Endovascular treatment of acute basilar artery occlusion: A systematic review and meta‐analysis of first‐line stent retriever versus direct aspiration

Abstract Background The best choice between first‐line aspiration and stent retriever for acute basilar artery occlusion remains controversial. This study aims to perform a systematic review and meta‐analysis comparing the stent retriever and direct aspiration about reported recanalization rates and periprocedural complications. Method PubMed, Embase, Web of Science, Cochrane, and Clinical Trials were searched for the studies evaluating the efficacy and safety of first‐line aspiration versus stent retriever for acute basilar artery occlusion. A standard software program (Stata Corporation) was used for end‐point analyses. Statistical significance was defined as a p‐value less than .05. Results A total of 11 studies were involved in the current study, including 1014 patients. Regarding postoperative recanalization, the pooled analysis identified a significant difference in successful recanalization (odds ratio [OR] = 1.642; 95% confidence interval (95% CI): 1.099–2.453; p = .015) and complete recanalization (OR = 3.525; 95% CI: 1.306–2.872; p = .001) between the two groups in favor of the first‐line aspiration. Concerning the complications, the first‐line aspiration could achieve a lower rate of total complication (OR = .359; 95% CI: .229–.563; p < .001) and hemorrhagic complication (OR = .446, 95% CI: .259–.769; p = .004) than stent retriever. No significant difference was observed in postoperative mortality (OR = .966; p = .880), subarachnoid hematoma (OR = .171; p = .094), and parenchymal hematoma (OR = .799; p = .720). In addition, the pooled results revealed a significant difference in procedure duration between the two groups in favor of aspiration (WMD = −27.630, 95% CI: −50.958 to −4.302; p = .020). However, there was no significant difference in favorable outcome (OR = 1.149; p = .352) and rescue therapy (OR = 1.440; p = .409) between the two groups. Conclusion Given that the first‐line aspiration was associated with a higher rate of postoperative recanalization, a lower risk of postoperative complication, and a faster duration of the procedure, these findings support the aspiration may be more secure than a stent retriever.


INTRODUCTION
Acute basilar artery occlusion, a type of posterior circulation stroke, accounts for approximately 1%-4% of all stroke cases and has a high mortality risk (Demel & Broderick, 2015). Unlike hemispheric ischemia, which usually has a fast onset of localized symptoms, basilar artery occlusion syndromes might mimic other non-stroke diseases, causing neurological diagnosis to be delayed (Sarraj et al., 2015). The most frequent causes include atherosclerotic occlusion caused by local thrombosis due to severe stenosis and embolic occlusions, poor collateral circulation, and inadequate cerebral tissue perfusion (Zhao et al., 2023). It is crucial to restore blood perfusion by opening the occluded vessels on time. Several treatment approaches are currently available: thrombolytic therapy including intravenous thrombolysis and intraarterial thrombolysis, mechanical thrombectomy, or combinations of these (Wyszomirski et al., 2017;Yu & Higashida, 2022).
Intravenous thrombolysis refers to the systemic administration of recombinant tissue plasminogen activator. Theoretically, intravenous thrombolysis can initiate faster in most hospitals and the thrombolytic agent could reach the clot from both distal and proximal aspects. Intra-arterial thrombolysis allows for a higher local concentration of fibrinolytic while maintaining a lower systemic concentration (Lindsberg et al., 2012). In randomized trials, the effectiveness of endovascular treatment for basilar artery occlusions has been established recently, demonstrating its superiority over medical treatment alone (Jovin et al., 2022;Malik et al., 2022;Tao et al., 2022). Mechanical thrombectomies, such as aspiration thrombectomy, angioplasty with stenting, and stent retriever thrombectomy, have been tested with variable recanalization and clinical outcomes (Marmagkiolis et al., 2015). Stent retrievers have risen to prominence in the last few years.
The majority of stent retrievers utilized for mechanical thrombectomy are self-expanding tubular stent-like devices with sophisticated mesh designs that allow better clot integration and removal (Piasecki et al., 2022). This procedure recanalizes the vessel, allowing high rates of prompt flow restoration but leading to in-stent restenosis and in-stent thrombosis.
Catheter technology advancements have provided flexible and large-bore catheters that can safely navigate intracerebral circulation.
A direct aspiration first-pass technique has shown equivalent recanalization rates and neurological recovery to stent retriever thrombectomy when used either alone or in conjunction with stent retrievers (Nogueira et al., 2018;Turk et al., 2015). Direct aspiration is thought to facilitate recanalization and reduce the expense of endovascular interventions (Turk et al., 2014). A direct aspiration first-pass technique is a fast, simple, efficient, and safe strategy to achieve revascularization in patients. The best choice for basilar artery occlusion remains controversial. This study aims to perform a systematic review and metaanalysis comparing the stent retriever and direct aspiration concerning reported recanalization rates and periprocedural complications. and "basilar artery occlusion," which were also in combination with Boolean logic. In addition, other potentially relevant studies were manually discovered from references of eligible research or reviews on this subject.

Inclusion and exclusion criteria
All retrieved publications were independently extracted by two investigators. Studies were included in this meta-analysis if they fulfilled the following predefined criteria: (1) randomized controlled trials or observational cohort studies in English; (2) comparison of the safety of aspiration and stent retriever in treating basilar artery occlusion; and (3) one or more outcomes were reported.
The exclusion criteria were listed as follows: (1) animal study; (2) the data in the study could not be extracted; (3) studies that were not comparative, such as case reports, reviews, conference or commentary articles, letters, surveys, or satisfaction studies; (4) studies only equipped with a single-arm design; and (5) studies not meeting inclusion criteria.

Data extraction and outcome measures
Two authors independently extracted baseline characteristics, primary outcomes, and secondary outcomes from each eligible included study by using a form prepared in advance. Baseline data included first author, year of publication, study period, sample size, sex, age, and initial NIHSS score. Any question was discussed and resolved until a final decision. The primary end point of this meta-analysis included successful recanalization (defined as Thrombolysis in Cerebral Ischemia 2b or 3), complete recanalization (defined as Thrombolysis in Cerebral Ischemia 3), total complication, hemorrhagic complication, mortality, subarachnoid hematoma, parenchymal hematoma, a favorable outcome, rescue therapy, and procedure duration. Rescue therapy encompasses a range of interventions aimed at overcoming the potential failure of initial endovascular thrombectomy. These interventions may include switching to an alternative endovascular thrombectomy technique, employing angioplasty, utilizing adjuvant stenting, administering thrombolytics, and implementing antiplatelet medications.

Quality assessment
The quality assessment of each included study was conducted by two independent authors. The Newcastle-Ottawa Scale was used to evaluate the quality of observational cohort studies included in this study, which gives a score out of a possible total of nine stars (Guo et al., 2023). Any disagreement during the quality assessment procedure was resolved by consulting with the corresponding author.

Statistical analysis
This study adopted a standard software program (Stata Corporation) for end-point analyses. To assess the heterogeneity among the studies, we utilized the Higgins I-square (I 2 ), a metric that represents the proportion of variability attributable to differences between studies.
When the I 2 value was below 50%, it indicated homogeneity in the end-point measure. In such cases, we conducted a meta-analysis using a fixed-effect model, following the guidelines outlined in the Cochrane Handbook for Systematic Reviews of Interventions. Conversely, if the I 2 value exceeded 50%, we employed a random-effects model for the analysis. Meanwhile, as the included studies were not randomized controlled trials providing relative risk ratios, the outcomes of discontinuous outcomes (successful recanalization, complete recanalization, total complication, hemorrhagic complication, mortality, subarachnoid hematoma, parenchymal hematoma, favorable outcome, and rescue therapy) were expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Procedure duration, the continuous end point, was represented as a weighted mean difference (WMD) with 95% CIs.
Statistical significance was defined as a p-value less than .05.

Search results
According to the constructed searching strategy, 1446 research papers were found in our systematic search across four databases (PubMed, Embase, Web of Science, Cochrane, and Clinical Trials). Figure 1 illustrates the study selection procedure. In brief, a total of 924 duplicated publications were removed in the process of importing the searching articles to the Endnote software. Of 522 articles, 454 were excluded for various reasons (case reports, case series, reviews, letters, metaanalysis, and irrelevant articles) via screening the title and abstract.

Study characteristics and quality assessment
Demographic characteristics and details regarding the study design of the involved studies are summarized in Table 1  Gerber et al.

F I G U R E 3
Forest plot for assessing postoperative total complications.

F I G U R E 4
Forest plot for assessing postoperative mortality.

F I G U R E 5
Forest plot for assessing postoperative hematoma.

Procedure duration
Procedure duration was a continuous variable, a total of three studies reported data on the outcome of procedure duration. It was represented as a WMD with 95% CIs. The pooled results revealed a significant difference between the two groups in favor of aspiration (heterogeneity p = .051; I 2 = 66.4%; WMD = −27.630, 95% CI: −50.958 to −4.302; p = .020; Figure 8). More details are shown in Table 3.

DISCUSSION
Basilar artery occlusion is a rare kind of acute stroke; clinical outcomes vary, but the condition can be fatal Mortimer et al., 2012). Due to the fact that patients with basilar artery occlusion were typically not included in trials of endovascular thrombectomy for large-vessel occlusion ischemic stroke, the efficiency of this treatment was unknown until recently . Previous studies indicated that recanalized patients experience significantly better results than unrecanalized patients, and it was well acknowledged that endovascular thrombectomy provides high rates of recanalization . Importantly, numerous studies have demonstrated that in patients with basilar artery occlusion, stent retrievers might also produce a high rate of recanalization and functional independence (Gory et al., 2016;Phan et al., 2016). A first-line aspiration, according to many researchers, has advanced quickly, demonstrated efficacy and safety for recanalization for acute ischemic stroke (Vargas et al., 2017), and it may be superior to stent retrievers (Lapergue et al., 2016). This study aimed to compare the stent retriever and direct aspiration concerning reported recanalization rates and periprocedural complications. In this intention-to-treat meta-analysis of the retrospective and prospective cohort study, our findings substantiated that first-line aspiration, as compared to stent retriever, led to a notable enhancement in recanalization rates, accompanied by a significant reduction in both procedural complications and duration in patients with acute basilar artery occlusion.
Before the evolution in endovascular thrombectomy devices, three small single-center retrospective studies evaluated the postoperative revascularization of aspiration and stent retriever in basilar artery occlusion in 31 (18 in aspiration vs. 13 in stent retriever), 33 (20 in aspiration vs. 13 in stent retriever), and 50 (16 in aspiration vs. 34 in stent retriever) patients (Choi et al., 2020;Gerber et al., 2017;Son et al., 2016). A significant discrepancy in the two groups was found F I G U R E 6 Forest plot for assessing postoperative favorable outcome.

F I G U R E 7
Forest plot for assessing postoperative rescue therapy.

F I G U R E 8
Forest plot for assessing postoperative procedure duration.

TA B L E 3
The outcomes of this meta-analysis.

Studies numbers
Direct aspiration

Stent retriever Effect estimates 95% CIs p-Value I 2 (%) p-Value
The results concerning post-operation recanalization of aspiration vs. stent retriever with reference to postoperative revascularization. In 100 patients with basilar artery obstruction, Gory et al. (2018) further verified these findings and found that aspiration was related to noticeably greater odds (2.6-fold) of complete revascularization. In contrast, the level of complete revascularization did not differ between the two devices in a previous meta-analysis, but the aspiration group had a higher rate of successful revascularization (Ye et al., 2019). In this study, we identified a significant difference in successful recanalization (OR = 1.642; 95% CI: 1.099-2.453; p = .015) and complete recanalization (OR = 1.936; 95% CI: 1.306-2.872; p = .001) between the two groups in favor of the first-line aspiration. Importantly, our pooled results suggested that the first-line aspiration technique achieves a faster recanalization for patients with acute basilar artery occlusion compared with the stent retriever (WMD = −27.630, 95% CI: −50.958 to −4.302; p = .020).
Aspiration is theoretically simpler than stent retrieval because the aspiration catheter does not need to pass through the blood clot to reach the proximal end of the thrombus. However, it is important to note that this situation is not universally applicable. There are instances where reaching the thrombus solely with the aspiration catheter proves challenging, particularly in elderly patients with elongated vessels. In such cases, the support of a microwire or microcatheter becomes essential. This reliance on additional devices also accounts for the occurrence of a nonzero perforation rate in aspiration procedures. Besides that, no significant discrepancies were found with reference to rescue therapy (53 of 208 vs. 57 of 292; OR = 1.440, 95% CI: .606-3.421; p = .409); therefore, there is no additional time for preparing another pass or for switching to other rescue therapies.
Our data also supported the notion that aspiration therapy was a safer approach than stent retrieval. Aspiration treatment was recommended in each of the five studies that showed complications after surgery. None of the other four investigations, however, demonstrated a statistically significant difference in complications between the two groups, with the exception of the study by (Abdelrady et al., 2023) The combined data revealed that individuals who underwent aspiration had a lower incidence of total complications than those who under- However, it is important to note that there was a trend in favor of aspiration, indicating that vascular perforation may result from blind wire passage. The basilar artery is more susceptible to this possibility than the anterior circulation, which is more susceptible to hemorrhagic consequences (Choi et al., 2020).
Although thromboembolism is a more common cause of ischemic stroke with large and medium size vessel occlusion in the anterior circulation, the underlying etiology of basilar artery occlusion is often associated with cardioembolism, large artery atherosclerosis, and other mechanisms such as dissection and vasculopathy (Buchman & Merkler, 2019). Importantly, basilar artery occlusion stemming from atherosclerotic disease tends to be linked with unfavorable clinical outcomes (Lee et al., 2017;Mutke et al., 2023). During a basilar artery occlusion, atherosclerotic occlusions are commonly observed in proximal locations, whereas thromboembolic occlusions tend to occur more frequently in distal locations (Mutke et al., 2023). Patients diagnosed with atherosclerotic or embolic basilar artery occlusion may necessitate distinct treatment approaches and might experience varying benefits from the best endovascular stroke therapy. In addition, firstline approaches will probably be tailored to the specific etiology of stroke, and it is possible that aspiration thrombectomy may not be suitable or could potentially pose risks for patients with atherosclerotic vascular disease.
To the best of my knowledge, this is the second meta-analysis assessing the efficacy and safety of the stent retriever and direct aspiration with regard to reported recanalization rates and periprocedural complications. Ye et al. (2019) included 5 cohort studies (2 prospective and 3 retrospective) and 476 cases, they indicated a similar observation with our study. It is clear that this study included more studies with larger numbers of patients. The following limitations of this study should be noted. The included studies' participant characteristics and primary inclusion and exclusion criteria for trials differ, potentially leading to bias. There was some heterogeneity across the included trials in terms of study methods, patient characteristics, and clinical outcome criteria. Meanwhile, for the subgroup analysis, we could not divide the participants into groups with different follow-up times due to relatively little reported data. Although we included 11 studies (3 prospective and 8 retrospective studies), none of them were randomized controlled trials. It is necessary to conduct additional randomized controlled trials with larger sample numbers to verify this conclusion.

CONCLUSION
Endovascular treatment using the first-line aspiration was associated with a higher rate of recanalization, a lower risk of postoperative complication, and a shorter duration of the procedure. Based on this evidence, these findings support the aspiration may be more secure than a stent retriever. However, given that the limitations arose from this analysis, more evidence-based performance is needed to supplement this opinion.

AUTHOR CONTRIBUTIONS
Yanmei Ju and Hongxin Jiang designed and conceptualized the study.
Yongbin Wang and Juan Zhang finished data extraction from literature search. It was Juan Zhang who created the tables and figures. Each contributor made a significant contribution to the paper's composition as well as providing valuable intellectual insight.

CONFLICT OF INTEREST STATEMENT
The authors report no conflicts of interest.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding authors upon reasonable request.