Mechanical thrombectomy for acute ischemic stroke in the posterior circulation: assessment of efficacy and outcome and identification of prognostic factors

Abstract

Background

Mechanical thrombectomy (MT) is well-established in the treatment of acute ischemic anterior circulation stroke. However, there is no evidence from randomized trials or meta-analyses that MT is safe and effective in the treatment of patients with acute ischemic posterior circulation stroke (PCS).

Purpose

To evaluate the clinical and procedural factors associated with recanalization and outcome of patients with PCS treated with MT.

Material and Methods

Forty-three patients with PCS (median age 73 years) who underwent treatment with MT were included. Data including demographics, baseline stroke severity, radiological imaging, procedure and post-procedure complications were documented. Clinical outcome was evaluated using the modified Rankin Scale (mRS). The patients were classified into two groups based on clinical outcome (favorable vs. unfavorable mRS after 90 days).

Results

Median baseline National Institute of Health Stroke Scale (NIHSS) was 17. Twenty patients were eligible for intravenous thrombolysis and received recombinant tissue plasminogen activator before MT. Successful recanalization was observed in 88.4% of patients. After 90 days, favorable outcome (defined as mRS 0–2) was achieved in 26 patients; six patients had an unfavorable outcome (mRs >2). Final mortality rate was 25.5%. Baseline NIHSS, onset to reperfusion time, procedure duration, and successful recanalization had a statistically significant association with outcome. Failed recanalization and occurrence of intracranial hemorrhage were found to be associated with a higher mortality rate.

Conclusion

MT is feasible and effective method in treatment of PCS. Baseline NIHSS and onset to reperfusion time were found to be independent predictive factors of clinical outcome.

Keywords

Mechanical thrombectomy acute ischemic stroke posterior circulation prognostic factors

Introduction

Mechanical thrombectomy (MT) is well established in its role in the treatment of acute ischemic anterior circulation stroke (ACS) due to large vessel occlusion (1). In contrast to ACS, there is little evidence from randomized trials or meta-analyses that MT is a safe and effective treatment for patients presenting with posterior circulation stroke (PCS). Although the incidence of PCS is significantly lower than that of ACS, evidence has shown that these strokes can have devastating effects on patients and are associated with high morbidity and mortality (2,3). Conventional treatment of PCS is associated with a high rate of poor outcomes (4,5). Therefore, endovascular techniques are widely implemented in the treatment of PCS. Recent reports comparing outcomes after MT in ACS and PCS suggest that MT in PCS is associated with a lower rate of symptomatic intracranial hemorrhage (ICH) and similar effectiveness compared to ACS (6). On the other hand, authors of the ENDOSTROKE Study demonstrated that recanalization of the basilar artery did not significantly predict clinical outcome in patients with PCS (7). According to authors of the ENDOSTROKE Study, other factors such as initial stroke severity and premorbid status are more important in the prediction of outcome.

The aim of the present study was to evaluate clinical and procedural factors associated with recanalization and outcome of patients with acute ischemic PCS treated with MT.

Material and Methods

In this retrospective, single-center study, we evaluated the medical records of patients who underwent MT for ischemic PCS from January 2016 to January 2020.

The inclusion criteria were as follows: (i) acute occlusion of the posterior circulation confirmed by digital subtraction angiography (DSA) and treated with MT. Patients with isolated occlusion of the P1 segment of the posterior cerebral artery (PCA) and V4 of the vertebral artery were included; (ii) time from onset of symptoms to reperfusion was within 24 h; (iii) baseline National Institute of Health Stroke Scale (NIHSS) score ≥ 6; and (iv) reasonable cognitive and functional premorbid status (modified Ranking Scale [mRS] = 0–3).

Clinical information—including age, gender, risk factors (e.g. cardiovascular disease, diabetes mellitus, hypertension, atrial fibrillation, smoking, and dyslipidemia), baseline medication, history of stroke, and NIHSS score of all patients—was collected.

Cerebral baseline imaging was performed with multi-slice computed tomography (CT) by either non-contrast CT or CT angiogram or magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), time-of-flight (TOF), and fluid-attenuated inversion recovery (FLAIR) to determine the diagnosis of acute ischemic PCS. Patients who arrived within a window time of < 4.5 h from the onset of symptoms and with no contraindications were treated with intravenous (i.v.) thrombolysis (rt-PA) at a dose of 0.9 mg/kg in accordance with The Polish Neurological Society Guidelines for the Management of Patients with Ischemic Stroke (8).

Clinical outcomes of death rate, NIHSS score at discharge, and mRS after 90 days were collected from medical records or from direct contact with patients. Favorable results were defined as a mRS of 0–2.

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The present study was approved by the institutional review board (approval no. KE-0254/285/2019).

Endovascular procedure

MT was performed by two endovascular neuroradiologists under either general anesthesia or local anesthesia with sedation. All patients were treated with direct aspiration, stent retriever, or a combination of both under intraoperative DSA biplane imaging. In all patients, an 8-F femoral sheath was introduced, and initial angiography performed from the guiding catheter (NeuronMax, Penumbra, Alameda, CA, USA) placed in the dominant vertebral artery. Once the occlusion was confirmed, MT was performed with either an aspiration catheter (ACE 64 or ACE 68, Penumbra, Alameda, CA, USA), stent retriever (Solitaire, EV3, Irvine, CA, USA), or a combination of both (Solumbra technique). Recanalization status was evaluated by the modified treatment in cerebral infarction (mTICI) score based on evaluation of DSA by at least two independent observers. Successful recanalization was defined as mTICI 2b–3 with an unsuccessful recanalization defined as mTICI of 0–2a (Fig. 1).

Fig. 1.

CT angiogram of a 36-year-old male patient with BAO and initial NIHSS score of 34 points (a–c). Initial angiography confirmed vessel occlusion (d, e). Final angiography shows complete recanalization (f). The patient was discharged after nine days of hospitalization in good clinical condition with no neurological impairments (NIHSS score = 0). Follow-up mRS at 90 days was 0. BAO, Basilar Artery Occlusion; CT, computed tomography; mRS, modified Ranking Scale; NIHSS, National Institute of Health Stroke Scale.

Follow-up

Routine non-contrast brain CT was performed within 24 h of intervention to evaluate brain infarction and screen for ICH. In addition, all patients underwent at least two transcranial Doppler (TCD) ultrasound examinations. Complications related to the procedure (e.g. arterial perforation, dissection, hematomas at puncture site) and adverse events occurring during hospitalization were noted. Clinical outcome was assessed based on the mRS score after three months (90 days). The mRS was determined by either direct contact with the patients or, in case of the patient’s death, with their families.

Statistical analysis

All analyses were conducted using StatSoftStatistica 13.1 PL package. Continuous variables are presented as median value (range) whereas categorical variables as n (%). The patients were classified into two groups based on clinical outcome (favorable versus unfavorable mRS after 90 days) and comparisons were made on demographic data, initial NIHSS score, risk factors, and use of i.v. rt-PA. Procedural data including timings, recanalization success, procedural and post-procedural complications were also compared, along with clinical outcomes including mortality and mRS score at 90 days. Differences between groups were examined using Student’s t-test, Pearson’s Chi-square test, or the Mann–Whitney U test. Statistical significance was defined as P ≤ 0.05.

Results

A total of 43 patients were selected for the study (19 men, 24 women; median age = 73 years; age range =36–95 years). Demographic data including risk factors, medication history, initial NIHSS score, site of occlusion, and procedural timings are presented in Table 1. The median NIHSS score at admission was 17 (range = 7–34). The majority of patients were hypertensive (>139/89 mmHg; median blood pressure = 149/95 mmHg) and had elevated serum glucose level (>99 mg/dL; median = 136 mg/dL) on admission. Risk factors included: hypertension (88%); smoking (54%); atrial fibrillation (44%); and dyslipidemia (42%). Regular medications before stroke included statins (35%), antiplatelet agents (28%), novel oral anticoagulants (NOAC) (26%), and vitamin K antagonists (VKA) (5%). Twenty patients (46.5%) were eligible for and received i.v. rt-PA before the intervention. The median duration of cerebral ischemia before admission was 120 min and the average duration of the intervention (defined as groin to reperfusion) was 51 min. The median time from onset to reperfusion was 230 min.

Table 1.

Demographics and medical history of study participants (n = 43; 19 men, 44.2%; 24 women, 55.8%).

Demographic data
Median age (years)	73 (36–95)
Median NIHSS	17 (7–34)
Median blood pressure (mmHg)	149/95
Blood glucose (mg/dL)	137 (90–185)
Risk factors
Smoking	23 (54)
Cardiovascular disease	11 (26)
Hypertension	38 (88)
Atrial fibrillation	19 (44)
History of stroke/TIA	9 (21)
Hyperlipidemia	18 (42)
Diabetes mellitus	15 (35)
Medication on admission
Antiplatelet	12 (28)
Vitamin K antagonists	2 (5)
NOAC	11 (26)
Statin	15 (35)
Timings (min)
Onset to arrival	120 (30–240)
Onset to needle	146 (50–270)
Onset to reperfusion	230 (100–340)
Groin to reperfusion	51 (15–110)
Occluded vessel
Basilar artery	23 (53)
Vertebral artery	Right – 7 (16)	Left – 5 (12)
Posterior cerebral artery P1	Right – 5 (12)	Left – 3 (7)
mTICI after intervention
Successful (2b–3)	38 (88.4)
Unsuccessful (0–2a)	5 (11.6)

Values are given as n (%) or median (range).

mTICI, modified treatment in cerebral infarction; NIHSS, National Institute of Health Stroke Scale; NOAC, novel oral anticoagulant; TIA, transient ischemic attack.

DSA imaging showed occlusion in the following sites: basilar artery (53%); V4 segment of vertebral artery (right 16%, left 12%); and P1 segment of the PCA (right 12%, left 7%). In each patient, aspiration was first attempted and if this was unsuccessful after five attempts, the Solitare stent retriever was used. The stent retriever was used in 13 (30.2%) patients. Successful recanalization (defined as mTICI 2b–3) was observed in 38/43 (88.4%) patients after the intervention. Recanalization was unsuccessful (mTICI 0–2a) in 5 (11.6%) patients. There were no intra-procedural complications noted.

All patients were evaluated using the NIHSS 24 h after the procedure. The average NIHSS score after 24 h was 9 (range = 2–24), which indicates significant improvement. Median hospitalization time was 17 days (range = 2–110 days). In 4 (9.3%) patients, hematoma at the site of the arterial puncture occurred, with one patient requiring surgical intervention. Symptomatic ICH defined on the basis of the European Cooperative Acute Stroke Study III (ECASS III) criteria (9) was observed in 5 (11.6%) patients. The intrahospital mortality rate was 10 (23.3%). Thirty-three patients who survived to discharge were followed up. After 90 days, favorable outcome (mRS = 0–2) was achieved in 26 (78.8%) patients and an unfavorable outcome (mRs > 2) in 6 (18.2%) patients. One patient died during the follow-up period, resulting in a final mortality rate of 25.6% (11/43).

Prognostic factors

A comparison of two groups based on outcome (favorable versus non-favorable) is presented in Table 2. There was a statistically significant difference in baseline NIHSS score on admission and in procedural details (onset to reperfusion time, procedural time, and mTICI) between the two groups. Baseline NIHSS score was significantly higher in patients who had an unfavorable outcome compared to those with a favorable outcome (21 vs. 15, P = 0.006). Moreover, shorter times from onset to reperfusion (213 min vs. 256 min) and groin puncture to reperfusion time (43 min vs. 62 min) were significant factors associated with a favorable outcome (P = 0.021 and P = 0.004, respectively). Finally, the percentage of patients with successful recanalization was 100% in those with a favorable outcome, compared to 70.6% in those with an unfavorable outcome (P = 0.003).

Table 2.

Comparison of favorable versus unfavorable groups (based on mRs at 3-month follow-up).

	Favorable (mRS = 0–2) (n = 26)	Unfavorable (mRS > 2) (n = 17)	P value
Demographic data
Median age (years)	72	75	0.759*
Sex - men (n, ,%)	8 (47)	11 (42)	0.759^†
Median NIHSS	15	21	0.006 ^‡
Risk factors
Smoking	13 (50)	10 (59)	0.571^†
Cardiovascular disease	8 (31)	3 (18)	0.335^†
Hypertension	21 (81)	17 (100)	0.054^†
Atrial fibrillation	11 (42)	8 (47)	0.76^†
History of stroke/TIA	6 (23)	3 (18)	0.669^†
Dyslipidemia	11 (42)	7 (41)	0.941^†
Diabetes mellitus	10 (38)	5 (29)	0.543^†
Medication on admission
Antiplatelet	5 (19)	7 (41)	0.117^†
Vitamin K antagonist	2 (8)	0 (0)	0.242^†
NOAC	8 (31)	3 (18)	0.335^†
Statins	9 (35)	6 (35)	0.964^†
Antihypertensive drugs	21 (81)	17 (100)	0.054^†
Procedural data
Median onset to arrival (min)	108	140	0.096*
Median onset to needle (min)	145	146	0.575*
Median onset to groin (min)	170	193	0.249^‡
Median onset to reperfusion (min)	213	256	0.021 ^‡
Median duration of procedure (min)	43	62	0.004 ^‡
TICI positive (2b–3)	26 (100)	12 (70.6)	0.003 ^†
Intracranial hemorrhage	0 (0)	5 (29.4)	0.338^†
Anesthesia (general/local)	17/9	12/5	0.722^†

Values are given as n (%) unless otherwise indicated.Values in bold are statistically significant values that means P < 0.05.

*Mann–Whitney test.

^†Chi-square Pearson test

^‡Student’s t-test.

NIHSS, National Institute of Health Stroke Scale; NOAC, novel oral anticoagulant; TIA, transient ischemic attack; TICI, treatment in cerebral infarction.

By comparing patients based on the final mortality, we observed significant differences in percentage of successful recanalization (64% in patients who died compared to 97% in patients who survived, P = 0.003). Moreover, the percentage of patients with symptomatic ICH was significantly higher in those who died (P = 0.003).

In total, 20 (46.5%) patients received rt-PA before the intervention. There was no statistically significance difference between patients who received rt-PA and those who did not in terms of favorable outcome (P = 0.571) or mortality (P = 0.138).

Overall, 29 (67.4%) patients were treated under general anesthesia and 14 (32.6%) were treated with local anesthesia and sedation. There were no statistically significant differences observed when comparing the method of anesthesia in terms of favorable outcome (P = 0.722) or mortality (P = 0.755).

Discussion

The aim of the present study was to analyze the outcome of MT in patients with acute ischemic PCS in one institution over the period of four years and to evaluate the clinical and procedural factors associated with recanalization, outcome, and mortality. Successful recanalization, defined as mTICI 2b–3, was observed in 38/43 (88.4%) patients, which is within the range of successful recanalization achieved in other studies (10 –15). Favorable clinical outcome was observed in 26/43 (60.5%) patients and 11 patients died, resulting in a final mortality rate of 25.6%. In the mentioned studies, favorable clinical outcome rates are in the range of 22.5%–56.2% and mortality rates are in the range of 12.0%–40.9%. Symptomatic ICH was seen in 5 (11.6%) patients.

The present study shows some major findings. NIHSS on admission appears to be linked to outcome. Baseline NIHSS score was significantly higher in those who had an unfavorable outcome (mRS > 2 group) compared with those with a favorable outcome (mRS = 0–2) (21 vs. 15, P = 0.006). These findings are consistent with observations made by authors of similar reports (12,14,16). However, some studies suggest that NIHSS score has a relatively poor sensitivity in patients with PCS treated with MT (3,17).

Successful recanalization is associated with a significantly increased rate of functional independence (mRS = 0–2) at three-month follow-up and a reduced risk of death. The percentage of patients with successful recanalization in the favorable and unfavorable outcome groups were 100% and 70.6%, respectively (P = 0.003). Comparison of patients who survived with those who died also presented significant difference in rates of successful recanalization (64% in those who died compared to 97% in those who survived, P = 0.003). Previous studies showed that successful recanalization of basilar artery was related to a twofold reduction in mortality (15,18).

Occurrence of ICH appears to be associated with a significantly increased risk of death (P = 0.003). We observed symptomatic ICH in 5 (11.6%) patients, which was more frequent than in other studies (4%–5%) (19 –21). This, however, might be attributed to our relatively small sample size.

In the present study, we did not find any statistically significant effects of using rt-PA on either outcome, prognosis, mortality, or hemorrhagic complications. The debate on use of rt-PA before MT is still ongoing. The authors of the DIRECT-MT Protocol established non-inferiority of direct endovascular thrombectomy without i.v. thrombolysis before or during the procedure with regard to functional outcomes (19). On the other hand, similar trials claim that non-inferiority for direct MT could not be proven (20). Therefore, at present, according to guidelines, all eligible patients should receive alteplase before thrombectomy.

Another issue is the optimal anesthetic approach during endovascular therapy. General anesthesia is associated with less pain and movement during the procedure which facilitates endovascular surgery. However, conscious sedation is associated with less time from onset to reperfusion, which was an independent factor of favorable outcome in the present study. The median time from onset to reperfusion was 213.1 ± 57.3 min in the favorable outcome group and 255.9 ± 65.8 min in the unfavorable outcome group. Systematic reviews and observational studies describing patients with ACS reported worse outcomes from general anesthesia compared with conscious sedation during endovascular therapy (21,22). However, Zhang et al. (23) recently published a study showing the opposite results. As far as type of anesthesia used, we did not observe significant differences in terms of favorable outcome and mortality.

The present study has some limitations: small sample size; retrospective study design; and single-center study. There was also no unified scoring of brainstem infarction and penumbra area conducted from diagnostic imaging (e.g. posterior circulation Acute Stroke Prognosis Early CT Score [pcASPECTS]).

In conclusion, our study indicates that MT is a feasible and effective method in the treatment of PCS. NIHSS on admission and the recanalization rate were important predictors of favorable outcome at the 90-day follow-up, whereas successful recanalization and absence of ICH were associated with a significantly increased rate of survival.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Maciej Szmygin

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