Mechanical thrombectomy for acute ischemic stroke
Authors:
Jamary Oliveira Filho, MD, MS, PhD
Owen B Samuels, MD
Section Editor:
Jose Biller, MD, FACP, FAAN, FAHA
Deputy Editor:
John F Dashe, MD, PhD
All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Mar 2018. | This topic last updated: Mar 26, 2018.

INTRODUCTION — Timely restoration of cerebral blood flow using reperfusion therapy is the most effective maneuver for salvaging ischemic brain tissue that is not already infarcted. There is a narrow window during which this can be accomplished, since the benefit of reperfusion decreases over time.

This topic will review the use of mechanical thrombectomy for acute ischemic stroke. The approach to reperfusion therapy for acute ischemic stroke, including the use of intravenous alteplase (recombinant tissue plasminogen activator or tPA), is reviewed elsewhere. (See "Approach to reperfusion therapy for acute ischemic stroke" and "Intravenous thrombolytic therapy for acute ischemic stroke: Therapeutic use".)

OVERVIEW OF REPERFUSION THERAPY — For eligible patients with acute ischemic stroke, intravenous alteplase (recombinant tissue plasminogen activator or tPA) is first-line therapy, provided that treatment is initiated within 4.5 hours of clearly defined symptom onset (table 1). Because the benefit of alteplase is time dependent, it is critical to treat patients as quickly as possible. Eligible patients should receive intravenous alteplase without delay even if mechanical thrombectomy is being considered. (See "Intravenous thrombolytic therapy for acute ischemic stroke: Therapeutic use".)

Mechanical thrombectomy is indicated for patients with acute ischemic stroke due to a large artery occlusion in the anterior circulation who can be treated within 24 hours of the time last known to be well (ie, at neurologic baseline), regardless of whether they receive intravenous alteplase for the same ischemic stroke event, as discussed in the sections that follow.

Two issues may limit the widespread clinical use of mechanical thrombectomy. First, only an estimated 10 percent of patients with acute ischemic stroke have a proximal large artery occlusion in the anterior circulation and present early enough to qualify for mechanical thrombectomy within 6 hours [1-4]. Second, only a few stroke centers have sufficient resources and expertise to deliver this therapy. However, eligible patients can receive standard treatment with intravenous tPA if they present to hospitals where thrombectomy is not an option, and those with qualifying anterior circulation strokes can then be transferred, a strategy called "drip and ship" [5], to tertiary stroke centers where intra-arterial thrombectomy is available.

EFFICACY OF MECHANICAL THROMBECTOMY — Early intra-arterial treatment with second-generation mechanical thrombectomy devices is safe and effective for reducing disability and is superior to standard treatment with intravenous thrombolysis alone for the treatment of acute ischemic stroke caused by a documented large artery occlusion in the proximal anterior circulation (figure 1 and figure 2).

Benefit of early treatment — Five multicenter, open-label randomized controlled trials (MR CLEAN [6], ESCAPE [7], SWIFT PRIME [8], EXTEND-IA [9], and REVASCAT [10]) demonstrated that early intra-arterial treatment with second-generation mechanical thrombectomy devices 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 [1,11-17]. The number needed to treat (NNT) for one additional person to achieve functional independence in these trials ranged from approximately 3 to 7.5 [6-10,18,19].

In a meta-analysis of these trials, with pooled patient-level data for 1287 subjects, the rate of functional independence (ie, a 90-day modified Rankin scale [mRS] score of 0 to 2) was significantly greater for the intervention group compared with the control group (46 versus 27 percent, odds ratio [OR] 2.35, 95% CI 1.85-2.98) [11]. Similarly, mechanical thrombectomy led to significantly reduced disability as indicated by an improvement of ≥1 points on the mRS at 90 days (adjusted OR 2.49, 95% CI 1.76-3.53). Mechanical thrombectomy was beneficial across a wide range of patient subgroups, including age ≥80 years, high initial stroke severity, and those not treated with intravenous alteplase. There was no significant difference between the mechanical thrombectomy and control groups for rates of symptomatic intracranial hemorrhage or 90-day mortality.

When the positive results of the MR CLEAN trial were announced in late 2014, the remaining trials were stopped early on the basis of positive interim efficacy analyses. All of the trials enrolled overlapping but not identical patient populations and had generally similar results:

The open-label MR CLEAN trial, which was the largest and most inclusive of the five trials, enrolled 500 adults (mean age 65 years, range 23 to 96 years) with an angiographically confirmed proximal arterial occlusion in the anterior circulation and randomly assigned them to treatment with intra-arterial therapy within 6 hours of symptom onset or to usual care [6]. The method of intra-arterial therapy was left to the discretion of the local interventionalist, but mechanical thrombectomy with retrievable stents was used in 82 percent. Approximately 90 percent of subjects in both groups received intravenous thrombolysis (median time to treatment: 80 minutes) prior to randomization. Assessment was blinded, and analysis was by intention-to-treat.

Compared with usual therapy, the group assigned to intra-arterial treatment had significantly improved outcomes at 90 days as determined by lower scores on the mRS (table 2) (adjusted common odds ratio [OR] 1.67, 95% CI 1.21-2.30). The intra-arterial treatment group had a significantly higher rate of functional independence (ie, an mRS score of 0 to 2) at 90 days compared with usual treatment (32.6 versus 19.1 percent, absolute risk difference, 13.5 percent, 95% CI 5.9-21.2). The NNT for one additional patient to achieve functional independence was 7.4.

At two years, the benefit of intra-arterial treatment on functional outcome was similar to the results at 90 days, as determined by lower scores on the mRS (OR 1.68, 95% CI 1.15-2.45) [18].

The ESCAPE trial enrolled 316 adults (no upper age limit) with disabling ischemic stroke caused by a proximal intracranial large artery occlusion in the anterior circulation up to 12 hours after symptom onset. Subjects were randomly assigned to standard care plus endovascular treatment with thrombectomy devices or standard care only [7]. Patients with large infarct core on CT scan or poor collateral circulation on CT angiography were excluded. Approximately 75 percent of subjects in both groups were treated with intravenous alteplase. Among patients assigned to the thrombectomy group, the median time from symptom onset to first reperfusion was 241 minutes. At 90 days after treatment, the thrombectomy group had a significantly higher rate of functional independence (defined as an mRS score of 0 to 2) compared with the control group (53 versus 29 percent) and a significantly lower mortality rate (10 versus 19 percent). The NNT for one additional patient to achieve functional independence was 4.2. The thrombectomy group was significantly more likely to have lower scores on the mRS (common OR 2.6, 95% CI 1.7-3.8).

Thrombectomy appeared to be beneficial for all prespecified subgroups, including those ages >80 and ≤80 years, men and women, subjects with moderate strokes, subjects with severe strokes, and those treated or not treated with intravenous alteplase.

The SWIFT PRIME trial enrolled 196 adults ages 18 to 80 years with acute ischemic stroke and confirmed occlusion of a large artery in the anterior circulation who could be treated with mechanical thrombectomy within 6 hours of symptom onset [8]. Subjects were randomly assigned to treatment with the Solitaire FR thrombectomy device or no thrombectomy. All patients in both treatment groups received intravenous alteplase (recombinant tissue plasminogen activator or tPA) within 4.5 hours of stroke onset. Patients with large areas of infarction on advanced neuroimaging were excluded. At 90 days, thrombectomy led to a shift to lower disability levels on the mRS and to a significantly higher rate of functional independence, defined by an mRS of 0 to 2 (60 versus 35 percent). The NNT for one additional patient to achieve functional independence was 4.

The EXTEND-IA trial randomly assigned 70 subjects with ischemic stroke who were receiving intravenous alteplase to intra-arterial treatment with the Solitaire FR thrombectomy device or to continue alteplase alone [9]. Patients without evidence of salvageable brain tissue or core infarction volume ≥70 mL were excluded. The median time from stroke onset to reperfusion in those treated with thrombectomy was 248 minutes. At 90 days, the thrombectomy group had a significantly higher rate of functional independence compared with the control group (71 versus 40 percent). The NNT for one additional patient to achieve functional independence was 3.2.

The REVASCAT trial randomly assigned 206 patients with acute ischemic stroke to medical therapy plus intra-arterial treatment with the Solitaire stent retriever or medical therapy alone [10]. Most patients in both treatment arms received intravenous alteplase, and eligibility for the study included the presence of a proximal anterior circulation occlusion 30 minutes after the administration of alteplase. Thrombectomy led to higher rates of functional independence at 90 days (44 versus 28 percent; NNT 6.3) and a reduction in disability over the range of the mRS (adjusted OR for a one point improvement in the mRS score, 1.7, 95% CI 1.05-2.8). There were no significant differences in the rates of symptomatic intracerebral hemorrhage or mortality. Similar outcomes were noted at 12 months follow-up [19].

Benefit of later treatment — Mechanical thrombectomy is effective when used beyond 6 hours for selected patients who have a clinical deficit that is disproportionally severe compared with the volume of infarction on imaging studies.

The open-label DAWN trial enrolled 206 adults with acute ischemic stroke who were last known to be normal 6 to 24 hours earlier; all had a stroke caused by occlusion of the intracranial internal carotid artery or the proximal middle cerebral artery and had a mismatch between the severity of the neurologic deficit, as measured by the National Institutes of Health Stroke Scale (median score 17 at baseline), and the infarct volume, as measured by automated software analysis using diffusion-weighted MRI or perfusion CT (median approximately 8 mL) [20]. Approximately 55 percent of the patients in the trial had a "wake-up" stroke (ie, they were last known to be well before going to bed and stroke symptoms were first noted upon awakening). Patients were randomly assigned to thrombectomy plus standard care or to standard care alone (control). The trial was stopped early for efficacy at the first interim analysis. The following observations were noted:

At 90 days, the rate of functional independence, as defined by a score of 0 to 2 on the modified Rankin scale, was greater for the thrombectomy group compared with the control group (49 versus 13 percent, adjusted difference 33 percent, 95% CI 24-44). The number needed to treat for one additional patient to achieve functional independence was 3. All other efficacy outcome measures also favored thrombectomy.

There was no significant difference between the thrombectomy and control groups in the rate of symptomatic intracranial hemorrhage (6 and 3 percent) or 90 mortality (19 and 18 percent).

The open-label DEFUSE 3 trial enrolled patients with ischemic stroke due to occlusion of the proximal middle cerebral artery or internal carotid artery who were last known to be well 6 to 16 hours earlier [21]. Patients were required to have an infarct size of <70 mL and a ratio of ischemic tissue volume to infarct volume of ≥1.8, as measured by automated software processing of diffusion-weighted MRI or CT perfusion imaging. The DEFUSE 3 trial was stopped early for efficacy after randomly assigning 182 patients to thrombectomy plus standard care or to standard care alone. Approximately one-half of the patients in the trial had a "wake-up" stroke. Patients assigned to thrombectomy were treated with stent retrievers or aspiration catheters. At 90 days, the percentage of patients who were functionally independent, defined as a modified Rankin scale score of 0 to 2, was higher with endovascular therapy compared with medical therapy alone (45 versus 17 percent, difference 28 percent), and therefore the number needed to treat for one additional patient to achieve functional independence was 3.6. There was also a trend to lower mortality with endovascular therapy (14 versus 26 percent). There was no significant difference between groups in the rate of symptomatic intracranial hemorrhage (7 and 4 percent) or serious adverse events (43 and 53 percent).

These data support the use of mechanical thrombectomy to treat acute ischemic stroke due to occlusion of the intracranial carotid or proximal middle cerebral artery for patients within 6 to 24 hours of the time last known to be well (ie, at neurologic baseline) who meet DAWN trial eligibility criteria, and for patients within 6 to 16 hours of the time last known to be well who meet DEFUSE 3 trial eligibility criteria.

Limitations to these trials include stopping early, which can overestimate treatment effects. However, this drawback is at least partially offset by the relatively large effect size demonstrated in both trials.

PATIENT SELECTION — Patients with ischemic stroke caused by a proximal large artery occlusion in the anterior circulation are candidates for intra-arterial mechanical thrombectomy if they present to, or can be transferred to, a stroke center with expertise in the use of second-generation stent retrievers for acute ischemic stroke (algorithm 1). Intra-arterial mechanical thrombectomy can be used in addition to treatment with intravenous alteplase (recombinant tissue plasminogen activator or tPA). Mechanical thrombectomy treatment should be started as quickly as possible, and should not be delayed to assess the response to intravenous tPA.

General criteria — For patients with acute ischemic stroke caused by a proximal large artery occlusion in the anterior circulation who can be treated within 24 hours of the time they were last known to be at their neurologic baseline, we recommend treatment with intra-arterial mechanical thrombectomy using a second-generation stent retriever device (algorithm 1), whether or not the patient received standard treatment with intravenous tPA, if the following general conditions are fulfilled:

Neuroimaging (eg, CT without contrast or diffusion-weighted MRI) is consistent with a small infarct core (ie, limited signs of early ischemic change) and excludes hemorrhage

Angiography (eg, CT angiography or MR angiography) demonstrates a proximal large artery occlusion in the anterior circulation

Thrombectomy is performed at a stroke center with appropriate expertise in the use of stent retrievers

The patient has a persistent, potentially disabling neurologic deficit

Thrombectomy can be started within 24 hours of the time last known to be well

The specific criteria for patients within 6 hours (see 'Within 6 hours' below) and for patients within 6 to 24 hours from the last time known to be at neurologic baseline (see '6 to 24 hours' below) are discussed in the sections that follow.

Many patients who are eligible for mechanical thrombectomy will be treated with intravenous alteplase prior to mechanical thrombectomy. Patients who are not candidates for intravenous alteplase can still be treated with mechanical thrombectomy if otherwise eligible according to the criteria outlined here and below.

Treatment with mechanical thrombectomy should be based upon individual patient characteristics. Patients with severe comorbidities prior to stroke onset (eg, pre-existing severe disability, life expectancy less than six months) are unlikely to benefit from mechanical thrombectomy.

Within 6 hours — For patients who can start treatment (femoral puncture) within 6 hours of symptom onset, we suggest using the following criteria for mechanical thrombectomy (algorithm 1), which are modified from those used in the MR CLEAN trial [6]:

A clinical diagnosis of acute stroke

A deficit on the National Institutes of Health Stroke Scale (NIHSS) (table 3) of ≥6 points (calculator 1) or any persistent neurologic deficit that is potentially disabling (see "Approach to reperfusion therapy for acute ischemic stroke", section on 'Disabling stroke deficits')

An Alberta Stroke Program Early CT Score (ASPECTS) score ≥6 on noncontrast brain CT or diffusion-weighted MRI (see 'ASPECTS method' below)

Brain CT or MRI scan ruling out intracranial hemorrhage

Intracranial arterial occlusion of the distal intracranial internal carotid artery (ICA), or the M1 or M2 segments of the middle cerebral artery (MCA), or the A1 or A2 segments of the anterior cerebral artery (ACA), demonstrated with CT angiography, MR angiography, or digital subtraction angiography

Age ≥18 years

Others have used somewhat different, more selective criteria. As examples:

Guidelines from the American Heart Association/American Stroke Association (AHA/ASA) recommend mechanical thrombectomy for those with no significant prestroke disability (ie, a modified Rankin scale score of ≤1) and a causative occlusion of the ICA or the M1 segment of the MCA [22].

Both the ESCAPE and EXTEND-IA trials restricted eligibility to patients who were functioning independently prior to stroke onset [7,9].

ESCAPE also required evidence of moderate-to-good collateral circulation, defined as the filling of ≥50 percent of the MCA territory pial circulation on CT angiography. The time window in ESCAPE was up to 12 hours from stroke onset, but few patients were enrolled beyond 6 hours [7].

EXTEND-IA required evidence of salvageable brain tissue and an ischemic core lesion volume of <70 mL on CT perfusion imaging [9].

6 to 24 hours — The DAWN and DEFUSE 3 trials selected patients for treatment beyond 6 hours using imaging-based criteria [20,21]. For patients with ischemic stroke caused by a large artery occlusion in the proximal anterior circulation who are evaluated at stroke centers with automated infarct determination, we recommend mechanical thrombectomy when DAWN or DEFUSE criteria are fulfilled (algorithm 1).

Eligibility criteria based upon the DAWN trial for patients who can start treatment (femoral puncture) within 6 to 24 hours of time last known to be at neurologic baseline are as follows [20]:

Failed or contraindicated for intravenous alteplase

A deficit on the NIHSS (table 3) of ≥10 points (calculator 1)

No significant prestroke disability: baseline modified Rankin scale (mRS) score ≤1

Baseline infarct involving less than one third of the territory of the MCA on CT or MRI

Intracranial arterial occlusion of the ICA or the M1 segment of the MCA

A clinical-core mismatch according to age:

Age ≥80 years: NIHSS ≥10 and an infarct volume <21 mL

Age <80 years: NIHSS 10 to 19 and an infarct volume <31 mL

Age <80 years: NIHSS ≥20 and an infarct volume <51 mL

Eligibility criteria based upon the DEFUSE 3 trial for patients who can start treatment (femoral puncture) within 6 to 16 hours of time last known to be at neurologic baseline are as follows [21]:

A deficit on the NIHSS (table 3) of ≥6 points (calculator 1)

Only slight or no prestroke disability: baseline mRS score ≤2

Arterial occlusion of the cervical or intracranial ICA (with or without tandem MCA lesions) or the M1 segment of the MCA demonstrated on MR angiography or CT angiography

A target mismatch profile on CT perfusion or MRI defined as an ischemic core volume <70 ml, a mismatch ratio (the volume of the perfusion lesion divided by the volume of the ischemic core) >1.8, and a mismatch volume (volume of perfusion lesion minus the volume of the ischemic core) >15 mL

Age 18 to 90 years

For patients with ischemic stroke caused by a large artery occlusion in the proximal anterior circulation who are evaluated at stroke centers that do not use automated infarct volume determination, we suggest mechanical thrombectomy (algorithm 1) if treatment can be started within 6 to 24 hours of the time last known to be well and there is a clinical-ASPECTS mismatch, such as an NIHSS ≥10 and ASPECTS ≥6 (see 'ASPECTS method' below) [23]. However, this approach has not been evaluated in rigorous controlled trials.

Posterior circulation stroke — Although the benefits are uncertain, mechanical thrombectomy 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 [22]. Mechanical thrombectomy is proven effective only for select patients with acute ischemic stroke caused by a proximal intracranial arterial occlusion in the anterior circulation; the trials that established the benefit of mechanical thrombectomy largely excluded patients with posterior circulation infarcts. (See 'Efficacy of mechanical thrombectomy' above.)

Data from uncontrolled observational studies and registries suggest that endovascular therapy for basilar artery occlusion leads to a higher rate of good functional outcomes (approximately 30 to 40 percent) and lower mortality (approximately 30 percent) than expected when compared with outcomes among patients who did not receive endovascular therapy [24-26]. By comparison, a systematic review identified 76 patients receiving intravenous thrombolysis with alteplase for basilar artery occlusion found that the rate of good functional outcome was approximately 22 percent, and mortality was approximately 50 percent [27].

ASPECTS method — The Alberta Stroke Program Early CT score (ASPECTS) was developed to provide a simple and reliable method of assessing ischemic changes on head CT scan in order to identify acute stroke patients unlikely to make an independent recovery despite thrombolytic treatment [28]. The ASPECTS method has also been adopted to assess the extent of ischemia on diffusion-weighted MRI (DWI); the ability to detect early ischemic changes by ASPECTS was similar on noncontrast CT and DWI [29].

The ASPECTS value is calculated from two standard axial CT cuts; one at the level of the thalamus and basal ganglia, and one just rostral to the basal ganglia (figure 3 and figure 4) [28,30].

The ASPECTS method divides the middle cerebral artery (MCA) territory into 10 regions of interest.

Subcortical structures are allotted three points: one each for caudate, lentiform nucleus, and internal capsule.

MCA cortex is allotted seven points:

Four of these points come from the axial CT cut at the level of the basal ganglia, with one point for insular cortex and one point each for M1, M2, and M3 regions (anterior, lateral, and posterior MCA cortex).

Three points come from the CT cut just rostral to the basal ganglia, with one point each for M4, M5, and M6 regions (anterior, lateral, and posterior MCA cortex).

One point is subtracted for an area of early ischemic change, such as focal swelling or parenchymal hypoattenuation, for each of the defined regions.

Therefore, a normal CT scan has an ASPECTS value of 10 points, while diffuse ischemic change throughout the MCA territory gives a value of 0.

PROCEDURE — General anesthesia or conscious sedation may be used for the procedure, depending upon local preference and experience (see 'Anesthesia' below). Only second-generation stent retriever devices should be used for mechanical thrombectomy. (See 'Devices' below.)

Catheterization is performed with femoral artery puncture. The catheter is guided to the internal carotid artery 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 [22,31]. In a meta-analysis of five trials that evaluated treatment within six hours of symptom onset, over 500 patients received mechanical thrombectomy and substantial reperfusion (mTICI score of 2b or 3) was achieved in 71 percent of this group [17].

Following the procedure, most centers monitor patients in an intensive care unit setting until stable.

Devices — A number of mechanical thrombectomy devices are approved in the United States and Europe for clot removal within 8 hours of acute stroke symptom onset in selected patients. These include the first-generation Merci Retriever and Penumbra System devices, and the second-generation Solitaire Flow Restoration Device and Trevo Retriever. 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 [32-34]. 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 [35,36]. In light of these data and the positive thrombectomy trials discussed above [6-10], which preferentially used the second-generation devices, only the second-generation devices should be used to treat patients with acute ischemic stroke.

Catheter aspiration devices are another option for mechanical thrombectomy, and some data suggest that they can achieve technical rates of revascularization similar to stent retrievers [37]. However, second-generation stent retrievers are preferred for mechanical thrombectomy [22].

Anesthesia — Either conscious sedation or general anesthesia may be used for procedural sedation during mechanical thrombectomy. The anesthetic technique should be chosen based upon individual patient risk factors, preferences, and institutional experience [22].

The type of anesthesia used for mechanical thrombectomy in patients with ischemic stroke may have some impact on short- and long-term outcomes, but data are inconsistent [38-41]. A 2017 systematic review and meta-analysis found that for six studies (including three randomized controlled trials) performed during the second-generation stent-retriever era, there was no significant difference between general anesthesia and non-general anesthesia in the odds of good neurologic outcome (odds ratio [OR] 0.84, 95% CI 0.67-1.06) or 90-day mortality (OR 1.27, 95% CI 0.93-1.75) [41]. The only randomized trial in the meta-analysis that directly tested general anesthesia versus conscious sedation in this setting included 150 patients and found no significant difference between the two types of anesthesia for the outcome of early neurologic improvement [39]. Subjects assigned to general anesthesia were more likely to achieve functional independence at three months, but small patient numbers lower the confidence in this result [39].

The overall results of the 2017 meta-analysis, which included 22 studies, showed that general anesthesia was associated with a higher odds of death and a lower odds of good functional outcome after endovascular therapy [41]. These findings were largely driven by the inclusion of retrospective, observational studies that were done before the advent of second-generation stent-retrievers.

In the subsequent AnStroke trial (not included in the meta-analysis) of 90 patients treated with endovascular therapy for acute ischemic stroke, there was no difference between the general anesthesia and conscious sedation groups for neurologic outcome at three months after stroke [42].

Blood pressure management — We suggest keeping systolic blood pressure between 150 to 180 mmHg prior to reperfusion, and targeting systolic blood pressure to <140 mmHg once reperfusion is achieved with mechanical thrombectomy. However, the optimal blood pressure range with mechanical thrombectomy is not well-defined, and there are few data to guide periprocedural management [22].

Many patients undergoing mechanical thrombectomy will have been treated with intravenous alteplase (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. It is reasonable to apply this same blood pressure parameter for patients not treated with intravenous tPA, as 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'.)

Keeping the systolic blood pressure ≥150 mmHg may be useful for maintaining adequate collateral blood flow during the time the large artery remains occluded [7,22]. Once reperfusion is achieved with mechanical thrombectomy, a lower blood pressure (eg, systolic blood pressure <140 mmHg) is a reasonable target [20].

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) [6]. Device-related serious adverse events are uncommon but include access site hematoma and pseudoaneurysm, arterial perforation, and arterial dissection [7-10]. Transient intraprocedural vasospasm is also uncommon but is sometimes treated.

Mechanical thrombectomy is not associated with increased rates of symptomatic intracranial hemorrhage or mortality. In meta-analysis of 5 trials, with pooled patient-level data for 1287 subjects, there was no significant difference between the intervention population and control population for 90-day symptomatic intracranial hemorrhage (4.4 versus 4.3 percent) or mortality (15 versus 19 percent) [11].

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

Early intra-arterial treatment with second-generation mechanical thrombectomy devices 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.)

For patients with ischemic stroke caused by a large artery occlusion in the proximal anterior circulation who can start treatment (femoral puncture) within 6 hours of stroke symptom onset, we recommend treatment with intra-arterial mechanical thrombectomy using a second-generation stent retriever device (algorithm 1), whether or not the patient received treatment with intravenous alteplase (recombinant tissue plasminogen activator or tPA), if the following conditions are fulfilled (Grade 1A) (see 'General criteria' above and 'Within 6 hours' above):

Neuroimaging (eg, CT without contrast or diffusion-weighted MRI) is consistent with a small infarct core (eg, limited signs of early ischemic change; an Alberta Stroke Program Early CT Score [ASPECTS] score ≥6) and excludes hemorrhage

The patient has a persistent, potentially disabling neurologic deficit

Thrombectomy is performed at a stroke center with expertise in the use of stent retrievers

Mechanical thrombectomy can reduce disability when started 6 to 24 hours from the time last seen well for patients who have a clinical deficit that is disproportionally severe compared with the volume of infarction on imaging studies (see 'Benefit of later treatment' above). The volume of infarction can be measured directly at stroke centers with automated software, or can be estimated from noncontrast CT or diffusion MRI using the ASPECTS method at stroke centers without automated infarct volume determination. (See '6 to 24 hours' above.)

For patients with ischemic stroke caused by a large artery occlusion in the proximal anterior circulation who are evaluated at stroke centers with automated infarct determination (algorithm 1), we recommend mechanical thrombectomy (Grade 1B) if the following conditions are fulfilled:

-Treatment can be started within 6 to 24 hours of the time last known to be well and there is a clinical-core mismatch as defined by the DAWN trial, or

-Treatment can be started within 6 to 16 hours of the time last known to be well and there is an imaging-target mismatch as defined by the DEFUSE 3 trial.

For patients with ischemic stroke caused by a large artery occlusion in the proximal anterior circulation who are evaluated at stroke centers that do not use automated infarct volume determination (algorithm 1), we suggest mechanical thrombectomy if treatment can be started within 6 to 24 hours of the time last known to be well and there is a clinical-ASPECTS mismatch (eg, National Institutes of Health Stroke Scale [NIHSS] ≥10 and ASPECTS ≥6) (Grade 2C).

Although the benefits are uncertain, mechanical thrombectomy 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. (See 'Posterior circulation stroke' above.)

Only second-generation stent retriever devices should be used for mechanical thrombectomy. (See 'Procedure' above.)

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