Anticoagulants for preventing recurrence following presumed non-cardioembolic ischaemic stroke or transient ischaemic attack

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.

Effect of race/ethnicity on the efficacy of warfarin: potential implications for prevention of stroke in patients with atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia seen in clinical practice. It affects approximately 6% of persons over 65 years of age and is independently associated with a 4- to 5-fold higher risk of ischaemic stroke and a 2-fold higher risk of death. Randomized controlled trials have shown that treatment with adjusted-dose oral vitamin K antagonists (primarily warfarin with a target international normalized ratio [INR] of 2.0-3.0) reduces the relative risk of ischaemic stroke by two-thirds (an approximately 3% reduction in annual absolute risk), but is associated with a 0.2% excess annual absolute risk of intracranial haemorrhage (ICH). However, in 'real world' studies, the risk reductions in ischaemic stroke with warfarin have been significantly lower (25-50% relative risk reduction) than in selected trial samples. Moreover, more than 90% of patients enrolled in the sentinel trials were White/European. This raises the question of whether the beneficial results of warfarin can be extrapolated to persons of colour. Important differences in stroke risk profile and responsiveness to warfarin exist across racial/ethnic groups, such that one cannot assume a priori that there is a net benefit of warfarin therapy for AF patients of all racial/ethnic groups.Among patients with ischaemic stroke, AF is more likely to be implicated as the cause of stroke in the White population than in other racial/ethnic groups. Furthermore, AF may be a stronger predictor of ischaemic stroke among the White population than in Black or Hispanic/Latino populations. Approximately one-third of strokes in AF patients are noncardioembolic. Warfarin has been shown to be ineffective in preventing recurrent noncardioembolic strokes. Many persons of colour with AF have other risk factors that predispose them to noncardioembolic stroke, which may partially explain why warfarin has been reported to be less efficacious in preventing strokes in non-White patients with AF, even after adjustment for co-morbidities and anticoagulation monitoring. Notably, the background incidence of ICH is higher in Black, Hispanic and Asian patients than in White patients. Any greater than expected increases in bleeding secondary to anticoagulation may potentially offset any benefit gained from cardioembolic stroke reduction, although this has not been fully resolved.Finally, there are racial/ethnic differences in the prevalence of certain polymorphisms in genes that influence warfarin pharmacokinetics and pharmacodynamics (e.g. cytochrome P450 2C9 and vitamin K epoxide reductase). The Asian population generally appear to require the lowest daily dose of warfarin to maintain a given INR target, with the White population requiring an intermediate daily dose and the Black population requiring the highest daily dose. These differences must be taken into account when administering warfarin in order to minimize the risk of under- or over-anticoagulation.In summary, warfarin is highly effective in preventing ischaemic strokes in White patients with AF at a modestly higher risk of ICH. Whether the same net clinical benefit extends to persons of colour is unproven. Given the rapidly changing demographic nationally and internationally, additional research is needed to resolve this important question.

Low-molecular-weight heparins or heparinoids versus standard unfractionated heparin for acute ischaemic stroke

BACKGROUND

Low-molecular-weight heparins and heparinoids are anticoagulants that may be associated with lower risks of haemorrhage and more powerful antithrombotic effects than standard unfractionated heparin. This is an updated version of the original Cochrane review first published in Issue 1, 1995 and previously updated in Issue 2, 2005.

OBJECTIVES

To compare the effects of low-molecular-weight heparins or heparinoids with those of unfractionated heparin in people with acute, confirmed or presumed, ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched June 2007). In addition we searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2007), MEDLINE (1966 to June 2007) and EMBASE (1980 to June 2007). For previous versions of this review we searched MedStrategy (1995) and also contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing heparinoids or low-molecular-weight heparins with standard unfractionated heparin in people with acute ischaemic stroke. We only included trials where treatment was started within 14 days of stroke onset.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion, assessed trial quality and extracted the data.

MAIN RESULTS

Nine trials involving 3137 people were included. Four trials compared a heparinoid (danaparoid), four trials compared low-molecular-weight heparin (enoxaparin or certoparin), and one trial compared an unspecified low-molecular-weight heparin with standard unfractionated heparin. Allocation to low-molecular-weight heparin or heparinoid was associated with a significant reduction in the odds of deep vein thrombosis compared with standard unfractionated heparin (odds ratio (OR) 0.55, 95% confidence interval (CI) 0.44 to 0.70). However, the number of more major events (pulmonary embolism, death, intracranial or extracranial haemorrhage) was too small to provide a reliable estimate of the benefits and risks of low-molecular-weight heparins or heparinoids compared with standard unfractionated heparin for these, arguably more important, outcomes. Insufficient information was available to assess effects on recurrent stroke or functional outcome.

AUTHORS' CONCLUSIONS

Since the last version of this review none of the three new relevant studies with 2397 participants have provided additional information to change the conclusions. Treatment with a low-molecular-weight heparin or heparinoid after acute ischaemic stroke appears to decrease the occurrence of deep vein thrombosis compared with standard unfractionated heparin, but there are too few data to provide reliable information on their effects on other important outcomes, including death and intracranial haemorrhage.

The value of non-contrast harmonic transthoracic echocardiography for the detection of left ventricular thrombi in patients with cardiomyopathy: comparison with contrast-enhanced magnetic resonance imaging

We sought to assess the value of non-contrast enhanced transthoracic harmonic echocardiography (TEE) for the visualization of left ventricular thrombi in 34 patients with cardiomyopathy. Results were compared to contrast-enhanced magnetic resonance imaging as reference standard. Maximal thrombus size was quantified with both modalities. Magnetic resonance imaging demonstrated thrombi in 15 patients. In these subjects echocardiography was negative in seven patients. Thrombi were excluded in 19 patients with magnetic resonance while echocardiography was deemed positive in 5 subjects. Thrombus size by ce-CMR was not different for clots visualized or not visualized by echocardiography (P = 0.71). Moreover, observer agreement was superior for ce-CMR (kappa = 0.94) as compared to TTE (kappa= 0.71). Non-contrast-enhanced harmonic TTE has limited value for the visualization of thrombi in patients with cardiomyopathy.

Thrombophilien bei Patienten mit isch�mischem Schlaganfall

Patients with ischemic stroke are sometimes found to have an underlying inherited (deficiency of protein C, protein S, antithrombin III, activated protein C resistance, prothrombin gene mutation, hyperhomocysteinemia) or acquired thrombophilia (lupus anticoagulant and anticardiolipin antibodies, hyperhomocysteinemia). Patient selection for thrombophilia screening is, therefore, a frequent question in managing patients with ischemic stroke. In this review we discuss patient selection and timing for laboratory tests for thrombophilia screening in stroke patients based on a literature review and we calculated overall costs per year in Germany for testing patients older than 18 years with an ischemic stroke of undetermined cause. As there is a lack of studies comparing anticoagulation with antiplatelet therapy in patients with diagnosed thrombophilia, laboratory screening for thrombophilia even in a selected group of patients with cryptogenic ischemic stroke remains of questionable value at present. An exception appears to be testing for lupus anticoagulant and anticardiolipin antibodies in younger patients with suspected antiphospholipid syndrome (two positive test results necessary), because anticoagulation seems to be superior to aspirin in patients with antiphospholipid syndrome.

Antithrombotic and thrombolytic therapy for ischemic stroke

Antithrombotic therapy is the mainstay of treatment for stroke prevention. Multiple antiplatelet agents are now proven options for patients at risk for stroke, whereas warfarin anticoagulation remains the preferred therapy for most patients with atrial fibrillation. Recent clinical trials have clarified the role of anticoagulation in acute stroke and in secondary prevention of noncardioembolic stroke. Intravenous tissue plasminogen activator is the only approved therapy for patients with acute ischemic stroke. Intra-arterial thrombolysis is emerging as a promising therapy in selected patients.