Mechanical Thrombectomy for Hyperacute Vertebrobasilar Ischemic Stroke via Nondominant Vertebral Artery : Clinical Experience and Considerations

Article information

J Korean Neurosurg Soc. 2024;.jkns.2024.0104
Publication date (electronic) : 2024 August 28
doi : https://doi.org/10.3340/jkns.2024.0104
1Department of Neurosurgery, Jeju National University Hospital, Jeju National University College of Medicine, Jeju, Korea
2Department of Neurosurgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea
3Department of Neurosurgery, Jeju National University Hospital, Jeju National University College of Nursing, Jeju, Korea
4Department of Neurology, Jeju National University Hospital, Jeju National University College of Medicine, Jeju, Korea
5Department of Neurology, Konkuk University Medical Center, Seoul, Korea
6Department of Neurosurgery, Hallym University College of Medicine, Chuncheon, Korea
Address for reprints : Jong-Kook Rhim Department of Neurosurgery, Jeju National University Hospital, Jeju National University College of Medicine, 15 Aran 13-gil, Jeju 63241, Korea Tel : +82-64-717-1620, Fax : +82-64-717-1656, E-mail : nsrhim@gmail.com
*Previous presentation : Society of Neurointerventional Surgery 20th Annual Meeting E-Poster Presentation, The Korean Neurosurgical Society 42nd Spring Conference Oral Presentation.
Received 2024 May 23; Revised 2024 August 15; Accepted 2024 August 22.

Abstract

Objective

The dominant vertebral artery (VA) approach is primarily considered in mechanical thrombectomy (MT) for acute occlusion of the vertebrobasilar (VB) artery. As accessing the dominant artery is sometimes difficult, we present our experience treating acute VB stroke via a nondominant VA approach through a comparison with the dominant VA approach.

Methods

Among 2785 patients diagnosed with hyperacute ischemic stroke between January 2014 and December 2022, 50 patients with VB ischemic stroke underwent recanalization therapy through either dominant, nondominant, or bilateral VA approach. We evaluated patient characteristics and clinical course, highlighting the pros and cons of the access routes.

Results

The patients with hyperacute VB ischemic stroke were predominantly male (72%), with a mean age of 68.12 years and an initial National Institutes of Health Stroke Scale score mean of 17.1. Large-artery atherosclerosis (48%) and cardioembolism (36%) were the main etiologic factors in the Trial of Org 10172 in Acute Stroke Treatment classification. After thrombectomy, 45 cases (90%) had final modified thrombolysis in cerebral infarction score of 2b or higher. In summary, 41 patients were treated through the dominant VA, and eight patients underwent the nondominant VA approach. However, there was no statistically significant difference in functional outcome or mortality between the two approaches.

Conclusion

In MT for VB occlusions, nondominant VA approach may be an option in situations when the vessel is accessible, stable, or less risky, as recanalization can be achieved without rescue balloon angioplasty and/or stenting.

INTRODUCTION

Compared to the anterior circulation, the posterior circulation supplies critical organs and has two access routes, lower blood volume, and sufficient collaterals. Thus, hyperacute posterior circulation ischemic stroke often results in permanent deficits. Posterior circulation strokes account for 20–25% of ischemic strokes and have high mortality and morbidity rates. For instance, basilar artery (BA) occlusion has a mortality rate of 41–95% [10]. However, recent advances in endovascular treatment have brought attention to mechanical thrombectomy (MT) as a viable treatment option for acute ischemic strokes. Randomized controlled trials, such as MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) and REVASCAT (Endovascular Revascularization With Solitaire Device Versus Best Medical Therapy in Anterior Circulation Stroke Within 8 Hours) revealed that MT reduced post-stroke disability and increased the rate of functional independence in patients with acute anterior circulation strokes [2]. Multicenter studies, such as the prospective multicenter registry in Revascularization in Ischemic Stroke Patients (REVASK), also showed that MT in posterior circulation strokes had a similar recanalization rate and lower symptomatic bleeding rate than that of anterior circulation strokes [11]. However, the endovascular treatment versus standard medical treatment for vertebrobasilar artery occlusion (BEST) trial, a multicenter, randomized trial, did not show benefits of MT over standard medical therapy alone [9].

While there are mixed results on the advantage of MT in vertebrobasilar (VB) strokes, the procedure remains as the last measure for treating acute strokes that are not re-canalized by medical therapy, or those with a large penumbra-to-core ratio or thrombus burden. Cohen et al. [5] have shown that stent-retriever-based thrombectomy is feasible through either a patent or occluded vertebral artery (VA). However, research comparing the differences between dominant and nondominant VA approaches has been scarce. Liang et al. [8] have argued superiority of the dominant approach in VA-BA tandem occlusions, but did not compare the statistical difference between the two groups.

The dominant VA, which is defined as having the larger diameter (side to side diameter difference ≥0.3 mm) or as being connected to the BA in a straighter fashion, is the traditionally preferred path for thrombectomy [6]. However, it can also be occluded, causing delays in time to perfusion and affecting patient outcomes. This study compares the clinical outcomes of dominant and nondominant VA access routes for acute VB strokes and discusses instances in which taking the nondominant VA pathway was more beneficial.

MATERIALS AND METHODS

The study protocol was approved by the Institutional Review Board of Jeju National University, and the requirements for written informed consent were waived due to its retrospective nature (IRB No. 2023-11-005).

Patient population

During a 9-year period (January 2014 to December 2022), 2785 patients diagnosed with hyperacute ischemic stroke were admitted to Jeju National University Hospital and 372 of them underwent MT. Among them, 50 were diagnosed with VB ischemic stroke and underwent MT through either dominant, nondominant, or bilateral VAs and were followed up for 6 months for this single-center retrospective cohort study.

Stroke evaluation and endovascular procedure

All patients were examined, and their radiologic images were reviewed by at least two specialists (neurologist, neurosurgeon, radiologist, or emergency medicine specialist). Computed tomography angiography (CTA) was the primary tool in diagnosing acute VB stroke, and magnetic resonance (MR) imaging was taken optionally. The primary treatment plan was established by analyzing the early phase, late phase, and venous phase CTA images. The team decided on the access route, whether the VA was patent or not, and whether to assess the perfusion status based on CTA. Recombinant tissue plasminogen activator (rt-PA) was injected to all patients without contraindications.

After femoral access, the more easily accessible VA was chosen by neuro-interventionists. If a long segment of one VA was packed with thrombus or if a guiding catheter could not indwell inside the VA due to structural reasons, the other VA was chosen for access. Because the arteries were mostly narrow, balloon-guided catheters were rarely introduced. Thrombo-aspiration was the first treatment option, and when it was insufficient, a stent retriever was applied. Balloon angioplasty or stent insertion was introduced when recanalization failed after several attempts.

Factors affecting recanalization and prognosis

Several factors associated with recanalization were analyzed in this study. The length of steno-occlusive lesion was classified as short segment if the lesion involved only one segment of the parent artery, and long segment if it involved multiple segments.

Variations in collaterals were also analyzed in this study. Yan et al. [12] previously described posterior communicating artery (PCoA) – posterior cerebral artery (PCA) segment 1 (P1) scores as follows : 1) 0 points, absence of a bilateral anterior-to-posterior circulation connection; 2) 1 point, presence of a unilateral PcoA-to-P1 connection, but with PcoA or P1 hypoplasia; 3) 2 points, presence of a unilateral normal PcoA-to-P1 connection or a bilateral PcoA-to-P1 connection, but with either PcoA or P1 hypoplasia; 4) 3 points, presence of a bilateral PcoA-to-P1 connection, but with one normal side combined with contralateral PcoA or P1 hypoplasia, and 5) 4 points, presence of bilateral connections between a normal PcoA and P1. Primary collaterals were dichotomized into good (2–4 points) and poor (0 or 1 point) collateral state [12].

Clot migration was also analyzed as a factor that can affect thrombectomy outcome and was classified as follows : 1) no migration throughout the procedure; 2) large vessel occlusion by thrombus migration, followed by additional thrombectomy; 3) small vessel occlusion without large vessel occlusion, but further thrombectomy was performed due to the occlusion involving key functional area; and 4) no further procedure was done despite thrombus migration due to absence of significant flow compromise.

Atrial fibrillation (Af) is an ischemic stroke etiology related to atherosclerosis. Patients with Af were further classified into three groups : patients who were taking anticoagulant medication before stroke, those who were not taking medication despite being diagnosed with Af, and those first diagnosed with Af at stroke attack or during hospitalization.

Plaque rupture and thromboembolism migration were analyzed during the initial digital subtraction angiogram (DSA) in patients classified as having a large-artery atherosclerosis (LAA) origin within the TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Further analysis included determining whether the flow was compromised or whether the contrast filling pattern was heterogeneous just around the VA-posterior inferior cerebellar artery (PICA) junction or VA ostium. Such cases were further classified into three groups : those involving PICA, those involving VA ostium, and others. Tandem cases were defined as severe stenosis or occlusion of the vertebral ostium ipsilateral to its intracranial occlusion.

Statistical analysis

All statistics were performed with IBM SPSS v29 (SPSS, Chicago, IL, USA). When comparing the characteristics of dominant and nondominant VA access, statistical difference of continuous variables such as age, National Institutes of Health Stroke Scale (NIHSS) score, puncture-to-clot (PTC) time, clotto-end of procedure (CTE) time were tested using independent sample’s t-test and the results were reported as the mean and standard deviation, or the median value. Statistical comparison of categorical variables such as sex, Af, intravenous rt-PA, poor PcoA-P1 score, suction thrombectomy, rescue angioplasty/stent, and modified thrombolysis in cerebral infarction (mTICI) scale score of 2b or higher were tested using the chi-squared test. When testing variables related to outcome such as mRS score of 0–2 and mortality at 6 months, cases that were lost at follow-up were excluded. A 2-sided p<0.05 was used to indicate statistical significance.

RESULTS

Baseline characteristics

Among the study population of 50 patients, the mean age was 68.1±11.6 years (range, 49–92). The population was male dominant (male : female, 36 : 14), and it was further classified into four groups based on the location of steno-occlusive lesions : four had VB insufficiency, two had VA occlusions, 15 had VB occlusions, 27 had BA occlusions, and two had PCA occlusions. Eight cases had tandem lesions.

The mean initial NIHSS score was 17.1±10.7. Ten cases had valvular heart disease (20%), none involved wake-up strokes, and five cases occurred during hospitalization. According to TOAST classification, LAA was the most common etiology (n=24), followed by cardioembolism (CE, n=18), stroke of undetermined etiology (n=6), and stroke of other determined etiology (n=2). The initial angiogram indicated that 20 cases (40%) were long-segment and 30 (60%) were short-segment occlusions. The collaterals were classified as good in 15 (30%) and poor in 35 (70%) cases. The dominant VA was mainly left (n=37, 74%) versus right (n=8, 16%). Ten unilateral VA cases are defined by having a nondominant VA pattern of the following : PICA terminating VA (n=2), VA ostium occlusion (n=4), VA segment 4 hypoplasia (n=2), and VA segment 2 or 3 occlusion (n=2). Intravenous rt-PA injection was performed in 12 cases (24%). The general characteristics of the cohort are summarized in Table 1.

General characteristics of the study population (n=50)

Access routes and procedural results

The neuro-interventionists involved in this study followed the main treatment paradigm summarized in Fig. 1. ‘Difficult access to VB’ is defined as cases in which the approach was disturbed during either symptomatic main lesion navigation (near occlusion of VA ostium, VA segment 4 around PICA ostium, or subclavian artery) or involved device access failure. MT was performed with dominant VA access in all cases with unilateral VA or unremarkable dominant VA.

Fig. 1.

Flow diagram of VA access choice and recanalization modalities. ‘Difficult access to VB’ is defined as a case in which the approach was disturbed during either symptomatic main lesion navigation (near occlusion of VA ostium, VA segment 4 around PICA ostium, or subclavian artery) or involved device access failure. VB : vertebrobasilar, VA : vertebral artery, MT : mechanical thrombectomy, RAS : rescue angioplasty and/or stent insertion.

Dominant VA access for MT

Of the 50 patients with acute posterior circulation stroke, dominant VA access was selected as the thrombectomy treatment route in 41 patients (82%). The mean age of the group was 68.4±11.5 years, and was predominantly male (n=29, 70.7%). The main occlusion site was the BA (n=25, 61.0%) and the occlusions were mostly short segments (n=22, 53.7%) with the mean NIHSS score of 16.8. In terms of etiology based on TOAST classification, 20 (48.8%) were LAA, and 16 (39.0%) were CE origins. Classic guiding catheter was used instead of balloon guiding catheter and thrombo-aspiration was the first treatment modality for 18 patients (43.9%). Rescue angioplasty and/or stenting were performed in 16 cases (39.0%) and additional MT due to clot migration was performed in six cases (14.6 %). Thirty-six cases (87.8%) had a final mTICI scale score of 2b or higher, indicating successful recanalization. The median PTC time was 21 minutes, and the median CTE time was 22 minutes.

Nondominant VA route for MT

Eight cases were selected for the nondominant VA approach for initial access. The reasons for selecting the nondominant VA approach were as following : 1) near occlusion of the dominant VA ostium (n=5); 2) navigation failure (n=2); and 3) subclavian artery occlusion (n=1) with examples shown in Fig. 2. The mean age of the group was 64.6±11.6 years (p=0.401), and was predominantly male (n=7, 87.5%). The main occlusion site was the BA (n=7, 87.5%) and the occlusions were mostly short segments (n=6, 75%) with the mean NIHSS score of 18.6. The initial TOAST classification for stroke etiology indicated that three were LAA, two were CE, and the other three had different origins. Aspiration catheter was used in three cases, stent retriever was used in one case, and both aspiration catheter and stent retriever were used in four cases. None of the cases needed rescue angioplasty and/or stenting, and additional MT by clot migration was performed in three cases (37.5%). All cases resulted in full recanalization with mTICI scale score of 2b or higher, and the median PTC time was 27 minutes and the median CTE time was 37.5 minutes (Table 2).

Fig. 2.

Nondominant vertebral artery (VA) access examples. A : Bilateral VA roadmap image. The thick arrow shows near occlusion of the VA ostium in leftmost image, and the thin arrow shows mid-basilar artery occlusion in the preprocedural angiogram in center image. The rightmost image shows recanalization by mechanical thrombectomy through the nondominant VA route. B : Arrow shows the thrombus as a filling defect in leftmost image. The aspiration catheter could not be advanced to the lesion site, so the contralateral nondominant VA approach was used in center image. Postprocedural image showed removed thrombus in rightmost image. C : The subclavian artery was completely occluded in the volume rendering image (arrow shows the occlusion).

Comparison of characteristics of VB ischemic stroke in dominant VA and nondominant VA access (n=49)

Bilateral VA access through both dominant and nondominant VA routes

A single case was treated through bilateral VA access. A stent retriever was applied to the BA occlusion through the dominant VA, but the resulting flow was not sufficient. Additional procedures failed due to instability of the guiding catheter despite reinforcement. After multiple attempts, an indwelling guiding catheter was placed in the proximal segment of the nondominant VA and was engaged tightly, arresting the flow. This lesion was considered to be in-situ stenosis with occlusion, and rescue balloon angioplasty and stent insertion were performed. The mean angiogram-to-perfusion time was 225 minutes, and the final mTICI score was 2b.

Overall outcomes

Six-month follow-up mRS was obtained for the 50 patients with VB strokes who underwent MT. Overall, 14 patients showed favorable functional outcomes with mRS scores of 0–2 at 6 months (28%), and seven patients were lost to follow-up. Amongst the dominant group, 11 (30.6%) showed favorable functional outcome, nine (25.0%) were deceased, and five were lost at 6-month follow-up. Amongst the nondominant group, three (50%) showed favorable outcome, one was deceased (16.7%) and two were lost at 6-month follow-up. There was no statistically significant difference in functional outcome (p=0.350) or mortality (p=0.657) between the dominant and nondominant VA approaches.

DISCUSSION

VB strokes are interruptions of blood flow to the posterior circulation [1]. The fastest access is the best choice for thrombectomy, and flow reconstruction is its main aim. The VA supplies posterior circulation in various patterns : two VAs might coexist as dominant and nondominant, or only one VA might be patent while the other VA terminates at the PICA level.

Neuro-interventionists aim to select an approach that results in the most effective outcome with the fastest possible recanalization. Hence, many factors should be considered in each case including the following : CTA or MR, DSA, history of vascular intervention, the neurological status of the patients, laboratory findings, considerations on whether or not a guiding catheter could support any micro-device, where the thrombus was lodged, which VA route could reach the occlusion faster, and which devices were best for recanalization. Bilateral VA patency evaluation through preprocedural CTA or magnetic resonance angiography provides decisive clues for choosing which VA to access. For instance, routes with high arch angle or severe tortuosity are undesirable when making a VA selection.

Furthermore, a neuro-interventionist should be equipped with flexibility to try novel maneuvers when various unexpected situations arise. For example, when a balloon-guiding catheter is inaccessible, one should also consider using the guiding catheter for flow arrest.

Steno-occlusion of the VA accounts for approximately 20% of posterior circulation ischemia, and the VA segment 1 is the most commonly involved segment [3]. In a case of BA occlusion with a thromboembolism suspected to originate from the VA ostial atheroma, the entire VA is suspected to be filled with thrombus and further thrombus formation can aggravate BA occlusion. In this study, nondominant VA approach was used in such cases to avoid the main etiologic lesion (VA ostium atherosclerosis) and MT was applied to basilar occlusion directly through the nondominant VA.

Blind navigation is inevitable in some cases during thrombectomy. Flow stagnation in the angiogram can be attributed to a large thrombus burden, severe stenosis, tandem lesion, or contralateral flow augmentation. Furthermore, thrombus migration is speculated to be more common in posterior circulation stroke than in anterior circulation stroke, and in most cases, dominant VA occlusions have more thrombus than nondominant VA occlusions. Chen et al. [4] have also indicated that dominant VA may be associated with essential risk factors for posterior circulation strokes. If a major etiology exists in the dominant VA, a large thrombus amount is expected, and suction thrombectomy should be introduced. In such cases, a balloon-guiding catheter cannot be introduced, and multiple procedures can aggravate risk of thrombus migration. Therefore, cases with major etiology in the dominant VA are good candidates for the nondominant VA approach as it can circumvent existing thrombus.

One disadvantage of the nondominant VA approach is its small and tortuous caliber which can increase risk of dissection. However, the simultaneously occurring flow arrest due to low caliber can also allow easier thrombus removal. Furthermore, when BA flow is restored through a nondominant VA, an augmented retrograde flow can halt plaque migration, stabilizing the plaque at the dominant VA.

Clinicians have suggested that increased blood flow and volume can result in structural damage to the VA endothelium [7]. Hence, in VA ostial steno-occlusive cases, taking the nondominant VA approach eliminates additional procedures to stabilize the VA. To further validate advantages of the nondominant approach, follow-up studies on cases in which the VA ostium atherosclerotic stenosis was left untouched and only basilar thromboembolism was removed are necessary.

In this study, no additional procedures (rescue balloon angioplasty with/without stent insertion) were needed after the nondominant approach (p=0.031). Furthermore, there was no significant difference in the final mTICI grade (p=0.297) directly, and functional outcome (p=0.350) or mortality (p=0.657) between the two approaches at 6-month follow-up, hinting advantages of nondominant approach in certain cases.

This study has several limitations including lack of sample size and selection bias. Although the study encompasses 9 years of acute ischemic stroke patients admitted to Jeju National University Hospital, posterior circulation stroke is scarce compared to anterior circulation stroke, hence leading to only 50 total cases of VB artery occlusion that went through MT. Furthermore, nondominant VA approach was only selected within cases with occlusion of the dominant VA ostium, navigation failure, and subclavian artery occlusion. Since the dominant artery approach has been the classical pathway to take in MT, neuro-interventionists aimed to adhere to the principle, only allowing exceptions by necessity for the nondominant VA approach, but also allowing selection bias to this study. Lastly, due to the study’s few nondominant cases (n=8) and its retrospective nature, the study is not free from confounding bias.

For these reasons, future large-scale multi-center study is needed to validate effectiveness and generalizability of the nondominant approach, and a prospective study should also be considered. Further research on novel approaches is needed to optimize MT for acute occlusion of the VB artery.

CONCLUSION

The dominant VA remains the preferred access route for the fastest treatment. However, nondominant VA may be an option in situations when it is accessible, stable, or less risky, as flow restoration can be achieved faster than via dominant VA access.

Notes

Conflicts of interest

No potential conflict of interest relevant to this article was reported.

Informed consent

Informed consent was obtained from all individual participants included in this study.

Author contributions

Conceptualization : GYL, CHY, JKR; Data curation : GYL, CHY, JKR; Formal analysis : GYL, CHY, CHK, JGK, JDJ, YNC, JSH, JJP, JPJ, JKR; Funding acquisition : JKR; Methodology : GYL, CHY, JKR; Project administration : GYL, CHY, JKR; Visualization : GYL, JJP, JPJ, JKR; Writing - original draft : GYL, JKR; Writing - review & editing : GYL, CHY, CHK, JGK, JDJ, YNC, JSH, JJP, JPJ, JKR

Data sharing

None

Preprint

None

Acknowledgements

This work was supported by a research grant from Jeju National University Hospital in 2022.

References

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Article information Continued

Fig. 1.

Flow diagram of VA access choice and recanalization modalities. ‘Difficult access to VB’ is defined as a case in which the approach was disturbed during either symptomatic main lesion navigation (near occlusion of VA ostium, VA segment 4 around PICA ostium, or subclavian artery) or involved device access failure. VB : vertebrobasilar, VA : vertebral artery, MT : mechanical thrombectomy, RAS : rescue angioplasty and/or stent insertion.

Fig. 2.

Nondominant vertebral artery (VA) access examples. A : Bilateral VA roadmap image. The thick arrow shows near occlusion of the VA ostium in leftmost image, and the thin arrow shows mid-basilar artery occlusion in the preprocedural angiogram in center image. The rightmost image shows recanalization by mechanical thrombectomy through the nondominant VA route. B : Arrow shows the thrombus as a filling defect in leftmost image. The aspiration catheter could not be advanced to the lesion site, so the contralateral nondominant VA approach was used in center image. Postprocedural image showed removed thrombus in rightmost image. C : The subclavian artery was completely occluded in the volume rendering image (arrow shows the occlusion).

Table 1.

General characteristics of the study population (n=50)

Characteristic Value
Age (years) 68.12 (49–92)
Gender
 Male 36 (72.0)
 Female 14 (28.0)
Severe stroke (≥21 NIHSS) 20 (40.0)
Atrial fibrillation 13 (26.0)
In-hospital stroke 5 (10.0)
Intravenous rt-PA 12 (24.0)
Initial angiogram finding
 VB insufficiency 4 (8.0)
 VA occlusion 2 (4.0)
 Basilar artery occlusion 27 (54.0)
 VB occlusion 15 (30.0)
 PCA occlusion 2 (4.0)
PCoA-P1 score
 Good 15 (30.0)
 Poor 35 (70.0)
TOAST
 Large-artery atherosclerosis 24 (48.0)
 Cardioembolism 18 (36.0)
 Others 8 (16.0)
Access route
 Dominant VA 41 (82.0)
 Nondominant VA 8 (16.0)
 Bilateral VA 1 (2.0)
Modality
 Thromboaspiration 21
 Stent retriever 9
 Solumbra technique 20
 Rescue angioplasty/stent 15
Additional thrombectomy by clot migration 9 (18.0)
Puncture-to-clot time (minutes) 25.56
Clot-to-end of procedure time (minutes) 60.72
Outcome
 Successful mTICI 45 (90.0)
 Favorable mRS at 6 months 14 (28.0)

Values are presented as mean (range) or number (%). Favorable mRS grade 0–2. Successful mTICI scale, score ≥2b. NIHSS : National Institutes of Health Stroke Scale, rt-PA : recombinant tissue plasminogen activator, VB : vertebrobasilar, VA : vertebral artery, PCA : posterior cerebral artery, PCoA : posterior communicating artery, P1 : posterior cerebral artery segment 1, TOAST : Trial of Org 10172 in Acute Stroke Treatment, mTICI : modified thrombolysis in cerebral infarction, mRS : modified Rankin scale

Table 2.

Comparison of characteristics of VB ischemic stroke in dominant VA and nondominant VA access (n=49)

Dominant VA access (n=41) Nondominant VA access (n=8) p-value
Male 29 (70.7) 7 (87.5) 0.326
Age (years) 68.4±11.5 64.6±11.6 0.401
NIHSS 16.8 (1–38) 18.6 (2–35) 0.671
Atrial fibrillation 10 (24.4) 2 (25.0) 0.971
IV rt-PA treatment 11 (26.8) 1 (12.5) 0.389
Basilar artery occlusion 25 (61.0) 7 (87.5)
Long segment occlusion 19 (46.3) 1 (12.5)
Poor PcoA-P1 score 29 (70.7) 5 (62.5) 0.644
Large-artery atherosclerosis 20 (48.8) 3 (37.5)
Cardioembolism 16 (39.0) 2 (25.0)
Suction thrombectomy 18 (43.9) 3 (37.5) 0.738
Rescue angioplasty/stent 16 (39.0) 0 (0.0) 0.031
Additional MT by clot migration 6 (14.6) 3 (37.5) 0.127
PTC (minutes) 21 (7–76) 27 (6–40) 0.977
CTE (minutes) 22 (0–417) 37.5 (17–86) 0.492
mTICI score ≥2b 36 (87.8) 8 (100.0) 0.297
mRS score 0–2 at 6 months* 11 (30.6) 3 (50.0) 0.350
Mortality at 6 months* 9 (25.0) 1 (16.7) 0.657

Values are presented as mean±standard deviation, median (interquartile range), or number (%).

*

For mRS score and mortality, cases lost at 6-month follow-up are excluded.

VB : vertebrobasilar, VA : vertebral artery, NIHSS : National Institutes of Health Stroke Scale, IV : intravenous, rt-PA : recombinant tissue plasminogen activator, PCoA : posterior communicating artery, P1 : posterior cerebral artery segment 1, MT : mechanical thrombectomy, PTC : puncture-to-clot time, CTE : clot-to-end of procedure time, mTICI : modified treatment in cerebral ischemia, mRS: modified Rankin scale