thrombectomy group had a higher numerical rate of symptomatic intracranial hemorrhage (6.1 versus 2.7 percent, OR 2.07, 95% CI 0.79-5.41), but the difference was not statistically significant. Benefit with collateral flow MT improves outcomes for patients who have preserved collateral flow by CTA in the ischemic territory, as shown by the MR CLEAN-LATE trial [58]. The trial enrolled 535 adults presenting in the 6- to 24-hour time window with an acute anterior circulation stroke due to large vessel occlusion who had some degree of collateral flow in the MCA territory of the affected hemisphere by single-phase CTA or the arterial phase of multiphase CTA; patients eligible for MT by DAWN or DEFUSE 3 trials were excluded. Enrolled patients were randomly assigned in a 1:1 ratio to MT or no MT (control). The median age was 74 years, the median NIHSS score was 10, the median ASPECTS was 9 and 8 in the treatment and control groups, respectively, and the median time to randomization was approximately 11.5 hours. At 90 days, functional independence (an mRS score of 0 to 2) was achieved by more patients in the thrombectomy group compared with the control group (39 versus 34 percent), but the difference just missed statistical significance (OR 1.54, 95% CI 0.98-2.43). The thrombectomy group had improved outcomes compared with the control group by the median mRS (3 versus 4) and a shift in the distribution of the mRS scores favoring thrombectomy (OR 1.67, 95% CI 1.20-2.32). Mortality was lower in the thrombectomy group, but the difference was not statistically significant (24 versus 30 percent, OR 0.72, 95% CI 0.44-1.18), while symptomatic intracranial hemorrhage was more frequent in the thrombectomy group (7 versus 4 percent, OR 4.59, 95% CI 1.49-14.10). Earlier studies also suggested that moderate to good collateral flow status on CTA is useful for identifying patients who are likely to benefit from MT [8,24,59,60]. https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 12/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate Posterior circulation stroke Although the benefits are uncertain, MT may be a reasonable treatment option for patients with acute ischemic stroke caused by occlusion of the basilar artery, vertebral arteries, or posterior cerebral arteries when performed at centers with appropriate expertise [8,61-67]. Basilar artery occlusion There is moderate-quality evidence that MT is beneficial for patients of Chinese ancestry who can be treated within 24 hours of moderate to severe stroke (an NIHSS score 10) caused by a basilar artery occlusion if the posterior circulation ASPECTS (pc- ASPECTS) score is consistent with a limited extent of ischemia [68,69]. ATTENTION trial The ATTENTION trial evaluated patients from China with moderate to severe stroke (with an NIHSS 10) due to basilar artery occlusion who were within 12 hours of the estimated time of stroke onset and had a limited degree of early ischemic change, as quantified by the pc-ASPECTS [68]. Patients were randomly assigned in a 2:1 ratio to medical care plus endovascular thrombectomy or medical care alone (control). At baseline, the median NIHSS score was 24 in each group. Approximately one-third of patients in each group received intravenous thrombolysis. At 90 days, the rate of good functional status (ie, an mRS score of 0 to 3) was higher in the thrombectomy group compared with the control group (46 versus 23 percent, adjusted RR 2.06, 95% CI 1.46-2.91) and the mortality rate was lower in the thrombectomy group (37 versus 55 percent, RR 0.66, 95% CI 0.52-0.82). The rate of functional independence (ie, an mRS score of 0 to 2) was also higher in the thrombectomy group (33 versus 11 percent, RR 3.17, 95% CI 1.84-5.46), and results for most secondary outcomes favored thrombectomy. Symptomatic intracranial hemorrhage occurred in 5 percent of cases in the thrombectomy group versus none in the control group. MT was associated with procedural complications in 14 percent of patients, including one death caused by arterial perforation. BAOCHE trial The BAOCHE trial from China evaluated patients within 6 to 24 hours after stroke onset due to basilar artery occlusion [69]. Patients were randomly assigned in a 1:1 ratio to MT plus medical care with medical care alone. The trial was stopped early after an interim analysis suggested superiority of thrombectomy. At baseline, the median NIHSS was 20 for the thrombectomy group and 19 for the control group. The rate of intravenous thrombolysis was 14 percent in the thrombectomy group and 21 percent in the control group. At 90 days, the rate of good functional status (ie, an mRS score of 0 to 3) was higher in the thrombectomy group compared with the control group (46 versus 24 percent, RR 1.81, 95% CI 1.26-2.60), and the rate of functional independence (ie, an mRS score of 0 to 2) was also higher in the thrombectomy group (39 versus 14 percent, RR 2.64, 95% CI 1.54- 4.50). There was a trend for lower mortality at 90 days favoring the thrombectomy group (31 versus 42 percent, RR 0.75, 95% CI 0.54-1.04). Symptomatic intracranial hemorrhage https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 13/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate occurred more often in the thrombectomy group (6 versus 1 percent, RR 5.18, 95% CI 0.64- 42.18). Procedural complications occurred in 11 percent of the thrombectomy group. The ATTENTION and BAOCHE trial results are not generalizable to all patients with basilar artery stroke. The Chinese population has higher rates of large artery intracranial atherosclerotic disease relative to other populations, and many patients in the thrombectomy groups of both trials were also treated with angioplasty and/or stenting of the basilar artery. The low rates of treatment with intravenous thrombolysis in both trials may have reduced the rates of good outcomes particularly affecting the control groups and biased the results in favor of thrombectomy. Earlier trials were also limited by methodologic issues. A randomized trial (BEST) comparing endovascular treatment (MT) with standard medical care for patients with acute vertebrobasilar occlusion who could be treated within eight hours was stopped early for slow recruitment and high crossover rate after enrolling 131 patients [61]. Compared with standard medical care, patients assigned to endovascular therapy had similar rates of favorable outcome and 90-day mortality by intention-to-treat analysis. The BASICS trial of 300 patients with acute ischemic stroke attributed to basilar artery occlusion found no statistically significant difference in outcomes for endovascular therapy compared with medical therapy [63]. However, there was a nonsignificant trend of benefit with endovascular treatment in both trials [61,63]. Larger randomized controlled trials in more diverse populations are needed to assess the efficacy of endovascular therapy for posterior circulation stroke due to large artery occlusion. PROCEDURE Overview General anesthesia or conscious sedation may be used for the procedure, depending upon local preference and experience. (See 'Anesthesia' below.) Catheterization is commonly performed with femoral artery puncture. The catheter is guided to the internal carotid artery (ICA) and beyond to the site of the intracranial large artery occlusion. The stent retriever is then inserted through the catheter to reach the clot. The stent retriever is deployed and grabs the clot, which is removed as the device is pulled back. The initial goal is to achieve reperfusion, defined by a modified Thrombolysis in Cerebral Infarction (mTICI) perfusion grade 2b (anterograde reperfusion of more than half in the downstream target arterial territory) or grade 3 (complete anterograde reperfusion of the downstream target arterial territory) ( table 4), as early as possible [8,70]. In a meta-analysis of five trials that evaluated treatment within 6 hours of symptom onset, over 500 patients received mechanical thrombectomy (MT), https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 14/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate and substantial reperfusion (mTICI score of 2b or 3) was achieved in 71 percent of this group [34]. Following the procedure, most centers monitor patients in an intensive care unit setting until stable. Devices Both second-generation stent retrievers and catheter aspiration devices can be used for MT. The choice between them depends mainly upon local expertise and availability [71]. In some cases, treatment using stent retrievers and aspiration techniques in combination may be appropriate. Stent retrievers Several MT devices are approved in the United States and Europe for clot removal in patients with acute ischemic stroke due to large artery occlusion. These include the first-generation Merci Retriever and Penumbra System devices, the second- generation Solitaire Flow Restoration Device and Trevo Retriever, and the third-generation Tigertriever. The first-generation Merci and Penumbra devices may increase recanalization rates in carefully selected patients, but their clinical utility for improving outcomes after stroke is unproven [72-74]. When compared directly with the Merci retriever in small randomized trials, the second-generation Solitaire and Trevo neurothrombectomy devices achieved significantly higher reperfusion rates and better patient outcomes [75,76]. In a single-arm study, the Tigertriever device achieved higher reperfusion rates, improved patient outcomes, and had similar safety outcomes compared with historical controls from studies of the Solitaire and Trevo devices [77]. In light of these data and the positive thrombectomy trials discussed above [22,24-27], which preferentially used the second-generation devices, only the second-generation or later devices should be used to treat patients with acute ischemic stroke. Catheter aspiration devices Catheter aspiration devices are another option for MT. This method employs a catheter to aspirate the thrombus as the first approach to performing thrombectomy; if aspiration alone does not achieve reperfusion after one or more passes, a stent retriever can be inserted through the catheter to complete the thrombectomy. Mounting evidence suggests that catheter aspiration devices can attain rates of revascularization [36,78] and good functional outcome [79,80] that are similar to the rates achieved with second-generation stent retrievers. The open-label, multicenter COMPASS trial randomly assigned 270 patients within 6 hours of symptom onset to MT with either catheter aspiration as first-pass treatment or stent retriever first-line [79]. At 90 days, a good functional outcome (modified Rankin Scale [mRS] score of 0 to 2) was achieved by a similar number of patients in each treatment group (52 versus 50 percent for aspiration https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 15/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate first-pass and stent retriever first-line, respectively), indicating that aspiration first-pass was noninferior to stent retriever first-line treatment. In addition, secondary efficacy and angiographic outcome measures did not differ between treatment groups, and there were no significant differences in mortality, symptomatic intracranial hemorrhage, or other safety outcomes. One trial found a trend to higher rates of near-total or total reperfusion for combined stent retriever plus aspiration compared with stent retriever alone, but the difference did not achieve statistical significance (64.5 versus 57.9 percent, risk difference 6.6 percent, 95% CI -3.0 to 16.2) [81]. Anesthesia Either monitored anesthesia care (also called conscious sedation) or general anesthesia may be used for procedural sedation during MT. The anesthetic technique should be chosen based upon individual patient risk factors, preferences, and institutional experience [8]. (See "Anesthesia for endovascular therapy for acute ischemic stroke in adults", section on 'Choice of anesthetic technique: General anesthesia versus monitored anesthesia care'.) The type of anesthesia used for MT in patients with ischemic stroke may have some impact on short- and long-term outcomes, as reviewed in detail separately. (See "Anesthesia for endovascular therapy for acute ischemic stroke in adults", section on 'Literature comparing general anesthesia with monitored anesthesia care or conscious sedation'.) Risk of periprocedural antithrombotics There is no indication for the routine use of periprocedural antithrombotic agents. Based upon the results of the MR CLEAN-MED trial, the use of periprocedural aspirin or unfractionated heparin in patients undergoing endovascular therapy for acute ischemic stroke increases the risk of symptomatic hemorrhagic transformation and may increase the risk of worse outcomes [82]. However, antithrombotic agents may be indicated in specific instances (eg, if a stent gets deployed, or if there is distal embolism). Blood pressure management Admission systolic blood pressure (SBP) does not seem to impact the benefit of MT, as shown by the HERMES meta-analysis of seven trials with individual data from 1753 patients randomly assigned to MT or standard care (control) [83]. The meta- analysis found a nonlinear association between admission SBP and functional outcome measured by the mRS, with an inflection point at an SBP of 140 mmHg. Admission SBPs above 140 mmHg were associated with worse functional outcomes and higher mortality rates. However, there was no interaction between admission SBP and the effect of MT. At 90 days, the median mRS was lower (ie, functional outcome was better) with MT for both patients with an admission SBP <140 mmHg (median mRS 2, versus 3 for controls) and patients with an admission SBP 140 mmHg (median mRS 3, versus 4 for controls). The benefit of MT for a shift https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 16/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate towards a better functional outcome ordinal mRS was also similar for patients with admission SBP <140 mmHg (adjusted common OR 2.06, 95% CI 1.56-2.71) and patients with admission SBP 140 mmHg (OR 1.84, 95% CI 1.46-2.31). We suggest keeping SBP between 150 and 180 mmHg prior to reperfusion; SBP 150 mmHg may be useful for maintaining adequate collateral blood flow during the time the large artery remains occluded [8,24]. Some experts suggest no use of antihypertensives prior to reperfusion unless SBP exceeds 200 mmHg for patients not being treated with intravenous thrombolysis, or unless SBP exceeds 185 mmHg for patients who are candidates for intravenous thrombolysis [84]. However, the optimal blood pressure range with MT is not well defined, and there is no proven benefit of aggressive early blood pressure reduction after reperfusion [8,85-88]. Earlier evidence supported keeping SBP <160 to 170 mmHg for patients with successful reperfusion (ie, mTICI 2b or 3) and targeting SBP of 170 mmHg for patients with less successful reperfusion (ie, mTICI 0 to 2a) [84]. Other reports suggested targeting SBP to <140 mmHg after successful reperfusion [48,89]. More intensive blood pressure lowering (eg, targeting SBP <120 mmHg) may be harmful, particularly in Asian populations where the prevalence of large artery atherosclerosis is high [90,91]. Many patients undergoing MT will have been treated with intravenous thrombolytic therapy (recombinant tissue plasminogen activator or tPA) in the first hours after stroke symptom onset and should be managed accordingly, with systolic/diastolic blood pressure maintained at 180/105 mmHg during and for 24 hours following alteplase infusion or tenecteplase injection; a higher blood pressure may increase the risk of hemorrhage in ischemic brain regions even when thrombolytic agents are not used. (See "Intravenous thrombolytic therapy for acute ischemic stroke: Therapeutic use", section on 'Management of blood pressure'.) Adverse effects In the MR CLEAN trial, clinical signs of a new ischemic stroke in a different vascular territory within 90 days of treatment were more common in the intra-arterial group compared with no endovascular therapy (5.6 versus 0.4 percent) [22]. Device-related serious adverse events are uncommon but include access site hematoma and pseudoaneurysm, arterial perforation, and arterial dissection [24-27]. Transient intraprocedural vasospasm is also uncommon but is sometimes treated. MT in general is not associated with increased rates of symptomatic intracranial hemorrhage (sICH) or mortality. In a meta-analysis of five trials, with pooled patient-level data for 1287 subjects, there was no significant difference between the intervention population and control population for 90-day sICH (4.4 versus 4.3 percent) or mortality (15 versus 19 percent) [28]. https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 17/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate Limited evidence suggests recent anticoagulation with an oral vitamin K antagonist (VKA), but not a direct oral anticoagulant (DOAC), may increase the risk of sICH or mortality for patients undergoing MT [92,93]. In a 2022 meta-analysis of 15 nonrandomized studies, VKA use compared with no oral anticoagulant use was associated with an increased risk of sICH (8.4 versus 6.5 percent, OR 1.49, 95% CI 1.10-2.02) and mortality (32.8 versus 24.2 percent, OR 1.67, 95% CI 1.35-2.06), whereas DOAC use compared with no oral anticoagulant use was associated with no increased risk of sICH (2.7 versus 5.9 percent, OR 0.80, 95% CI 0.45-1.44) or mortality (26.9 versus 23.0 percent, OR 1.27, 95% CI 0.96-1.70) [92]. Approach to tandem lesions Fifteen to 30 percent of patients eligible for MT present with tandem lesions characterized by extracranial carotid artery stenosis or occlusion and a downstream, ipsilateral intracranial large vessel occlusion [22,24,27,94]. MT is directed at revascularization of the intracranial occlusion, but the best approach to management of the extracranial carotid lesion is uncertain [94,95]. Options include acute treatment of the extracranial carotid lesion with stent placement (anterograde or retrograde), angioplasty alone, or thrombo-aspiration alone, versus deferred or no revascularization of the extracranial carotid artery lesion ( figure 4) [96]. Deferred revascularization options include eventual carotid endarterectomy or carotid artery stenting. (See "Management of symptomatic carotid atherosclerotic disease".) Available data from observational studies suggest that acute carotid stenting for patients with tandem lesions who are undergoing MT is associated with a higher rate of favorable outcomes at 90 days compared with no stenting [97,98]. A subgroup analysis from one study further suggests that stenting is associated with improved outcomes in patients with carotid lesions caused by atherosclerosis but not in patients with carotid lesions caused by dissection [98]. Rescue therapy for failed MT Approximately 8 to 30 percent of patients fail to achieve substantial reperfusion with MT, with failure defined by mTICI scores ( table 4) of 2a or less [28,99-101]. In such cases, urgent rescue therapy with intracranial angioplasty/stenting, intravenous glycoprotein IIb/IIIa inhibitors, or intravenous P2Y12 receptor inhibitors is sometimes attempted [99]. Limited observational data suggest that these interventions are safe [99,102], but prospective studies are lacking, and the optimal approach is uncertain. Intracranial stenting is the best-studied option [103-105]. The retrospective, multicenter SAINT study of patients who failed MT compared those who received acute rescue stenting (n = 107) with propensity-score matched patients who did not receive rescue stenting (n = 107) [103]. At 90 days, rescue stenting was associated with a shift to lower rates of disability in the overall mRS score distribution (adjusted OR 3.74, 95% CI 2.16-6.57), increased functional independence (34.6 versus 6.5 percent, OR 10.91, 95% CI 4.11-28.92), decreased mortality (29.9 versus 43.0 percent, https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 18/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate OR 0.49, 95% CI 0.25-0.94), and comparable rates of symptomatic intracranial hemorrhage (7.5 versus 11.2 percent, OR 0.87, 95% CI 0.31-2.42). These results are limited by retrospective design and wide confidence intervals, and further study is needed to determine the benefit of this intervention for failed MT. Adjunct intra-arterial thrombolysis Some patients have poor clinical outcomes after MT despite successful reperfusion (ie, a modified Thrombolysis in Cerebral Infarction [mTICI] 2b or 3) of the target large artery; one possible but controversial explanation is persisting impaired reperfusion of the microcirculation (the "no-reflow" phenomenon) [106,107]. The Chemical Optimization of Cerebral Embolectomy (CHOICE) trial investigated the use of adjunct intra- arterial thrombolysis with alteplase to treat hypothesized persistent thrombi in the microcirculation after angiographically successful MT [108]. At 90 days, more patients achieved an excellent neurologic outcome (an mRS score of 0 to 1) with intra-arterial alteplase compared with placebo (59 versus 40.4 percent, adjusted absolute risk reduction 18.4 percent, 95% CI 0.3- 36.4 percent). There was no increased risk of intracranial hemorrhage or mortality with intra- arterial alteplase. Limitations of the CHOICE trial include early stopping (due to slow recruitment and inability to obtain placebo), which can lead to overestimation of treatment effects, small patient numbers (and resulting wide confidence intervals with a lower limit of only 0.3 percent absolute risk reduction), and the protocol allowing premature stopping (and therefore potential underdosing) of intravenous alteplase infusion started before the onset of thrombectomy [108,109]. Thus, the benefit of this approach requires confirmation in larger trials. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Stroke in adults".) SUMMARY AND RECOMMENDATIONS Efficacy of mechanical thrombectomy Early intra-arterial treatment with mechanical thrombectomy (MT) is safe and effective for reducing disability and is superior to standard treatment with intravenous thrombolysis alone for ischemic stroke caused by a documented large artery occlusion in the proximal anterior circulation. (See 'Efficacy of mechanical thrombectomy' above.) Patient selection for anterior circulation stroke https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 19/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate Who to treat For patients with acute ischemic stroke, we recommend treatment with intra-arterial MT, whether or not the patient received treatment with intravenous thrombolytic therapy, if the following conditions are met (Grade 1B): Brain imaging using CT without contrast or diffusion-weighted MRI (DWI) excludes hemorrhage and is consistent with an Alberta Stroke Program Early CT Score (ASPECTS) 3. (See 'Role of ASPECTS method' above.) CT angiography (CTA) or MR angiography (MRA) demonstrates a proximal large artery occlusion in the anterior circulation as the cause of the ischemic stroke. The patient has a persistent, potentially disabling neurologic deficit (eg, a National Institutes of Health Stroke Scale [NIHSS] score 6). The patient can start treatment (femoral puncture) within 24 hours of the time last known to be well. This recommendation applies when thrombectomy is performed at a stroke center with appropriate expertise in the use of endovascular therapy. Benefit may be most likely when imaging confirms the presence of salvageable brain tissue (eg, a mismatch by DAWN or DEFUSE 3 criteria). Who not to treat We would not treat with MT for patients who have any of the following findings (see 'Who not to treat' above): Presence of a large established hypodensity on head CT beyond the more subtle, early ischemic changes assessed by ASPECTS (see 'Role of ASPECTS method' above) No ischemic penumbra (ie, no mismatch suggesting no salvageable brain tissue) identified if CT perfusion (CTP) or DWI/PWI (perfusion-weighted MRI) is performed, particularly if the infarct core is large Presence of a large core infarct (eg, defined by an ASPECTS <6 or imaging showing a core volume 50 mL) and severe prestroke comorbidities (eg, pre-existing severe disability such as modified Rankin Scale [mRS] 4 to 5 or life expectancy less than six months) Individualized decisions The decision to employ MT needs to be carefully individualized for patients with anterior circulation stroke who do not precisely match the inclusion or exclusion criteria as listed above. Examples include patients with imaging evidence of salvageable brain tissue who are beyond the 24-hour time window, https://www.uptodate.com/contents/mechanical-thrombectomy-for-acute-ischemic-stroke/print 20/46 7/6/23, 12:04 PM Mechanical thrombectomy for acute ischemic stroke - UpToDate medium vessel occlusion (eg, anterior cerebral artery beyond the A1 segment, middle cerebral artery [MCA] beyond the proximal M2 segment), or minor stroke (NIHSS 5). Use in posterior circulation stroke Although the benefits are uncertain, MT within 24 hours of the time last known to be well may be a reasonable treatment option for patients with acute ischemic stroke caused by occlusion of the basilar artery, vertebral arteries, or posterior cerebral arteries when performed at centers with appropriate expertise. Moderate-quality evidence supports the benefit of MT for patients of Chinese ancestry with basilar artery occlusion who have an NIHSS score 10, indicating a moderate to severe stroke; a posterior circulation ASPECTS (pc-ASPECTS) of 6, indicating a limited extent of ischemic change on brain imaging; and who can be treated within 24 hours of time last known to be well. (See 'Posterior circulation stroke' above.) Procedure Second-generation stent retriever devices or catheter aspiration devices should be used for MT. Other aspects of the MT procedure, including anesthesia, blood pressure management, and adverse events, are discussed above. (See 'Procedure' above.) Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Campbell BC, Donnan GA, Lees KR, et al. Endovascular stent thrombectomy: the new standard of care for large vessel ischaemic stroke. Lancet Neurol 2015; 14:846. 2. Furlan AJ. Endovascular therapy for stroke it's about time. N Engl J Med 2015; 372:2347. 3. 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