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Ann Indian Acad Neurol. 2017 Jul-Sep; 20(3): 211–216.
PMCID: PMC5586113

Acute Ischemic Stroke Treatment Using Mechanical Thrombectomy: A Study of 137 Patients

Abstract

Background:

Mechanical thrombectomy (MT) is the most effective treatment in large vessel occlusion (LVO). We have analyzed our initial experience of MT of 137 patients in anterior circulation (AC) and posterior circulation (PC) LVO using Solitaire stent retriever device.

Methods:

Retrospective cohort analysis of 112 AC and 25 PC acute ischemic strokes was done considering various baseline characteristics, risk factors, National Institute of Health Stroke Scale (NIHSS) change, revascularization rate, complications, and functional outcome at 3 months using modified Rankin score.

Results:

Out of 137 patients, occlusion was found in M1 segment (44.5%), carotid T occlusion (37.2%), and basilar artery (18.2%). Atrial fibrillation was important risk factor for Carotid T occlusion. 50.4% patients received intravenous thrombolysis. Baseline mean NIHSS in AC was 15.5 (±4.32), and PC was 19 (±5.5). Tandem lesions were noted in 14.6%. There was significant difference in mean door-to-needle time for AC and PC (220 ± 80.6 and 326 ± 191.8 min, respectively). Mean time to revascularization for AC (39.5 ± 14.1) and PC (42.2 ± 19.4) was similar. Procedural success (modified thrombolysis in cerebral infarction ≥2b) observed in AC and PC was 92.9% and 84%, respectively (P = 0.154). NIHSS at admission between 5 and 15 and immediate postprocedure NIHSS improvement >4 was associated with significant better clinical outcome at 3 months. Overall complication rate was about 15.3% including symptomatic intracranial hemorrhage in 8.1% and 6.6% deaths.

Conclusion:

MT is safe treatment and equally effective for both AC and PC LVO. With careful patient selection, clinical outcome in PC was comparable to AC despite delayed presentation and higher baseline NIHSS.

Keywords: Acute ischemic stroke, large vessel occlusion, mechanical thrombectomy, stent retriever

INTRODUCTION

The corner stone of treatment in acute ischemic stroke (AIS) is revascularization. National Institute of Neurological Disorders and Stroke trial (NINDS study Group) revolutionalized management of AIS using recombinant tissue plasminogen (rtPA) within 3 hours. This trial showed reduction in stroke morbidity by 30%.[1] Eventually, treatment window period was increased to 4.5 h after ECASS III.[2] Unfortunately, intravenous thrombolysis (IVT) has higher failure rate in large vessel occlusion (LVO).[3] Intra-arterial urokinase achieved 66% recanalization in LVO and also prolonged the window period for acute stroke intervention up to 6 h.[4]

Mechanical thrombectomy (MT) with newer thrombectomy devices has many advantages compared to thrombolysis in LVO stroke. Recent five randomized control trials (RCTs) (SWIFT PRIME, REVASCAT, MR CLEAN, EXTEND-IA, and ESCAPE) have proved superiority of MT using stent retrievers over the best medical management using IVT.[5,6,7,8,9]

In this study, we report our multicenter experience and retrospective analysis of 137 patients who were subjected to MT postthrombolysis or primarily (if IVT was contraindicated) and present our experience of MT using Solitaire Flow Restoration (Solitaire FR) stent retriever in anterior circulation (AC) and posterior circulation (PC) AIS.

METHODS

Consecutive 137 patients who underwent MT for AIS with a Solitaire FR with or without IVT at various centers in Mumbai and its suburban areas from January 2014 to December 2016 were retrospectively analyzed in this study. Following parameters were documented: demographics (age, sex), the National Institute of Health Stroke Scale (NIHSS), early ischemic changes and initial imaging documenting site of vessel occlusion, time between symptoms onset and start of treatment (onset to needle time), procedural time intervals (needle to reperfusion), and result of recanalization (modified thrombolysis in cerebral infarction (mTICI).[10]

All eligible patients received intravenous (IV) rtPA unless contraindicated. Patients with LVO who received IV rtPA were simultaneously shifted for MT. In remaining patients, MT was done as primary therapy. Patients with NIHSS < 4 and who had spontaneous improvement were not included (Spontaneous improvement was defined as drop in NIHSS to ≤4) [Figure 1]. For analysis purpose, we divided patients into two groups according to their baseline NIHSS score: between 5–15 and >15. The study flow chart is shown in Figure 1. Informed consent was obtained from each patient or family member before administering IV rtPA and performing the endovascular procedure.

Figure 1
Study design flow chart

Diffusion-weighted imaging (DWI) was used for assessing the extent of the ischemic lesion and magnetic resonance angiography to identify and locate the site of vessel occlusion wherever possible. T2-weighted and Fluid-attenuated inversion recovery imaging was used to determine the timing of the ischemic lesions. In other patients, computed tomography (CT) scan and CT angiography brain were done. In the PC, the exclusion criteria were based on the radiological appearances on DWI. CT-Perfusion was not used.

Procedural success rate was defined by 2b and 3 grades on mTICI scale, indicating reperfusion of more than 50% of the affected territory. Neurological outcome 24–48 h after the procedure, at discharge or 7 days (which was earlier) and after 90 days, was measured by NIHSS. We defined early neurologic improvement as decrease of at least 4 points in the NIHSS score. Functional outcome was evaluated at discharge and 90 days using the modified Rankin Scale (mRS). Clinical outcomes were divided into favorable (mRS 0–2) and unfavorable (mRS 3–6).

Symptomatic intracranial hemorrhage was defined according to the ECASS-II (European Cooperative Acute Stroke Study-II) definition: any intracerebral hemorrhage with an increase of at least 4 NIHSS points within 24 h or resulting in death.[11]

Exclusion criteria included were established large infarct, absence of evidence of major vessel occlusion, distal occlusion (M2 and beyond), presence of intracranial hemorrhage, NIHSS <4, and spontaneous NIHSS improvement (decline in NIHSS score of 4 or above).

Mechanical thrombectomy procedure protocol

Procedure was performed through femoral artery access with Solitaire FR stent retriever. Solitaire FR (EV3, Irvine, California, USA) is a stent-based thrombectomy system with a closed cell design and a longitudinal split section. The device is delivered through a standard microcatheter (inner lumen diameter of 0.021 inches or 0.027 inches) through a 0.014-inch microwire. Solitaire FR serves dual function, namely, immediate FR by creating temporary bypass through the thrombus and also acts as a clot retriever, trapping thrombus into its cells.

8F balloon guide catheter navigated over Terumo wire and placed in the ipsilateral cervical internal carotid artery (ICA). In PC strokes, 6F (070) guiding catheter was used. The microcatheter was navigated distal to the clot. Solitaire FR is delivered through the microcatheter and deployed over the thrombus. The balloon guide catheter was inflated to provide proximal ICA occlusion and flow arrest during the recovery of the stent retriever. Subsequently, the Solitaire FR and microcatheter were slowly recovered as a unit under constant aspiration with 50-mL syringe through the balloon guide catheter. A control angiogram was performed to confirm recanalization mTICI ≥2b. In case, recanalization was not achieved, this sequence was repeated. In few cases, a third pass was needed to achieve recanalization, and in one patient, 2 stents were used together at the same time.

Postoperative management

All patients underwent CT brain immediately after MT and repeat CT brain was done 24 hours later. Low-dose aspirin (75 mg) was started after 24 h after ruling out hemorrhage in CT scan. In patients in whom acute stent placement was done, loading dose of dual antiplatelets (300 mg aspirin and 300 mg clopidogrel) was given immediately followed by maintenance dose (aspirin 75 mg and clopidogrel 75 mg). Anticoagulants were given for cardiogenic embolism if there were no hemorrhagic changes without massive infarction.

Data collection and statistics

Data were collected in standard pro forma from in patient case records and follow-up records on outdoor patient department. In this study, Statistical analyses were performed using IBM SPSS statistical software for Windows, version 19.0, Armonk, NY:IBM Corp. USA.

Descriptive analysis

Continuous variables were summarized using summary statistics (number of observations, mean, and standard deviation [SD] with range). Categorical values were estimated using frequencies and percentages.

Tests of significance

In this study association between NIHSS score, posterior or AC with outcome was estimated by Chi-square test. Other variables, type of vessels, and changes in NIHSS score were also analyzed by Chi-square test. All values were reported base on two-sided and all the statistical tests were interpreted at 5% level of significance level (P < 0.05). Multivariate analysis was done on risk factors.

RESULTS

From January 2014 to December 2016, 137 consecutive patients (87 males and 50 females) with mean age 57 (SD ± 11.96, range 22–87 years) were treated with Solitaire FR in the setting of AIS. Our cohort was heterogeneous including 25 (18.25%) of PC occlusion cases, apart from 112 (81.75%) of AC. Target vessel was only M1 segment of MCA in 61 (44.5%) patients while in 51 (37.2%) patients, occlusion involved the distal ICA and M1. In 25 (18.2%) patients, the target artery was the basilar artery (BA).

The baseline characteristics of 137 patients analyzed in this study are summarized in Table 1. Multivariate analysis of risk factors revealed atrial fibrillation significantly associated with carotid T occlusions (P = 0.001).

Table 1
Characteristic features of the study group including demographic data and clinical outcome

There was significant difference in baseline NIHSS and door-to-needle time in anterior and PC (P < 0.05). However, there was no difference in time needed to open the artery (revascularization time) between anterior and PC.

Procedural success as measured in terms of recanalization rates (mTICI ≥2b) in anterior and PC cases [Figure 2] showed no significant difference in recanalization rates in anterior and PC. Association between outcomes in anterior and PC is summarized in Table 2. There was no significant difference in the outcome.

Figure 2
Comparison of TICI outcome in anterior and posterior circulation.
Table 2
Association between circulation and outcome

Occluded arteries could be opened with TICI flow ≥2b in 125 cases (91.2%). In 121 cases (88.32%) of procedures, successful revascularization was achieved within one or 2 passes. TICI flow significantly associated with good clinical outcome [Figures [Figures22 and and3].3]. Twenty (14.6%) patients required additional endovascular procedure: three patients underwent intracranial balloon angioplasty, 17 patients needed stent deployment (intracranial stent in 5 patients and extracranial in 12 patients).

Figure 3
Procedural success rate and its correlation with functional outcome (modified Rankin Score) at 90 days

Patients with improvement of NIHSS ≥4 after 24 h from baseline showed statistically significant good outcome as compared to patients with improvement of NIHSS <4. Patients with NIHSS at admission between 5 and15 did well at 3 months as compared to patients with NIHSS >15 [Table 3].

Table 3
Association between National Institute of Health Stroke Scale and outcome

Table 4 gives an account of comparison of AC patients of the present study with previous major RCTs. Major differences in our study are younger mean age, higher number of males (71%), carotid occlusion in 45.5%, better recanalization rate (92.9%), more use of general anesthesia, and better functional outcome at 90 days. For outcome comparison, we have separately considered patients with BA occlusions because these trials did not include PC strokes, and these are known to be associated with poor prognosis.[12]

Table 4
Comparison between major randomized control trials

Overall complication (major and minor) rate in this study was 15.3% [Table 1]. Puncture site complications were developed in 3 (2.2%) patients in the form of local groin hematoma in 2 and femoral artery pseudoaneurysm in 1 patient. We observed 6.6% mortality rate [Table 1]. Cause of death was major intracranial hemorrhage in 3 patients, large infarct with edema in 2, chest infection in 2, acute coronary syndrome in 1, and major gastrointestinal hemorrhage in 1 patient.

DISCUSSION

This study highlights our experience with Solitaire FR stent retriever in MT in LVO stroke. This study demonstrated that MT in clinical practice can achieve similar results as in published RCTs. It also demonstrated the MT can be successfully applied to BA occlusion (BAO). Our cohort had 5.1% (7/137) of patients who were more than 80 years old. Successful revascularization was achieved in all cases, and 42.8% (3/7) had good outcome at 90 days. In MR CLEAN, 16% of patients were 80 years or older and this subgroup had a positive treatment effect. Similarly, ESCAPE showed benefit for all subgroups including the elderly.[7,9] Azkune Calle et al. reported successful recanalization in older stroke patients (>80 years) with half of them achieving a good functional outcome 3 months after stroke. Thus, advanced age should not preclude the use of endovascular revascularization with mechanical devices.[13]

Despite baseline NIHSS being significantly higher in patients with PC stroke (P = 0.001), there was no significant difference in terms of revascularization time, vascular flow (mTICI), and final clinical outcome (mRS) at 90 days. However, NIHSS has its limitations, as it is more weighted toward AC and may not predict the severity in PC strokes.[14]

Our MT experience is outside RCTs and tests its application in real world scenario. These results are not only encouraging, acceptable but also in line with the results of various RCTs [Table 4]. Mean age, mean baseline NIHSS, symptom to needle time, and needle to revascularization were comparable. Fewer patients in this study received IV rtP (50.4%) as compared to all major RCTs. This is due to ineligibility of 49.6% of patients for IV rtPA administration because of delayed presentation (out of window period) and contraindications. In this study, 63.39% of patients with AC stroke achieved good outcome which is in coherence with these RCTs. Single M2 occlusions were included in REVASCAT, MR CLEAN, and ESCAPE RCTs in 9.8%, 7.7%, and 3.7% of patients, respectively. During outcome analysis, most of these RCTs have combined M1 and single M2 occlusions together. However, in our study, we had not included occlusion beyond M1.

Acute BAO accounts for 6%–10% of intracranial LVO and is associated with a very poor outcome.[12] BAO also has highest mortality rate of all types of ischemic stroke, with a morbidity and mortality rate of acute BAO of 80%–90% without active intervention.[15] The therapeutic time window for endovascular therapy in acute occlusion of BA remains unknown.[16] The PC system may have a stronger tolerance to ischemia and hypoxia due to greater white matter structure and better collaterals than AC.[17] The BA International Cooperation Study investigated the relationship between time to recanalization therapy and functional outcome in BAO. Patients had an increased risk of poor functional outcomes with increasing time to recanalization therapy. A significantly increased risk of poor outcome seems to occur when recanalization therapy is started more than 6 h, after symptom onset of acute BAO.[15,17] In our study, despite delayed intervention, clinical outcome was not statistically significant. We were able to achieve successful revascularization in 21 (84%) cases with mean needle to recanalization min 42.20 (±19.4). Nearly48% of cases had good outcome at 3 months follow-up. In our study, better outcome in PC stroke could be probably due to selection bias and cherry picking of cases which did not have extensive brain stem insult despite BAO.

In the study by Du et al. using Solitaire device, the mean time from symptom onset to recanalization was 579.00 ± 188.78 min (range: 360–960 min), and 38.1% of patients had a good clinical outcome at 3 months follow-up.[15] In a recent meta-analysis of stent retriever thrombectomy in BAO, which pooled the event rates for mortality in 15 observational series, the mortality rates were highly variable among all studies ranging from 6% to 46%.[17] In our study, we observed mortality rate of 8% in PC group.

In our study, we observed that lower baseline NIHSS had better functional outcome at 90 days compared to those with higher NIHSS. This was applicable in both anterior as well as PC groups. This finding is in coherence when compared with previous studies. Median reduction in NIHSS at 24 h in various RCTs was 4, 10, and 13 in MR CLEAN, ESCAPE, and EXTEND 1 A, respectively.[7,8,9] The best functional outcome correlated the highest reduction in NIHSS at 24 h (RESVASCAT 71% vs. MR CLEAN 32.6%).[6,7] In our study, we found that reduction in NIHSS >4 was associated with good outcome.

Revascularization rates with the Solitaire FR stent ranged between 84% and 100%, and good clinical outcome ranges between 33% and 55%.[18] In this study, overall revascularization rate was 91.2% and good clinical outcome was 60.6% which is comparable to previous studies.

Solitaire FR was easily navigated to the occlusion point. Its deployment across the thrombus was obtained in all cases, and in 79 (57.7%) cases, successful recanalization was achieved in the first attempt. On multiple occasions, thrombus was found in the 50 ml syringe used for manual aspiration during device retrieval. It is possible that stent in these cases just facilitated clot retrieval by displacing and mobilizing the thrombus into the balloon guiding catheter which was aspirated with 50 ml syringe.

Tandem occlusions of ICA or MCA can be treated with stenting even in acute setting during MT.[19,20] Management of such cases with antiplatelets is challenging. The use of antiplatelets in immediate postthrombectomy period is unavoidable to prevent stent occlusion. On the other hand, antiplatelets increase the risk of hemorrhagic complications. This study includes 14.6% of cases of tandem occlusion. In 2.2% of cases, angioplasty alone was done while 12.4% of cases, stent was deployed.

An expert consensus statement of the Society of NeuroInterventional Surgery and the Neurocritical Care Society[21] recommends the use of general anesthesia for patients with severe agitation, low level of consciousness (Glasgow coma scale <8), loss of airway protective reflexes, or respiratory compromise.[21] We preferred conscious sedation whenever possible. GA was administered in 59.9% of cases. In two cases, procedure was started under local anesthesia and converted to GA as patient became uncooperative.

Overall complication (major and minor) rate in our series was 15.3%. Symptomatic intracranial hemorrhage in 8.1% (n = 11) of cases, which is slightly more than 5.7%, shown in the mechanical EVT meta-analysis by Badhiwala et al.[22] Lower symptomatic intracerebral hemorrhage rate (2.5%) was identified by Campbell et al. in Solitaire thrombectomy meta-analysis.[23] We believe that higher rate of hemorrhagic conversion of infarcts was probably related to reperfusion injury as we achieved higher rate of recanalization.

The limitations of this study are its retrospective design with patients having heterogeneous baseline characteristics. There is also large difference in sample size between anterior and PC. Distal occlusions were not included in this study.

CONCLUSION

We observed no difference in efficacy and outcome in AC and PC stroke. Despite delayed presentation and high NIHSS score in PC stroke, and 3 months’ outcome was comparable with AC. This multicenter retrospective study shows that use of Solitaire FR is safe and achieves good revascularization rates and functional outcomes in patients with AIS and large artery occlusion. MT is feasible in real-world setting in India and results are comparable to RCTs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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