures. Baseline CT–Alberta Stroke Program Early CT Score was numerically higher in the TACT-MeVO group but did not differ significantly (P = 0.069). Median puncture-to-recanalization/procedure-end time was 59 vs. 71 min (P = 0.014). One-pass completion was achieved in 6/7 (85.7%) vs. 23/45 procedures (51.1%; P = 0.117), and final modified Thrombolysis in Cerebral Infarction ≥2b in 7/7 (100%) vs. 39/45 procedures (86.7%; P = 0.580). Any subarachnoid hemorrhage occurred in 2/7 vs. 8/45 procedures (P = 0.608); both TACT-MeVO events were asymptomatic. Three-month modified Rankin Scale score 0–2 did not differ significantly (5/7 vs. 16/45; P = 0.104). A post hoc comparison with 29 procedures using conventional combined thrombectomy also showed a shorter procedural time (59 vs. 70 min; P = 0.004).

Conclusion

TACT-MeVO was technically feasible in this initial 7-procedure experience. Comparative findings are descriptive; superiority or safety cannot be inferred because of the small sample, baseline imbalance, and historical comparator.

Introduction

Endovascular thrombectomy has become the standard of care for acute ischemic stroke caused by proximal large vessel occlusion. In contrast, the role of thrombectomy in medium vessel occlusion (MeVO) remains unclear. MeVOs, including those involving the M2 or M3 segments of the middle cerebral artery, A2 or A3 segments of the anterior cerebral artery, and P2 or P3 segments of the posterior cerebral artery, account for a substantial proportion of acute ischemic strokes and may cause disabling neurological deficits despite their relatively distal location.^1,2) Among these lesions, M2 occlusions are particularly heterogeneous in terms of vessel caliber, branching pattern, tortuosity, and eloquence of the supplied territory, making patient selection and procedural strategy clinically challenging.^1,3)

Recent randomized trials have tempered enthusiasm for routine thrombectomy in unselected patients with MeVO. ESCAPE-MeVO and DISTAL did not demonstrate superior functional outcomes with endovascular treatment compared with best medical treatment or usual care, and they raised concerns regarding symptomatic intracranial hemorrhage and procedure-related harm.^4,5) Conversely, ORIENTAL-MeVO suggested a potential benefit of thrombectomy in patients with moderate-to-severe deficits, although this benefit was accompanied by a higher risk of symptomatic intracranial hemorrhage.⁶⁾ These mixed results indicate that the future of MeVO thrombectomy may depend not only on appropriate patient selection but also on the refinement of safer and more efficient techniques.

Several technical approaches have been used to treat M2 and distal occlusions, including stent retriever thrombectomy, direct aspiration, and combined techniques. Appropriately sized stent retrievers have enabled the treatment of more distal and tortuous arteries. However, manipulation within small vessels may increase the risk of vasospasm, endothelial injury, dissection, perforation, or subarachnoid hemorrhage.⁷⁾ Direct aspiration is an attractive strategy because of its simplicity and the potentially reduced need for distal device deployment. However, in small-caliber vessels, precise engagement of the thrombus with the aspiration catheter can be technically difficult, and experimental studies have suggested that aspiration may induce arterial collapse, particularly in smaller vessels or those under proximal flow arrest.^8,9) In addition, the suction force decreases with increasing distance between the catheter tip and the thrombus, emphasizing the importance of stable catheter–clot interactions during aspiration thrombectomy.¹⁰⁾

Combined techniques using a stent retriever and an aspiration catheter have been proposed to improve clot capture and first-pass reperfusion. A previous systematic review suggested that combined techniques for distal MeVO may achieve higher first-pass reperfusion rates and lower symptomatic intracranial hemorrhage rates than single-device techniques, although the available evidence remains observational and heterogeneous.¹¹⁾ Mini-pinning and related techniques have also shown that the coordinated use of a small stent retriever and a low-profile aspiration catheter is feasible for distal occlusions.¹²⁾ Nevertheless, when the entire stent–catheter system is retrieved from an M2 branch toward a proximal guide catheter, traction on the tortuous M2–M1 axis may contribute to vessel shift, which may be undesirable in fragile MeVO anatomies.

To address these issues, we developed a telescope-assisted combined thrombectomy (TACT) technique for M2 occlusion, called TACT-MeVO. In this technique, a large-bore aspiration catheter is positioned in the M1 segment as the proximal receiving catheter, whereas a small-bore aspiration catheter and an appropriately sized stent retriever are used as a combined unit at the M2 occlusion site. The distal system is then retrieved into the large-bore aspiration catheter positioned in the M1 segment to shorten the distal retrieval distance and potentially limit vessel shift (Fig. 1). This technical note describes the procedural concept of TACT-MeVO and reports our initial single-center experience in patients with acute ischemic stroke due to M2 occlusion. The accompanying historical-protocol comparison is provided only as exploratory, descriptive context and was not designed to establish the superiority of TACT-MeVO.

Fig. 1. Conceptual comparison of conventional combined thrombectomy and the TACT-MeVO technique. (A) In conventional combined thrombectomy, the stent retriever and aspiration catheter are withdrawn from the M2 segment toward the BGC, creating a long retrieval vector along the tortuous M2–M1 axis that may transmit traction to the vessel. (B) In TACT-MeVO, a large-bore aspiration catheter is positioned in the M1 segment as a receiving catheter, and the distal combined unit, consisting of a small-bore aspiration catheter and a stent retriever, is retrieved into it under aspiration. This configuration shortens the distal retrieval path and is intended to limit traction and vessel shift. This proposed effect is conceptual and was not quantitatively assessed in this study. (C) The inset illustrates a potential limitation of direct aspiration: remote aspiration may induce vessel collapse without effective clot engagement, particularly in small-caliber vessels.

BGC, balloon-guiding catheter; TACT-MeVO, telescope-assisted combined thrombectomy for medium vessel occlusion

Materials and Methods

Study design and patient population

This was a single-center, retrospective, observational study of consecutive thrombectomy procedures performed in patients with acute ischemic stroke due to M2 occlusion at Nagoya City University Hospital between May 2015 and April 2026. The unit of analysis was the thrombectomy procedure. One patient underwent 2 procedures for recurrent M2 occlusion; therefore, 52 procedures in 51 patients were included. The procedures were divided into 2 groups according to the procedural protocol: the historical-protocol group, in which the thrombectomy strategy was selected at the discretion of the operator, and the TACT-MeVO group, in which telescope-assisted combined thrombectomy was used as the first-line strategy for M2 occlusion. The historical-protocol group comprised 45 procedures performed between May 2015 and January 2025, whereas the TACT-MeVO group comprised 7 procedures performed between May 2025 and April 2026. Treatment allocation was not randomized but was determined by the procedural protocol in use during each period.

The occlusion site was determined using the initial diagnostic cerebral angiogram obtained immediately before thrombectomy. Cases initially suspected to have distal M1 occlusion on preprocedural imaging were included if the angiogram demonstrated that the occlusion was located in the M2 segment. Proximal and distal M2 occlusions were defined as those located ≤10 mm and >10 mm distal to the main middle cerebral artery bifurcation/trifurcation, respectively, according to the anatomical definitions used in the ESCAPE-MeVO trial.¹³⁾ Baseline clinical and imaging variables, including age, sex, vascular risk factors, prestroke modified Rankin Scale (mRS) score, baseline National Institutes of Health Stroke Scale (NIHSS) score, intravenous thrombolysis, occlusion site, and Alberta Stroke Program Early CT Score (ASPECTS), were retrospectively collected from medical records and imaging databases. All available pretreatment non-contrast CT scans were systematically reviewed, and CT-ASPECTS was recorded irrespective of whether pretreatment MRI had also been performed. Diffusion-weighted imaging (DWI)–ASPECTS was recorded separately when pretreatment DWI was available and was not substituted for CT-ASPECTS. CT-ASPECTS and DWI-ASPECTS were available for 49 and 21 of the 52 procedures, respectively.

This study was approved by the Nagoya City University Institutional Review Board (approval no. 60-26-0041). The requirement for written informed consent was waived due to the retrospective nature of the study, and information regarding the study was disclosed using an opt-out approach.

TACT-MeVO technique

The TACT-MeVO technique is a telescope-assisted combined thrombectomy strategy for M2 occlusion. The main concept of this technique is to position a large-bore aspiration catheter in the M1 segment as a proximal receiving catheter and retrieve the distal combined system, consisting of a small-bore aspiration catheter and an appropriately sized stent retriever, into the large-bore catheter. This approach is intended to shorten the distal retrieval distance and potentially limit vessel shift during clot retrieval.

An 8-Fr balloon-guiding catheter was placed in the cervical internal carotid artery. A coaxial system consisting of a 0.014-inch microguidewire, a 0.021-inch microcatheter, a small-bore aspiration catheter, and a large-bore aspiration catheter was advanced into the intracranial circulation. The aspiration catheter system was selected based on device availability, operator preference, and coaxial compatibility. Accordingly, device configurations were not standardized across the 7 TACT-MeVO procedures. To ensure length compatibility, large- and small-bore aspiration catheters were used as same-manufacturer paired systems: Vecta 71 132-cm plus Vecta 46 146-cm catheters (Stryker, Kalamazoo, MI, USA), SALVA 71 132-cm plus SALVA 41 147-cm catheters (Nipro, Osaka, Japan), and CEREGLIDE 71 125-cm plus CEREGLIDE 42 142-cm catheters (Cerenovus, Johnson & Johnson, Irvine, CA, USA). A large-bore aspiration catheter was placed in the proximal M1 segment. The thrombus was then crossed using a 0.014-inch microguidewire and a 0.021-inch microcatheter, and an appropriately sized stent retriever, selected at the operator’s discretion according to vessel caliber and thrombus location, was deployed across the occlusive thrombus.

After deployment of the stent retriever, the 0.021-inch microcatheter was removed before aspiration was initiated through the small-bore aspiration catheter because the presence of the microcatheter within the small-bore aspiration catheter may reduce the effective aspiration lumen. During microcatheter removal, the fully deployed stent retriever served as an anchor to maintain the position of the system.

Continuous aspiration was then performed using the small-bore aspiration catheter, which was carefully advanced to the proximal face of the thrombus to achieve clot engagement and pinning. With continuous aspiration maintained through the small-bore aspiration catheter, the stent retriever and the small-bore aspiration catheter were retrieved together as a single combined unit into the large-bore aspiration catheter positioned in the M1 segment. Manual aspiration with a syringe was performed using the large-bore aspiration catheter during retrieval. After the distal system was withdrawn into the large-bore catheter, angiography was performed to assess reperfusion (Fig. 2).

Fig. 2. Step-by-step illustration of the TACT-MeVO technique. (A) After crossing the thrombus with a 0.014-inch microguidewire and a 0.021-inch microcatheter, an appropriately sized stent retriever is deployed across the thrombus. (B) A large-bore aspiration catheter is positioned in the proximal M1 segment as a receiving catheter. The microcatheter is removed, and a small-bore aspiration catheter is advanced to the proximal face of the thrombus under continuous aspiration. The thrombus is pinned between the small-bore aspiration catheter and the deployed stent retriever. (C) The stent retriever and small-bore aspiration catheter are retrieved together as a single combined unit into the large-bore aspiration catheter while aspiration is maintained through both aspiration catheters. This telescope-assisted retrieval shortens the distal retrieval path and is intended to limit traction on the M2–M1 axis; its effect on vessel shift was not quantitatively assessed.

TACT-MeVO, telescope-assisted combined thrombectomy for medium vessel occlusion

If sufficient reperfusion was not achieved after the first pass, the subsequent thrombectomy strategy was determined at the discretion of the treating operator. Vessel displacement during retrieval was not quantitatively assessed in this retrospective study.

Outcomes

Procedural outcomes included puncture-to-recanalization or procedure-end time, number of device passes, one-pass completion, first-pass reperfusion, final reperfusion status, and procedure-related complications. Successful reperfusion was defined as a final modified Thrombolysis in Cerebral Infarction (mTICI) score of 2b or higher, whereas excellent reperfusion was defined as an mTICI score of 2c or higher. These thresholds were applied separately to first-pass and final reperfusion outcomes. Procedure-related complications included vasospasm, vessel perforation, dissection, distal embolization within the treated vascular territory, and embolization to a new territory.

Anatomical and angiographic variables were retrospectively assessed using procedural DSA. The M1–M2 angle was measured on the anteroposterior projection. The distance from the main middle cerebral artery bifurcation to the occlusion, M1 diameter, and target M2 diameter were also measured. When the target M2 segment could not be adequately visualized before recanalization, its diameter was measured after recanalization. Postretrieval vasospasm was graded according to the estimated diameter reduction as none/minimal (<25%), mild (≥25% to <50%), moderate (≥50% to <75%), or severe (≥75%). Flow limitation and any treatment administered for vasospasm were recorded separately.

Safety outcomes included any subarachnoid hemorrhage, symptomatic subarachnoid hemorrhage, asymptomatic and symptomatic intracranial hemorrhage or hyperdensity, and other procedure-related complications. Available immediate postprocedural CT or cone-beam CT and follow-up CT obtained at approximately 24 hours were retrospectively reviewed. Definite hemorrhagic findings were classified according to the Heidelberg Bleeding Classification.¹⁴⁾ Transient hyperdensities that resolved on follow-up imaging and were considered possible contrast staining were not assigned a definite Heidelberg category but were conservatively included in the intracranial hemorrhage/hyperdensity analysis. Any subarachnoid hemorrhage was broadly defined as any postprocedural subarachnoid hyperdensity on imaging, including definite subarachnoid hemorrhage and possible contrast staining with a subarachnoid pattern when hemorrhage could not be excluded. A hemorrhagic finding was classified as symptomatic when neurological deterioration corresponding to an increase of ≥4 points in the NIHSS score was documented; all other hemorrhagic findings were classified as asymptomatic.

Clinical outcomes were assessed using the mRS scores at 90 days. A favorable functional outcome was defined as an mRS score of 0–2 at 90 days.

Statistical analysis

Continuous variables are presented as medians with interquartile ranges and were compared using the Mann–Whitney U-test. Categorical variables are presented as numbers and percentages and were compared using Fisher’s exact test. Analyses were performed on a per-procedure basis. One patient contributed 2 procedures, and no adjustment for within-patient clustering was applied because all other patients contributed only 1 procedure. Missing data were analyzed using available cases, with the applicable denominators reported.

This study was an exploratory analysis of an initial experience with TACT-MeVO and was not designed or powered to test the superiority of TACT-MeVO. No formal sample-size calculation was performed. Given the small TACT-MeVO group (7 procedures) and the limited number of outcome events, propensity-score matching and multivariable adjustment, including adjustment for CT-ASPECTS, were not performed; the former would have yielded a very small and potentially unstable matched sample, and the latter would have been prone to overfitting. Accordingly, only unadjusted comparisons are presented. All P values should be interpreted as exploratory and descriptive. No adjustment for multiple comparisons was performed.

To explore potential temporal confounding, treatment-year distributions were summarized for both groups. Within the historical-protocol group, associations between treatment year and procedural time (puncture-to-recanalization or procedure-end time) and between treatment year and first-pass mTICI ≥2b reperfusion were assessed using Spearman’s rank correlation. Two additional exploratory analyses were performed using the same unadjusted group-comparison methods described above. The 1st was a temporal sensitivity analysis comparing historical-protocol procedures performed during 2022–2025 with all TACT-MeVO procedures performed during 2025–2026. The 2022 calendar-year cutoff was selected because Code AIS, an institution-wide protocol for acute stroke triage and treatment-team activation, was implemented at the study institution early in 2022 and was previously associated with a substantial reduction in door-to-puncture time.¹⁵⁾ The calendar-year cutoff also retained a reasonably sized historical comparator group for this exploratory analysis. The 2nd was a post hoc technique-specific analysis comparing 29 historical-protocol procedures treated with conventional combined thrombectomy as the first-pass strategy with the 7 TACT-MeVO procedures. Conventional combined thrombectomy was defined as first-pass use of a stent retriever together with an intracranial aspiration catheter, without an additional large-bore aspiration catheter positioned in the M1 segment as a receiving catheter.

Statistical analyses were performed using EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan), a graphical user interface for the R software (R Foundation for Statistical Computing, Vienna, Austria). All P values were 2-sided, and P <0.05 was considered nominally significant.

Results

Patient characteristics

A total of 52 consecutive thrombectomy procedures were performed in 51 patients with acute ischemic stroke due to M2 occlusion during the study period. One patient underwent 2 procedures for recurrent M2 occlusion. Of the 52 procedures, 45 were classified into the historical-protocol group and 7 into the TACT-MeVO group. The baseline characteristics are summarized in Table 1. The TACT-MeVO group was numerically younger and had a lower baseline NIHSS score than the historical-protocol group, although these differences were not statistically significant (median age, 75 vs. 82 years; P = 0.110; median NIHSS score, 14 vs. 17; P = 0.555). Dyslipidemia was less frequent (0% vs. 46.5%; P = 0.033), and CT-ASPECTS was numerically higher in the TACT-MeVO group but did not differ significantly (10 [10–10] vs. 9 [8–10]; P = 0.069; CT-ASPECTS available in 6/7 and 43/45 procedures).

Table 1. Baseline characteristics.

Variable	Overall (N = 52)	Historical protocol (N = 45)	TACT-MeVO (N = 7)	P value
Demographics and baseline severity
Age, years	80 [73.8–85]	82 [74–85]	75 [71–78]	0.110
Female sex	28/52 (53.8%)	23/45 (51.1%)	5/7 (71.4%)	0.430
Pre-stroke mRS	0 [0–2]	0 [0–2]	0 [0–1]	0.824
Baseline NIHSS	17 [12–22.2]	17 [13–22]	14 [9–21]	0.555
In-hospital onset	7/52 (13.5%)	5/45 (11.1%)	2/7 (28.6%)	0.235
Left-sided occlusion	34/52 (65.4%)	30/45 (66.7%)	4/7 (57.1%)	0.682
Vascular risk factors
Hypertension	37/50 (74.0%)	32/43 (74.4%)	5/7 (71.4%)	1.000
Diabetes mellitus	10/50 (20.0%)	10/43 (23.3%)	0/7 (0.0%)	0.319
Dyslipidemia	20/50 (40.0%)	20/43 (46.5%)	0/7 (0.0%)	0.033
Atrial fibrillation	21/35 (60.0%)	15/28 (53.6%)	6/7 (85.7%)	0.203
Current smoking	6/30 (20.0%)	4/24 (16.7%)	2/6 (33.3%)	0.571
Imaging and acute treatment
CT-ASPECTS	9 [8–10]	9 [8–10] (n = 43)	10 [10–10] (n = 6)	0.069
DWI-ASPECTS	7 [7–8]	7 [7–8] (n = 18)	10 [8.5–10] (n = 3)	0.118
MRI performed	28/52 (53.8%)	24/45 (53.3%)	4/7 (57.1%)	1.000
Intravenous thrombolysis	24/52 (46.2%)	22/45 (48.9%)	2/7 (28.6%)	0.430
Occlusion anatomy
Treated M2 division				0.698
Superior division	25/52 (48.1%)	21/45 (46.7%)	4/7 (57.1%)
Inferior division	27/52 (51.9%)	24/45 (53.3%)	3/7 (42.9%)
M2 occlusion location				0.694
Proximal M2 (≤10 mm)	20/52 (38.5%)	18/45 (40.0%)	2/7 (28.6%)
Distal M2 (>10 mm)	32/52 (61.5%)	27/45 (60.0%)	5/7 (71.4%)
M1–M2 angle, °	103 [76–131]	107.5 [80.5–135.5]	80 [69–92]	0.095
Bifurcation-to-occlusion distance, mm	14.2 [6.3–17.4]	14.1 [4.1–18.2]	14.9 [10.4–15.4]	0.717
M1 diameter, mm	3.0 [2.6–3.4]	3.0 [2.6–3.4]	2.7 [2.3–3.5]	0.591
Target M2 diameter, mm	2.2 [1.8–2.5]	2.2 [1.8–2.6]	2.0 [1.7–2.3]	0.360
Stroke etiology				0.549
Cardioembolic	39/52 (75.0%)	33/45 (73.3%)	6/7 (85.7%)
Cancer-related	3/52 (5.8%)	3/45 (6.7%)	0/7 (0.0%)
Other embolic/ESUS	5/52 (9.6%)	5/45 (11.1%)	0/7 (0.0%)
Atherothrombotic	3/52 (5.8%)	3/45 (6.7%)	0/7 (0.0%)
Dissection	1/52 (1.9%)	1/45 (2.2%)	0/7 (0.0%)
Other	1/52 (1.9%)	0/45 (0.0%)	1/7 (14.3%)

Values are median [IQR] or n/N (%). N denotes thrombectomy procedures; 1 patient contributed 2 procedures. P values: Mann–Whitney U-test for continuous variables; Fisher’s exact test for categorical variables. Proximal and distal M2 occlusions were defined as those located ≤10 mm and >10 mm distal to the main middle cerebral artery bifurcation/trifurcation, respectively, according to the anatomical definitions used in the ESCAPE-MeVO trial. The M1–M2 angle was measurable in 51/52 procedures. CT-ASPECTS and DWI-ASPECTS were available in 49/52 and 21/52 procedures, respectively; group-specific denominators are shown where data were missing. All P values are exploratory and descriptive; no adjustment was made for multiple comparisons.

ASPECTS, Alberta Stroke Program Early CT Score; DWI, diffusion-weighted imaging; ESUS, embolic stroke of undetermined source; IQR, interquartile range; M1, 1st segment of the middle cerebral artery; M2, 2nd segment of the middle cerebral artery; mRS, modified Rankin Scale; NIHSS, National Institutes of Health Stroke Scale; TACT-MeVO, telescope-assisted combined thrombectomy for medium vessel occlusion

Regarding occlusion anatomy, the TACT-MeVO group had a numerically smaller M1–M2 angle (80° [69–92°] vs. 107.5° [80.5–135.5°]; P = 0.095). No statistically significant differences were observed in the proximal/distal M2 distribution, bifurcation-to-occlusion distance, M1 diameter, or target M2 diameter.

Procedural and angiographic outcomes

The procedural and angiographic outcomes are shown in Table 2. TACT-MeVO was used as the predefined first-line strategy in all 7 procedures. Device configurations were not uniform: 3 aspiration–catheter combinations and 3 stent retriever models in 5 size configurations were used. Detailed procedural characteristics of the 7 TACT-MeVO procedures are provided in Supplementary Table 1.

Table 2. Procedural and clinical outcomes.

Variable	Overall (N = 52)	Historical protocol (N = 45)	TACT-MeVO (N = 7)	P value
Workflow metrics
Door-to-puncture time, min	124 [67–151.5]	123.5 [67–145.5]	152 [75–196.5]	0.298
Puncture-to-recanalization/procedure-end time, min	69 [58.5–90.5]	71 [60–110.5]	59 [51–61.5]	0.014
Number of passes	1 [1–2]	1 [1–2]	1 [1–1]	0.127
One-pass completion	29/52 (55.8%)	23/45 (51.1%)	6/7 (85.7%)	0.117
First-pass technique
Stent retriever alone	3/52 (5.8%)	3/45 (6.7%)	0/7 (0.0%)
Aspiration alone	9/52 (17.3%)	9/45 (20.0%)	0/7 (0.0%)
Conventional combined thrombectomy	29/52 (55.8%)	29/45 (64.4%)	0/7 (0.0%)
Other	4/52 (7.7%)	4/45 (8.9%)	0/7 (0.0%)
TACT-MeVO	7/52 (13.5%)	0/45 (0.0%)	7/7 (100%)
Device configuration in TACT-MeVO cases
Aspiration catheter pair
Vecta 71 + Vecta 46	—	—	2/7 (28.6%)	—
SALVA 71 + SALVA 41	—	—	1/7 (14.3%)	—
CEREGLIDE 71 + CEREGLIDE 42	—	—	4/7 (57.1%)	—
Stent retriever
Solitaire X 3 × 20 mm	—	—	1/7 (14.3%)	—
Solitaire X 3 × 40 mm	—	—	1/7 (14.3%)	—
Trevo NXT 3 × 32 mm	—	—	3/7 (42.9%)	—
EmboTrap III 5 × 22 mm	—	—	1/7 (14.3%)	—
EmboTrap III 5 × 37 mm	—	—	1/7 (14.3%)	—
Angiographic outcomes
First-pass mTICI ≥2b	29/52 (55.8%)	23/45 (51.1%)	6/7 (85.7%)	0.117
First-pass mTICI ≥2c	19/52 (36.5%)	16/45 (35.6%)	3/7 (42.9%)	0.697
Final mTICI ≥2b	46/52 (88.5%)	39/45 (86.7%)	7/7 (100.0%)	0.580
Final mTICI ≥2c	26/52 (50.0%)	23/45 (51.1%)	3/7 (42.9%)	1.000
Safety outcomes
Any SAH	10/52 (19.2%)	8/45 (17.8%)	2/7 (28.6%)	0.608
Symptomatic SAH	4/52 (7.7%)	4/45 (8.9%)	0/7 (0.0%)	1.000
Asymptomatic intracranial hemorrhage/hyperdensity	12/52 (23.1%)	10/45 (22.2%)	2/7 (28.6%)	0.656
Symptomatic intracranial hemorrhage	6/52 (11.5%)	6/45 (13.3%)	0/7 (0.0%)	0.580
Any vasospasm	17/52 (32.7%)	14/45 (31.1%)	3/7 (42.9%)	0.670
Moderate-to-severe vasospasm	6/52 (11.5%)	5/45 (11.1%)	1/7 (14.3%)	1.000
Flow-limiting or treatment-requiring vasospasm	1/52 (1.9%)	1/45 (2.2%)	0/7 (0.0%)	1.000
Vessel perforation	1/52 (1.9%)	1/45 (2.2%)	0/7 (0.0%)	1.000
Procedure-related dissection	0/52 (0.0%)	0/45 (0.0%)	0/7 (0.0%)	—
Distal embolization within the target territory	8/52 (15.4%)	6/45 (13.3%)	2/7 (28.6%)	0.291
Embolization to a new territory	1/52 (1.9%)	1/45 (2.2%)	0/7 (0.0%)	1.000
Functional outcomes
3-month mRS	3 [2–4]	3 [2–4]	2 [1–2.5]	0.053
3-month mRS 0–2	21/52 (40.4%)	16/45 (35.6%)	5/7 (71.4%)	0.104
90-day mortality (mRS 6)	3/52 (5.8%)	3/45 (6.7%)	0/7 (0.0%)	1.000

Values are median [IQR] or n/N (%). N denotes thrombectomy procedures; 1 patient contributed 2 procedures. P values: Mann–Whitney U-test for continuous variables; Fisher’s exact test for categorical variables. All P values are exploratory and descriptive. 3-month mRS reflects the updated complete follow-up data (N=52). Any SAH included trace, clinically silent subarachnoid hyperdensities and possible contrast staining when hemorrhage could not be excluded. Intracranial hemorrhage was classified according to the Heidelberg Bleeding Classification. Symptomatic hemorrhage was defined by an increase of ≥4 points in the NIHSS score; hemorrhage not meeting this clinical criterion was classified as asymptomatic. Vasospasm was graded as none/minimal (<25%), mild (≥25% to <50%), moderate (≥50% to <75%), or severe (≥75% diameter reduction). Device configuration was summarized only for TACT-MeVO cases; no statistical comparison was performed. Door-to-puncture and puncture-to-recanalization/procedure-end times were available in 51/52 procedures (historical protocol, 44/45; TACT-MeVO, 7/7).

CEREGLIDE, Cerenovus, Johnson & Johnson, Irvine, CA, USA; EmboTrap III, Cerenovus, Johnson & Johnson; IQR, interquartile range; mRS, modified Rankin Scale; mTICI, modified Thrombolysis in Cerebral Infarction; NIHSS, National Institutes of Health Stroke Scale; SAH, subarachnoid hemorrhage; SALVA, Nipro, Osaka, Japan; Solitaire X, Medtronic, Irvine, CA, USA; TACT-MeVO, telescope-assisted combined thrombectomy for medium vessel occlusion; Trevo NXT, Stryker, Kalamazoo, MI, USA; Vecta, Stryker

The door-to-puncture time did not differ significantly between the groups. The median puncture-to-recanalization or procedure-end time was 59 [51–61.5] min in the TACT-MeVO group and 71 [60–110.5] min in the historical-protocol group (P = 0.014). One-pass completion and first-pass mTICI ≥2b reperfusion were each achieved in 6/7 (85.7%) TACT-MeVO procedures and 23/45 (51.1%) historical-protocol procedures (both P = 0.117). First-pass mTICI ≥2c reperfusion was achieved in 3/7 (42.9%) and 16/45 (35.6%) procedures (P = 0.697).

In the 1 TACT-MeVO procedure that was not completed in a single pass, the same TACT-MeVO strategy was repeated, resulting in final mTICI 2b reperfusion after the second pass. Final mTICI ≥2b reperfusion was achieved in 7/7 (100.0%) TACT-MeVO procedures and 39/45 (86.7%) historical-protocol procedures (P = 0.580), whereas final mTICI ≥2c reperfusion was achieved in 3/7 (42.9%) and 23/45 (51.1%), respectively (P = 1.000). These unadjusted comparisons are exploratory and descriptive. No temporal association with procedural time or first-pass reperfusion was detected within the historical cohort, and the shorter procedural time persisted in the recent-era sensitivity analysis (Supplementary Table 2).

Safety and functional outcomes

The safety and functional outcomes are summarized in Table 2. Any subarachnoid hemorrhage (SAH) was observed in 2/7 (28.6%) TACT-MeVO procedures and 8/45 (17.8%) historical-protocol procedures (P = 0.608). Of the 2 findings in the TACT-MeVO group, 1 was classified as definite SAH (Heidelberg Bleeding Classification class 3c) and the other as possible contrast staining with an SAH pattern. Both were asymptomatic according to the prespecified NIHSS criterion. Symptomatic SAH occurred in 0/7 and 4/45 (8.9%) procedures, respectively (P = 1.000). Representative images of all SAH cases are shown in Supplementary Fig. 1, and detailed Heidelberg classifications are provided in Supplementary Table 3.

Asymptomatic intracranial hemorrhage or hyperdensity was observed in 2/7 (28.6%) TACT-MeVO procedures and 10/45 (22.2%) historical-protocol procedures (P = 0.656), whereas symptomatic intracranial hemorrhage occurred in 0/7 and 6/45 (13.3%), respectively (P = 0.580).

Any vasospasm occurred in 3/7 (42.9%) and 14/45 (31.1%) procedures (P = 0.670), including moderate-to-severe vasospasm in 1/7 (14.3%) and 5/45 (11.1%), respectively (P = 1.000). No flow-limiting or treatment-requiring vasospasm occurred in the TACT-MeVO group. One vessel perforation occurred in the historical-protocol group, whereas no procedure-related dissection occurred in either group. Distal embolization within the target territory occurred in 2/7 (28.6%) and 6/45 (13.3%) procedures (P = 0.291).

At 3 months, the median mRS score was 2 [1–2.5] in the TACT-MeVO group and 3 [2–4] in the historical-protocol group (P = 0.053). An mRS score of 0–2 was achieved in 5/7 (71.4%) and 16/45 (35.6%), respectively, with no statistically significant difference (P = 0.104). Ninety-day mortality was 0/7 and 3/45 (6.7%), respectively (P = 1.000). These unadjusted safety and functional outcomes are descriptive and do not establish the safety or superiority of TACT-MeVO.

In the post hoc technique-specific comparison, 29 historical procedures treated with conventional combined thrombectomy as the first-pass strategy were compared with the 7 TACT-MeVO procedures. The M1–M2 angle was smaller in the TACT-MeVO group (80° [69–92°] vs. 114° [84–143°]; P = 0.048). Puncture-to-recanalization or procedure-end time was shorter with TACT-MeVO (59 [51–61.5] vs. 70 [63–88] min; P = 0.004), whereas one-pass completion was numerically higher but not statistically different (6/7 [85.7%] vs. 15/29 [51.7%]; P = 0.200). No statistically significant differences were observed in final reperfusion, hemorrhagic complications, vasospasm, or 3-month functional outcomes (Supplementary Table 4). This post hoc comparison was exploratory and unadjusted.

Representative case

A representative example is shown in Fig. 3. A 75-year-old woman with atrial fibrillation receiving warfarin therapy presented with left hemiparesis, hemispatial neglect, and dysarthria. The baseline NIHSS and CT-ASPECTS scores were 17 and 10, respectively. CTA suggested right M2 occlusion. Intravenous thrombolysis was administered 50 min after arrival, followed by thrombectomy.

Fig. 3. Representative angiographic case treated with the TACT-MeVO technique. (A) Preprocedural anteroposterior angiogram demonstrating occlusion at the origin of the superior division of the right M2 segment. The dotted line indicates the expected course of the occluded superior M2 branch. (B) Postprocedural angiogram showing complete reperfusion of the superior M2 division after a single pass. Arrows indicate the recanalized M2 branch. The arrowhead indicates transient distal M1 vasospasm, which subsequently improved without treatment. (C) Intraprocedural working-projection image during aspiration and retrieval, demonstrating the device configuration of the TACT-MeVO technique. The CEREGLIDE 71 catheter is positioned in the M1 segment as a receiving catheter, whereas the CEREGLIDE 42 catheter and EmboTrap III 5 × 22-mm stent retriever constitute the distal combined unit.

CEREGLIDE, Cerenovus, Johnson & Johnson, Irvine, CA, USA; EmboTrap III, Cerenovus, Johnson & Johnson; TACT-MeVO, telescope-assisted combined thrombectomy for medium vessel occlusion

Diagnostic angiography confirmed occlusion at the origin of the superior division of the right M2 segment (Fig. 3A). TACT-MeVO was performed using CEREGLIDE 71 and CEREGLIDE 42 aspiration catheters and an EmboTrap III 5 × 22-mm stent retriever (all Cerenovus, Johnson & Johnson). The large-bore aspiration catheter was positioned in the M1 segment, and the small-bore aspiration catheter and stent retriever were retrieved together into the M1 receiving catheter under aspiration. Complete reperfusion (final mTICI 3) was achieved after a single pass 50 min after puncture, with transient distal M1 vasospasm that improved without treatment (Fig. 3B). The intraprocedural device configuration is shown in Fig. 3C. No postprocedural hemorrhage occurred. The NIHSS score improved to 0, and the 3-month mRS score was 0.

Discussion

In this technical note, we describe TACT-MeVO and report our initial 7-procedure experience. The technique was feasible in all 7 procedures, with final mTICI ≥2b reperfusion achieved in all cases. In the exploratory unadjusted comparison, the puncture-to-recanalization or procedure-end time was shorter with TACT-MeVO, whereas differences in one-pass completion and first-pass reperfusion were not statistically significant. Any SAH was numerically more frequent with TACT-MeVO (2/7 vs. 8/45), although both TACT-MeVO events were asymptomatic and no symptomatic hemorrhage occurred. Three-month functional outcomes did not differ significantly. Given the small sample, baseline imbalances, heterogeneous device configurations, and historical comparator, these findings are descriptive and do not establish the superiority or safety of TACT-MeVO.

The role of thrombectomy in MeVOs remains controversial. Earlier observational studies and meta-analyses suggested that thrombectomy for M2 or distal occlusions is technically feasible and may achieve high rates of reperfusion.^16,17) More recently, randomized trials have reported mixed results. ESCAPE-MeVO and DISTAL did not show clinical superiority of endovascular treatment over medical management and raised concerns regarding procedural harm, including symptomatic intracranial hemorrhage.^4,5) In contrast, ORIENTAL-MeVO suggested a benefit of thrombectomy in patients with moderate-to-severe deficits, although symptomatic intracranial hemorrhage was more frequent in the thrombectomy group.⁶⁾ These findings suggest that MeVO thrombectomy should not be regarded as a smaller version of large vessel thrombectomy. Instead, careful patient selection and refinement of safer, less traumatic, and more efficient techniques are essential.

M2 thrombectomy is technically challenging because M2 branches are smaller, more tortuous, and anatomically variable, with substantial interindividual differences in vessel caliber and supplied territory.^1,3) Device manipulation may cause vasospasm, endothelial injury, perforation, dissection, or subarachnoid hemorrhage. Although direct aspiration is attractive because of its simplicity, achieving stable catheter–clot engagement can be difficult in small-caliber vessels. Experimental and computational studies suggest that aspiration may induce arterial collapse, particularly in small vessels, and that suction force decreases as the distance between the catheter tip and thrombus increases, underscoring the importance of close and stable clot engagement.^8–10)

The TACT-MeVO technique adds a large-bore aspiration catheter positioned in the M1 segment as a receiving catheter to conventional combined thrombectomy. The distal unit, consisting of a small-bore aspiration catheter and an appropriately sized stent retriever, is retrieved into this catheter under aspiration. This configuration is intended to maintain clot engagement while shortening the retrieval distance along the M2–M1 axis, potentially limiting traction and vessel shift. However, vessel movement was not quantitatively assessed; therefore, this proposed mechanical advantage remains conceptual.

Despite the additional coaxial setup, procedural time was shorter with TACT-MeVO, and this finding persisted in the post hoc comparison with 29 conventional combined-thrombectomy procedures. This comparison was restricted to procedures using a stent retriever and an intracranial aspiration catheter without the M1 receiving-catheter configuration, although the detailed retrieval maneuvers varied. One-pass completion and first-pass reperfusion were numerically more frequent with TACT-MeVO but did not differ significantly. Previous studies have suggested potential first-pass benefits of combined techniques, and the mini-pinning technique demonstrated the feasibility of combining a small stent retriever with a low-profile aspiration catheter.^11,12) However, because the comparison was post hoc and unadjusted and the TACT-MeVO group had a smaller M1–M2 angle, these findings do not establish an independent procedural advantage of TACT-MeVO.

Any SAH was numerically more frequent with TACT-MeVO (2/7 vs. 8/45). Although both TACT-MeVO events were asymptomatic, the estimate is imprecise because of the small sample and broad definition that included possible contrast staining. Moreover, TACT-MeVO routinely uses a stent retriever and still requires lesion crossing, device deployment, and distal catheter manipulation, each of which may cause vessel injury. Thus, the observed SAH could be related to these device manipulations rather than the telescoping maneuver itself, an important consideration given the hemorrhagic concerns reported in recent MeVO trials.^4–6) The absence of symptomatic hemorrhage in 7 procedures does not establish safety, and the present data do not demonstrate a reduction in radiographic or symptomatic hemorrhage.

Functional outcomes did not differ significantly between the groups. The numerically better outcomes in the TACT-MeVO group may reflect its numerically higher CT-ASPECTS, younger age, lower baseline NIHSS, small sample size, and historical comparator; adjusted analysis was not feasible. Within the historical cohort, treatment year was not associated with procedural time or first-pass reperfusion, and the shorter procedural time persisted in the recent-era sensitivity analysis (Supplementary Table 2). Nevertheless, residual confounding from changes in devices, workflow, operator experience, imaging selection, and perioperative management cannot be excluded. Therefore, the functional outcomes cannot be attributed to TACT-MeVO, and the present findings support only its technical feasibility and further prospective evaluation.

This study has several limitations. First, it was a retrospective, single-center study with only 7 TACT-MeVO procedures and heterogeneous device configurations, precluding reliable estimates of efficacy or safety. Second, treatment was nonrandomized, and the historical comparator included various techniques performed during a different era. Residual temporal confounding cannot be excluded despite the sensitivity analyses. Third, baseline imbalances remained: dyslipidemia was less frequent in the TACT-MeVO group than in the overall historical-protocol group, whereas the M1–M2 angle was smaller than in the conventional combined-thrombectomy subgroup; CT-ASPECTS, age, and NIHSS differed only numerically. The small sample precluded matching or multivariable adjustment. Fourth, angiographic and hemorrhagic outcomes were not independently adjudicated, and postprocedural imaging included both conventional and cone-beam CT, complicating the distinction between hemorrhage and contrast staining. Fifth, anatomical measurements were retrospective and primarily based on 2-dimensional angiography; 3D tortuosity and vessel shift were not quantified. Thus, the proposed vessel-shift–reducing effect remains conceptual. Finally, the selected M2 occlusions treated at an experienced center limit generalizability. Larger prospective multicenter studies with standardized imaging and quantitative vessel-motion assessment are required.

Conclusion

TACT-MeVO is a telescope-assisted combined thrombectomy technique for M2 occlusion, in which a small-bore aspiration catheter and an appropriately sized stent retriever are retrieved as a combined unit into a large-bore aspiration catheter positioned in the M1 segment. In this initial 7-procedure experience, TACT-MeVO was technically feasible. The comparative procedural, hemorrhagic, and functional outcomes were exploratory and do not establish superiority, efficacy, or safety because of the small sample, heterogeneous device configurations, baseline imbalances, and historical comparator. Further prospective studies with standardized imaging and quantitative assessment of vessel movement are required.

Disclosure Statement

The authors declare no conflicts of interest. This study received no specific grants from any funding agency in the public, commercial, or not-for-profit sectors.