A Study of Ef ﬁ cacy and Outcomes of Two Techniques of Mechanical Thrombectomy in Acute Ischemic Stroke

Background Endovascular mechanical thrombectomy (A Direct Aspiration First Pass Technique [ADAPT] and Solitaire stent retrieval techniques) as an emergency reperfusion therapy in acute ischemic stroke patients avoids secondary brain insult and thereby prevents permanent neurological de ﬁ cits. As studies comparing the two thrombectomy procedures are scarce, we evaluated their ef ﬁ cacy. Methods In thisprospective observationalstudydoneatManipalHospitalsBangalore, 75 patients were separated into two groups based on the ﬁ nal reperfusion technique employed: ADAPT group with 39 patients who underwent


Introduction
Stroke is the second-leading global cause of death that occurs in about 33 million people annually, and ischemic stroke accounts for approximately 2.8 million deaths. 1 The neurological deficit in stroke is because of the cerebral infarction that occurs using intraarterial thrombolytics and modern mechanical thrombectomy techniques in the last two decades. 3,4][5][6] Stent retriever thrombectomy 7,8 and direct clot aspiration are the most commonly used mechanical thrombectomy techniques for reducing the time for revascularization, 5,6 while the former consists of closed-cell, self-expanding stents that are fully deployable and retrievable supplemented by balloon guide catheter inflation where necessary, the latter, called ADAPT-A Direct Aspiration, First Pass Technique, uses front-line aspiration alone to remove the thrombus through a highly trackable, atraumatic, large-bore aspiration catheter.
Controversies exist about the most relevant thrombectomy technique and additionally, studies that compared safety and effectiveness of the above two modalities are limited. 9,10In view of the above, we aimed to compare the effectiveness of ADAPT and stent retriever techniques in acute stroke intervention.

Methods
Following a prospective observational study design, our objectives were to compare the clinical and functional outcomes using the National Institutes of Health Stroke Scale (NIHSS) 11 and the mRS (modified Rankin scale), 12 respectively, and reperfusion rates using modified treatment in cerebral infarction (mTICI) score. 13We recruited 75 acute ischemic stroke patients undergoing mechanical thrombectomy, in our institution from May 1, 2018 to May 31, 2021 and follow-up visits were scheduled at 1 and 3 months in addition to 24 hours postintervention.The sample size was calculated, considering 95% confidence intervals, a power of 80%, and the proportion of successful recanalization after ADAPT and Solitaire stent retrieval procedure from a previous similar study. 9Patients above 18 years of age with confirmed acute ischemic stroke on neuroimaging; those with middle cerebral artery occlusion/ intracranial internal carotid artery occlusion/ posterior circulation vessel involvement; and those treatable by mechanical thrombectomy within 24 hours of stroke onset, with bridging therapy (previous IV recombinant tissue plasminogen activator) or standalone thrombectomy were included.Whereas, those referred for acute ischemic stroke after 24hrs of stroke onset time; with mild stroke symptomsdefined by a presentation NIHSS score less than 6 without aphasia; functional dependence prior to stroke onsetdefined as a pre-stroke mRS score of more than 3; and any intracranial hemorrhage were excluded.Biochemical and electrocardiographic results were recorded for patients with suspected acute ischemic stroke; NIHSS and mRS scores at presentation, magnetic resonance imaging brain and magnetic resonance angiography of the cerebral vessels, were also done.Eligibility for endovascular reperfusion therapy was determined based on the clinical profile and after ruling out known contraindications.The time of symptom onset, time of onset to femoral puncture (ictus to start of thrombectomy), and time from femoral puncture to reperfusion (start of thrombectomy to reperfusion on cerebral angiogram) were also recorded.For patients eligible for mechanical thrombectomy, an informed consent was obtained and one of the two techniques-Contact Aspiration technique (ADAPT) and Stent Retriever technique (Solitaire)was done.Procedures were done by two operators, working together, to achieve successful reperfusion of occluded vessel at quickest possible rate and minimal complications.At least two attempts at revascularization were performed using the primary endovascular technique before switching to the other procedure (noted as rescue therapy) if needed.Antiplatelet therapy, statins, and other supportive measures were administered to all the patients irrespective of the intervention group.
The angiographic (rate of successful recanalization defined as mTICI 2c-3); clinical (degree of disability assessed by overall distribution of the mRS score at 3 months, functional independence as defined by a 3 months mRS score of 2 or lower, change in NIHSS) score at 24 hours, death due to any cause at 3 months); and adverse events (infarct in a new vascular territory, presence of intracerebral edema leading to parenchymal mass effect, intracranial hemorrhage on imaging at 24 hours, and symptomatic patients requiring decompressive craniectomy as a life-saving measure) were evaluated.For patients who were lost to follow-up (due to death) at 1 or 3 months, the condition on the last day of examination was regarded as the final follow-up.IBM SPSS version 21 was used for statistical analysis of data-unpaired t test for comparison of age, and chi-squared analysis for all the other categorical variables were done.A p-value less than 0.05 was considered significant.

Results
Demographic, angiographic, and clinical profile were obtained for 75 patients who underwent emergency endovascular mechanical thrombectomy for acute ischemic stroke.These patients were followed up at 24 hours, 1, and 3 months postintervention, for evaluating their functional outcome.Solitaire device and ADAPT technique were used in 36 (48%) and 39 (52%) patients, respectively.Basic details of the patients in the two groups are as illustrated in ►Table 1 and as noted, the presentation findings were not significantly different between the two groups.
Indian Journal of Neurosurgery © 2024.The Author(s).
A Study of Efficacy and Outcomes of Two Techniques of Mechanical Thrombectomy in Acute Ischemic Stroke Shavi et al.A Study of Efficacy and Outcomes of Two Techniques of Mechanical Thrombectomy in Acute Ischemic Stroke Shavi et al.
A significantly higher number of patients in the ADAPT group achieved a mTICI score of 2C and 3-both at the end of all procedures, and at the end of first-line strategy alone (►Table 3).All-cause mortality at 3 months was significantly greater in the solitaire group (27.8 vs. 0%; p ¼ 0.015), but the computed tomography scan findings were not (►Table 4).Further, decompressive craniotomy was done in 30.6 and 20.5% of the patients in the solitaire and ADAPT groups, respectively (p ¼ 0.318).

Discussion
Recanalization and reperfusion strategies form the mainstay of treatment for acute ischemic stroke, as they reverse the neurological deficits by reopening of the occluded vessel.As a majority of the reperfusion therapy trials used stent retriever techniques, questions regarding the safety and efficacy of aspiration thrombectomy techniques as a firstline therapy remained unaddressed, owing to the limited literature.Therefore, we compared the two techniques for patients with acute ischemic stroke and large vessel occlusion.

Angiographic Outcome
As per previous literature that reported an mTICI score of 2c or 3 as successful revascularization, 14,15 we compared it between the two groups for angiographic outcome.Overall, as 65 patients from both groups showed successful revascularization, mechanical thrombectomy can be  A Study of Efficacy and Outcomes of Two Techniques of Mechanical Thrombectomy in Acute Ischemic Stroke Shavi et al.
considered an effective reperfusion strategy.In addition, the greater revascularization within the ADAPT group is similar to that demonstrated in a study by Lapergue et al 9 that showed a 16.5% greater success rate within the ADAPT group (82.3 vs. 68.9%;p ¼ 0.022).On the contrary, ASTER trial 10 found no significant difference between contact aspiration and stent retriever groups.However, higher rate of successful revascularization for ADAPT in our study could be attributed to the following reasons: most of the patients in the ADAPT group (48.7%) presented earlier than 3 hours as compared to Solitaire group (36.1%) leading to the assumption of formation of organized clot and difficult clot retrieval in the Solitaire group (however statistically this was not proven to be significant as highlighted in ►Table 5); second, as stent retriever requires passing it through the clot, it might result in a higher rate of distal emboli, leading to incomplete revascularization.Third, repeated use of old stent devices in patients could also lead to inefficient clot retrieval and revascularization

Clinical Outcome
Almost half of the patients in our study (36/75) attained functional independence at 3 months matching the results of endovascular treatment for Small Core and Anterior circulation Proximal occlusion with Emphasis on minimizing CT to recanalization times (ESCAPE) trial (53%). 16Unlike our study, Contact Aspiration Versus Stent Retriever for Successful Revascularization (ASTER) trial 10 could not depict a significant difference in the NIHSS score at 24 hours between the two techniques of thrombectomy.The degree of disability in the present study was also lesser for patients within the ADAPT group reflected through lesser mRS scores and a favorable shift at 3 months (OR ¼ 1.502).
According to the reperfusion hypothesis, reversal of penumbra is possible with restoration of blood flow, hence thrombectomy when done within this viable time window, is capable of reversing the mRS scores as well.Further, the revised 2018 American Heart Association/American Stroke Association guidelines recommend-stent retriever thrombectomy, even when done for patients presenting after 24 hours assures good clinical outcomes. 17This justifies the better postintervention outcomes depicted in the patients within both groups of our study.

Mortality
The overall mortality rate of 13% at 3 months in our study is almost similar to that in the EXTEND 1A (9%) 3 and ESCAPE (10.4%) 16 trials.It was significantly greater in the solitaire group.

Adverse Events
More number of patients within the solitaire group in our study had adverse events, namely, development of intracranial bleed, new ischemic strokes, and development of mass effect secondary to cerebral edema-in line with previous studies by Kowoll et al, 18 Turk et al, 19 and Blanc et al 20 that found greater proportion of symptomatic hemorrhages, and lower rates of embolization and symptomatic intracranial hemorrhages, respectively, for contact aspiration.The number of patients who underwent decompressive craniectomy in our study (25%) was greater than that in another study (12%). 10Some limitations of our study include smaller sample size; not being a blinded trial; significantly higher baseline NIHSS score in the Solitaire group, which may have affected the outcome; and a short follow-up period that prevents drawing concrete conclusions.

Conclusion
Within the above limitations, the overall clinical outcome was good irrespective of the mechanical thrombectomy technique employed, but better results in terms of functional and angiographic outcomes were obtained in favor of ADAPT.Future studies with larger sample size, longer follow-up period, and those that determine the effectiveness of the intervention at various sites of vessel occlusion through a subgroup analysis are recommended.

Table 1
Comparison of demographics and other findings between the two groups, analyzed using unpaired t-test for age and chisquared analysis for the other categorical variables Study of Efficacy and Outcomes of Two Techniques of Mechanical Thrombectomy in Acute Ischemic Stroke Shavi et al.
Indian Journal of Neurosurgery © 2024.The Author(s).AIndian Journal of Neurosurgery © 2024.The Author(s).

Table 5
Distribution by time gap from onset to reperfusion Abbreviations: NS, not specified; S, specified.

Table 3
Intergroup comparison of rate of successful recanalization, analyzed using chi-squared analysis

Table 4
Intergroup comparison of CT scan findings at 24 hours postintervention and mortality at 3 months, analyzed using chisquared analysis a Significant at p < 0.05.