Challenges of acute endovascular stroke trials

Key design elements of successful acute ischemic stroke treatment trials

PURPOSE

We review key design elements of positive randomized controlled trials (RCTs) in acute ischemic stroke (AIS) treatment and summarize their main characteristics.

METHOD

We searched Medline, Pubmed and Cochrane databases for positive RCTs in AIS treatment. Trials were included if (1) they had a randomized controlled design, with (at least partial) blinding for endpoints, (2) they tested against placebo (or on top of standard therapy in a superiority design) or against approved therapy; (3) the protocol was registered and/or published before trial termination and unblinding (if required at study commencement); (4) the primary endpoint was positive in the intention to treat analysis; and (5) the study findings led to approval of the investigational product and/or high ranked recommendations. A topical approach was used, therefore the findings were summarized as a narrative review.

FINDINGS

Seventeen positive RCTs met the inclusion criteria. The majority of trials included less than 1000 patients (n = 15), had highly selective inclusion criteria (n = 16), used the modified Rankin score as a primary endpoint (n = 15) and had a frequentist design (n = 16). Trials tended to be national (n = 12), investigator-initiated and performed with public funding (n = 11).

DISCUSSION

Smaller but selective trials are useful to identify efficacy in a particular subgroup of stroke patients. It may also be of advantage to limit the number of participating countries and centers to avoid heterogeneity in stroke management and bureaucratic burden.

CONCLUSION

The key characteristics of positive RCTs in AIS treatment described here may assist in the design of further trials investigating a single intervention with a potentially high effect size.

Impact of Initial Imaging Protocol on Likelihood of Endovascular Stroke Therapy

Background and Purpose:

Noncontrast head CT and CT perfusion (CTP) are both used to screen for endovascular stroke therapy (EST), but the impact of imaging strategy on likelihood of EST is undetermined. Here, we examine the influence of CTP utilization on likelihood of EST in patients with large vessel occlusion (LVO).

Methods:

We identified patients with acute ischemic stroke at 4 comprehensive stroke centers. All 4 hospitals had 24/7 CTP and EST capability and were covered by a single physician group (Neurology, NeuroIntervention, NeuroICU). All centers performed noncontrast head CT and CT angiography in the initial evaluation. One center also performed CTP routinely with high CTP utilization (CTP-H), and the others performed CTP optionally with lower utilization (CTP-L). Primary outcome was likelihood of EST. Multivariable logistic regression was used to determine whether facility type (CTP-H versus CTP-L) was associated with EST adjusting for age, prestroke mRS, National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Score, LVO location, time window, and intravenous tPA (tissue-type plasminogen activator).

Results:

Among 3107 patients with acute ischemic stroke, 715 had LVO, of which 403 (56%) presented to CTP-H and 312 (44%) presented to CTP-L. CTP utilization among LVO patients was greater at CTP-H centers (72% versus 18%, CTP-H versus CTP-L, P <0.01). In univariable analysis, EST rates for patients with LVO were similar between CTP-H versus CTP-L (46% versus 49%). In multivariable analysis, patients with LVO were less likely to undergo EST at CTP-H (odds ratio, 0.59 [0.41–0.85]). This finding was maintained in multiple patient subsets including late time window, anterior circulation LVO, and direct presentation patients. Ninety-day functional independence (odds ratio, 1.04 [0.70–1.54]) was not different, nor were rates of post-EST PH-2 hemorrhage (1% versus 1%).

Conclusions:

We identified an increased likelihood for undergoing EST in centers with lower CTP utilization, which was not associated with worse clinical outcomes or increased hemorrhage. These findings suggest under-treatment bias with routine CTP.

Streamlined triage and transfer protocols improve door-to-puncture time for endovascular thrombectomy in acute ischemic stroke

OBJECTIVE

Shorter time from symptom onset to treatment is associated with improved outcomes in patients who undergo mechanical thrombectomy for treatment of acute ischemic stroke due to emergent large vessel occlusion. In this work, we detail pre-thrombectomy process improvements in a multi-hospital network and report the effect on door-to-puncture time in patients undergoing mechanical thrombectomy.

PATIENTS AND METHODS

A streamlined workflow was adopted to minimize door-to-puncture time. Key features of this workflow included rapid and concurrent clinical and radiological evaluation with point-of-care image interpretation, pre-transfer IV thrombolysis and CTA for transferred patients, immediate transport to the angiography suite potentially before neurointerventional radiology team arrival, and minimalist room setup. Door-to-puncture time was measured prospectively and analyzed retrospectively for 78 consecutive patients treated between January 2015 and December 2015. Statistical analysis was performed using the F-test on individual coefficients of a linear regression model.

RESULTS

From quarter 1 to quarter 4, the number of thrombectomies performed increased by 173% (11 patients to 30 patients, p = 0.002), and there was a significant increase in the proportion of transferred patients that underwent pre-transfer CTA (p = 0.04). During this interval, overall median door-to-puncture time decreased by 74% (147 min to 39 min, p < 0.001); this decrease was greatest in transferred patients with pre-transfer CTA (81% decrease, 129 min to 25 min, p < 0.001) and smallest in patients presenting directly to the emergency department (52% decrease, 167 min to 87 min, p < 0.001).

CONCLUSION

Simple workflow improvements to streamline in-hospital triage and perform critical workup at transferring hospitals can produce reductions in door-to-puncture time.

[Acute stroke thrombectomy: evidence and indications]

From 2014 to 2015, the five pivotal stroke trials (MR CLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME and REVASCAT) have shown that stroke thrombectomy clearly improved functional outcome of patients with occlusion of the internal carotid artery or the M1 portion of the middle cerebral artery, with a baseline National Institutes of Health Stroke Scale score of ≥6, with a baseline Alberta Stroke Program Early Computed Tomography Score of ≥6, and who could receive thrombectomy within a 6-hour window of symptom onset. In 2018, the efficacy of stroke thrombectomy for patients with late-presenting stroke up to 16 to 24 hours of onset and who had clinical imaging mismatch or target mismatch was also established by the DAWN and the DEFUSE3 trials. Nowadays, stroke thrombectomy, therefore, have become a "standard of care" and acute stroke patients with large vessel occlusion should receive stroke thrombectomy if they meet top-tier evidence criteria.

Wide Variability in Prethrombectomy Workflow Practices in the United States: A Multicenter Survey

BACKGROUND AND PURPOSE

Clinical outcomes in patients with acute ischemic stroke caused by large vessel occlusion depend on the speed and quality of workflows leading to mechanical thrombectomy. In the absence of universally accepted best practices for workflow, developing stroke hospitals can benefit from improved awareness of real-world workflows in effect at experienced centers. To this end, we surveyed prethrombectomy workflow practices at stroke centers throughout the United States.

MATERIALS AND METHODS

E-mail and phone interviews were conducted with neurointerventional team members at 30 experienced, endovascular-capable stroke centers. Questions were chosen to reflect workflow components of triage, team activation, transport, case setup, and anesthesia.

RESULTS

There is wide variation in prethrombectomy workflows. At 53% of institutions, nonphysician staff respond to stroke alerts alongside physicians. Imaging triage involves noninvasive angiography or perfusion imaging at 97% and 63% of institutions, respectively. Neurointerventional consultation is initiated before the completion of neuroimaging at 86% of institutions, and the team is activated before a final treatment decision at 59%. The neurointerventional team most commonly arrives within 30 minutes. Patients may be transported to the neuroangiography suite before team arrival at 43% of institutions. Procedural trays are set up in advance of team arrival at 13% of centers; additional thrombectomy devices are centrally stored at 54%. A power injector for angiographic runs is consistently used at 43% of institutions. Anesthesiology routinely supports thrombectomies at 67% of institutions.

CONCLUSIONS

Prethrombectomy workflows vary widely between experienced centers. Improved awareness of real-world workflows and their variations may help to guide institutions in designing their own protocols of care.

Assessing the efficacy of endovascular therapy in stroke treatments: updates from the new generation of trials

INTRODUCTION

For the past 20 years, intravenous recombinant tissue plasminogen activator (rt-PA) has been the only proven treatment for acute ischemic stroke. Large arteries such as the internal carotid artery, the middle cerebral artery and the basilar artery supply blood to large volumes of brain tissue. When occluded, these vessels may have low response rates to rt-PA resulting in devastating injury and death. Areas covered: In 2013, three trials evaluating the efficacy of mechanical thrombectomy in acute stroke were neutral, however, lessons learned from these trials resulted in a second generation of five trials in 2015 and a sixth in 2016 which all demonstrated significant benefit for select patients. Here we will review the evidence behind these new trials and. introduce new questions such as models of care, techniques of thrombectomy, the role of rt-PA, modes of anesthesia, the management of late presenting and wake up strokes among other real world challenges facing stroke medicine now that the thrombectomy is an evidence based treamtnent Expert commentary: The mechanical thrombectomy is now the new standard of care and with that comes the need to find ways to provide it to all who will benefit.

A Critical Review of Alberta Stroke Program Early CT Score for Evaluation of Acute Stroke Imaging

Assessment of ischemic stroke lesions on computed tomography (CT) or MRI using the Alberta Stroke Program Early CT Score (ASPECTS) is widely used to guide acute stroke treatment. We aimed to review the current evidence on ASPECTS. Originally, the score was developed for standardized lesion assessment on non-contrast CT (NCCT). Early studies described ASPECTS as a predictor of functional outcome and symptomatic intracranial hemorrhage after iv-thrombolysis with a threshold of ≤7 suggested to identify patients at high risk. Following studies rather pointed toward a linear relationship between ASPECTS and functional outcome. ASPECTS has also been applied to assess perfusion CT and diffusion-weighted MRI (DWI). Cerebral blood volume ASPECTS proved to be the best predictor of outcome, outperforming NCCT-ASPECTS in some studies. For DWI-ASPECTS varying thresholds to identify patients at risk for poor outcome were reported. ASPECTS has been used for patient selection in three of the five groundbreaking trials proving efficacy of mechanical thrombectomy published in 2015. ASPECTS values predict functional outcome after thrombectomy. Moreover, treatment effect of thrombectomy appears to depend on ASPECTS values being smaller or not present in low ASPECTS, while patients with ASPECTS 5–10 do clearly benefit from mechanical thrombectomy. However, as patients with low ASPECTS values were excluded from recent trials data on this subgroup is limited. There are several limitations to ASPECTS addressed in a growing number of studies. The score is limited to the anterior circulation, the template is unequally weighed and correlation with lesion volume depends on lesion location. Overall ASPECTS is a useful and easily applicable tool for assessment of prognosis in acute stroke treatment and to help guide acute treatment decisions regardless whether MRI or CT is used. Patients with low ASPECTS values are unlikely to achieve good outcome. However, methodological constraints of ASPECTS have to be considered, and based on present data, a clear cutoff value to define “low ASPECTS values” cannot be given.

No space left for intravenous thrombolysis in acute stroke: PROS

Five recently published RCTs (MR CLEAN, EXTEND-IA, SWIFT PRIME, REVASCAT and ESCAPE) employing mechanical thrombectomy with modern stent retriever devices clearly demonstrated the superiority of endovascular treatment compared to thrombolysis alone, which is now considered standard first-line therapy for selected patients with acute severe ischemic stroke and large vessel in the anterior circulation. RCT results led to recommendations outlined in "Mechanical thrombectomy in acute ischemic stroke by ESO-Karolinska Stroke Update 2014/2015, supported by ESO, ESMINT, ESNR and EAN". Moreover, endovascular procedures in the 5 RCTs to date were performed at high-volume referral centers with, in some trials, rigid requirements for the interventionalist to participate, which may have contributed substantially to the excellent results, supporting the concept of centralization of intra-arterial thrombolysis resources and expertise. Therefore, patients with suspected large-artery occlusion and deemed candidates for thrombectomy, should be treated at a Comprehensive Stroke Centre with 24/7 endovascular treatment services. There seems to be limited space left for intravenous thrombolysis alone in acute stroke patients with large-vessel occlusions as thrombectomy plus thrombolysis continues to be reported as being superior with regard to outcome.

Effect of waivers of consent on recruitment in acute stroke trials: A systematic review

There is urgent need for clinical trials of novel interventions to reduce the burden of acute ischemic stroke. A key impediment to such trials is slow recruitment. Since obtaining written informed consent in the setting of acute stroke is especially challenging, some experts have endorsed relaxing the requirement for informed consent by permitting verbal consent or waivers to facilitate recruitment. This systematic review of 36 randomized controlled trials of acute interventions for ischemic stroke assesses whether alternatives to written informed consent are associated with increased recruitment rates. After the exclusion of 2 outlier trials that differed from other trials in conduct and interventions studied, no association was observed on univariable analysis (8.9 participants/month in trials requiring written consent vs 6.1 participants/month in trials with alternatives, p = 0.43) or multivariable analysis (when adjusting for the number of centers, number of countries, and exclusions based on modified Rankin Scale scores). Alternatives to written informed consent in acute stroke trials may enable trial designs that would not be feasible otherwise. However, we did not find evidence that, within traditional trial designs, such alternatives are associated with faster recruitment.

Added Benefit of Stent Retriever Technology for Acute Ischemic Stroke: A Pooled Analysis of the NINDS tPA, SWIFT, and STAR Trials

BACKGROUND

Endovascular treatment is increasingly being used in acute stroke care. However, although stent retrievers show improved flow restoration rates, their clinical benefits have been uncertain.

OBJECTIVE

To assess the incremental effect of using stent retrievers compared with intravenous tissue plasminogen activator (IV tPA; alteplase) alone or placebo/control.

METHODS

We conducted a pooled analysis of 4 studies using stent retrievers (Solitaire), IV tPA, or placebo/control. We applied the ischemic stroke risk score (www.sorcan.ca/iscore) to each participant to adjust for differences in baseline characteristics. We used a shift analysis to account for the potential benefits across the entire modified Rankin scale score at 90 days, adjusting for time-to-treatment, baseline Alberta Stroke Program Early CT score, and ischemic stroke risk score.

RESULTS

Of the 915 participants in this analysis, 312 (34.1%) patients received placebo, 312 (34.1%) received tPA alone, 131 (14.4%) received stent retrievers alone, and 160 (17.5) received combined therapy (IV tPA plus stent retrievers). The shift analysis revealed that more patients remained independent at 90 days if receiving stent retrievers alone (number needed to treat 3.5) or combined with tPA (number needed to treat 3.1) compared with tPA alone. After adjustment, participants receiving stent retrievers alone (odds ratio, 2.95; 95% confidence interval, 1.48-5.89) or combined with tPA (odds ratio, 4.45; 95% confidence interval, 2.40-8.27) were more likely to be independent at 90 days compared with tPA alone.

CONCLUSION

Patients with acute ischemic stroke who received IV tPA or revascularization therapies had a higher likelihood of achieving independence at 3 months. Stent retriever technology combined with tPA was associated with the greatest benefit compared with placebo, tPA alone, or endovascular therapy alone.

Choosing a Hyperacute Stroke Imaging Protocol for Proper Patient Selection and Time Efficient Endovascular Treatment: Lessons from Recent Trials

Recently, several prospective randomized control trials regarding endovascular treatment for patients with intracranial large artery occlusions causing acute ischemic stroke have been successfully reported. Effort to minimize time delays to endovascular treatment, patient selection and the use of retrievable stent were important factors for the success of these trials. The inclusion and exclusion criteria for each of these trials did include differences in imaging protocols. In this review, we focus on the importance of baseline non-invasive angiography prior to deciding endovascular treatment. Then imaging protocols are described for each trial according to measurement of infarct volume and collateral grading.

Endovascular stent thrombectomy: the new standard of care for large vessel ischaemic stroke

BACKGROUND

Results of initial randomised trials of endovascular treatment for ischaemic stroke, published in 2013, were neutral but limited by the selection criteria used, early-generation devices with modest efficacy, non-consecutive enrollment, and treatment delays.

RECENT DEVELOPMENTS

In the past year, six positive trials of endovascular thrombectomy for ischaemic stroke have provided level 1 evidence for improved patient outcome compared with standard care. In most patients, thrombectomy was performed in addition to thrombolysis with intravenous alteplase, but benefits were also reported in patients ineligible for alteplase treatment. Despite differences in the details of eligibility requirements, all these trials required proof of major vessel occlusion on non-invasive imaging and most used some imaging technique to exclude patients with a large area of irreversibly injured brain tissue. The results indicate that modern thrombectomy devices achieve faster and more complete reperfusion than do older devices, leading to improved clinical outcomes compared with intravenous alteplase alone. The number needed to treat to achieve one additional patient with independent functional outcome was in the range of 3·2-7·1 and, in most patients, was in addition to the substantial efficacy of intravenous alteplase. No major safety concerns were noted, with low rates of procedural complications and no increase in symptomatic intracerebral haemorrhage. WHERE NEXT?: Thrombectomy benefits patients across a range of ages and levels of clinical severity. A planned meta-analysis of individual patient data might clarify effects in under-represented subgroups, such as those with mild initial stroke severity or elderly patients. Imaging-based selection, used in some of the recent trials to exclude patients with large areas of irreversible brain injury, probably contributed to the proportion of patients with favourable outcomes. The challenge is how best to implement imaging in clinical practice to maximise benefit for the entire population and to avoid exclusion of patients with smaller yet clinically important potential to benefit. Although favourable imaging identifies patients who might benefit despite long delays from symptom onset to treatment, the proportion of patients with favourable imaging decreases with time. Health systems therefore need to be reorganised to deliver treatment as quickly as possible to maximise benefits. On the basis of available trial data, intravenous alteplase remains the initial treatment for all eligible patients within 4·5 h of stroke symptom onset. Those patients with major vessel occlusion should, in parallel, proceed to endovascular thrombectomy immediately rather than waiting for an assessment of response to alteplase, because minimising time to reperfusion is the ultimate aim of treatment.

Thrombectomy within 8 hours after symptom onset in ischemic stroke

BACKGROUND

We aimed to assess the safety and efficacy of thrombectomy for the treatment of stroke in a trial embedded within a population-based stroke reperfusion registry.

METHODS

During a 2-year period at four centers in Catalonia, Spain, we randomly assigned 206 patients who could be treated within 8 hours after the onset of symptoms of acute ischemic stroke to receive either medical therapy (including intravenous alteplase when eligible) and endovascular therapy with the Solitaire stent retriever (thrombectomy group) or medical therapy alone (control group). All patients had confirmed proximal anterior circulation occlusion and the absence of a large infarct on neuroimaging. In all study patients, the use of alteplase either did not achieve revascularization or was contraindicated. The primary outcome was the severity of global disability at 90 days, as measured on the modified Rankin scale (ranging from 0 [no symptoms] to 6 [death]). Although the maximum planned sample size was 690, enrollment was halted early because of loss of equipoise after positive results for thrombectomy were reported from other similar trials.

RESULTS

Thrombectomy reduced the severity of disability over the range of the modified Rankin scale (adjusted odds ratio for improvement of 1 point, 1.7; 95% confidence interval [CI], 1.05 to 2.8) and led to higher rates of functional independence (a score of 0 to 2) at 90 days (43.7% vs. 28.2%; adjusted odds ratio, 2.1; 95% CI, 1.1 to 4.0). At 90 days, the rates of symptomatic intracranial hemorrhage were 1.9% in both the thrombectomy group and the control group (P=1.00), and rates of death were 18.4% and 15.5%, respectively (P=0.60). Registry data indicated that only eight patients who met the eligibility criteria were treated outside the trial at participating hospitals.

CONCLUSIONS

Among patients with anterior circulation stroke who could be treated within 8 hours after symptom onset, stent retriever thrombectomy reduced the severity of post-stroke disability and increased the rate of functional independence. (Funded by Fundació Ictus Malaltia Vascular through an unrestricted grant from Covidien and others; REVASCAT ClinicalTrials.gov number, NCT01692379.).

[Intravenous thrombolysis for acute ischemic stroke: past, present and future]

The efficacy of intravenous thrombolysis using alteplase, a recombinant tissue plasminogen activator (IV t-PA) within a 4.5-hour time window for acute ischemic stroke patients has been well established. However, a tight time window allows a minority of stroke patients to receive IV t-PA, and low recanalization rates of large intracranial artery occlusions limit the efficacy of IV t-PA. To overcome the limitations of IV t-PA, clinical trials regarding IV t-PA based on DWI-PWI mismatch or DWI-FLAIR mismatch, next-generation agents of t-PA, dose modification of alteplase, sonothrombolysis, and so on are going on worldwide. Shortening of the time of door to treatment (needle or femoral puncture) plays a very important role to enhance the efficacy of acute reperfusion therapy including IV t-PA and acute stroke endovascular therapy, and as a consequence, it could contribute to improve the entire stroke outcomes due to an increase of acute reperfusion therapy-eligible patients.

Relevance of blood-brain barrier disruption after endovascular treatment of ischemic stroke: dual-energy computed tomographic study

BACKGROUND AND PURPOSE

Computed tomographic (CT) high attenuation (HA) areas after endovascular therapy for acute ischemic stroke are a common finding indicative of blood-brain barrier disruption. Dual-energy CT allows an accurate differentiation between HA areas related to contrast staining (CS) or to brain hemorrhage (BH). We sought to evaluate the prognostic significance of the presence of CS and BH after endovascular therapy.

METHODS

A prospective cohort of 132 patients treated with endovascular therapy was analyzed. According to dual-energy CT findings, patients were classified into 3 groups: no HA areas (n=53), CS (n=32), and BH (n=47). The rate of new hemorrhagic transformations was recorded at follow-up neuroimaging. Clinical outcome was evaluated at 90 days with the modified Rankin Scale (poor outcome, 3-6).

RESULTS

Poor outcome was associated with the presence of CS (odds ratio [OR], 11.3; 95% confidence interval, 3.34-38.95) and BH (OR, 10.4; 95% confidence interval, 3.42-31.68). The rate of poor outcome despite complete recanalization was also significantly higher in CS (OR, 9.7; 95% confidence interval, 2.55-37.18) and BH (OR, 15.1; 95% confidence interval, 3.85-59.35) groups, compared with the no-HA group. Patients with CS disclosed a higher incidence of delayed hemorrhagic transformation at follow-up (OR, 4.5; 95% confidence interval, 1.22-16.37) compared with no-HA patients.

CONCLUSIONS

Blood-brain barrier disruption, defined as CS and BH on dual-energy CT, was associated with poor clinical outcomes in patients with stroke treated with endovascular therapies. Moreover, isolated CS was associated with delayed hemorrhagic transformation. These results support the clinical relevance of blood-brain barrier disruption in acute stroke.

Endovascular treatment for Small Core and Anterior circulation Proximal occlusion with Emphasis on minimizing CT to recanalization times (ESCAPE) trial: methodology

ESCAPE is a prospective, multicenter, randomized clinical trial that will enroll subjects with the following main inclusion criteria: less than 12 h from symptom onset, age > 18, baseline NIHSS >5, ASPECTS score of >5 and CTA evidence of carotid T/L or M1 segment MCA occlusion, and at least moderate collaterals by CTA. The trial will determine if endovascular treatment will result in higher rates of favorable outcome compared with standard medical therapy alone. Patient populations that are eligible include those receiving IV tPA, tPA ineligible and unwitnessed onset or wake up strokes with 12 h of last seen normal. The primary end-point, based on intention-to-treat criteria is the distribution of modified Rankin Scale scores at 90 days assessed using a proportional odds model. The projected maximum sample size is 500 subjects. Randomization is stratified under a minimization process using age, gender, baseline NIHSS, baseline ASPECTS (8-10 vs. 6-7), IV tPA treatment and occlusion location (ICA vs. MCA) as covariates. The study will have one formal interim analysis after 300 subjects have been accrued. Secondary end-points at 90 days include the following: mRS 0-1; mRS 0-2; Barthel 95-100, EuroQOL and a cognitive battery. Safety outcomes are symptomatic ICH, major bleeding, contrast nephropathy, total radiation dose, malignant MCA infarction, hemicraniectomy and mortality at 90 days.