Ancrod for the treatment of acute ischemic brain infarction. The Ancrod Stroke Study Investigators

Defibrinogen Therapy for Acute Ischemic Stroke: 1332 Consecutive Cases

This study aimed to examine the effectiveness of defibrinogen therapy on functional recovery and safety among 1332 consecutive ischemic stroke patients who had not received intravenous thrombolysis with recombinant tissue plasminogen activator. Stroke patients undergoing conservative and relatively individualized multiple-day dosing regimens of defibrinogen therapy between January 1, 2008 and May 30, 2016 were enrolled. Data were analyzed according to functional success (Barthel Index of 95 or 100, mRS of 0 or 1) and safety variables (intracranial hemorrhage, mortality and stroke recurrence). At 12 months, 18.62% (203/1087) of patients were lost to follow-up. The functional success rates were 39.84% (526/1320) and 42.23% (459/1087) as assessed by BI at 3 months and 12 months, respectively. Fifteen patients had asymptomatic intracranial hemorrhage within 24 hours after the initial defibrase administration. During the 14 days after hospitalization, 12 patients were diagnosed with symptomatic intracranial hemorrhage (sICH) and a total of 12 patients died from all causes. At 3 months, 56 patients were dead and 21 patients had recurrent stroke. The percentage of death and recurrence of stroke at 12 months were 6.81% and 3.22%, respectively. Results from the historical control showed no significant differences of functional success were detected between the patients treated with rt-PA within 6 hours of stroke onset in NINDS II and the patients treated with defibrase within 6 hours after stroke in the present study. The multiple-day dosing regimen of defibrinogen therapy using defibrase applied in the present study could achieve functional improvement among acute ischemic stroke patients, with low risks of mortality when compared with other similar studies. However, the efficacy and safety of such a defibrinogenating therapy is needed to be verified by RCTs with large sample size.

[Intravenous thrombolysis in ischemic stroke: Therapeutic perspectives]

New therapeutic strategies are under evaluation to improve the treatment of acute ischemic stroke (AIS). Approaches combining intravenous (IV) thrombolysis with recombinant tissue plasminogen activator (rt-PA) and antithrombotic agents are currently evaluated. The combination of IV rt-PA and aspirin showed a high rate of intracranial hemorrhage whereas the association of rt-PA and eptifibatide seems more promising. The results of recent studies evaluating the administration of eptifibatide or argatroban in conjunction with conventional IV thrombolysis with rt-PA are expected to clarify the safety and efficacy of these treatments. More fibrin-specific plasminogen activators, tenecteplase and desmoteplase, are also investigated. These fibrinolytic agents showed a favorable safety profile but their efficacy in AIS remains uncertain. While phase III studies, DIAS-3 and DIAS-4, evaluating IV desmoteplase up to nine hours after stroke onset did not meet the primary endpoint, the results of studies comparing IV tenecteplase and IV rt-PA are expected.

Pharmacological and genetic depletion of fibrinogen protects from kidney fibrosis

Fibrinogen (Fg) has been implicated in the pathogenesis of several fibrotic disorders by acting as a profibrotic ligand for a variety of cellular surface receptors and by modulating the provisional fibrin matrix formed after injury. We demonstrated increased renal Fg expression after unilateral ureteral obstruction and folic acid (FA) nephropathy in mice, respectively. Urinary Fg excretion was also increased in FA nephropathy. Using in vitro and in vivo approaches, our results suggested that IL-6 mediates STAT3 activation in kidney fibrosis and that phosphorylated (p)STAT3 binds to Fgα, Fgβ, and Fgγ promoters in the kidney to regulate their transcription. Genetically modified Fg heterozygous mice (∼75% of normal plasma Fg levels) exhibited only 3% kidney interstitial fibrosis and tubular atrophy after FA nephropathy compared with 24% for wild-type mice. Fibrinogenolysis through Ancrod administration after FA reduced interstitial fibrosis more than threefold compared with vehicle-treated control mice. Mechanistically, we show that Fg acts synergistically with transforming growth factor (TGF)-β1 to induce fibroblast proliferation and activates TGF-β1/pSMAD2 signaling. This study offers increased understanding of Fg expression and molecular interactions with TGF-β1 in the progression to kidney fibrosis and, importantly, indicates that fibrinogenolytics like Ancrod present a treatment opportunity for a yet intractable disease.

Intravenous tenecteplase in acute ischemic stroke: an updated review

Tenecteplase in a genetically engineered variant of alteplase. Although the two have the same mechanism of action, tenecteplase has properties that makes it a seemingly more advantageous thrombolytic. Because of its rapid single-bolus administration, its use is favored over alteplase in the treatment of acute myocardial infarction. Over the past few years, several clinical studies have been conducted to assess the safety, feasibility, and efficacy of tenecteplase in ischemic stroke. In spite of the mixed results of these studies, experimentation with tenecteplase continues in from of clinical trials. In this article, the utility of tenecteplase in ischemic stroke will be discussed.

Plasminogen activators and ischemic stroke: conditions for acute delivery

Appropriate acute treatment with plasminogen activators (PAs) can significantly increase the probability of minimal or no disability in selected ischemic stroke patients. There is a great deal of evidence showing that intravenous recombinant tissue PAs (rt-PA) infusion accomplishes this goal, recanalization with other PAs has also been demonstrated in the development of this treatment. Recanalization of symptomatic, documented carotid or vertebrobasilar arterial territory occlusions have also been achieved by local intra-arterial PA delivery, although only a single prospective double-blinded randomized placebo-controlled study has been reported. The increase in intracerebral hemorrhage with these agents by either delivery approach underscores the need for careful patient selection, dose-appropriate safety and efficacy, proper clinical trial design, and an understanding of the evolution of cerebral tissue injury due to focal ischemia. Principles underlying the evolution of focal ischemia have been expanded by experience with acute PA intervention. Several questions remain open that concern the manner in which PAs can be applied acutely in ischemic stroke and how injury development can be limited.

Drug treatment of acute ischemic stroke

Acute ischemic stroke (AIS) is the fourth leading cause of death and the leading cause of adult disability in the USA. AIS most commonly occurs when a blood vessel is obstructed leading to irreversible brain injury and subsequent focal neurologic deficits. Drug treatment of AIS involves intravenous thrombolysis with alteplase (recombinant tissue plasminogen activator [rtPA]). Intravenous alteplase promotes thrombolysis by hydrolyzing plasminogen to form the proteolytic enzyme plasmin. Plasmin targets the blood clot with limited systemic thrombolytic effects. Alteplase must be administered within a short time window to appropriate patients to optimize its therapeutic efficacy. Recent trials have shown this time window may be extended from 3 to 4.5 hours in select patients. Other acute supportive interventions for AIS include maintaining normoglycemia, euthermia and treating severe hypertension. Urgent anticoagulation for AIS has generally not shown benefits that exceed the hemorrhage risks in the acute setting. Urgent antiplatelet use for AIS has limited benefits and should only promptly be initiated if alteplase was not administered, or after 24 hours if alteplase was administered. The majority of AIS patients do not receive thrombolytic therapy due to late arrival to emergency departments and currently there is a paucity of acute interventions for them. Ongoing clinical trials may lead to further medical breakthroughs to limit the damage inflicted by this devastating disease.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Fibrinogen depleting agents for acute ischaemic stroke

BACKGROUND

Fibrinogen depleting agents reduce fibrinogen in blood plasma, reduce blood viscosity and hence increase blood flow. This may help remove the blood clot blocking the artery and re-establish blood flow to the affected area of the brain after an ischaemic stroke. The risk of haemorrhage may be less than with thrombolytic agents. This is an update of a Cochrane review first published in 1997 and last updated in 2003.

OBJECTIVES

To assess the effect of fibrinogen depleting agents in patients with acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (July 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 7), the Chinese Stroke Trials Register (September 2011), MEDLINE (1950 to July 2011), EMBASE (1980 to July 2011) and Web of Science Conference Proceedings (1990 to July 2011). In addition, we searched six Chinese databases, four ongoing trials registers (July 2011) and relevant reference lists. For previous versions of the review, we handsearched journals and contacted researchers in China and Japan and relevant drug companies.

SELECTION CRITERIA

Randomised trials of fibrinogen depleting agents started within 14 days of stroke onset, compared with control in patients with definite or possible ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted the data. We resolved disagreement by discussion.

MAIN RESULTS

We included eight trials involving 5701 patients. Six trials tested ancrod and two trials tested defibrase (patients were treated for less than three hours to less than 48 hours). Allocation concealment was adequate in seven trials. Fibrinogen depleting agents marginally reduced the proportion of patients who were dead or disabled at the end of follow-up (risk ratio (RR) 0.95, 95% confidence Interval (CI) 0.90 to 0.99, 2P = 0.02). There was no statistically significant difference in death from all causes during the scheduled treatment or follow-up period. There were fewer stroke recurrences in the treatment group than in the control group (RR 0.67, 95% CI 0.49 to 0.92, 2P = 0.01). However, symptomatic intracranial haemorrhage was about twice as common in the treatment group compared with the control group (RR 2.42, 95% CI 1.65 to 3.56, 2P < 0.00001).

AUTHORS' CONCLUSIONS

The current evidence is promising but not yet sufficiently robust to support the routine use of fibrinogen depleting agents for the treatment of acute ischaemic stroke. Further trials are needed to determine whether there is worthwhile benefit, and if so, which categories of patients are most likely to benefit.

Adjunctive and alternative approaches to current reperfusion therapy

BACKGROUND AND PURPOSE

Current ischemic stroke reperfusion therapy consists of intravenous thrombolysis given in eligible patients after review of a noncontrast CT scan and a time-based window of opportunity. Rapid clot lysis has a strong association with clinical improvement but remains incomplete in many patients. This review appraises novel adjunctive or alternative approaches to current reperfusion strategies being tested in all trial phases. Summary of Review- Alternative approaches to current reperfusion therapy can be separated into 4 main categories: (1) combinatory approaches with other drugs or devices; (2) novel systemic thrombolytic agents; (3) endovascular medical or mechanical reperfusion treatments; and (4) noninvasive or minimally invasive methods to augment cerebral blood flow and alleviate intracranial blood flow steal.

CONCLUSIONS

Reperfusion treatments must be provided as fast as possible in patients most likely to benefit. Patients who fail to rapidly reperfuse may benefit from other strategies that maintain collateral flow or protect tissue at risk.

Hyperacute therapies for childhood stroke: a case report and review of the literature

Objective. The optimal management of pediatric patients with arterial ischemic stroke (AIS) is not known. Despite this, goal-oriented, time-sensitive therapies geared to rapid reestablishment of arterial blood flow are occasionally applied with beneficial effects. The inconsistent approach to AIS is in part due to a lack of knowledge and preparedness. Methods. Case report of a 12-year-old male with right middle cerebral artery (MCA) occlusion resulting in dense left hemiplegia and mutism and review of the literature. Intervention(s). Mechanical thrombectomy, intra-arterial administration of rt-PA, vasodilators, and platelet inhibitors, and systemic anticoagulation and subsequent critical care support. Results. Restoration of right MCA blood flow and complete resolution of neurologic deficits. Conclusion. We report the gratifying outcome of treatment of a case of AIS in a pediatric patient treated with hyperacute therapies geared to arterial recanalization and subsequent neurologic critical care and review the pertinent literature. Guidelines for the emergency room management of pediatric AIS from prospective, randomized trials are needed.

Current endovascular treatment of acute stroke and future aspects

Acute ischemic stroke remains a condition of high morbidity and mortality. Until now, the only established therapy has been intravenous (IV) tissue-type plasminogen activator (tPA). Only 3-10% of patients with acute ischemic stroke receive this treatment. On the basis of data from part 3 of the European Collaborative Acute Stroke Study (ECASS III), the time window for beneficial treatment of ischemic stroke with IV tPA has been extended from 3 to 4.5h after the onset of stroke symptoms. Beyond that window of opportunity, and additionally to IV treatment, interventional stroke therapy has assumed an important role for the treatment of acute ischemic stroke. Currently, new promising pharmacological and mechanical treatment options are being established as routine procedures to achieve a further improved outcome for stroke patients.

Ancrod for acute ischemic stroke: a new dosing regimen derived from analysis of prior ancrod stroke studies

BACKGROUND

Ancrod, a fibrinogen-reducing agent, has been evaluated as treatment beginning within 3 or 6 hours of onset of acute ischemic stroke with inconsistent results. The data sets from these studies provide an opportunity to determine whether ancrod-related variables are associated with efficacy and safety.

OBJECTIVE

This post hoc analysis of data from the Stroke Treatment with Ancrod Trial (STAT) analyzed ancrod-related variables as potential determinants of efficacy or safety. The resulting hypotheses were then tested in the European STAT (ESTAT) database.

METHODS

The relationships between ancrod-related variables and the outcomes of efficacy and symptomatic intracranial hemorrhage (ICH) were analyzed using a 3-stage multivariate process.

RESULTS

Good clinical outcome at 3 months based on the Barthel Index occurred almost twice as often in rapid defibrinogenators (>or=30 mg/dL/h) (52%) as in slow defibrinogenators (26%), with no increase in mortality or symptomatic ICH. Compared with a 20.7% incidence of symptomatic ICH in patients with mean post-9-hour fibrinogen levels less than or equal to 60 mg/dL, symptomatic ICH incidence was 0.8% in those with mean levels greater than 60 mg/dL (with no loss of efficacy). There were no symptomatic ICHs among 220 North American patients with mean levels greater than 70 mg/dL. It was hypothesized that an initial controlled rapid ancrod infusion with mean post-9-hour fibrinogen levels greater than 70 mg/dL would yield superior efficacy and safety. Such ESTAT patients had statistically significant efficacy versus placebo and a marked reduction in the incidence of symptomatic ICH versus patients taking ancrod with lower maintenance fibrinogen levels.

CONCLUSION

Modifications to ancrod dosing may substantially improve efficacy while reducing the rate of symptomatic ICH.

Management of acute ischemic stroke

Stroke is the third leading cause of death and the leading cause of disability in the United States. This article summarizes the management of acute ischemic stroke, including conventional and novel therapies. The article provides an overview of the initial management, diagnostic work-up, treatment options, and supportive measures that need to be considered in the acute phase of ischemic stroke.

Critical care of acute ischemic stroke

Stroke is the third leading cause of death and the leading cause of disability in the United States. This article summarizes the critical care of acute ischemic stroke, including conventional and novel therapies. The article provided an overview of the initial management, diagnostic workup, treatment options, and supportive measures that need to be considered in the acute phase of ischemic stroke.

Established treatments for acute ischaemic stroke

This article reviews the recommended management of patients presenting to accident and emergency departments with acute ischaemic stroke, and focuses on thrombolysis. The review includes initial management, recommended clinical, laboratory, and radiographic examinations. Appropriate general medical care, consisting of monitoring of oxygenation, fever, blood pressure, and blood glucose concentrations are examined. Criteria for thrombolysis with intravenous recombinant tissue plasminogen activator (rt-PA) are discussed. Complications of rt-PA therapy, such as haemorrhagic transformation and angio-oedema, are reviewed. An approach to management of rt-PA complications is outlined. Only a small percentage of acute ischaemic stroke patients meet criteria for rt-PA; therefore, alternative acute treatment strategies are also discussed. Acute medical and neurological complications in stroke patients are analysed, along with recommendations for treatment.

Intravenous ancrod for acute ischaemic stroke in the European Stroke Treatment with Ancrod Trial: a randomised controlled trial

BACKGROUND

Intravenous tissue plasminogen activator is the only approved specific treatment for acute ischaemic stroke. Ancrod, a natural defibrinogenating agent from snake venom, has proved to have a favourable effect when given within 3 h after an acute ischaemic stroke. The European Stroke Treatment with Ancrod Trial was undertaken to assess the effects of ancrod when given within 6 h.

METHODS

1222 patients with an acute ischaemic stroke were included in this randomised double-blind placebo-controlled trial. Brain CT scans were done to exclude intracranial haemorrhages and large evolving ischaemic infarctions. Patients were randomly assigned ancrod (n=604) or placebo (n=618). The primary outcome was functional success at 3 months (survival, Barthel Index of 95 or 100, or return to prestroke level). The analysis was by intention-to-treat. This trial is registered with ClinicalTrials.gov, trial number NCT00343174.

FINDINGS

Functional success at 3 months did not differ between patients given ancrod (42%) and those given placebo (42%) (p=0.94, OR=0.99, 95% CI, 0.76-1.29).

INTERPRETATION

On the basis of our findings, ancrod should not be recommended for use in acute ischaemic stroke beyond 3 h.

Thrombolytic treatment of acute cerebral infarction

Stroke is a common cause of death and disability throughout the world. Acute neurologic deficits due to ischemic injury deserve rapid recognition and diagnosis in order to provide effective therapy. Intravenous tissue plasminogen activator (t-PA) provided to carefully selected patients that can be treated within 3 hours of stroke onset results in improved outcome in these patients. Intra-arterial administration of t-PA within a 6-hour window is performed at several academic centers in patients with middle cerebral and other intracranial artery occlusions based on results of one randomized clinical trial and numerous case reports. Although acute therapy of ischemic stroke has received much attention since the approval of intravenous t-PA, only a small percentage of individuals suffering a stroke actually receive t-PA. This article will review the optimal management of the acute stroke patient and discuss thrombolytic clinical trials that have been completed as well as those that are in progress.

Antithrombotic trials in acute ischaemic stroke: a selective review

Stroke is a common cause of morbidity and mortality throughout the US and the world. Given the highly disabling nature of this disease, it is important to provide acute therapy when indicated to improve individual outcomes. Recombinant tissue plasminogen activator (rt-PA) is, at present, the only approved drug for the treatment of acute strokes due to cerebral ischaemia. It can be given intravenously within a 3-h window of the onset of neurological deficits. Intra-arterial administration of rt-PA within a 6-h window is performed at several academic centres in patients with middle cerebral and other intracranial artery occlusions based on results of a randomised clinical trial. Other thrombolytic agents are being studied in randomised trials. Although acute therapy of ischaemic stroke has received much attention since the approval of rt-PA, only a small percentage of individuals actually receive rt-PA. This article will review the main thrombolytic agents and the trials performed thus far, as well as examine some important ongoing trials. How administration of acute thrombolytic therapy may evolve in the future will also be addressed.

Pathophysiology of focal cerebral ischemia: a therapeutic perspective

The pathophysiology of cerebral ischemia is best understood in animal models of stroke. Within minutes of interrupted blood flow, mitochondria are deprived of substrate, which prevents adenosine triphosphate generation and results in membrane depolarization. This leads to increased intracellular calcium and sodium concentration followed by generation of free radicals and initiation of apoptosis. Glutamate release from ischemic neurons contributes to cellular damage. Each step in this complex, interdependent series of events offers a potential point to intervene and prevent neuronal death. Although many human trials in acute stroke therapy have had disappointing results, many promising therapies are in the pipeline, including hypothermia and free-radical inhibitors. Herein, the author discusses the pathophysiology of focal cerebral ischemia as has been revealed in rodent models and reviews the major human trials according to treatment mechanism.

Frequency and risk factors for spontaneous hemorrhagic transformation of cerebral infarction

OBJECTIVE

Hemorrhagic transformation of cerebral infarction (HTI) occurs spontaneously but its frequency and risk factors are uncertain with mixed results in previous studies. We aimed to determine the overall frequency of and risk factors for HTI.

METHODS

We performed a systematic review according to Cochrane Collaboration methods of published reports of HTI with reliable, systematic follow-up with computed tomography or magnetic resonance imaging.

RESULTS

In all, 28 observational studies and 19 randomized controlled trials in stroke were identified that included follow-up imaging data. Problems with inconsistent definitions or small and biased patient populations limited detailed interpretation. The overall frequency of any HTI in untreated patients was 8.5% (95% confidence interval 7%-10%). Severe HTI (i.e., HTI accompanied by neurologic deterioration or parenchymal hematoma formation) occurred in 1.5% (95% confidence interval 0.8%-2.2%). The frequency of HTI increased markedly with increasing use of antithrombotic or thrombolytic drugs. Magnetic resonance imaging detected more HTI than did computed tomography. The published data were generally inadequate to undertake more detailed analysis of risk factors. However, in the 8 studies that did provide the information, HTI was associated with large infarcts, mass effect, hypodensity observed early after the stroke, and age older than 70 years, but not hypertension or cardioembolic stroke.

CONCLUSIONS

Severe HTI is uncommon in patients not receiving antithrombotic or thrombolytic agents. The methods used to assess the frequency of and risk factors for HTI, particularly a standard of definitions in future prospective studies, could be improved.

Acute treatment for ischemic stroke in 2004

The last decade witnessed significant and unprecedented advances in the treatment of acute ischemic stroke. Intravenous tissue plasminogen activator and defibrinogenating agent are both now approved by the Food and Drug Administration for treatment of acute ischemic stroke within 3 h of symptom onset. Trials involving intra-arterial thrombolysis have demonstrated clinical benefit in patients treated within 6 h of symptom onset. The future for the development of new and better treatment for ischemic stroke looks very promising. Currently, induced hypothermia, laser evaporation, mechanical thrombectomy, angioplasty with stent placement, the combination of neuroprotective agents with thrombolysis, and the combination of intravenous with intra-arterial thrombolysis are being investigated.

Fibrinogen depleting agents for acute ischaemic stroke

BACKGROUND

Fibrinogen depleting agents reduce fibrinogen in blood plasma, reduce blood viscosity and hence increase blood flow. This may help remove the blood clot blocking the artery and re-establish blood flow to the affected area of the brain after an ischaemic stroke. The risk of haemorrhage may be less than with thrombolytic agents.

OBJECTIVES

The objective of this review was to assess the effect of fibrinogen depleting agents in patients with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched May 2003). In addition we searched the following electronic databases: EMBASE (1980-October 2001), China Biological Medicine Database (CBM-disc 1981- December 2002), Chinese Stroke Trials Register (1996 - December 2002) and Index of Scientific and Technical Proceedings (Web of Science Proceedings [1990-October 2001]). We handsearched relevant journals and contacted Chinese and Japanese researchers and drug companies.

SELECTION CRITERIA

Randomised and quasi-randomised trials of fibrinogen depleting agents started within 14 days of stroke onset, compared with control in patients with definite or possible ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the inclusion criteria, assessed trial quality and extracted the data.

MAIN RESULTS

Five trials involving 2926 patients were included. A further trial (ESTAT) has not yet been published in full. Four trials tested ancrod and one trial tested defibrase. Allocation concealment was adequate in four trials. Fibrinogen depleting agents moderately reduced the proportion of patients who were dead or disabled at the end of follow up (Relative risk [RR] 0.90, 95% Confidence Interval [CI] 0.82 to 0.98, 2P=0.02). There was no statistically significant difference in death from all causes during the scheduled treatment period (RR 0.71, 95% CI 0.44 to 1.13) and at the end of follow-up (RR 0.98, 95% CI 0.78 to 1.24). There was a non-significant excess of symptomatic intracranial haemorrhages with treatment (RR 2.64, 95%CI 0.96 to 7.30, 2P=0.06).

REVIEWER'S CONCLUSIONS

Fibrinogen depleting agents are promising. However more data, particularly ESTAT data, are needed before more reliable conclusions can be drawn.

Stroke--acute interventions

The reduction of blood flow to parts of the brain is the cause of ischemic stroke leading to functional deficits and, if prolonged, to irreversible neurological and morphological defects. The fast reperfusion, therefore is the most important therapeutic strategy and was proven to be effective in clinical trials. Steps to intervene with secondary biochemical, molecular, or inflammatory disturbances were not successful so far. Since direct therapeutic interventions are limited, the general management of the stroke victim is of utmost importance--and was shown to be most successful in dedicated stroke units. Acute therapeutic interventions in ischemic stroke can only be successful as long as tissue in the area of the ischemic compromise is still viable. The area of irreversible damage can be identified and distinguished from the penumbral zone, i.e., tissue with impaired function but preserved morphology by functional imaging modalities, like positron emission tomography (PET) or perfusion-(PW) and diffusion-weighted (DW) magnetic resonance imaging (MRI). In such studies it was demonstrated that a large portion of the final infarct is irreversibly affected in the first few hours in many patients. A considerable tissue volume is viable but critically hypoperfused; a smaller portion of the final infarct is sufficiently perfused and in this area secondary and delayed biochemical and molecular mechanisms contribute to the damage. Based on this concept the improvement of perfusion within the time window of opportunity must be the primary goal in treatment of ischemic stroke, and neuroprotective and other strategies can only play a supportive and additive role. That this is the case can be seen from the results of many controlled therapeutic trials, in which up to now only thrombolytic therapy with a 3 h time window for systemic and a 6 h time window for intraarterial application proved its efficacy, whereas all trials with neuroprotective, anti-inflammatory or anti-apoptotic strategies failed. Since the direct treatment strategies are limited the acute management of stroke victims is of utmost importance: This can be achieved optimally in dedicated stroke units in which the outcome was significantly improved over the regular care. It is still to be investigated if invasive strategies--e.g., craniectomy and hypothermia--or the combination of reperfusion and neuroprotective therapy can improve the outcome after ischemic stroke.

Acute ischemic stroke management

The use of thrombolytic therapy represents one of many recent developments in the management of acute ischemic stroke. The development of stroke teams and protocols has been driven by these new demands for an urgent response to ischemic stroke. The short time window of 3 hours for therapy with intravenous recombinant tissue plasminogen activator requires efficient evaluation and treatment of stroke patients and also necessitates a rigorous approach to blood pressure management, electrolytes, fluids, and temperature. Anticoagulation has not been proven to safely prevent progression or early recurrence of stroke, but antiplatelet therapy is worthwhile.

Acute ischemic stroke therapy

Acute ischemic stroke is a medical emergency that requires rapid evaluation and treatment. Prehospital and emergency department care can be streamlined to meet those goals. Intravenous rt-PA therapy improves outcome in selected patients with ischemic stroke if given within 3 hours of stroke onset, but offers no benefit beyond that time window. Intra-arterial thrombolytic therapy and intravenous defibrogenating agents may also be beneficial in selected patients. Newer thrombolytic agents such as aspirin and heparin in acute ischemic stroke treatment have been clarified by recent trials.

Update on therapies for acute ischemic stroke

Acute ischemic stroke is now considered a neurological emergency for which there are new therapies. Neurosurgeons and neurologists need to remain apprised of advances in this field. The authors discuss approved and emerging therapies for patients suffering from acute ischemic stroke, based on a review of recent publications. Currently, intravenous tissue-type plasminogen activator is the only Food and Drug Administration–approved therapy for acute ischemic stroke. Intraarterial delivery of thrombolytics is a promising treatment and may be effective in selected patients. Other therapies for acute cerebral ischemia are intriguing but still in the investigational stages.

Neuroprotection of Acute Ischemic Stroke: Where are We?

Neuroprotective treatments for acute ischemic stroke are targeted at the large array of cellular biochemical and metabolic disturbances that occur after focal brain ischemia to prevent the evolution of injury toward irreversibility. Enhanced comprehension about the pathophysiology of focal brain ischemia has expanded the number of neuroprotective modalities under development and identification of the most likely target for these therapies. Many of the neuroprotective interventions are targeted at reducing calcium influx into ischemic cells and the downstream consequences of excessive intracellular calcium. Other neuroprotective strategies include: free radical scavengers, hyperpolarization of resting transmembrane potentials, and inhibition of the inflammatory response and growth factors. Some interventions potentially may enhance recovery and have neuroprotective effects (i.e., basic fibroblast growth factor [bFGF] and citicoline). Despite the lack of proven clinical efficacy with any neuroprotective intervention, the future will hopefully yield convincing evidence that neuroprotection can be effective and then be ultimately combined with thrombolysis to maximize improvement after ischemic stroke.

Heparin-mediated extracorporeal LDL/fibrinogen precipitation--H.E.L.P.--in coronary and cerebral ischemia

Cerebral and myocardial infarctions share common aspects of pathobiochemistry. The central problem is the oxygen supply of the infarcted region. To maintain this supply, H.E.L.P.-apheresis (Heparin-mediated Extracorporeal LDL/Fibrinogen Precipitation) has already proven beneficial in the prevention and therapy of myocardial infarction. Since H.E.L.P.-apheresis can lower significantly plasma viscosity and erythrocyte aggregation without reducing the oxygen transport capacity, patients with cerebral infarction (stroke) may also benefit from our experiences in myocardial ischemia. The system is designed to remove selectively plasma fibrinogen, LDL-cholesterol and lipoprotein(a) from blood circulation, simultaneously. The removal of the plasma compounds is achieved by extracorporeal precipitation with heparin at low pH. Excess heparin is completely removed by an adsorber before the plasma is given back to the patient. H.E.L.P.-apheresis has proved to be safe in patients with coronary heart disease and allows a controlled reduction of thrombogenic plasma compounds. It is therefore hoped to be effective also in patients with acute ischemic stroke.

Snake venoms and the hemostatic system

Snake venoms are complex mixtures containing many different biologically active proteins and peptides. A number of these proteins interact with components of the human hemostatic system. This review is focused on those venom constituents which affect the blood coagulation pathway, endothelial cells, and platelets. Only highly purified and well characterized snake venom proteins will be discussed in this review. Hemostatically active components are distributed widely in the venom of many different snake species, particularly from pit viper, viper and elapid venoms. The venom components can be grouped into a number of different categories depending on their hemostatic action. The following groups are discussed in this review: (i) enzymes that clot fibrinogen; (ii) enzymes that degrade fibrin(ogen); (iii) plasminogen activators; (iv) prothrombin activators; (v) factor V activators; (vi) factor X activators; (vii) anticoagulant activities including inhibitors of prothrombinase complex formation, inhibitors of thrombin, phospholipases, and protein C activators; (viii) enzymes with hemorrhagic activity; (ix) enzymes that degrade plasma serine proteinase inhibitors; (x) platelet aggregation inducers including direct acting enzymes, direct acting non-enzymatic components, and agents that require a cofactor; (xi) platelet aggregation inhibitors including: alpha-fibrinogenases, 5'-nucleotidases, phospholipases, and disintegrins. Although many snake venoms contain a number of hemostatically active components, it is safe to say that no single venom contains all the hemostatically active components described here. Several venom enzymes have been used clinically as anticoagulants and other venom components are being used in pre-clinical research to examine their possible therapeutic potential. The disintegrins are an interesting group of peptides that contain a cell adhesion recognition motif, Arg-Gly-Asp (RGD), in the carboxy-terminal half of their amino acid sequence. These agents act as fibrinogen receptor (integrin GPIIb/IIIa) antagonists. Since this integrin is believed to serve as the final common pathway leading to the formation of platelet-platelet bridges and platelet aggregation, blockage of this integrin leads to inhibition of platelet aggregation regardless of the stimulating agent. Clinical trials suggest that platelet GPIIb/IIIa blockade is an effective therapy for the thrombotic events and restenosis frequently accompanying cardiovascular and cerebrovascular disease. Therefore, because of their clinical poten tial, a large number of disintegrins have been isolated and characterized.

Etiopathogenesis of cardiovascular disease: hemostasis, thrombosis, and vascular medicine

The role of hemostatic variables (which promote hemostatic plugs and thrombi) and rheological variables (which affect blood flow) in the pathogenesis of vascular diseases (ischemic heart disease, stroke, and peripheral arterial disease) is reviewed, with emphasis on epidemiological studies. Rheological variables are consistently associated with both prevalent and incident cardiovascular disease. These associations are only partly explained by conventional risk factors. The predictive value of plasma viscosity for cardiovascular events is partly explained by fibrinogen, and partly by lipoproteins. The associations of whole blood viscosity with cardiovascular disease are partly explained by plasma viscosity and partly by hematocrit. White cell count, but not platelet count, predicts ischemic heart disease events. Cigarette smokers have higher levels of rheological variables than non-smokers, these increases are partly or wholly reversible in ex-smokers. Lipoprotein reduction by pravastatin lowers plasma and whole-blood viscosity, which may be one mechanism through which lipid lowering produces an early reduction in cardiovascular events. Data from the Edinburgh Artery Study suggest that viscosity is related both to the extent of atherosclerosis, and to ischemia in the presence of a given degree of atherosclerotic stenoses. Among hemostatic variables, fibrinogen, factor VIII: vWF complex, tpA antigen, and fibrin D-dimer are associated with both prevalent and incident cardiovascular disease. Again, these associations are only partly explained by conventional risk factors They suggest that endothelial disturbance and increased fibrin turnover may play roles in cardiovascular disease. Hemostatic and rheological variables are therefore associated with both prevalent and incident cardiovascular disease, and may be mechanisms through which risk factors such as smoking, hyperlipidemia and infections (including oral infections) promote vascular events.

A systematic review of randomized evidence for fibrinogen-depleting agents in acute ischemic stroke

OBJECTIVE

To assess the efficacy and safety of fibrinogen-depleting agents (snake venom extracts) in the treatment of acute ischemic stroke.

METHODS

A systematic review of all the relevant randomized controlled trials (RCTs) was performed. RCTs were identified from the Cochrane Stroke Group's Specialized Trial Register, additional electronic and hand searching, and personal contact with pharmaceutical companies. We included all completed and unconfounded truly or quasi-randomized trials in patients with ischemic stroke comparing fibrinogen depleting agents with control started within 14 days of the stroke onset. The Peto method was used for analysis.

RESULTS

Eight completed and two ongoing RCTs have been identified so far. Only three trials using ancrod (182 patients) met the inclusion criteria. Ancrod was associated with a significant reduction in early deaths (5.6% v 16%; odds ratio [OR], 0.33; 95% confidence interval [CI], 0.13 to 0.85; 2P=.02) suggesting that treatment of 100 patients would avoid about 10 early deaths. The frequency of asymptomatic intracranial hemorrhage shown by computed tomography was similar between ancrod-treated and control groups (7.6% v 9.6%; OR, 0.78; 95% CI, 0.26 to 2.33; 2P=.65). No major intracranial or extracranial hemorrhages or recurrent ischemic strokes occurred in the ancrod-allocated patients. There were nonsignificant trends in favor of ancrod in death from any cause (OR, 0.57; 95% CI, 0.27 to 1.23; 2P=.15) and death or disability (OR, 0.52; 95% CI, 0.26 to 1.03; 2P=.06) at the end of trial follow-up.

CONCLUSIONS

There were too few patients and outcome events to draw reliable conclusions from the present data. Although ancrod-like agents appeared promising, their routine use cannot be recommended at the moment. Two ongoing trials (including about 1,000 patients in total) will provide more data. Future trials should test simpler fixed-dose regimens to allow better generalizability.

Ancrod in the treatment of acute ischaemic stroke

Ancrod converts fibrinogen into soluble fibrin products, resulting in a decrease in plasma fibrinogen and blood viscosity, and also induces the release of endogenous tissue-type plasminogen activator from the vessel wall. These activities suggest that treating patients with acute ischaemic stroke with ancrod might result in improved cerebral blood flow and patient outcome. Two large randomised placebo-controlled studies have evaluated treatment with ancrod in patients with acute ischaemic stroke. In the first, patients were treated within 6 hours of symptom onset: this was not successful in quickly lowering fibrinogen levels to the target range (0.7 to 1.0 g/L) and the results were inconclusive. However, a post hoc analysis suggested that treatment with ancrod was effective in patients whose fibrinogen level was reduced to less than 1.3 g/L within 6 hours of starting treatment. A second larger study is still in progress, but preliminary results in patients treated within 3 hours of onset of ischaemic stroke are available and indicate that the target fibrinogen level of less than 1 g/L within 6 hours of instituting treatment is being achieved in most patients.

MRI study on delayed ancrod therapy of focal cerebral ischaemia in rats

The therapeutic window for efficient post-treatment of focal cerebral ischaemia with the fibrinogen lowering agent ancrod was studied by magnetic resonance imaging (MRI) in spontaneously hypertensive rats (SHR). Ancrod or vehicle solution (0.9% NaCl) were i.v. infused (0.12 IU/kg per min) via implanted mini pumps starting 0.5, 1.5, 3 or 6 h after permanent proximal middle cerebral artery occlusion and lasting until brain mapping by multislice T2-weighted magnetic resonance imaging in vivo 24 h after middle cerebral artery occlusion. Plasma fibrinogen concentrations were measured before middle cerebral artery occlusion, before pump implantation and after magnetic resonance imaging. Total brain lesion volumes as determined by magnetic resonance imaging 24 h after middle cerebral artery occlusion were 131 +/- 36 (188 +/- 28)*, 151 +/- 39 (194 +/- 39)*, 147 +/- 44 (207 +/- 33)* and 209 +/- 60 (214 +/- 42) mm3 in rats with 0.5, 1.5, 3 and 6 h, respectively, delay of ancrod treatment (means +/- S.D., 8-11 animals/group, corresponding control groups in parentheses, *P < 0.05). Continuous i.v. ancrod infusions reduced plasma fibrinogen levels significantly (P < 0.05) in all ancrod-treated groups as compared to vehicle-treated controls until the end of the experiments 24 h after middle cerebral artery occlusion. In conclusion, significant cerebroprotection was achieved even when the onset of ancrod therapy for lowering of the plasma fibrinogen level was delayed for up to 3 h. To the best of our knowledge no drug efficacy has been reported so far with a therapeutic window of 3 h after permanent middle cerebral artery occlusion in spontaneously hypertensive rats suggesting that ancrod may provide an efficient therapy of acute human stroke.

Acute stroke therapies

It is likely that thrombolytic agents will play a role in the management of acute ischemic stroke in well-selected patients, intravenous administration is most practicable. However, intra-arterial administration via superselective catheterization is an alternative option that may offer advantages is certain settings (e.g., angiography suite, intraoperatively). Tissue plasminogen activators appear safer than streptokinase. Fibrinolytic agents offer the unproven potential for improving stroke outcome with less risk of intracranial bleeding. LMWHs can be administrated subcutaneously with minimal blood monitoring. These agents may prove more useful for secondary stroke prevention rather than acute treatment. Introduction of other agents like monoclonal antibodies directed against leukocyte adhesion molecules, aspirin, or ticlopidine offer other potential approaches to improving stroke outcome.

Clinical potential for the use of neuroprotective agents. A brief overview

"Stroke treatment seems to be entering a golden age ...." Fisher's observation not only applies to ischemic stroke, but to all the conditions described above, and in the future, possibly (and quite speculatively), to other neurologic diseases, such as multiple sclerosis, amyotrophic lateral sclerosis, even radiation therapy and Bell's palsy. Physicians must sharpen their criteria for decisions regarding therapy and must" ... be prepared to accept what is actually known from scientific data ... rather than to rely on instinct, clinical impression, or the need to do something rather than nothing."