Wake-up stroke: Dawn of a new era

Surrogate biomarkers of outcome for wake-up ischemic stroke

Background

Wake-up ischemic stroke (IS) has been usually excluded from acute stroke therapy options for being outside of the safe treatment window. We identified risk factors, and clinical or molecular biomarkers that could be therapeutic targets for wake-up stroke prevention, thus hopefully leading to a decrease in its mortality and disability in medium to long-term outcome.

Methods

4251 ischemic stroke (IS) patients from a prospectively registered database were recruited; 3838 (90.3%) had known onset-symptom time, and 413 (9.7%) were wake-up strokes. The main endpoint was to analyze the association between different serum biomarkers with wake-up IS episodes and their progression. Leukocytes count, serum levels of C-reactive protein, fibrinogen, interleukin 6 (IL-6), and vitamin D were analyzed as inflammation biomarkers; N-terminal pro-B-type Natriuretic-Peptide and microalbuminuria, used as atrial/endothelial dysfunction biomarkers; finally, glutamate levels as excitotoxicity biomarker. In addition, demographic, clinical and neuroimaging variables associated with the time-evolution of wake-up IS patients and functional outcome at 3 months were evaluated. Good and poor functional outcome were defined as mRS ≤2 and mRS > 2 at 3 months, respectively.

Results

Wake-up IS showed a poorer outcome at 3-months than in patients with known on-set-symptom time (59.1% vs. 48.1%; p < 0.0001). Patients with wake-up IS had higher levels of inflammation biomarkers; IL-6 levels at admission (51.5 ± 15.1 vs. 27.8 ± 18.6 pg/ml; p < 0.0001), and low vitamin D levels at 24 h (5.6 ± 5.8 vs. 19.2 ± 9.4 ng/ml; p < 0.0001) are worthy of attention. In a logistic regression model adjusted for vitamin D, OR was 15.1; CI 95%: 8.6–26.3, p < 0.0001. However, we found no difference in vitamin D levels between patients with or without clinical-DWI mismatch (no: 18.95 ± 9.66; yes: 17.84 ± 11.77 ng/mL, p = 0.394). No difference in DWI volume at admission was found (49.3 ± 96.9 ml in wake-up IS patients vs. 51.7 ± 98.2 ml in awake IS patients; p = 0.895).

Conclusions

Inflammatory biomarkers are the main factors that are strongly associated with wake-up IS episodes. Wake-up IS is associated with lower vitamin D levels. These data indicate that vitamin D deficiency could become a therapeutic target to reduce wake-up IS events.

Time to Wake-Up: Extending the Window for Management of Unknown-Onset Strokes

The term "Wake-Up Stroke" is applied to a patient who displays no symptoms before sleep, but wakes with neurologic deficits suggestive of stroke. The current guidelines for acute ischemic stroke limit intravenous tissue plasminogen activator use to stroke patients in whom symptom onset or last known well is less than 4.5 hours. Approximately one-third of acute ischemic stroke patients present with unknown time of symptom onset and are often not eligible for intravenous reperfusion therapy in clinical practice. This review provides an overview of several earlier trials that used advanced neuroimaging to determine eligibility for reperfusion therapy in patients with unknown stroke onset. The reassuring results of these earlier trials that led to recent thrombolysis trials specifically targeted at "wake-up stroke" patients are discussed in this review. Ongoing studies aim to expand our knowledge regarding the safety and efficacy of thrombolysis in these patients.

Adjuvant High-Flow Normobaric Oxygen After Mechanical Thrombectomy for Anterior Circulation Stroke: a Randomized Clinical Trial

Adjuvant neuroprotective therapies for acute ischemic stroke (AIS) have demonstrated benefit in animal studies, albeit without human translation. We investigated the safety and efficacy of high-flow normobaric oxygen (NBO) after endovascular recanalization in anterior circulation stroke. This is a prospective randomized controlled study. Eligible patients were randomized to receive high-flow NBO by a Venturi mask (FiO2 50%, flow 15 L/min) or routine low-flow oxygen supplementation by nasal cannula (flow 3 L/min) after vessel recanalization for 6 h. Patient demographics, procedural metrics, complications, functional outcomes, symptomatic intracranial hemorrhage (sICH), and infarct volume were assessed. A total of 91 patients were treated with high-flow NBO. NBO treatment revealed a common odds ratio of 2.2 (95% CI, 1.26 to 3.87) favoring the distribution of global disability scores on the mRS at 90 days. The mortality at 90 days was significantly lower in the NBO group than in the control group, with an absolute difference of 13.86% (rate ratio, 0.35; 95% CI, 0.13-0.93). A significant reduction of infarct volume as determined by MRI was noted in the NBO group. The median infarct volume was 9.4 ml versus 20.5 ml in the control group (beta coefficient, - 20.24; 95% CI, - 35.93 to - 4.55). No significant differences were seen in the rate of sICH, pneumonia, urinary infection, and seizures between the 2 groups. This study suggests that high-flow NBO therapy after endovascular recanalization is safe and effective in improving functional outcomes, decreasing mortality, and reducing infarct volumes in anterior circulation stroke patients within 6 h from stroke onset.

Automated CT Perfusion Imaging to Aid in the Selection of Patients With Acute Ischemic Stroke for Mechanical Thrombectomy: A Health Technology Assessment

BACKGROUND

Stroke is a sudden interruption in the blood supply to a part of the brain, causing loss of neurological function. It is the third leading cause of death in Canada and affects mainly older people. In the acute setting, neuroimaging is integral to stroke evaluation and decision-making. The neuroimaging results guide patient selection for mechanical thrombectomy. Using automated image processing techniques facilitates efficient review of this information and communication between centres. We conducted a health technology assessment of automated CT perfusion imaging as a tool for selecting stroke patients with anterior circulation occlusion for mechanical thrombectomy. This assessment included an evaluation of clinical effectiveness, cost-effectiveness, and the budget impact of publicly funding automated CT perfusion imaging.

METHODS

We performed a systematic literature search of the clinical evidence. We assessed the risk of bias of each study using QUADAS-2 or the Cochrane risk-of-bias tool, and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic economic literature search and approximated cost-effectiveness based on previous analyses. We also analyzed the budget impact of publicly funding automated CT perfusion imaging to evaluate people with acute ischemic stroke in Ontario.

RESULTS

Automated CT perfusion imaging had a sensitivity of 84% for identifying the infarct core (dead tissue that does not recover despite restoring blood flow with mechanical thrombectomy), compared with diffusion-weighted MRI imaging at 24 hours. One study reported that 7% of patients were misclassified with respect to eligibility for mechanical thrombectomy (either erroneously classified as eligible or erroneously classified non-eligible). Two randomized controlled trials (DEFUSE 3 and DAWN) demonstrated the efficacy of mechanical thrombectomy up to 24 hours after stroke onset, with patient selection guided by automated CT perfusion imaging. These data showed that a significantly higher proportion of patients in the mechanical thrombectomy group achieved functional independence compared with the standard care group (DEFUSE 3: risk ratio: 2.67 [95% confidence interval 1.60-4.48]; DAWN: adjusted rate difference: 33% [95% credible interval 21%-44%]; GRADE: Moderate).A previous health technology assessment in stroke patients presenting at 0 to 6 hours after stroke symptom onset and the results from recent randomized controlled trials for patients presenting at 6 to 24 hours informed the evaluation of cost-effectiveness. Mechanical thrombectomy informed by automated CT perfusion imaging to assess eligibility is likely to be cost-effective for patients presenting at 6 to 24 hours after stroke symptom onset. The annual budget impact of publicly funding automated CT perfusion imaging in Ontario over the next 5 years would be $1.3 million in year 1 and $0.9 million each year thereafter. Some of the costs of automated CT perfusion imaging could be offset by avoiding unnecessary patient transfers between hospitals.

CONCLUSIONS

Automated CT perfusion imaging has an acceptable sensitivity and specificity for detecting brain areas that have been affected by stroke. In patients selected for mechanical thrombectomy using automated CT perfusion imaging, there was significant improvement in functional independence. Mechanical thrombectomy informed by automated CT perfusion imaging is likely to be cost-effective. We estimate that publicly funding automated CT perfusion imaging in Ontario would result in additional costs of $1.3 million in year 1 and $0.9 million per year thereafter.

Detrimental and Beneficial Effect of Autophagy and a Potential Therapeutic Target after Ischemic Stroke

Autophagy, a physiologic mechanism that promotes energy recycling and orderly degradation through self-regulated disassembly of cellular components, helps maintain homeostasis. A series of evidences suggest that autophagy is activated as a response to ischemia and has been well-characterized as a therapeutic target. However, the role of autophagy after ischemia remains controversial. Activated-autophagy can remove necrotic substances against ischemic injury to promote cell survival. On the contrary, activation of autophagy may further aggravate ischemic injury, causing cell death. Therefore, the present review will examine the current understanding of the precise mechanism and role of autophagy in ischemia and recent neuroprotective therapies on autophagy, drug therapies, and nondrug therapies, including electroacupuncture (EA).

Intravenous Administration of Standard Dose Tirofiban after Mechanical Arterial Recanalization is Safe and Relatively Effective in Acute Ischemic Stroke

To investigate the safety and efficacy of intravenous administration of a standard dose of glycoprotein-IIb/IIIa inhibitor tirofiban after vessel recanalization by mechanical thrombectomy in acute ischemic stroke. A consecutive series of patients (n=112) undergoing endovascular ischemic stroke intervention therapy were enrolled. 81 patients were eligible for intravenous (IV) tirofiban treatment for 24 hours after mechanical thrombectomy. The incidence of symptomatic intracranial hemorrhage (sICH), death, National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS) were assessed. In the 81 patients receiving tirofiban, 52 patients (64.2%) were treated with IV rt-PA before mechanical thrombectomy. sICH was found in 2 (2.5%) patients with no fatal ICH. Four patients died during 3 months after stroke onset. Successful recanalization with thrombolysis in cerebral infarction (TICI) score ≥2b was achieved in 75 of 81 patients (92.6%) after mechanical thrombectomy. The average number of passes with Solitaire stent retriever was 1.3. At 3 months, 55 of 81 patients (67.9%) had favorable outcomes (mRS<=2). The intravenous application of a standard dose of tirofiban post-Solitaire stent retriever thrombectomy and intravenous thrombolysis appears to be safe and relatively effective in acute ischemic stroke.

How should we treat patients who wake up with a stroke? A review of recent advances in management of acute ischemic stroke

Acute ischemic strokes account for 85% of all strokes and are the fifth leading cause of mortality in the United States. About one in five of all ischemic strokes occur during sleep and are not noticed until the patient wakes up with neurological deficits. There is growing evidence to support that a significantly higher number of stroke patients could benefit from more aggressive care, especially those patients who wake up with strokes. There is increasing research to support a physiologically-based approach based on advanced imaging rather than simply a time-based determination of whether or not a patient would benefit from reperfusion. Advanced imaging such as CT-Perfusion and MR DWI-FLAIR can be used to establish the age of the lesion and determine the extent of the brain tissue that is salvageable. If physicians could identify those patients with wake-up strokes that are candidates for intervention, there may be opportunity to treat 3 million more people, reducing long term disability and healthcare expenditures. Patients who are in the window for IV rtPA should receive it as soon as possible as well as be evaluated for mechanical thrombectomy. For those who are out of the window for IV rtPA, consider further imaging such as CTP and MR brain for diffusion-weighted sequences to evaluate for potential endovascular intervention. If a large vessel occlusion is present and imaging demonstrates a small infarct core and a large area of salvageable tissue, mechanical thrombectomy may be beneficial for the best possible functional outcome.

Reporting Compliance of Stroke Trials: Cross-Sectional Analysis

BACKGROUND

The FDA mandates timely reporting of all clinical trials conducted in the United States. However, often the results are not reported in a timely manner, resulting in wastage of finite resources. We assessed the reporting of results of completed stroke trials and compared the reporting trends between U.S. and non-U.S. stroke trials.

METHODS

We assessed consecutive clinical stroke trials registered as completed in ClinicalTrials.gov between January 1, 2008 and January 1, 2015. Descriptive data collected included study phase, study type, participant age, number of enrolled patients, study locations, start and primary completion dates, result availability, time to reporting (months), sponsorship, funding sources, and publication status. We also performed manual search for stroke trials in Pubmed, Web of Science, and Google scholar.

RESULTS

Out of a total 140 completed trials, 39 trials (35,359 patients) involved at least 1 U.S. center and 101 trials (58,542 patients) were conducted in non-U.S. centers. Of the trials involving at least a single U.S. center, 31 of 39 (79%) reported their results, whereas only 6 of 31 (19%) reported their results within 1 year. Of the trials conducted at non-U.S. centers, 72 of 101 (71%) reported their results, whereas results for 24 of 72 (33%) trials were available within a year of completion. The time to reporting of results was significantly lower for all the included clinical trials in the 2012-2014 period (P < .001, Cohen's d = .726) as compared to the 2008-2011 period.

CONCLUSION

Only one-fifth of completed stroke trials involving at least a single U.S. center report their results within 1 year. Additionally, every fifth completed trial involving stroke patients at U.S. centers remain unreported.

Interaction of incidental microbleeds and prior use of antithrombotics with early hemorrhagic transformation: Causative or protective?

BACKGROUND

Gradient echo (GRE) sequence of magnetic resonance imaging (MRI) is a sensitive tool to detect hemorrhagic transformation (HT) and old cerebral microbleeds (CMBs). Presence of CMBs and prior use of antithrombotics pose a risk of HT in ischemic stroke. We evaluated the association of CMBs and antithrombotic use with resultant HT in acute ischemic stroke (AIS).

METHODS

This retrospective study included AIS patients admitted to our center between January 2009 and August 2010 who underwent GRE-weighted MRI within 48 h of admission. Demographic and clinical data including diabetes mellitus, hypertension, hyperlipidemia, prior intake of antiplatelets/anticoagulants/statins, and presence of CMBs at admission were collected and compared between patients who developed HT and those who did not. We did a multivariate analysis using logistic regression to assess the effect of CMBs and prior use of antithrombotic agents on the risk of development for early HT in ischemic stroke.

RESULTS

Of 529 AIS patients, 81 (15%) were found to have HT during the initial hospital course. CMBs were found in only 9 of 81 patients (11%) with HT and in 40 out of remaining 448 patients (9%) who did not develop HT. The presence of CMBs was not associated with increased risk of HT (P = 0.53). However, prior use of antiplatelets (33% vs. 47% in the patients without HT, P = 0.02) was associated with decreased risk of HT in ischemic stroke.

CONCLUSION

Presence of incidental CMBs was not associated with increased risk for early HT of an ischemic stroke. Interestingly, the prior intake of antiplatelets was found to be protective against HT of ischemic stroke.