Valproic acid selectively increases vascular endothelial tissue-type plasminogen activator production and reduces thrombus formation in the mouse

Essentials Stimulating endogenous fibrinolysis could be a novel antithrombotic strategy. The effect of valproic acid on endothelial tissue plasminogen activator in mice was investigated. Valproic acid increased tissue plasminogen activator expression in vascular endothelium. Valproic acid reduced fibrin deposition and thrombus formation after vascular injury.

SUMMARY

Background The endogenous fibrinolytic system has rarely been considered as a target to prevent thrombotic disease. Tissue-type plasminogen activator (t-PA) production is potently increased by histone deacetylase (HDAC) inhibitors in endothelial cells in vitro, but whether this translates into increased vascular t-PA production and an enhanced fibrinolytic capacity in vivo is unknown. Objectives To determine whether the HDAC inhibitor valproic acid (VPA) stimulates production of t-PA in the vasculature of mice, and whether VPA pretreatment affects fibrin deposition and clot formation after mechanical vessel injury. Methods Mice were injected with VPA twice daily for up to 5 days. t-PA mRNA, and antigen expression in the mouse aorta and the circulating levels of t-PA were determined. Fibrin and thrombus dynamics after mechanical vessel injury were monitored with intravital confocal microscopy. Potential effects of VPA on platelets and coagulation were investigated. Results and Conclusions We found that VPA treatment increased vascular t-PA production in vivo and, importantly, that VPA administration was associated with reduced fibrin accumulation and smaller thrombi in response to vascular injury, but still was not associated with an increased risk of bleeding. Furthermore, we observed that higher concentrations of VPA were required to stimulate t-PA production in the brain than in the vasculature. Thus, this study shows that VPA can be dosed to selectively manipulate the fibrinolytic system in the vascular compartment and reduce thrombus formation in vivo.

Ethnic Comparison of Clinical Characteristics and Ischemic Stroke Subtypes Among Young Adult Patients With Stroke in Hawaii

BACKGROUND AND PURPOSE

Native Hawaiians and other Pacific Islanders (NHOPI) with ischemic stroke have younger age of stroke onset compared with whites. However, ethnic differences in stroke subtypes in this population have been inadequately studied.

METHODS

Consecutive young adult patients (aged ≤55 years) who were hospitalized for ischemic stroke between 2006 and 2012 at a tertiary center in Honolulu were studied. Clinical characteristics and stroke subtypes based on pathophysiological TOAST classification (Trial of Org 10172) of NHOPI and Asians were compared with whites.

RESULTS

A total of 427 consecutive young adult (mean age, 46.7±7.8 years) patients (NHOPI 45%, Asians 38%, and whites 17%) were studied. NHOPI had a higher prevalence of hypertension, diabetes mellitus, prosthetic valve, higher body mass index, hemoglobin A1c, and lower high-density lipoprotein than whites (all P<0.05). Stroke subtype distribution was not different between the ethnic groups. Specifically, the prevalence of small-vessel disease was similar between NHOPI (26.6%), whites (28.4%), and Asians (24.8%). In the univariate analyses, the use of intravenous tissue-type plasminogen activator was lower among NHOPI (4.7%; P=0.01) and Asians (3.1%; P=0.002) than among whites (12.5%). In the multivariable model, NHOPI (odds ratio, 0.35; 95% confidence interval, 0.12-0.98) and Asians (odds ratio, 0.23; 95% confidence interval, 0.07-0.74) were less likely to be treated with intravenous tissue-type plasminogen activator than whites.

CONCLUSIONS

NHOPI have greater cardiovascular risk factors than whites, but there were no differences in stroke subtypes between the ethnic groups. Furthermore, NHOPI and Asians may be less likely to be treated with intravenous tissue-type plasminogen activator than whites.

How a CT-Direct Protocol at an American Comprehensive Stroke Center Led to Door-to-Needle Times Less Than 30 Minutes

BACKGROUND AND PURPOSE

The safety and efficacy of intravenous tissue plasminogen activator (IV tPA) following acute ischemic stroke (AIS) is dependent on its timely administration. In 2014, our Comprehensive Stroke Center designed and implemented a computed tomography-Direct protocol to streamline the evaluation process of suspected patients with AIS, with the aim of reducing door-to-needle (DTN) times. The objectives of our study were to describe the protocol development and implementation process, and to compare DTN times and symptomatic intracranial hemorrhage (sICH) rates before and after protocol implementation.

METHODS

Data were prospectively collected for patients with AIS receiving IV tPA between January 1, 2010, and May 31, 2015. The DTN times, examined as median times and time treatment windows, and sICH rates were compared pre- and postimplementation.

RESULTS

Two hundred ninety-five patients were included in the study. After protocol implementation, median DTN times were significantly reduced (38 vs 28 minutes; P < .001). The distribution of patients treated in the three time treatment windows described below changed significantly, with an increase in patients with DTN times of 30 minutes or less, and a decrease in patients with DTN times 31 to 60 minutes and over 60 minutes (P < .001). There were two cases of sICH prior to implementation and one sICH case postimplementation.

CONCLUSIONS

The implementation of a protocol that streamlined the processing of suspected patients with AIS significantly reduced DTN time without negatively impacting patient safety.

α1 -antitrypsin Pittsburgh and plasmin-mediated proteolysis

Essentials Patients with α-1-antitrypsin (α1-AT) Pittsburgh exhibit a mild bleeding tendency. A new case of α1-AT Pittsburgh with suspected high antifibrinolytic potential was studied. We showed that α1-AT Pittsburgh inhibits tissue plasminogen activator and plasmin. The antifibrinolytic potential of the variant contributes to explaining the mild bleeding phenotype.

SUMMARY

α1 -Antitrypsin (α1 -AT) Pittsburgh has a Met358 to Arg substitution at the reactive Met-Ser site of α1 -AT, which enables the protein to act as a potent thrombin inhibitor. Four patients with α1 -AT Pittsburgh have been described to date. An additional young girl was recently diagnosed with α1 -AT Pittsburgh in our center after presenting with a large hematoma in the forearm. Interestingly, all of these patients showed a potent thrombin inhibitor in the plasma and a mild bleeding phenotype. This observation suggests that the in vivo consequences of the mutation may contribute to the maintenance of normal hemostatic balance. We assessed inhibition of the fibrinolytic system by the variant protein by evaluating the fibrinolysis inhibitory potential of the patient's plasma, purified wild-type α1 -AT and purified Pittsburgh α1 -AT with an electrophoretic zymography system, western blotting, and clot fibrinolysis. Our results indicate that the patient's plasma and purified α1 -AT Pittsburgh have strong potential to inhibit tissue-type plasminogen activator and plasmin.

Safety and Preliminary Efficacy of Early Tirofiban Treatment After Alteplase in Acute Ischemic Stroke Patients

BACKGROUND AND PURPOSE

We investigated whether early initiation of tirofiban, a glycoprotein IIb/IIIa antagonist, is safe, can reduce the risk of reocclusion, and improve outcomes in acute ischemic stroke patients after alteplase.

METHODS

Forty-one patients received alteplase followed by intravenous tirofiban infusion for at least 24 hours. The incidence of symptomatic intracranial hemorrhage, systematic bleedings, and death was recorded. The National Institutes of Health stroke scale score was evaluated at 24 hours and at day 7 (or discharge). Modified Rankin scale was assessed at 3 months. Outcomes for these patients were compared with a propensity score-matched historical cohort with alteplase only.

RESULTS

The incidence of symptomatic intracranial hemorrhage, death, or systematic bleedings (P=1.00) was not increased in the alteplase/tirofiban group. At 24 hours, fewer patients experienced reocclusion in the alteplase/tirofiban group (2.4% versus 22.0%; P=0.025). At day 7 or discharge, the median National Institutes of Health stroke scale score was significantly lower in the alteplase/tirofiban group (1 versus 6; P=0.002). At 3 months, more patients had favorable outcomes of modified Rankin scale 0 to 1 (70.7% versus 46.2%; P=0.026).

CONCLUSIONS

Intravenous tirofiban immediately after alteplase seems to be safe and potentially more effective when compared with alteplase alone for selected stroke patients.

CLINICAL TRIAL REGISTRATION

URL: http://www.chictr.org.cn/. Unique identifier: ChiCTR-TRC-14004630.

How Patient Demographics, Imaging, and Beliefs Influence Tissue-Type Plasminogen Activator Use: A Survey of North American Neurologists

BACKGROUND AND PURPOSE

Understanding physician decision making is increasingly recognized as an important topic of study, especially in stroke care. We sought to characterize the process of acute stroke decision making among neurologists in the United States and Canada from clinical and epistemological perspectives.

METHODS

Using a factorial design online survey, respondents were presented with clinical data to mimic an acute stroke encounter. The history, examination, computed tomographic (CT) scan, CT angiogram, and CT perfusion were presented in sequence, and respondents rated their diagnostic confidence and likelihood of treatment with tissue-type plasminogen activator after each element. Patient age, race, sex, and CT perfusion imaging results were randomized, whereas the rest of the clinical presentation was held constant.

RESULTS

We collected 715 responses, of which 473 (66%) were complete. Diagnostic certainty and likelihood of treatment with tissue-type plasminogen activator rose incrementally as additional clinical data were provided. Diagnostic certainty and treatment likelihood were strongly influenced by the clinical history and the CT scan. Other factors such as physicians' personal beliefs or biases were not influential. Respondents' accuracy in interpreting CT angiographic and CT perfusion images was variable and generally low.

CONCLUSIONS

Diagnostic certainty and likelihood of treatment with tissue-type plasminogen activator increase with additional clinical data, with the history being the most important factor for diagnostic and treatment decisions. Respondents had difficulty in interpreting the results of CT perfusion scans although they had little impact on treatment decisions. We did not identify treatment bias based on patient age, race, or sex.

Tissue-Type Plasminogen Activator-A296-299 Prevents Impairment of Cerebral Autoregulation After Stroke Through Lipoprotein-Related Receptor-Dependent Increase in cAMP and p38

BACKGROUND AND PURPOSE

The sole Food and Drug Administration-approved treatment for stroke is tissue-type plasminogen activator (tPA), but its brief therapeutic window and complications of treatment constrain its use. One limitation may be its potential to exacerbate impairment of cerebral autoregulation after stroke. Vasodilation is maintained by elevations in cAMP. However, cAMP levels fall after stroke because of overactivation of N-methyl-d-aspartate receptors by toxic levels of glutamate, an effect that is exacerbated by tPA. Binding of wild-type (wt) tPA to the low-density lipoprotein-related receptor (LRP) mediates dilation. We propose that binding of wt-tPA to N-methyl-d-aspartate receptor reduces cAMP and impairs vasodilation. We hypothesize that tPA-A(296-299), a variant that is fibrinolytic but cannot bind to N-methyl-d-aspartate receptor, preferentially binds to LRP and increases cAMP and p38, limiting autoregulation impairment after stroke.

METHODS

Stroke was induced by photothrombosis in pigs equipped with a closed cranial window, cerebral blood flow determined by microspheres, and cerebrospinal fluid cAMP and p38 determined by ELISA.

RESULTS

Stroke decreased cerebral blood flow. Cerebral blood flow was reduced further during hypotension, indicating impairment of autoregulation. Autoregulation was further impaired by wt-tPA, which was prevented by MK801 and tPA-A(296-299). Protection by tPA-A(296-299) was blocked by anti-LRP Ab, the LRP antagonist receptor-associated protein, and the p38 inhibitor SB 203580, but not by control IgG. Stroke reduced cerebrospinal fluid cAMP, which was reduced further by wt-tPA, but augmented by tPA-A(296-299). Cerebrospinal fluid p38 was unchanged by wt-tPA, increased by tPA-A(296-299), and decreased by anti-LRP Ab and receptor-associated protein.

CONCLUSIONS

tPA-A(296-299) prevents impairment of cerebral autoregulation after stroke through an LRP-dependent increase in cAMP and p38.

Efficacy of Alteplase in a Mouse Model of Acute Ischemic Stroke: A Retrospective Pooled Analysis

BACKGROUND AND PURPOSE

The debate over the fact that experimental drugs proposed for the treatment of stroke fail in the translation to the clinical situation has attracted considerable attention in the literature. In this context, we present a retrospective pooled analysis of a large data set from preclinical studies, to examine the effects of early versus late administration of intravenous recombinant tissue-type plasminogen activator.

METHODS

We collected data from 26 individual studies from 9 international centers (13 researchers; 716 animals) that compared recombinant tissue-type plasminogen activator with controls, in a unique mouse model of thromboembolic stroke induced by an in situ injection of thrombin into the middle cerebral artery. Studies were classified into early (<3 hours) versus late (≥3 hours) drug administration. Final infarct volumes, assessed by histology or magnetic resonance imaging, were compared in each study, and the absolute differences were pooled in a random-effect meta-analysis. The influence of time of administration was tested.

RESULTS

When compared with saline controls, early recombinant tissue-type plasminogen activator administration was associated with a significant benefit (absolute difference, -6.63 mm(3); 95% confidence interval, -9.08 to -4.17; I(2)=76%), whereas late recombinant tissue-type plasminogen activator treatment showed a deleterious effect (+5.06 mm(3); 95% confidence interval, +2.78 to +7.34; I(2)=42%; Pint<0.00001). Results remained unchanged after subgroup analyses.

CONCLUSIONS

Our results provide the basis needed for the design of future preclinical studies on recanalization therapies using this model of thromboembolic stroke in mice. The power analysis reveals that a multicenter trial would require 123 animals per group instead of 40 for a single-center trial.

Direct Mechanical Intervention Versus Combined Intravenous and Mechanical Intervention in Large Artery Anterior Circulation Stroke: A Matched-Pairs Analysis

BACKGROUND AND PURPOSE

Five randomized controlled trials have consistently shown that mechanical thrombectomy (MT) in addition to best medical treatment (±intravenous tissue-type plasminogen activator) improves outcome after acute ischemic stroke in patients with large artery anterior circulation stroke. Whether direct MT is equally effective as combined intravenous thrombolysis with MT (ie, bridging thrombolysis) remains unclear.

METHODS

We retrospectively compared clinical and radiological outcomes in 167 bridging patients with 255 patients receiving direct MT because of large artery anterior circulation stroke. We matched all patients from the direct MT group who would have qualified for intravenous tissue-type plasminogen activator with controls from the bridging group, using multivariate and propensity score analyses. Functional independence was defined as modified Rankin Scale score of 0 to 2.

RESULTS

From February 2009 to August 2014, 40 patients from the direct MT group would have qualified for bridging thrombolysis but were treated with MT only. Clinical and radiological characteristics did not differ from the bridging cohort, except for higher rates of hypercholesterolemia (P=0.019), coronary heart disease (P=0.039), and shorter intervals from symptom onset to endovascular intervention (P=0.01) in the direct MT group. Functional independence, mortality, and intracerebral hemorrhage rates did not differ (P>0.1). After multivariate matching analysis outcome in both groups did not differ, except for lower rates of asymptomatic intracerebral hemorrhage (P=0.023) and lower mortality (P=0.007) in the direct MT group.

CONCLUSIONS

In patients with large anterior circulation stroke, direct mechanical intervention seems to be equally effective as bridging thrombolysis. A randomized trial comparing direct MT with bridging therapy is warranted.

Streamlined Hyperacute Magnetic Resonance Imaging Protocol Identifies Tissue-Type Plasminogen Activator-Eligible Stroke Patients When Clinical Impression Is Stroke Mimic

BACKGROUND AND PURPOSE

Stroke mimics (SM) challenge the initial assessment of patients presenting with possible acute ischemic stroke (AIS). When SM is considered likely, intravenous tissue-type plasminogen activator (tPA) may be withheld, risking an opportunity to treat AIS. Although computed tomography is routinely used for tPA decision making, magnetic resonance imaging (MRI) may diagnose AIS when SM is favored but not certain. We hypothesized that a hyperacute MRI (hMRI) protocol would identify tPA-eligible AIS patients among those initially favored to have SM.

METHODS

A streamlined hMRI protocol was designed based on barriers to rapid patient transport, MRI acquisition, and post-MRI tPA delivery. Neurologists were trained to order hMRI when SM was favored and tPA was being withheld. The use of hMRI for tPA decision making, door-to-needle times, and outcomes were compared before hMRI implementation (pre-hMRI: August 1, 2011 to July 31, 2013) and after (post-hMRI, August 1, 2013, to January 15, 2015).

RESULTS

Post hMRI, 57 patients with suspected SM underwent hMRI (median MRI-order-to-start time, 29 minutes), of whom, 11 (19%) were diagnosed with AIS and 7 (12%) received tPA. Pre-hMRI, no tPA-treated patients were screened with hMRI. Post hMRI, 7 of 106 (6.6%) tPA-treated patients underwent hMRI to aid in decision making because of suspected SM (0% versus 6.6%; P=0.001). To ensure standard care was maintained after implementing the hMRI protocol, pre- versus post-hMRI tPA-treated cohorts were compared and did not differ: door-to-needle time (39 versus 37 minutes; P=0.63), symptomatic hemorrhage rate (4.5% versus 1.9%; P=0.32), and favorable discharge location (85% versus 89%; P=0.37).

CONCLUSIONS

A streamlined hMRI protocol permitted tPA administration to a small, but significant, subset of AIS patients initially considered to have SM.

Tissue-type plasminogen activator induces synaptic vesicle endocytosis in cerebral cortical neurons

The release of the serine proteinase tissue-type plasminogen activator (tPA) from the presynaptic terminal of cerebral cortical neurons plays a central role in the development of synaptic plasticity, adaptation to metabolic stress and neuronal survival. Our earlier studies indicate that by inducing the recruitment of the cytoskeletal protein βII-spectrin and voltage-gated calcium channels to the active zone, tPA promotes Ca(2+)-dependent translocation of synaptic vesicles (SVs) to the synaptic release site where they release their load of neurotransmitters into the synaptic cleft. Here we used a combination of in vivo and in vitro experiments to investigate whether this effect leads to depletion of SVs in the presynaptic terminal. Our data indicate that tPA promotes SV endocytosis via a mechanism that does not require the conversion of plasminogen into plasmin. Instead, we show that tPA induces calcineurin-mediated dynamin I dephosphorylation, which is followed by dynamin I-induced recruitment of the actin-binding protein profilin II to the presynaptic membrane, and profilin II-induced F-actin formation. We report that this tPA-induced sequence of events leads to the association of newly formed SVs with F-actin clusters in the endocytic zone. In summary, the data presented here indicate that following the exocytotic release of neurotransmitters tPA activates the mechanism whereby SVs are retrieved from the presynaptic membrane and endocytosed to replenish the pool of vesicles available for a new cycle of exocytosis. Together, these results indicate that in murine cerebral cortical neurons tPA plays a central role coupling SVs exocytosis and endocytosis.

A Review of the Mechanisms of Blood-Brain Barrier Permeability by Tissue-Type Plasminogen Activator Treatment for Cerebral Ischemia

Cerebrovascular homeostasis is maintained by the blood-brain barrier (BBB), which forms a mechanical and functional barrier between systemic circulation and the central nervous system (CNS). In patients with ischemic stroke, the recombinant tissue-type plasminogen activator (rt-PA) is used to accelerate recanalization of the occluded vessels. However, rt-PA is associated with a risk of increasing intracranial bleeding (ICB). This effect is thought to be caused by the increase in cerebrovascular permeability though various factors such as ischemic reperfusion injury and the activation of matrix metalloproteinases (MMPs), but the detailed mechanisms are unknown. It was recently found that rt-PA treatment enhances BBB permeability not by disrupting the BBB, but by activating the vascular endothelial growth factor (VEGF) system. The VEGF regulates both the dissociation of endothelial cell (EC) junctions and endothelial endocytosis, and causes a subsequent increase in vessel permeability through the VEGF receptor-2 (VEGFR-2) activation in ECs. Here, we review the possibility that rt-PA increases the penetration of toxic molecules derived from the bloodstream including rt-PA itself, without disrupting the BBB, and contributes to these detrimental processes in the cerebral parenchyma.

Epigenetic Regulation of Tissue-Type Plasminogen Activator in Human Brain Tissue and Brain-Derived Cells

The serine protease tissue-type plasminogen activator (t-PA) is involved in both vital physiological brain processes, such as synaptic plasticity, and pathophysiological conditions, such as neurodegeneration and ischemic stroke. Recent data suggest that epigenetic mechanisms play an important role in the regulation of t-PA in human endothelial cells. However, there are limited data on epigenetic regulation of t-PA in human brain-derived cells. We demonstrate that treatment of cultured human neurons and human astrocytes with the histone deacetylase inhibitors trichostatin A (TSA) and MS-275 resulted in a two- to threefold increase in t-PA mRNA and protein expression levels. Next, we performed a chromatin immunoprecipitation assay on treated astrocytes with antibodies directed against acetylated histones H3 and H4 (both markers of gene activation). Treatment with MS-275 and TSA for 24 hours resulted in a significant increase in H3 acetylation, which could explain the observed increase in t-PA gene activity after the inhibition of histone deacety-lation. Furthermore, DNA methylation analysis of cultured human neurons and astrocytes, as well as human postmortem brain tissue, revealed a stretch of unmethylated CpG dinucleotides in the proximal t-PA promoter, whereas more upstream CpGs were highly methylated. Taken together, these results implicate involvement of epigenetic mechanisms in the regulation of t-PA expression in the human brain.

LDL receptor-related protein-1 regulates NFκB and microRNA-155 in macrophages to control the inflammatory response

LDL receptor-related protein-1 (LRP1) is an endocytic and cell-signaling receptor. In mice in which LRP1 is deleted in myeloid cells, the response to lipopolysaccharide (LPS) was greatly exacerbated. LRP1 deletion in macrophages in vitro, under the control of tamoxifen-activated Cre-ER(T) fusion protein, robustly increased expression of proinflammatory cytokines and chemokines. In LRP1-expressing macrophages, proinflammatory mediator expression was regulated by LRP1 ligands in a ligand-specific manner. The LRP1 agonists, α2-macroglobulin and tissue-type plasminogen activator, attenuated expression of inflammatory mediators, even in the presence of LPS. The antagonists, receptor-associated protein (RAP) and lactoferrin (LF), and LRP1-specific antibody had the entirely opposite effect, promoting inflammatory mediator expression and mimicking LRP1 deletion. NFκB was rapidly activated in response to RAP and LF and responsible for the initial increase in expression of proinflammatory mediators. RAP and LF also significantly increased expression of microRNA-155 (miR-155) after a lag phase of about 4 h. miR-155 expression reflected, at least in part, activation of secondary cell-signaling pathways downstream of TNFα. Although miR-155 was not involved in the initial induction of cytokine expression in response to LRP1 antagonists, miR-155 was essential for sustaining the proinflammatory response. We conclude that LRP1, NFκB, and miR-155 function as members of a previously unidentified system that has the potential to inhibit or sustain inflammation, depending on the continuum of LRP1 ligands present in the macrophage microenvironment.

Recombinant tissue-type plasminogen activator transiently enhances blood-brain barrier permeability during cerebral ischemia through vascular endothelial growth factor-mediated endothelial endocytosis in mice

Recombinant tissue-type plasminogen activator (rt-PA) modulates cerebrovascular permeability and exacerbates brain injury in ischemic stroke, but its mechanisms remain unclear. We studied the involvement of vascular endothelial growth factor (VEGF)-mediated endocytosis in the increase of blood-brain barrier (BBB) permeability potentiated by rt-PA after ischemic stroke. The rt-PA treatment at 4 hours after middle cerebral artery occlusion induced a transient increase in BBB permeability after ischemic stroke in mice, which was suppressed by antagonists of either low-density lipoprotein receptor families (LDLRs) or VEGF receptor-2 (VEGFR-2). In immortalized bEnd.3 endothelial cells, rt-PA treatment upregulated VEGF expression and VEGFR-2 phosphorylation under ischemic conditions in an LDLR-dependent manner. In addition, rt-PA treatment increased endocytosis and transcellular transport in bEnd.3 monolayers under ischemic conditions, which were suppressed by the inhibition of LDLRs, VEGF, or VEGFR-2. The rt-PA treatment also increased the endocytosis of endothelial cells in the ischemic brain region after stroke in mice. These findings indicate that rt-PA increased BBB permeability via induction of VEGF, which at least partially mediates subsequent increase in endothelial endocytosis. Therefore, inhibition of VEGF induction may have beneficial effects after thrombolytic therapy with rt-PA treatment after stroke.

Tissue-type plasminogen activator triggers the synaptic vesicle cycle in cerebral cortical neurons

The active zone (AZ) is a thickening of the presynaptic membrane where exocytosis takes place. Chemical synapses contain neurotransmitter-loaded synaptic vesicles (SVs) that at rest are tethered away from the synaptic release site, but after the presynaptic inflow of Ca(+2) elicited by an action potential translocate to the AZ to release their neurotransmitter load. We report that tissue-type plasminogen activator (tPA) is stored outside the AZ of cerebral cortical neurons, either intermixed with small clear-core vesicles or in direct contact with the presynaptic membrane. We found that cerebral ischemia-induced release of neuronal tPA, or treatment with recombinant tPA, recruits the cytoskeletal protein βII-spectrin to the AZ and promotes the binding of SVs to βII-spectrin, enlarging the population of SVs in proximity to the synaptic release site. This effect does not require the generation of plasmin and is followed by the recruitment of voltage gated calcium channels (VGCC) to the presynaptic terminal that leads to Ca(+2)-dependent synapsin I phosphorylation, freeing SVs to translocate to the AZ to deliver their neurotransmitter load. Our studies indicate that tPA activates the SV cycle and induces the structural and functional changes in the synapse that are required for successful neurotransmission.

Benefits of Stroke Treatment Using a Mobile Stroke Unit Compared With Standard Management: The BEST-MSU Study Run-In Phase

BACKGROUND AND PURPOSE

Faster treatment with intravenous tissue-type plasminogen activator (tPA) is likely to improve outcomes. Optimizing prehospital triage by mobile stroke units (MSUs) may speed treatment times. The Benefits of Stroke Treatment Delivered Using a Mobile Stroke Unit (BEST-MSU) study was launched in May 2014 using the first MSU in the United States to compare stroke management using an MSU versus standard management (SM). Herein, we describe the results of the prespecified, nonrandomized run-in phase designed to obtain preliminary data on study logistics.

METHODS

The run-in phase consisted of 8 MSU weeks when all-patient care occurred on the MSU and 2 SM weeks when the MSU nurse met personnel on scene or at the emergency department to ensure comparability with MSU patients. Telemedicine was independently performed in 9 MSU cases.

RESULTS

Of 130 alerts, 24 MSU and 2 SM patients were enrolled. Twelve of 24 MSU patients received tPA on board; 4 were treated within 60 minutes of last seen normal, and 4 went on to endovascular treatment. There were no hemorrhagic complications. Four had primary intracerebral hemorrhage. Agreement on tPA eligibility between the onsite and telemedicine physician was 90%.

CONCLUSIONS

The run-in phase provided a tPA treatment rate of 1.5 patients per week, assured us that treatment within 60 minutes of onset is possible, and enabled enrollment of patients on SM weeks. We also recognized the opportunity to assess the effect of the MSU on endovascular treatment and intracerebral hemorrhage. Challenges include the need to control biased patient selection on MSU versus SM weeks and establish inter-rater agreement for tPA treatment using telemedicine.

Endovascular Therapy Is Effective and Safe for Patients With Severe Ischemic Stroke: Pooled Analysis of Interventional Management of Stroke III and Multicenter Randomized Clinical Trial of Endovascular Therapy for Acute Ischemic Stroke in the Netherlands Data

BACKGROUND AND PURPOSE

We assessed the effect of endovascular treatment in acute ischemic stroke patients with severe neurological deficit (National Institutes of Health Stroke Scale score, ≥20) after a prespecified analysis plan.

METHODS

The pooled analysis of the Interventional Management of Stroke III (IMS III) and Multicenter Randomized Clinical Trial of Endovascular Therapy for Acute Ischemic Stroke in the Netherlands (MR CLEAN) trials included participants with an National Institutes of Health Stroke Scale score of ≥20 before intravenous tissue-type plasminogen activator (tPA) treatment (IMS III) or randomization (MR CLEAN) who were treated with intravenous tPA ≤3 hours of stroke onset. Our hypothesis was that participants with severe stroke randomized to endovascular therapy after intravenous tPA would have improved 90-day outcome (distribution of modified Rankin Scale scores), when compared with those who received intravenous tPA alone.

RESULTS

Among 342 participants in the pooled analysis (194 from IMS III and 148 from MR CLEAN), an ordinal logistic regression model showed that the endovascular group had superior 90-day outcome compared with the intravenous tPA group (adjusted odds ratio, 1.78; 95% confidence interval, 1.20-2.66). In the logistic regression model of the dichotomous outcome (modified Rankin Scale score, 0-2, or functional independence), the endovascular group had superior outcomes (adjusted odds ratio, 1.97; 95% confidence interval, 1.09-3.56). Functional independence (modified Rankin Scale score, ≤2) at 90 days was 25% in the endovascular group when compared with 14% in the intravenous tPA group.

CONCLUSIONS

Endovascular therapy after intravenous tPA within 3 hours of symptom onset improves functional outcome at 90 days after severe ischemic stroke.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00359424 (IMS III) and ISRCTN10888758 (MR CLEAN).

Impacts of tissue-type plasminogen activator (tPA) on neuronal survival

Tissue-type plasminogen activator (tPA) a serine protease is constituted of five functional domains through which it interacts with different substrates, binding proteins, and receptors. In the last years, great interest has been given to the clinical relevance of targeting tPA in different diseases of the central nervous system, in particular stroke. Among its reported functions in the central nervous system, tPA displays both neurotrophic and neurotoxic effects. How can the protease mediate such opposite functions remain unclear but several hypotheses have been proposed. These include an influence of the degree of maturity and/or the type of neurons, of the level of tPA, of its origin (endogenous or exogenous) or of its form (single chain tPA versus two chain tPA). In this review, we will provide a synthetic snapshot of our current knowledge regarding the natural history of tPA and discuss how it sustains its pleiotropic functions with focus on excitotoxic/ischemic neuronal death and neuronal survival.

Combination Low-Dose Tissue-Type Plasminogen Activator Plus Annexin A2 for Improving Thrombolytic Stroke Therapy

Risk of hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and a short treatment time window comprises major challenges for tissue plasminogen activator (tPA) thrombolytic stroke therapy. Improving tPA therapy has become one of the highest priorities in the stroke field. This mini review article focuses on our recent efforts aimed at evaluating a novel combination approach of low-dose tPA plus recombinant annexin A2 (rA2, a tPA, and plasminogen co-receptor), which might enhance tPA thrombolytic efficacy, while reducing its associated complications related to intracerebral hemorrhagic transformation. Results of our experimental studies using a focal embolic stroke model in rats support the feasibility of the combination approach and suggest the potential for successful clinical translation.

Predictors of a Favorable Outcome after Recanalization in Patients with Cerebral Major Vessel Occlusion

BACKGROUND

Although tissue plasminogen activator and endovascular treatment were reported to be useful for recanalization in patients with major vessel occlusion (MVO), the outcome in some patients with recanalization was unfavorable. We could detect prolongation of the ipsilateral posterior cerebral artery (PCA) to the ischemic side on magnetic resonance angiography in some patients (ipsilateral-PCA sign). We investigated the predictors including radiological findings for a favorable outcome after successful recanalization.

METHODS

We included 76 patients with MVO of the anterior circulation and documented recanalization by treatment. We divided our patients into 2 groups: group F (modified Rankin scale [mRS] score = 0-2) and group UF (mRS score = 3-6). We compared biomarkers between the groups.

RESULTS

National Institutes of Health Stroke Scale (NIHSS) score before treatment in group F (8.5) was lower than that in group UF (16.0; P <.001). Sensitivity of the ipsilateral-PCA sign was commonly associated with group F (67.5% versus 19.4%, P <.001), and specificity of the sign was 80.6%. Absence of infarcts in the anterior cerebral artery (ACA) territory and ACA occlusion were also associated with a favorable outcome. In multivariate analysis, the ipsilateral-PCA sign and NIHSS score (≤ 10) were independent predictors of favorable outcome (odds ratio = 9.92, 95% confidence interval [CI] 2.71-36.23, P = .001; and odds ratio = 9.15, 95% CI 2.44-34.36, P = .001, respectively)

CONCLUSIONS

The ipsilateral-PCA sign and low NIHSS score (≤ 10) were predictors of a favorable outcome in patients with MVO and documented recanalization by treatments.

Effect of helicopter transport on neurological outcomes in a mouse model of embolic stroke with reperfusion: AIR-MICE pilot study

BACKGROUND

Patients often suffer a stroke at a significant distance from a center capable of delivering endovascular therapy, thus requiring rapid transport by helicopter emergency medical services while receiving a recombinant tissue plasminogen activator infusion that was initiated locally. But little is known about how a helicopter flight may impact the safety and efficacy of recombinant tissue plasminogen activator-induced reperfusion and patient outcomes.

AIM

To establish a new animal method to address with fidelity the safety and overall effect of helicopter emergency medical services during thrombolysis.

METHODS

Prospective randomized open blinded end-point study of an actual helicopter flight exposure. Adult C57BL/6 male mice were treated with a 10 mg/kg recombinant tissue plasminogen activator infusion two-hours after an embolic middle cerebral artery occlusion. Mice were randomized in pairs to simultaneously receive the infusion during a local helicopter flight or in a ground hangar.

RESULTS

Eighteen mice (nine pairs) were analyzed. The paired t-test analysis showed nonsignificant smaller infarction volumes in the helicopter-assigned animals (mean pair difference 33 mm(3) , P = 0·33). The amount of hemorrhagic transformation between the helicopter and ground groups was 4·08 vs. 4·56 μl, respectively (paired t-test, P = 0·45).

CONCLUSIONS

This study shows that helicopter emergency medical services do not have an inherent adverse effect on outcome in a mouse model of ischemic stroke with reperfusion. These results endorse the safety of the practice of using helicopter emergency medical services in stroke patients. The observed potential synergistic effect of helicopter-induced factors, such as vibration and changes in altitude, with reperfusion merits further exploration in animal experimental models and in stroke patients.

National Institutes of Health Stroke Scale Item Profiles as Predictor of Patient Outcome: External Validation on Safe Implementation of Thrombolysis in Stroke-Monitoring Study Data

BACKGROUND AND PURPOSE

National Institutes of Health Stroke Scale (NIHSS) item profiles that were recently proposed and validated may prove useful for clinical prognostication and research studies. We aimed to validate the NIHSS item profiles in hyper-acute stroke patients who received thrombolysis treatment (tissue-type plasminogen activator).

METHODS

We applied the latent class analysis probabilities of the profile membership generated from the derivation study onto NIHSS data from the Safe Implementation of Thrombolysis in Stroke-Monitoring Study (SITS-MOST). We separately considered NIHSS data collected within 3 hours and at ≈24 hours after stroke onset to obtain 2 sets of symptom groupings. The discrimination and calibration of both sets of symptom profiles were assessed from their association with outcomes. The outcome measures included modified Rankin Scale (mRS; using full distribution and dichotomized, mRS 0-1 or back to baseline) at day 90 and mortality by 90 days.

RESULTS

We obtained data for 6843 patients. Ordinal analysis of mRS showed odds of better outcome across the profiles, for each set of symptom profiles, adjusted for age, sex, and prestroke mRS. Dichotomized outcomes mirrored the ordinal findings. There were significant differences in prognostic discrimination ability for the dichotomized outcome measures between the 2 sets of symptom profiles, with the latter set (ie, 24-hour symptom profiles) performing better.

CONCLUSIONS

The NIHSS item profiles are individually associated with functional outcome and mortality in acute stroke patients treated with tissue-type plasminogen activator. Considering profiles of NIHSS subscores rather than only the total score is informative for prognostication, particularly for assessments collected 24 hours after stroke onset.

Relationships Between Imaging Assessments and Outcomes in Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Imaging findings can predict outcomes in patients with acute stroke. Relationships between imaging findings and clinical and imaging outcomes in patients randomized to intravenous tissue-type plasminogen activator-alone versus tissue-type plasminogen activator plus endovascular therapy (Solitaire device) in the Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke (SWIFT PRIME) study were assessed.

METHODS

We evaluated associations between imaging assessments (baseline mismatch profiles/ischemic core volumes and successful reperfusion) with imaging outcomes (27-hour infarct volume/growth) and clinical outcomes (modified Rankin Scale scores at 90 days). Imaging variables that predict favorable clinical outcomes were assessed in both univariate and multivariate models.

RESULTS

One hundred and ninety-five patients were included. Successful reperfusion and infarct volume (assessed at 27 hours) were powerful independent predictors of favorable clinical outcomes (modified Rankin Scale score of 0-2 at 90 days). Patients with the target mismatch profile at baseline had a higher rate of reperfusion, lesser infarct growth, smaller infarct volumes, and better clinical outcomes in the Solitaire plus tissue-type plasminogen activator (intervention) group than those in the tissue-type plasminogen activator-alone (control) group. Patients with larger mismatch volumes at baseline had a trend toward better treatment response in the intervention group than patients who had smaller (<50 mL) mismatch volumes.

CONCLUSIONS

Patients who achieved reperfusion had substantially more favorable clinical and imaging outcomes in both the intervention and the control groups. Infarct volume at 27 hours strongly correlated with clinical outcome at 90 days in both treatment groups. SWIFT PRIME patients with the target mismatch profile had a highly favorable response to endovascular therapy on both clinical and imaging outcomes. Both reperfusion and infarct volumes at 27 hours were powerful and independent predictors of 90-day clinical outcomes.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01657461.

Cost-Utility Analysis of Mechanical Thrombectomy Using Stent Retrievers in Acute Ischemic Stroke

Supplemental Digital Content is available in the text.

Recently, 5 randomized controlled trials demonstrated the benefit of endovascular therapy compared with intravenous tissue-type plasminogen activator in acute stroke. Economic evidence evaluating stent retrievers is limited. We compared the cost-effectiveness of intravenous tissue-type plasminogen activator alone versus mechanical thrombectomy and intravenous tissue-type plasminogen activator as a bridging therapy in eligible patients in the UK National Health Service.

Accuracy of the ABC/2 Score for Intracerebral Hemorrhage: Systematic Review and Analysis of MISTIE, CLEAR-IVH, and CLEAR III

BACKGROUND AND PURPOSE

The ABC/2 score estimates intracerebral hemorrhage (ICH) volume, yet validations have been limited by small samples and inappropriate outcome measures. We determined accuracy of the ABC/2 score calculated at a specialized reading center (RC-ABC) or local site (site-ABC) versus the reference-standard computed tomography-based planimetry (CTP).

METHODS

In Minimally Invasive Surgery Plus Recombinant Tissue-Type Plasminogen Activator for Intracerebral Hemorrhage Evacuation-II (MISTIE-II), Clot Lysis Evaluation of Accelerated Resolution of Intraventricular Hemorrhage (CLEAR-IVH) and CLEAR-III trials. ICH volume was prospectively calculated by CTP, RC-ABC, and site-ABC. Agreement between CTP and ABC/2 was defined as an absolute difference up to 5 mL and relative difference within 20%. Determinants of ABC/2 accuracy were assessed by logistic regression.

RESULTS

In 4369 scans from 507 patients, CTP was more strongly correlated with RC-ABC (r(2)=0.93) than with site-ABC (r(2)=0.87). Although RC-ABC overestimated CTP-based volume on average (RC-ABC, 15.2 cm(3); CTP, 12.7 cm3), agreement was reasonable when categorized into mild, moderate, and severe ICH (κ=0.75; P<0.001). This was consistent with overestimation of ICH volume in 6 of 8 previous studies. Agreement with CTP was greater for RC-ABC (84% within 5 mL; 48% of scans within 20%) than for site-ABC (81% within 5 mL; 41% within 20%). RC-ABC had moderate accuracy for detecting ≥5 mL change in CTP volume between consecutive scans (sensitivity, 0.76; specificity, 0.86) and was more accurate with smaller ICH, thalamic hemorrhage, and homogeneous clots.

CONCLUSIONS

ABC/2 scores at local or central sites are sufficiently accurate to categorize ICH volume and assess eligibility for the CLEAR-III and MISTIE III studies and moderately accurate for change in ICH volume. However, accuracy decreases with large, irregular, or lobar clots.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: MISTIE-II NCT00224770; CLEAR-III NCT00784134.

Low-Versus Standard-Dose Alteplase for Ischemic Strokes Within 4.5 Hours: A Comparative Effectiveness and Safety Study

BACKGROUND AND PURPOSE

The low-dose (0.6 mg/kg) alteplase strategy to treat acute ischemic stroke patients became widespread in East Asian countries, without rigorous testing against standard-dose (0.9 mg/kg) alteplase treatment. Our aim was to investigate the comparative effectiveness and safety of the low-dose versus standard-dose intravenous alteplase strategy.

METHODS

A total of 1526 acute ischemic stroke patients who qualified for intravenous alteplase and treated within 4.5 hours were identified from a prospective, multicenter, and nationwide stroke registry database. Primary outcomes were a modified Rankin scale score of 0 to 1 at 3 months after stroke and occurrence of symptomatic hemorrhagic transformation. Inverse probability of low-dose alteplase weighting by propensity scores was used to remove baseline imbalances between the 2 groups, and variation among centers were also accounted using generalized linear mixed models with a random intercept.

RESULTS

Low-dose intravenous alteplase was given to 450 patients (29.5%) and standard-dose intravenous alteplase to 1076 patients (70.5%). Low-dose alteplase treatment was comparable to standard-dose therapy according to the following adjusted outcomes and odds ratios (95% confidence intervals): modified Rankin scale score 0 to 1 at 3 months and 0.95 (0.68-1.32); modified Rankin scale 0 to 2 at 3 months and 0.84 (0.62-1.15); symptomatic hemorrhagic transformation and 1.05 (0.65-1.70); and 3-month mortality and 0.54 (0.35-0.83). The associations were unchanged when the analysis was limited to those without endovascular recanalization.

CONCLUSIONS

The low-dose alteplase strategy was comparable to the standard-dose treatment in terms of the effectiveness and safety.

Combined Approach to Lysis Utilizing Eptifibatide and Recombinant Tissue-Type Plasminogen Activator in Acute Ischemic Stroke-Full Dose Regimen Stroke Trial

BACKGROUND AND PURPOSE

The Combined Approach to Lysis Utilizing Eptifibatide and Recombinant Tissue-Type Plasminogen Activator (r-tPA; CLEAR) in Acute Ischemic Stroke (AIS) and CLEAR-Enhanced Regimen (CLEAR-ER) trials demonstrated safety of reduced dose r-tPA plus the glycoprotein 2b/3a inhibitor, eptifibatide, in AIS compared with r-tPA alone. The objective of the CLEAR-Full Dose Regimen (CLEAR-FDR) trial was to estimate the rate of symptomatic intracerebral hemorrhage (sICH) in AIS patients treated with the combination of full-dose r-tPA plus eptifibatide.

METHODS

CLEAR-FDR was a single-arm, prospective, open-label, multisite study. Patients aged 18 to 85 years treated with 0.9 mg/kg IV r-tPA within 3 hours of symptom onset were enrolled. After obtaining consent, eptifibatide (135 μg/kg bolus and 2-hour infusion at 0.75 μg/kg per minute) was administered. The primary end point was the proportion of patients who experienced sICH within 36 hours. An independent clinical monitor adjudicated if an sICH had occurred and an independent neuroradiologist reviewed all images. The stopping rule was 3 sICHs within the first 19 patients or 4 sICHs within 29 patients.

RESULTS

From October 2013 to December 2014, 27 patients with AIS were enrolled. Median age was 73 years (range, 34-85; interquartile range, 65-80) and median National Institute of Health stroke scale score was 12 (range, 6-26; interquartile range, 9-16). One sICH (3.7%; 95% confidence interval, 0.7%-18%) was observed.

CONCLUSIONS

These results demonstrate comparable safety of full-dose r-tPA plus eptifibatide with historical rates of sICH with r-tPA alone and support proceeding with a phase 3 trial evaluating full-dose r-tPA combined with eptifibatide to improve outcomes after AIS.

Cost-Effectiveness of Intra-Arterial Treatment as an Adjunct to Intravenous Tissue-Type Plasminogen Activator for Acute Ischemic Stroke

BACKGROUND AND PURPOSE

The objective of this study was to determine the cost-effectiveness of intra-arterial treatment within the 0- to 6-hour window after intravenous tissue-type plasminogen activator within 0- to 4.5-hour compared with intravenous tissue-type plasminogen activator alone, in the US setting and from a social perspective.

METHODS

A decision analytic model estimated the lifetime costs and outcomes associated with the additional benefit of intra-arterial therapy compared with standard treatment with intravenous tissue-type plasminogen activator alone. Model inputs were obtained from published literature, the Multicenter Randomized Clinical Trial of Endovascular Therapy for Acute Ischemic Stroke in the Netherlands (MR CLEAN) study, and claims databases in the United States. Health outcomes were measured in quality-adjusted life years (QALYs). Treatment benefit was assessed by calculating the cost per QALY gained. One-way and probabilistic sensitivity analyses were performed to estimate the overall uncertainty of model results.

RESULTS

The addition of intra-arterial therapy compared with standard treatment alone yielded a lifetime gain of 0.7 QALY for an additional cost of $9911, which resulted in a cost of $14 137 per QALY. Multivariable sensitivity analysis predicted cost-effectiveness (≤$50 000 per QALY) in 97.6% of simulation runs.

CONCLUSIONS

Intra-arterial treatment after intravenous tissue-type plasminogen activator for patients with anterior circulation strokes within the 6-hour window is likely cost-effective. From a societal perspective, increased investment in access to intra-arterial treatment for acute stroke may be justified.

Efficacy and mechanism of tanshinone IIA liquid nanoparticles in preventing experimental postoperative peritoneal adhesions in vivo and in vitro

Up to 90% of patients develop adhesion following laparotomy. Upregulating fibrinolysis within the peritoneum reduces adhesions. Tanshinone IIA (Tan IIA) promotes fibrinolysis in hepatic fibrosis and the cardiovascular system and may play a role in preventing adhesions. We report preparation and characterization of liquid nanoparticles of Tan IIA for intravenous administration and investigate its feasibility in clinical practice. Tan IIA liquid nanoparticles (Tan IIA-NPs) were prepared using the emulsion/solvent evaporation method. Adhesions were induced in Sprague–Dawley rats by injuring the parietal peritoneum and cecum, followed by intravenous administration of various Tan IIA-NP dosages. The adhesion scores for each group were collected 7 days after the initial laparotomy. The activity of tissue-type plasminogen activator (tPA) was measured from the peritoneal lavage fluid. The messenger RNA and protein expression levels of plasminogen activator inhibitor-1 (PAI-1) were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. TGF-β1 and collagen I expressions were measured immunohistochemically in the ischemic tissues. The effects of Tan IIA-NPs and free-Tan IIA on tPA and PAI-1 were measured in vitro in TGF-β1-induced HMrSV5 cells. Tan IIA-NPs exhibited small particle size, high encapsulation efficiency, good stability for storage, and safety for intravenous administration. Tan IIA-NPs were effective in preventing adhesion. Tan IIA-NPs increased tPA activity in peritoneal lavage fluid, and tPA mRNA and protein expression, and decreased PAI-1 mRNA and protein expression in the ischemic tissues. Moreover, Tan IIA-NPs decreased TGF-β1 and collagen I expressions in the ischemic tissues. Tan IIA-NPs administered via tail veins upregulated fibrinolysis in the peritoneum. In vitro studies showed that these effects may be mediated by the TGF-β signal pathway.

Altered plasma fibrin clot properties in essential thrombocythemia

Patients with increased thromboembolic risk tend to form denser fibrin clots which are relatively resistant to lysis. We sought to investigate whether essential thrombocythemia (ET) is associated with altered fibrin clot properties in plasma. Ex vivo plasma fibrin clot permeability coefficient (Ks), turbidimetry and clot lysis time (CLT) were measured in 43 consecutive patients with ET (platelet count from 245 to 991 × 10(3)/µL) and 50 control subjects matched for age, sex and comorbidities. Fibrinolysis proteins and inhibitors together with platelet activation markers were determined. Reduced Ks (-38%, p < 0.0001) and prolonged CLT (+34%, p < 0.0001) were observed in ET. The differences remained significant after adjustment for fibrinogen and platelet count. ET was associated with a slightly shorter lag phase (-5%, p = 0.01) and higher maximum absorbency of the turbidimetric curve (+6%, p < 0.001). The ET patients had higher plasma P-selectin by 193% (p < 0.00001) and platelet factor 4 (PF4) by 173% (p < 0.00001), with higher P-selectin observed in 19 (44%) patients with JAK-2 gene V617F mutation. Higher t-PA (+20%, p < 0.001), 23% higher plasminogen activator inhibitor-1, PAI-1 (+23%, p < 0.01) and unaltered thrombin-activatable fibrinolysis inhibitor, plasminogen and α2-antiplasmin activity were found in the ET group. Ks inversely correlated with fibrinogen, PF4 and C-reactive protein. CLT positively correlated only with PAI-1. Patients with ET display prothrombotic plasma fibrin clot phenotype including impaired fibrinolysis, which represents a new prothrombotic mechanism in this disease.

Tissue-type plasminogen activator-binding RNA aptamers inhibiting low-density lipoprotein receptor family-mediated internalisation

Recombinant tissue-type plasminogen activator (tPA, trade name Alteplase), currently the only drug approved by the US Food and Drug Administration and the European Medicines Agency for the treatment of cerebral ischaemic stroke, has been implicated in a number of adverse effects reportedly mediated by interactions with the low-density lipoprotein (LDL) family receptors, including neuronal cell death and an increased risk of cerebral haemorrhage. The tissue-type plasminogen activator is the principal initiator of thrombolysis in human physiology, an effect that is mediated directly via localised activation of the plasmin zymogen plasminogen at the surface of fibrin clots in the vascular lumen. Here, we sought to identify a ligand to tPA capable of inhibiting the relevant LDL family receptors without interfering with the fibrinolytic activity of tPA. Systematic evolution of ligands by exponential enrichment (SELEX) was employed to isolate tPA-binding RNA aptamers, which were characterised in biochemical assays of tPA association to low density lipoprotein receptor-related protein-1 (LRP-1, an LDL receptor family member); tPA-mediated in vitro and ex vivo clot lysis; and tPA-mediated plasminogen activation in the absence and presence of a stimulating soluble fibrin fragment. Two aptamers, K18 and K32, had minimal effects on clot lysis, but were able to efficiently inhibit tPA-LRP-1 association and LDL receptor family-mediated endocytosis in human vascular endothelial cells and astrocytes. These observations suggest that coadministration alongside tPA may be a viable strategy to improve the safety of thrombolytic treatment of cerebral ischaemic stroke by restricting tPA activity to the vascular lumen.

Normobaric hyperoxia slows blood-brain barrier damage and expands the therapeutic time window for tissue-type plasminogen activator treatment in cerebral ischemia

BACKGROUND AND PURPOSE

Prolonged ischemia causes blood-brain barrier (BBB) damage and increases the incidence of neurovasculature complications secondary to reperfusion. Therefore, targeting ischemic BBB damage pathogenesis is critical to reducing neurovasculature complications and expanding the therapeutic time window of tissue-type plasminogen activator (tPA) thrombolysis. This study investigates whether increasing cerebral tissue PO2 through normobaric hyperoxia (NBO) treatment will slow the progression of BBB damage and, thus, improve the outcome of delayed tPA treatment after cerebral ischemia.

METHODS

Rats were exposed to NBO (100% O2) or normoxia (21% O2) during 3-, 5-, or, 7-hour middle cerebral artery occlusion. Fifteen minutes before reperfusion, tPA was continuously infused to rats for 30 minutes. Neurological score, mortality rate, and BBB permeability were determined. Matrix metalloproteinase-9 was measured by gelatin zymography and tight junction proteins (occludin and cluadin-5) by Western blot in the isolated cerebral microvessels.

RESULTS

NBO slowed the progression of ischemic BBB damage pathogenesis, evidenced by reduced Evan blue leakage, smaller edema, and hemorrhagic volume in NBO-treated rats. NBO treatment reduced matrix metalloproteinase-9 induction and the loss of tight junction proteins in ischemic cerebral microvessels. NBO-afforded BBB protection was maintained during tPA reperfusion, resulting in improved neurological functions, significant reductions in brain edema, hemorrhagic volume, and mortality rate, even when tPA was given after prolonged ischemia (7 hours).

CONCLUSIONS

Early NBO treatment slows ischemic BBB damage pathogenesis and significantly improves the outcome of delayed tPA treatment, providing new evidence supporting NBO as an effective adjunctive therapy to extend the time window of tPA thrombolysis for ischemic stroke.

Safety of intravenous thrombolysis in stroke mimics: prospective 5-year study and comprehensive meta-analysis

BACKGROUND AND PURPOSE

Shortening door-to-needle time may lead to inadvertent intravenous thrombolysis (IVT) administration in stroke mimics (SMs). We sought to determine the safety of IVT in SMs using prospective, single-center data and by conducting a comprehensive meta-analysis of reported case-series.

METHODS

We prospectively analyzed consecutive IVT-treated patients during a 5-year period at a tertiary care stroke center. A systematic review and meta-analysis of case-series reporting safety of IVT in SMs and confirmed acute ischemic stroke were conducted. Symptomatic intracerebral hemorrhage was defined as imaging evidence of ICH with an National Institutes of Health Stroke scale increase of ≥4 points. Favorable functional outcome at hospital discharge was defined as a modified Rankin Scale score of 0 to 1.

RESULTS

Of 516 consecutive IVT patients at our tertiary care center (50% men; mean age, 60±14 years; median National Institutes of Health Stroke scale, 11; range, 3-22), SMs comprised 75 cases. Symptomatic intracerebral hemorrhage occurred in 1 patient, whereas we documented no cases of orolingual edema or major extracranial hemorrhagic complications. In meta-analysis of 9 studies (8942 IVT-treated patients), the pooled rates of symptomatic intracerebral hemorrhage and orolingual edema among 392 patients with SM treated with IVT were 0.5% (95% confidence interval, 0%-2%) and 0.3% (95% confidence interval, 0%-2%), respectively. Patients with SM were found to have a significantly lower risk for symptomatic intracerebral hemorrhage compared with patients with acute ischemic stroke (risk ratio=0.33; 95% confidence interval, 0.14-0.77; P=0.010), with no evidence of heterogeneity or publication bias. Favorable functional outcome was almost 3-fold higher in patients with SM in comparison with patients with acute ischemic stroke (risk ratio=2.78; 95% confidence interval, 2.07-3.73; P<0.00001).

CONCLUSIONS

Our prospective, single-center experience coupled with the findings of the comprehensive meta-analysis underscores the safety of IVT in SM.

Tissue plasminogen activator-independent roles of neuroserpin in the central nervous system

A number of studies have confirmed the existence of tissue-type plasminogen activator-independent roles of neuroserpin, a member of the serine protease inhibitor superfamily. In this review article, we aim to clarify this role. These unique roles of neuroserpin are involved in its neuroprotective effect during ischemic brain injury, its regulation of tumorigenesis, and the mediation of emotion and cognition through the inhibition of urokinase-type plasminogen activator and fibrinolysin, modification of Th cells, reducing plaque formation, promoting process growth and intracellular adhesion, and altering the expression of cadherin and nuclear factor kappa B.

To treat or not to treat? Pilot survey for minor and rapidly improving stroke

BACKGROUND AND PURPOSE

Minor strokes and rapidly improving stroke symptoms are frequent exclusions for intravenous tissue-type plasminogen activator. We explored factors influencing tissue-type plasminogen activator treatment decision for minor strokes/rapidly improving stroke symptoms.

METHODS

A pilot survey, including 110 case scenarios, was completed by 17 clinicians from 2 academic medical centers. Respondents were asked whether they would treat each case with tissue-type plasminogen activator at 60 minutes after emergency department admission. Cases varied by (1) National Institutes of Health Stroke Scale score at treatment decision time, (2) symptom pattern over time (improvement or worsening and then improving), (3) type of neurological deficit (3 main domains: motor, visual/sensory/ataxia, and language/neglect), and (4) age/occupation (4 profiles). Logistic regression was used to predict probability of omission (pO). A binomial regression model was used to predict probability of treatment decision.

RESULTS

Predicted probability of treatment decision was affected by National Institutes of Health Stroke Scale score (P<0.001) and age/occupation profiles (P<0.001) but not by symptom patterns (P=0.334). There were significant, albeit modest, main effects on probability of treatment decision for neurological domains. Responses were most likely omitted (P=0.027) for cases improvement pattern and language/neglect domain (pO=0.74; 95% confidence interval, 0.52-0.89) and with visual/sensory/ataxia domain (pO=0.74; confidence interval, 0.37-0.93) when compared with improvement pattern and motor domain (pO=0.17; confidence interval, 0.06-0.42) and to any worsening and then improving patterns (0.37<pO<0.56).

CONCLUSIONS

This pilot survey provides the first quantitative evidence that National Institutes of Health Stroke Scale score is not the only determinant of treatment decision. A National Institutes of Health Stroke Scale score of 2 is the potential equipoise point, with the least consensus on treatment decision. These preliminary findings require validation in larger population surveys.

Recombinant tissue-type plasminogen activator plus eptifibatide versus recombinant tissue-type plasminogen activator alone in acute ischemic stroke: propensity score-matched post hoc analysis

BACKGROUND AND PURPOSE

The Combined Approach to Lysis Utilizing Eptifibatide and rt-PA in Acute Ischemic Stroke-Enhanced Regimen (CLEAR-ER) trial demonstrated safety of recombinant tissue-type plasminogen activator (r-tPA) plus eptifibatide in acute ischemic stroke (AIS). CLEAR-ER randomized AIS patients (5:1) to 0.6 mg/kg r-tPA plus eptifibatide versus standard r-tPA (0.9 mg/kg). Interventional Management of Stroke III randomized AIS patients to r-tPA plus endovascular therapy versus standard r-tPA. Albumin in Acute Stroke Part 2 randomized patients to albumin±r-tPA versus saline±r-tPA. Our aim was to compare outcomes in CLEAR-ER combination arm patients to propensity score-matched r-tPA only subjects in Albumin in Acute Stroke Part 2 and Interventional Management of Stroke III.

METHODS

The primary outcome was 90-day severity-adjusted modified Rankin score (mRS) dichotomization based on baseline National Institutes of Health Stroke Scale. Secondary outcomes were 90-day mRS dichotomization as excellent (mRS, 0-1); mRS dichotomization as favorable (mRS, 0-2); and nonparametric analysis of the ordinal mRS.

RESULTS

Eighty-five combination arm CLEAR-ER subjects were matched with 169 Albumin in Acute Stroke Part 2 and Interventional Management of Stroke III trials' r-tPA only patients (controls). Median age in CLEAR-ER and control subjects was 68years; median National Institutes of Health Stroke Scale in the CLEAR-ER subjects was 11 and in control subjects 12. At 90 days, CLEAR-ER subjects had a nonsignificantly greater proportion of patients with favorable outcomes (45% versus 36%; unadjusted relative risks, 1.24; 95% confidence intervals, 0.91-1.69; P=0.18). Secondary outcomes were 52% versus 34% excellent outcomes (relative risks, 1.51; 95% confidence intervals, 1.13-2.02; P=0.007); 60% versus 53% favorable outcome (relative risks, 1.13; 95% confidence intervals, 0.90-1.41; P=0.31); and ordinal Cochran-Mantel-Haenszel P=0.10.

CONCLUSION

r-tPA plus eptifibatide showed a favorable direction of effect that was consistent across multiple approaches for AIS outcome evaluation. A phase III trial to establish the efficacy of r-tPA plus eptifibatide for improving AIS outcomes is warranted.

NURR1 involvement in recombinant tissue-type plasminogen activator treatment complications after ischemic stroke

BACKGROUND AND PURPOSE

Despite the effectiveness of recombinant tissue-type plasminogen activator (r-tPA) during the acute phase of ischemic stroke, the therapy remains limited by a narrow time window and the occurrence of occasional vascular side effects, particularly symptomatic hemorrhages. Our aim was to investigate the mechanisms underlying the endothelial damage resulting from r-tPA treatment in ischemic-like conditions.

METHODS

Microarray analyses were performed on cerebral endothelial cells submitted to r-tPA treatment during oxygen and glucose deprivation to identify novel biomarker candidates. Validation was then performed in vivo in a mouse model of thromboembolic stroke and culminated in an analysis in a clinical cohort of patients with ischemic stroke treated with thrombolysis.

RESULTS

The transcription factor NURR1 (NR4A2) was identified as a downstream target induced by r-tPA during oxygen and glucose deprivation. Silencing NURR1 expression reversed the endothelial-toxicity induced by the combined stimuli, a protective effect attributable to reduced levels of proinflammatory mediators, such as nuclear factor-kappa-beta 2 (NF-κ-B2), interleukin 1 alpha (IL1α), intercellular adhesion molecule 1 (ICAM1), SMAD family member 3 (SMAD3), colony stimulating factor 2 (granulocyte-macrophage; CSF2). The detrimental effect of delayed thrombolysis, in conditions in which NURR1 gene expression was enhanced, was confirmed in the preclinical stroke model. Finally, we determined that patients with stroke who had a symptomatic hemorrhagic transformation after r-tPA treatment exhibited higher baseline serum NURR1 levels than did patients with an asymptomatic or absence of cerebral bleedings.

CONCLUSIONS

Our results suggest that NURR1 upregulation by r-tPA during ischemic stroke is associated with endothelial dysfunction and inflammation and the enhancement of hemorrhagic complications associated to thrombolysis.

Initial body temperature in ischemic stroke: nonpotentiation of tissue-type plasminogen activator benefit and inverse association with severity

BACKGROUND AND PURPOSE

Body temperature (BT) is an important physiological factor in acute ischemic stroke. However, the relationship of initial BT to stroke severity and degree of benefit from thrombolytic therapy has been delineated incompletely.

METHODS

We analyzed the public data set of the 2 National Institute of Neurological Disorders and Stroke Tissue-Type Plasminogen Activator (tPA) stroke trials, comparing patients with lower (<37.0°C) and higher (≥37.0°C) presenting BT.

RESULTS

Among 595 patients (297 placebo and 298 tPA treated) with documented initial BT, 77.1% had initial BT <37.0°C and 22.9% ≥37.0°C. Patients with higher initial BT had lower baseline stroke severity in both tPA-treated patients (the National Institute of Health Stroke Scale median, 11 versus 15; P=0.05) and placebo-treated patients (median, 13 versus 16; P<0.01). Patients with higher initial BT also had lower infarction volume on computed tomography at 3 months in both tPA-treated patients (median, 9.6 versus 16.7 cm(3); P=0.08) and placebo-treated patients (median, 13.1 versus 28.1 cm(3); P=0.02), but no clinical outcome differences. Analysis of lytic treatment effect found no heterogeneity in the degree of tPA benefit in both higher and lower BT groups (≥37.0°C: odds ratio for the modified Rankin Scale 0-1 outcome, 2.55; 95% confidence interval, 1.05-6.21 and <37.0°C: odds ratio, 2.30; 95% confidence interval, 1.38-3.84; heterogeneity P=0.83).

CONCLUSIONS

In patients with hyperacute stroke, higher presenting temperatures are associated with less severe neurological deficits and reduced final infarct volumes. Presenting temperature does not modify the benefit of tPA on 3-month favorable outcome.

Sensitivity of diffusion- and perfusion-weighted imaging for diagnosing acute ischemic stroke is 97.5%

BACKGROUND AND PURPOSE

MRI using diffusion-weighted imaging (DWI) is the most sensitive diagnostic imaging modality for early detection of ischemia, but how accurate is it and how much does perfusion-weighted imaging (PWI) add to the sensitivity have to be known.

METHODS

In this single-center study, we collected epidemiological, imaging, and outcome data on all patients with stroke undergoing MRI-based treatment with intravenous tissue-type plasminogen activator at our center from 2004 to 2010. The DWI negative patients were identified, and we calculated the sensitivity and specificity of DWI and additional PWI for diagnosing acute ischemic stroke. We compared DWI positive and negative patients to identify characteristics associated with DWI negativity.

RESULTS

Five hundred sixty-nine consecutive patients were treated with intravenous tissue-type plasminogen activator on the basis of an acute MRI. A DWI lesion was evident in 518 patients. Forty-seven patients were DWI negative; however, a relevant PWI lesion was found in 33 of these patients. Four stroke mimics were treated with intravenous tissue-type plasminogen activator and 1 of these patients had a DWI lesion. Thus, 8% of all patients with stroke were DWI negative. The combination of DWI and PWI resulted in a sensitivity of 97.5% for the ischemic stroke diagnosis. DWI negativity was associated with less severe strokes, location in the posterior circulation, a longer time from onset to scan, and an improved 90-day outcome. The cause of small-vessel disease was more likely to be DWI negative.

CONCLUSIONS

The combination of DWI and PWI before intravenous tissue-type plasminogen activator confirms the diagnosis in 97.5% of all ischemic strokes.

Evolution of practice during the Interventional Management of Stroke III Trial and implications for ongoing trials

BACKGROUND AND PURPOSE

We explored changes in the patient population and practice of endovascular therapy during the course of the Interventional Management of Stroke (IMS) III Trial.

METHODS

Changes in baseline characteristics, use of baseline CT angiography, treatment times and specifics, and outcomes were compared between the first 4 protocols and the fifth and final protocol.

RESULTS

Compared with subjects treated in the first 4 protocol versions (n=610), subjects treated in fifth and final protocol (n=46) were older (75 versus 68 years, P<0.0002) and less likely to have a pretreatment Rankin of 0 (76% versus 89%, P=0.01), were more likely to have a pretreatment CT angiography (65% versus 45%, P=0.009), had quicker median times in the endovascular arm from onset to start of intra-arterial therapy (209 versus 250 minutes, P=0.002) and to reperfusion (269 versus 344 minutes, P<0.0001), had a higher mean dose of total tissue-type plasminogen activator in the endovascular arm (74.0 versus 63.7 mg, P<0.0001), and were less likely to receive intra-arterial tissue-type plasminogen activator as part of the endovascular procedure (16% versus 44%, P=0.015). There were no significant differences in functional and safety outcomes between subjects treated in the 2 treatments arms in either the first 4 protocols or fifth protocol although the small sample size in the fifth protocol provided limited power.

CONCLUSIONS

Endovascular technology and diagnostic approaches to acute stroke patients changed substantially during the IMS III Trial. Efforts to decrease the time to delivery of endovascular therapy were successful.

Microvascular thrombosis, fibrinolysis, ischemic injury, and death after cerebral thromboembolism are affected by levels of circulating α2-antiplasmin

OBJECTIVE

Ischemic stroke is primarily attributable to thrombotic vascular occlusion. Elevated α2-antiplasmin (a2AP) levels correlate with increased stroke risk, but whether a2AP contributes to the pathogenesis of stroke is unknown. We examined how a2AP affects thrombosis, ischemic brain injury, and survival after experimental cerebral thromboembolism.

APPROACH AND RESULTS

We evaluated the effects of a2AP on stroke outcomes in mice with increased, normal, or no circulating a2AP, as well as in mice given an a2AP-inactivating antibody. Higher a2AP levels were correlated with greater ischemic brain injury (rs=0.88, P<0.001), brain swelling (rs=0.82, P<0.001), and reduced middle cerebral artery thrombus dissolution (rs=-0.93, P<0.001). In contrast, a2AP deficiency enhanced thrombus dissolution, increased cerebral blood flow, reduced brain infarction, and decreased brain swelling. By comparison to tissue plasminogen activator (TPA), a2AP inactivation hours after thromboembolism still reduced brain infarction (P<0.001) and hemorrhage (P<0.05). Microvascular thrombosis, a process that enhances brain ischemia, was markedly reduced in a2AP-deficient or a2AP-inactivated mice compared with TPA-treated mice or mice with increased a2AP levels (all P<0.001). Matrix metalloproteinase-9 expression, which contributes to acute brain injury, was profoundly decreased in a2AP-deficient or a2AP-inactivated mice versus TPA-treated mice or mice with increased a2AP levels (all P<0.001). a2AP inactivation markedly reduced stroke mortality versus TPA (P<0.0001).

CONCLUSIONS

a2AP has profound, dose-related effects on ischemic brain injury, swelling, hemorrhage, and survival after cerebral thromboembolism. By comparison to TPA, the protective effects of a2AP deficiency or inactivation seem to be mediated through reductions in microvascular thrombosis and matrix metalloproteinase-9 expression.

Acute ischemic stroke and long-term outcome after thrombolysis: nationwide propensity score-matched follow-up study

BACKGROUND AND PURPOSE

Data on long-term outcome after intravenous tissue-type plasminogen activator (tPA) in ischemic stroke are limited. We examined the risk of long-term mortality, recurrent ischemic stroke, and major bleeding, including intracranial and gastrointestinal bleeding, in intravenous tPA-treated patients when compared with intravenous tPA eligible but nontreated patients with ischemic stroke.

METHODS

We conducted a register-based nationwide propensity score-matched follow-up study among patients with ischemic stroke in Denmark (2004-2011). Cox regression analysis was used to compute adjusted hazard ratios for all outcomes.

RESULTS

Among 4292 ischemic strokes (2146 intravenous tPA-treated and 2146 propensity score-matched nonintravenous tPA-treated patients), with a follow-up for a median of 1.4 years, treatment with intravenous tPA was associated with a lower risk of long-term mortality (adjusted hazard ratio, 0.66; 95% confidence interval, 0.49-0.88). The long-term risk of recurrent ischemic stroke (adjusted hazard ratio, 1.05; 95% confidence interval, 0.68-1.64) and major bleeding (adjusted hazard ratio, 0.59; 95% confidence interval, 0.24-1.47) did not differ significantly between the intravenous tPA-treated and nontreated patients.

CONCLUSIONS

Treatment with intravenous tPA in patients with ischemic stroke was associated with improved long-term survival.

Influence of dietary saturated fat intake on endothelial fibrinolytic capacity in adults

Approximately 50% of middle-aged and older adults in the United States regularly consume a diet high in saturated fat. High dietary saturated fat intake has been linked to promote atherothrombotic vascular disease. We tested the hypothesis that endothelial fibrinolytic function is diminished in middle-aged and older adults who habitually consume a diet high in saturated fat. Twenty-four healthy, sedentary middle-aged, and older adults (54 to 71 years) were studied: 10 (8 men and 2 women) with a dietary saturated fat intake <10% (lower saturated fat) of total calories and 14 (9 men and 5 women) with a dietary saturated fat intake ≥10% of total calories (high saturated fat). Net endothelial release of tissue-type plasminogen activator (t-PA), the primary activator of fibrinolysis, was determined, in vivo, in response to intrabrachial infusions of bradykinin (12.5 to 50.0 ng/100 ml tissue/min) and sodium nitroprusside (1.0 to 4.0 μg/100 ml tissue/min). Capacity of the endothelium to release t-PA in response to bradykinin was ∼30% less (p <0.05) in the high (from -0.7 ± 0.6 to 36.9 ± 3.3 ng/100 ml tissue/min) compared with the lower (from -0.3 ± 0.3 to 53.4 ± 7.8 ng/100 ml tissue/min) dietary saturated fat group. Moreover, total amount of t-PA released was significantly less (∼30%) (201 ± 22 vs 274 ± 29 ng/100 ml tissue) in the adults who reported consuming a diet high in saturated fat. These results indicate that the capacity of the endothelium to release t-PA is lower in middle-aged and older adults who habitually consume a diet high in saturated fat. In conclusion, endothelial fibrinolytic dysfunction may underlie the increased atherothrombotic disease risk with a diet high in saturated fat.

Geographic access to acute stroke care in the United States

BACKGROUND AND PURPOSE

Only 3% to 5% of patients with acute ischemic stroke receive intravenous recombinant tissue-type plasminogen activator (r-tPA) and <1% receive endovascular therapy. We describe access of the US population to all facilities that actually provide intravenous r-tPA or endovascular therapy for acute ischemic stroke.

METHODS

We used US demographic data and intravenous r-tPA and endovascular therapy rates in the 2011 US Medicare Provider and Analysis Review data set. International Classification of Diseases-Ninth Revision codes 433.xx, 434.xx and 436 identified acute ischemic stroke cases. International Classification of Diseases-Ninth Revision code 99.10 defined intravenous r-tPA treatment and International Classification of Diseases-Ninth Revision code 39.74 defined endovascular therapy. We estimated ambulance response times using arc-Geographic Information System's network analyst and helicopter transport times using validated models. Population access to care was determined by summing the population contained within travel sheds that could reach capable hospitals within 60 and 120 minutes.

RESULTS

Of 370,351 acute ischemic stroke primary diagnosis discharges, 14,926 (4%) received intravenous r-tPA and 1889 (0.5%) had endovascular therapy. By ground, 81% of the US population had access to intravenous-capable hospitals within 60 minutes and 56% had access to endovascular-capable hospitals. By air, 97% had access to intravenous-capable hospitals within 60 minutes and 85% had access to endovascular hospitals. Within 120 minutes, 99% of the population had access to both intravenous and endovascular hospitals.

CONCLUSIONS

More than half of the US population has geographic access to hospitals that actually deliver acute stroke care but treatment rates remain low. These data provide a national perspective on acute stroke care and should inform the planning and optimization of stroke systems in the United States.

Impact of time to treatment on tissue-type plasminogen activator-induced recanalization in acute ischemic stroke

BACKGROUND AND PURPOSE

Although tissue-type plasminogen activator (tPA) efficacy depends on time, it is unknown whether its effect on recanalization is time dependent. Information about likelihood of successful recanalization as a function of time to treatment may improve patient selection for advanced reperfusion strategies. We aimed to identify the impact of time to treatment on tPA-induced recanalization in patients with acute ischemic stroke.

METHODS

Consecutive patients with intracranial acute occlusion treated with intravenous tPA underwent transcranial Doppler examination before and 1 hour after tPA administration. Patients were categorized according to occlusion localization in proximal and distal occlusion. Sequential analysis of recanalization according to time to treatment was performed for every 30-minute cutoff point.

RESULTS

Overall (n=508), 54.3% had proximal and 45.7% had distal occlusion. Median time to treatment was 171.4±61.9 minutes, and 5.9% were treated >270 minutes. Recanalization occurred in 36.1% of patients. There was no linear association between time to treatment and time to recanalization, but sequential analysis showed that patients treated >270 minutes had a lower recanalization rate. Lower National Institutes of Health Stroke Scale score on admission (odds ratio [OR], 0.305; 95% confidence interval [CI], 0.1-0.933) and time to treatment ≤270 minutes (OR, 0.995; 95% CI, 0.99-0.999) emerged as independent predictors of recanalization. In patients with proximal occlusion, 41.8% recanalized. Time to treatment >90 minutes was associated with lower recanalization rate. However, only younger age (OR, 0.975; 95% CI, 0.952-0.999) and lower baseline National Institutes of Health Stroke Scale score (OR, 0.921; 95% CI, 0.855-0.993) independently predicted recanalization. In distal occlusion patients, male sex was the only independent predictor of recanalization (OR, 0.416; 95% CI, 0.195-0.887). None recanalized >270 minutes.

CONCLUSIONS

The effect of tPA on recanalization may decrease over time. Treatment >270 minutes predicted lack of recanalization, especially in distal occlusions.

Thrombolysis in ischemic stroke without arterial occlusion at presentation

BACKGROUND AND PURPOSE

None of the randomized trials of intravenous tissue-type plasminogen activator reported vascular imaging acquired before thrombolysis. Efficacy of tissue-type plasminogen activator in stroke without arterial occlusion on vascular imaging remains unknown and speculative.

METHODS

We performed a retrospective, multicenter study to collect data of patients who presented to participating centers during a 5-year period with ischemic stroke diagnosed by clinical examination and MRI and with imaging evidence of no vascular occlusion. These patients were divided into 2 groups: those who received thrombolytic therapy and those who did not. Primary outcome measure of the study was excellent clinical outcome defined as modified Rankin Scale of 0 to 1 at 90 days from stroke onset. Secondary outcome measures were good clinical outcome (modified Rankin Scale, 0-2) and perfect outcome (modified Rankin Scale, 0). Safety outcome measures were incidence of symptomatic intracerebral hemorrhage and poor outcome (modified Rankin Scale, 4-6).

RESULTS

A total of 256 patients met study criteria, 103 with thrombolysis and 153 without. Logistic regression analysis showed that patients who received thrombolysis had more frequent excellent outcomes with odds ratio of 3.79 (P<0.01). Symptomatic intracerebral hemorrhage was more frequent in thrombolysis group (4.9 versus 0.7%; P=0.04). Thrombolysis led to more frequent excellent outcome in nonlacunar group with odds ratio 4.90 (P<0.01) and more frequent perfect outcome in lacunar group with odds ratio 8.25 (P<0.01).

CONCLUSIONS

This study provides crucial data that patients with ischemic stroke who do not have visible arterial occlusion at presentation may benefit from thrombolysis.