Dipyridamole for Preventing Recurrent Ischemic Stroke and Other Vascular Events

Synthetic approaches and clinical application of representative small-molecule inhibitors of phosphodiesterase

Phosphodiesterases (PDEs) constitute a family of enzymes that play a pivotal role in the regulation of intracellular levels of cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Dysregulation of PDE activity has been implicated in diverse pathological conditions encompassing cardiovascular disorders, pulmonary diseases, and neurological disorders. Small-molecule inhibitors targeting PDEs have emerged as promising therapeutic agents for the treatment of these ailments, some of which have been approved for their clinical use. Despite their success, challenges such as resistance mechanisms and off-target effects persist, urging continuous research for the development of next-generation PDE inhibitors. The objective of this review is to provide an overview of the synthesis and clinical application of representative approved small-molecule PDE inhibitors, with the aim of offering guidance for further advancements in the development of novel PDE inhibitors.

The Critical Role of Equilibrative Nucleoside Transporter-2 in Modulating Cerebral Damage and Vascular Dysfunction in Mice with Brain Ischemia-Reperfusion

BACKGROUND

Cerebral vascular protection is critical for stroke treatment. Adenosine modulates vascular flow and exhibits neuroprotective effects, in which brain extracellular concentration of adenosine is dramatically increased during ischemic events and ischemia-reperfusion. Since the equilibrative nucleoside transporter-2 (Ent2) is important in regulating brain adenosine homeostasis, the present study aimed to investigate the role of Ent2 in mice with cerebral ischemia-reperfusion.

METHODS

Cerebral ischemia-reperfusion injury was examined in mice with transient middle cerebral artery occlusion (tMCAO) for 90 minutes, followed by 24-hour reperfusion. Infarct volume, brain edema, neuroinflammation, microvascular structure, regional cerebral blood flow (rCBF), cerebral metabolic rate of oxygen (CMRO2), and the production of reactive oxygen species (ROS) were examined following the reperfusion.

RESULTS

Ent2 deletion reduced the infarct volume, brain edema, and neuroinflammation in mice with cerebral ischemia-reperfusion. tMCAO-induced disruption of brain microvessels was ameliorated in Ent2-/- mice, with a reduced expression of matrix metalloproteinases-9 and aquaporin-4 proteins. Following the reperfusion, the rCBF of the wild-type (WT) mice was quickly restored to the baseline, whereas, in Ent2-/- mice, rCBF was slowly recovered initially, but was then higher than that in the WT mice at the later phase of reperfusion. The improved CMRO2 and reduced ROS level support the beneficial effects caused by the changes in the rCBF of Ent2-/- mice. Further studies showed that the protective effects of Ent2 deletion in mice with tMCAO involve adenosine receptor A2AR.

CONCLUSIONS

Ent2 plays a critical role in modulating cerebral collateral circulation and ameliorating pathological events of brain ischemia and reperfusion injury.

Treatment effect modification due to comorbidity: Individual participant data meta-analyses of 120 randomised controlled trials

BACKGROUND

People with comorbidities are underrepresented in clinical trials. Empirical estimates of treatment effect modification by comorbidity are lacking, leading to uncertainty in treatment recommendations. We aimed to produce estimates of treatment effect modification by comorbidity using individual participant data (IPD).

METHODS AND FINDINGS

We obtained IPD for 120 industry-sponsored phase 3/4 trials across 22 index conditions (n = 128,331). Trials had to be registered between 1990 and 2017 and have recruited ≥300 people. Included trials were multicentre and international. For each index condition, we analysed the outcome most frequently reported in the included trials. We performed a two-stage IPD meta-analysis to estimate modification of treatment effect by comorbidity. First, for each trial, we modelled the interaction between comorbidity and treatment arm adjusted for age and sex. Second, for each treatment within each index condition, we meta-analysed the comorbidity-treatment interaction terms from each trial. We estimated the effect of comorbidity measured in 3 ways: (i) the number of comorbidities (in addition to the index condition); (ii) presence or absence of the 6 commonest comorbid diseases for each index condition; and (iii) using continuous markers of underlying conditions (e.g., estimated glomerular filtration rate (eGFR)). Treatment effects were modelled on the usual scale for the type of outcome (absolute scale for numerical outcomes, relative scale for binary outcomes). Mean age in the trials ranged from 37.1 (allergic rhinitis trials) to 73.0 (dementia trials) and percentage of male participants range from 4.4% (osteoporosis trials) to 100% (benign prostatic hypertrophy trials). The percentage of participants with 3 or more comorbidities ranged from 2.3% (allergic rhinitis trials) to 57% (systemic lupus erythematosus trials). We found no evidence of modification of treatment efficacy by comorbidity, for any of the 3 measures of comorbidity. This was the case for 20 conditions for which the outcome variable was continuous (e.g., change in glycosylated haemoglobin in diabetes) and for 3 conditions in which the outcomes were discrete events (e.g., number of headaches in migraine). Although all were null, estimates of treatment effect modification were more precise in some cases (e.g., sodium-glucose co-transporter-2 (SGLT2) inhibitors for type 2 diabetes-interaction term for comorbidity count 0.004, 95% CI -0.01 to 0.02) while for others credible intervals were wide (e.g., corticosteroids for asthma-interaction term -0.22, 95% CI -1.07 to 0.54). The main limitation is that these trials were not designed or powered to assess variation in treatment effect by comorbidity, and relatively few trial participants had >3 comorbidities.

CONCLUSIONS

Assessments of treatment effect modification rarely consider comorbidity. Our findings demonstrate that for trials included in this analysis, there was no empirical evidence of treatment effect modification by comorbidity. The standard assumption used in evidence syntheses is that efficacy is constant across subgroups, although this is often criticised. Our findings suggest that for modest levels of comorbidities, this assumption is reasonable. Thus, trial efficacy findings can be combined with data on natural history and competing risks to assess the likely overall benefit of treatments in the context of comorbidity.

Cilostazol and isosorbide mononitrate for the prevention of progression of cerebral small vessel disease: baseline data and statistical analysis plan for the Lacunar Intervention Trial-2 (LACI-2) (ISRCTN14911850)

BACKGROUND

Cerebral small vessel disease (SVD) causes lacunar strokes (25% of all ischaemic strokes), physical frailty and cognitive impairment and vascular and mixed dementia. There is no specific treatment to prevent progression of SVD.

METHODS

The LACunar Intervention Trial-2 is an investigator-initiated prospective randomised open-label blinded-endpoint phase II feasibility study assessing cilostazol and isosorbide mononitrate for preventing SVD progression. We aimed to recruit 400 patients with clinically evident lacunar ischaemic stroke and randomised to cilostazol, isosorbide mononitrate, both or neither, in addition to guideline secondary ischaemic stroke prevention, in a partial factorial design. The primary outcome is feasibility of recruitment and adherence to medication; key secondary outcomes include: drug tolerability; recurrent vascular events, cognition and function at 1 year after randomisation; and safety (bleeding, falls, death). Data are number (%) and median (IQR).

RESULTS

The trial commenced on 5 February 2018 and ceased recruitment on 31 May 2021 with 363 patients randomised, with the following baseline characteristics: average age 64 (56.0, 72.0) years, female 112 (30.9%), stroke onset to randomisation 79.0 (27.0, 244.0) days, hypertension 267 (73.6%), median blood pressures 143.0 (130.0, 157.0)/83.0 (75.0, 90.0) mm Hg, current smokers 67 (18.5%), educationally achieved end of school examinations (A-level) or higher 118 (32.5%), modified Rankin scale 1.0 (0.0, 1.0), National Institutes Health stroke scale 1.0 (1.4), Montreal Cognitive Assessment 26.0 (23.0, 28.0) and total SVD score on brain imaging 1.0 (0.0, 2.0). This publication summarises the baseline data and presents the statistical analysis plan.

SUMMARY

The trial is currently in follow-up which will complete on 31 May 2022 with results expected in October 2022.

TRIAL REGISTRATION NUMBER

ISRCTN14911850.

The role of CYP2C19 genotyping to guide antiplatelet therapy following ischemic stroke or transient ischemic attack

Introduction

Clopidogrel is an antiplatelet agent recommended for secondary prevention of ischemic stroke (IS) and transient ischemic attack (TIA). Conversion of clopidogrel to its active metabolite by hepatic cytochrome P450-2C19 (CYP2C19) is essential for the inhibition of the P2Y12 receptor and subsequent platelet aggregation to prevent thrombotic events. CYP2C19 is highly polymorphic, with over 30 loss of function (LoF) alleles. This review considers whether there is sufficient data to support genotype guided antiplatelet therapy after stroke.

Areas covered

A systematic literature review retrieved articles, which describe the interaction between CYP2C19 genotype and clinical outcomes following IS or TIA when treated with clopidogrel. The review documents efforts to identify optimal antiplatelet regimens and explores the value genotype guided antiplatelet therapy. The work outlines the contemporary understanding of clopidogrel metabolism and appraises evidence linking CYP2C19 LoF variants with attenuated platelet inhibition and poorer outcomes.

Expert opinion

There is good evidence that CYP2C19 LoF allele carriers of Han-Chinese ancestry have increased risk for further vascular events following TIA or IS when treated with clopidogrel. The evidence base is less certain in other populations. The expansion of pharmacogenetics into routine clinical practice will facilitate further research and help tailor other aspects of secondary prevention.

Oral antithrombotic therapy for the prevention of recurrent cerebrovascular events

Stroke is frequently a disabling and even life-threatening condition that has an ischemic cause in most cases. Transient ischemic attack (TIA) is a lower-risk condition that still exposes to the risk of future major cardiovascular events. The causes of stroke can be classified as cardioembolic disease, large vessel disease, small vessel disease, undetermined, or others. Cardioembolic disease and atherothrombosis of large arteries are the most common underlying processes of ischemic stroke and TIA. Therefore, antithrombotic therapy is a central strategy in the pharmacological management of these patients. However, because antithrombotic therapy provides ischemic protection at the price of increased bleeding, defining the fine balance between efficacy and safety is a clinical challenge. Numerous trials have recently defined the current indications to the use of anticoagulant and antiplatelet therapy in patients with various subtypes of ischemic stroke or TIA. In this review, we provide an updated appraisal of the currently available evidence on the use of various oral antithrombotic agents for prevention of recurrent events after an ischemic stroke or TIA.

Toward a Molecular Basis of Cellular Nucleoside Transport in Humans

Nucleosides play central roles in all facets of life, from metabolism to cellular signaling. Because of their physiochemical properties, nucleosides are lipid bilayer impermeable and thus rely on dedicated transport systems to cross biological membranes. In humans, two unrelated protein families mediate nucleoside membrane transport: the concentrative and equilibrative nucleoside transporter families. The objective of this review is to provide a broad outlook on the current status of nucleoside transport research. We will discuss the role played by nucleoside transporters in human health and disease, with emphasis placed on recent structural advancements that have revealed detailed molecular principles of these important cellular transport systems and exploitable pharmacological features.

Data sharing: experience of accessing individual patient data from completed randomised controlled trials in vascular and cognitive medicine

OBJECTIVES

Meta-analysis based on individual patient data (IPD) from randomised trials is superior to using published summary data since it facilitates subgroup and multiple variable analyses. Guidelines and funders expect that researchers share IPD for bona fide analyses, but in practice, this is done variably. Here, we report the experience of obtaining IPD for two collaborative analysis studies.

SETTING

Two linked studies required IPD from published randomised trials. The leading researchers for eligible trials were approached and asked to share IPD including trial characteristics, patient demographics, baseline clinical data and outcome measures.

PARTICIPANTS

Participants in eligible randomised controlled trials included patients with or at risk of cognitive decline/vascular events.

PRIMARY AND SECONDARY OUTCOME MEASURES

Numbers (%) of trials where the leading researcher responded favourably/negatively or did not respond. If negative, reasons behind the response were collected. If positive, methods used to share IPD were recorded.

RESULTS

Across the two studies, 391 completed trials were identified. Email addresses for researchers were found for 313 (80%) of the trials. One hundred and forty-eight (47%) researchers did not respond despite being sent multiple emails. Following contact, positive initial responses were received from 92 researchers, resulting in IPD being shared for 78 trials. Eighty-seven (28%) researchers declined to share data; justifications were recorded. The median time from first request to accessing data in one study was 241 (IQR 383.3) days. IPD sources included: direct from researcher, via academic trial funders repository and a website requiring remote analysis of commercial data. Where data were shared, a variety of methods were used to transfer data.

CONCLUSION

Sharing of IPD from trials is desirable and a requirement of many funding bodies. However, accessing IPD faces multiple challenges including refusals to share, delays in access to data and having to perform analyses on a remote website.

TRIAL REGISTRATION

Not applicable.

Insights from Experiences on Antiplatelet Drugs in Stroke Prevention: A Review

Reduction of hazard risk of cerebral ischemic event (stroke, transient ischemic attack (TIA)) represents the hard point to be achieved from primary or secondary preventive strategy in the best clinical practice. However, results from clinical trials, recommendations, guidelines, systematic review, expert opinions, and meta-analysis debated on the optimal pharmacotherapy to achieve the objective. Aspirin and a number of antiplatelet agents, alone or in combination, have been considered from large trials focused on stroke prevention. The present review summarizes, discusses results from trials, and focuses on the benefits or disadvantages originating from antiplatelet drugs. Sections of the review were organized to show both benefits or consequences from antiplatelet pharmacotherapy. Conclusively, this review provides a potential synopsis on the most appropriate therapeutic approach for stroke prevention in clinical practice.

Triple versus guideline antiplatelet therapy to prevent recurrence after acute ischaemic stroke or transient ischaemic attack: the TARDIS RCT

BACKGROUND

Two antiplatelet agents are better than one for preventing recurrent stroke after acute ischaemic stroke or transient ischaemic attack (TIA). Therefore, intensive treatment with three agents might be better still, providing it does not cause undue bleeding.

OBJECTIVE

To compare the safety and efficacy of intensive therapy with guideline antiplatelet therapy for acute ischaemic stroke and TIA.

DESIGN

International prospective randomised open-label blinded end-point parallel-group superiority clinical trial.

SETTING

Acute hospitals at 106 sites in four countries.

PARTICIPANTS

Patients > 50 years of age with acute non-cardioembolic ischaemic stroke or TIA within 48 hours of ictus (stroke).

INTERVENTIONS

Participants were allocated at random by computer to 1 month of intensive (combined aspirin, clopidogrel and dipyridamole) or guideline (combined aspirin and dipyridamole, or clopidogrel alone) antiplatelet agents, and followed for 90 days.

MAIN OUTCOME MEASURES

The primary outcome was the incidence and severity of any recurrent stroke (ischaemic, haemorrhagic; assessed using the modified Rankin Scale) or TIA within 90 days by blinded telephone follow-up. Analysis using ordinal logistic regression was by intention to treat. Other outcomes included bleeding and its severity, death, myocardial infarction (MI), disability, mood, cognition and quality of life.

RESULTS

The trial was stopped early on the recommendation of the Data Monitoring Committee after recruitment of 3096 participants (intensive, n = 1556; guideline, n = 1540) from 106 hospitals in four countries between April 2009 and March 2016. The incidence and severity of recurrent stroke or TIA did not differ between intensive and guideline therapy in 3070 (99.2%) participants with data [93 vs. 105 stroke/TIA events; adjusted common odds ratio 0.90, 95% confidence interval (CI) 0.67 to 1.20; p = 0.47]. Major (encompassing fatal) bleeding was increased with intensive as compared with guideline therapy [39 vs. 17 participants; adjusted hazard ratio (aHR) 2.23, 95% CI 1.25 to 3.96; p = 0.006]. There were no differences between the treatment groups in all-cause mortality, or the composite of death, stroke, MI and major bleeding (aHR 1.02, 95% CI 0.77 to 1.35; p = 0.88).

LIMITATIONS

Patients and investigators were not blinded to treatment. The comparator group comprised two guideline strategies because of changes in national guidelines during the trial. The trial was stopped early, thereby reducing its statistical power.

CONCLUSIONS

The use of three antiplatelet agents is associated with increased bleeding without any significant reduction in recurrence of stroke or TIA.

FUTURE WORK

The safety and efficacy of dual antiplatelet therapy (combined aspirin and clopidogrel) versus aspirin remains to be defined. Further research is required on identifying individual patient response to antiplatelets, and the relationship between response and the subsequent risks of vascular recurrent events and bleeding complications.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN47823388.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 48. See the NIHR Journal Library website for further project information. The Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (TARDIS) vanguard phase was funded by the British Heart Foundation (grant PG/08/083/25779, from 1 April 2009 to 30 September 2012) and indirect funding was provided by the Stroke Association through its funding of the Stroke Trials Unit, Division of Clinical Neuroscience, University of Nottingham, Nottingham, UK. There was no commercial support for the trial and antiplatelet drugs were sourced locally at each site. The trial was sponsored by the University of Nottingham.

Combination Therapy with Dipyridamole and Clopidogrel for Secondary Stroke Prevention in Aspirin-Intolerant Patients After Myocardial Infarction: Results of a Nationwide Case-Control Study

BACKGROUND AND PURPOSE

Combination therapy with dipyridamole and clopidogrel in stroke prevention and long-term outcomes in aspirin-intolerant patients with acute myocardial infarction (AMI) and previous stroke are unknown. This nationwide study analyzed the impact of dipyridamole and clopidogrel on secondary stroke prevention and long-term outcomes in aspirin-intolerant stroke patients after AMI.

METHODS

This was a nationwide, case-control study involving 186,112 first AMI patients, 78,607 of whom had a previous history of stroke. In the final analysis, we included 4637 patients taking clopidogrel alone and 208 patients using a combination of clopidogrel and dipyridamole.

RESULTS

The 12-year survival rate was not different between clopidogrel and clopidogrel-dipyridamole groups (log-rank p = 0.6247). Furthermore, there were no differences in event-free survival after stroke (log-rank p = 0.6842), gastrointestinal (GI) bleeding (log-rank p = 0.9539), or intracerebral hemorrhage (ICH; log-rank p = 0.6191) between the two groups. Dipyridamole did not contribute significantly to AMI survival (hazard ratio 0.98, 95% confidence interval 0.84-1.15), and did not show benefits in any of the subgroups regardless of sex, age (younger or older than 75 years), comorbidities, percutaneous coronary intervention, or medications.

CONCLUSION

No differences were observed in the 12-year survival rate between clopidogrel and clopidogrel-dipyridamole groups. The two groups had balanced event-free survival in recurrent stroke, ICH, GI bleeding, and myocardial infarction.

Effectiveness and patient safety of platelet aggregation inhibitors in the prevention of cardiovascular disease and ischemic stroke in older adults - a systematic review

BACKGROUND

Platelet aggregation inhibitors (PAI) are among the most frequently prescribed drugs in older people, though evidence about risks and benefits of their use in older adults is scarce. The objectives of this systematic review are firstly to identify the risks and benefits of their use in the prevention and treatment of vascular events in older adults, and secondly to develop recommendations on discontinuing PAI in this population if risks outweigh benefits.

METHODS

Staged systematic review consisting of three searches. Searches 1 and 2 identified systematic reviews and meta-analyses. Search 3 included controlled intervention and observational studies from review-articles not included in searches 1 and 2. All articles were assessed by two independent reviewers regarding the type of study, age of participants, type of intervention, and clinically relevant outcomes. After data extraction and quality appraisal we developed recommendations to stop the prescribing of specific drugs in older adults following the Grading of Recommendations Assessment Development and Evaluation (GRADE) methodology.

RESULTS

Overall, 2385 records were screened leading to an inclusion of 35 articles reporting on 22 systematic reviews and meta-analyses, 11 randomised controlled trials, and two observational studies. Mean ages ranged from 57.0 to 84.6 years. Ten studies included a subgroup analysis by age. Overall, based on the evaluated evidence, three recommendations were formulated. First, the use of acetylsalicylic acid (ASA) for primary prevention of cardiovascular disease (CVD) in older people cannot be recommended due to an uncertainty in the risk-benefit ratio (weak recommendation; low quality of evidence). Secondly, the combination of ASA and clopidogrel in patients without specific indications should be avoided (strong recommendation; moderate quality of evidence). Lastly, to improve the effectiveness and reduce the risks of stroke prevention therapy in older people with atrial fibrillation (AF) and a CHA₂DS₂-VASc score of ≥ 2, the use of ASA for the primary prevention of stroke should be discontinued in preference for the use of oral anticoagulants (weak recommendation; low quality of evidence).

CONCLUSIONS

The use of ASA for the primary prevention of CVD and the combination therapy of ASA and clopidogrel for the secondary prevention of vascular events in older people may not be justified. The use of oral anticoagulants instead of ASA in older people with atrial fibrillation may be recommended. Further high quality studies with older adults are needed.

Remote Assessment of Platelet Function in Patients with Acute Stroke or Transient Ischaemic Attack

BACKGROUND

The TARDIS trial assessed the safety and efficacy of intensive versus guideline antiplatelet agents given for one month in patients with acute stroke or TIA. The aim of this substudy was to assess the effect of antiplatelet agents taken at baseline on platelet function reactivity and activation.

METHODS

Platelet function, assessed by remotely measured surface expression of P-selectin, was assessed in patients at their time of randomisation. Data are median fluorescence values.

RESULTS

The aspirin P-selectin test demonstrated that platelet expression was lower in 494 patients taking aspirin than in 162 patients not: mean 210 (SD 188) versus 570 (435), difference 360.3 (95% CI 312.2-408.4) (2p < 0.001). Aspirin did not suppress P-selectin levels below 500 units in 23 (4.7%) patients. The clopidogrel test showed that platelet reactivity was lower in 97 patients taking clopidogrel than in 585 patients not: 655 (296) versus 969 (315), difference 314.5 (95% CI 247.3-381.7) (2p < 0.001). Clopidogrel did not suppress P-selectin level below 860 units in 24 (24.7%) patients.

CONCLUSIONS

Aspirin and clopidogrel suppress stimulated platelet P-selectin, although one-quarter of patients on clopidogrel have high on-treatment platelet reactivity. Platelet function testing may be performed remotely in the context of a large multicentre trial. Trial registration ISRCTN47823388.

Baseline characteristics of the 3096 patients recruited into the 'Triple Antiplatelets for Reducing Dependency after Ischemic Stroke' trial

Background The risk of recurrence following ischemic stroke or transient ischemic attack is highest immediately after the event. Antiplatelet agents are effective in reducing the risk of recurrence and two agents are superior to one in the early phase after ictus. Design The triple antiplatelets for reducing dependency after ischemic stroke trial was an international multicenter prospective randomized open-label blinded-endpoint trial that assessed the safety and efficacy of short-term intensive antiplatelet therapy with three agents (combined aspirin, clopidogrel and dipyridamole) as compared with guideline treatment in acute ischemic stroke or transient ischemic attack. The primary outcome was stroke recurrence and its severity, measured using the modified Rankin Scale at 90 days. Secondary outcomes included recurrent vascular events, functional measures (cognition, disability, mood, quality of life), and safety (bleeding, death, serious adverse events). Data are number (%) or mean (standard deviation, SD). Results Recruitment ran from April 2009 to March 2016; 3096 patients were recruited from 106 sites in four countries (Denmark 1.6%, Georgia 2.7%, New Zealand 0.2%, UK 95.4%). Randomization characteristics included: age 69.0 (10.1) years; male 1945 (62.8%); time onset to randomization 29.4 (11.9) h; stroke severity (National Institutes for Health Stroke Scale) 2.8 (3.6); blood pressure 143.5 (18.2)/79.5 (11.4) mmHg; IS 2143 (69.2%), transient ischemic attack 953 (30.8%). Conclusion Triple antiplatelets for reducing dependency after ischemic stroke was a large trial of intensive/triple antiplatelet therapy in acute ischemic stroke and transient ischemic attack, and included participants from four predominantly Caucasian countries who were representative of patients in many western stroke services.

Treatment of intracerebral haemorrhage with tranexamic acid - A review of current evidence and ongoing trials

Purpose

Haematoma expansion is a devastating complication of intracerebral haemorrhage (ICH) with no established treatment. Tranexamic acid had been an effective haemostatic agent in reducing post-operative and traumatic bleeding. We review current evidence examining the efficacy of tranexamic acid in improving clinical outcome after ICH.

Method

We searched MEDLINE, EMBASE, CENTRAL and clinical trial registers for studies using search strategies incorporating the terms 'intracerebral haemorrhage', 'tranexamic acid' and 'antifibrinolytic'. Authors of ongoing clinical trials were contacted for further details.

Findings

We screened 268 publications and retrieved 17 articles after screening. Unpublished information from three ongoing clinical trials was obtained. We found five completed studies. Of these, two randomised controlled trials (RCTs) comparing intravenous tranexamic acid to placebo (n = 54) reported no significant difference in death or dependency. Three observational studies (n = 281) suggested less haematoma growth with rapid tranexamic acid infusion. There are six ongoing RCTs (n = 3089) with different clinical exclusions, imaging selection criteria (spot sign and haematoma volume), time window for recruitment and dosing of tranexamic acid.

Discussion

Despite their heterogeneity, the ongoing trials will provide key evidence on the effects of tranexamic acid on ICH. There are uncertainties of whether patients with negative spot sign, large haematoma, intraventricular haemorrhage, or poor Glasgow Coma Scale should be recruited. The time window for optimal effect of haemostatic therapy in ICH is yet to be established.

Conclusion

Tranexamic acid is a promising haemostatic agent for ICH. We await the results of the trials before definite conclusions can be drawn.

Medical and Surgical Management of Symptomatic Carotid Stenosis

Carotid bifurcation stenosis is an important cause of ischaemic stroke, particularly in patients with recent transient ischaemic attack or minor stroke. Large randomized trials of endarterectomy have shown that surgery reduces the risk of stroke in patients with ≥ 50% recently symptomatic carotid stenosis, and more recent research has gone some way to wards identifying which patients benefit the most. Individual risk modelling has been shown to be useful in selecting patients with the most to gain from endarterectomy for symptomatic stenosis, although timely surgery and optimal medical treatment are of equal importance.

Secondary Stroke Prevention with Antiplatelet Drugs: Have We Reached the Ceiling?

Patients with transient ischemic attack (TIA) or ischemic stroke carry a risk of recurrent stroke of between 5% and 20% per year. In patients with TIA or ischemic stroke of non-cardiac origin, antiplatelet drugs are able to decrease the relative risk of stroke by 11–15% and the risk of stroke, myocardial infarction, and vascular death by 15–22%. Aspirin is the most widely used drug. It is affordable and effective. Low doses of 50–325 mg aspirin are as effective as high doses and cause less gastrointestinal side-effects. The combination of aspirin with slow-release dipyridamole is superior to aspirin alone for stroke prevention but not for the prevention of cardiac events. The risk of major bleeding complications is not increased with the combination, which suggests that dipyridamole might act in another way than as antiplatelet drug. Clopidogrel is not superior to aspirin in unselected stroke patients but is superior in patients at high risk of recurrence. The combination of aspirin plus clopidogrel is not more effective than clopidogrel alone, but carries a higher bleeding risk. The most effective antiplatelet drugs, the GP IIb/IIIa antagonists, are not superior to aspirin and carry a higher risk of bleeding. These results indicate that any antiplatelet therapy with a more potent drug than aspirin will only have a marginally higher efficacy, which might be offset by a higher bleeding rate. Therefore, selection of patients who might benefit from antiplatelet therapy other than aspirin is important.

Synthesis and preliminary therapeutic evaluation of copper nanoparticles against diabetes mellitus and -induced micro- (renal) and macro-vascular (vascular endothelial and cardiovascular) abnormalities in rats

Current study synthesized and investigated the effect of low-dose copper nanoparticles (CuNPs) against diabetes mellitus and -induced experimental micro- (nephropathy) and macro-vascular (cardio and endothelium) complications.

Baseline characteristics, analysis plan and report on feasibility for the Prevention Of Decline in Cognition After Stroke Trial (PODCAST)

BACKGROUND

A common complication after stroke is development of cognitive impairment and dementia. However, effective strategies for reducing the risk of developing these problems remain undefined. Potential strategies include intensive lowering of blood pressure (BP) and/or lipids. This paper summarises the baseline characteristics, statistical analysis plan and feasibility of a randomised control trial of blood pressure and lipid lowering in patients post-stroke with the primary objective of reducing cognitive impairment and dementia.

METHODS

The Prevention Of Decline in Cognition After Stroke Trial (PODCAST) was a multi-centre prospective randomised open-label blinded-endpoint controlled partial-factorial internal pilot trial running in secondary and primary care. Participants without dementia were enrolled 3-7 months post ischaemic stroke or spontaneous intracerebral haemorrhage, and randomised to intensive versus guideline BP lowering (target systolic BP <125 mmHg versus <140 mmHg); patients with ischaemic stroke were also randomised to intensive or guideline lipid lowering (target LDL cholesterol <1.4 mmol/L versus <3 mmol/L). The primary outcome was the Addenbrooke's Cognitive Examination-Revised; a key secondary outcome was to assess feasibility of performing a large trial of one or both interventions. Data are number (%) or mean (standard deviation). The trial was planned to last for 8 years with follow-up between 1 and 8 years. The plan for reporting the main results is included as Additional file 2.

RESULTS

83 patients (of a planned 600) were recruited from 19 UK sites between 7 October 2010 and 31 January 2014. Delays, due to difficulties in the provision of excess treatment costs and to complexity of follow-up, led to few centres taking part and a much lower recruitment rate than planned. Patient characteristics at baseline were: age 74 (SD 7) years, male 64 (77 %), index stroke ischaemic 77 (93 %), stroke onset to randomisation 4.5 [SD 1.3] months, Addenbrooke's Cognitive Examination-Revised 86 (of 100, SD 8), Montreal Cognitive Assessment 24 (of 30, SD 3), BP 147/82 (SD 19/11) mmHg, total cholesterol 4.0 (SD 0.8) mmol/L and LDL cholesterol 2.0 (SD 0.7) mmol/L, modified Rankin Scale 1.1 (SD 0.8).

CONCLUSION

Limited recruitment suggests that a large trial is not feasible using the current protocol. The effects of the interventions on BP, lipids, and cognition will be reported in the main publication.

TRIAL REGISTRATION

ISRCTN85562386 registered on 23 September 2009.

Safety and efficacy of intensive vs. guideline antiplatelet therapy in high-risk patients with recent ischemic stroke or transient ischemic attack: rationale and design of the Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (TARDIS) trial (ISRCTN47823388)

RATIONALE

The risk of recurrence following a stroke or transient ischemic attack is high, especially immediately after the event.

HYPOTHESIS

Because two antiplatelet agents are superior to one in patients with non-cardioembolic events, more intensive treatment might be even more effective.

SAMPLE SIZE ESTIMATES

The sample size of 4100 patients will allow a shift to less recurrence, and less severe recurrence, to be detected (odds ratio 0·68) with 90% power at 5% significance.

METHODS AND DESIGN

Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (ISRCTN47823388) is comparing the safety and efficacy of intensive (combined aspirin, clopidogrel, and dipyridamole) vs. guideline antiplatelet therapy, both given for one-month. This international collaborative parallel-group prospective randomized open-label blinded-end-point phase III trial plans to recruit 4100 patients with acute ischemic stroke or transient ischemic attack. Randomization and data collection are performed over a secure Internet site with real-time data validation and concealment of allocation. Outcomes, serious adverse events, and neuroimaging are adjudicated centrally with blinding to treatment allocation.

STUDY OUTCOME

The primary outcome is stroke recurrence and its severity ('ordinal recurrence' based on modified Rankin Scale) at 90 days, with masked assessment centrally by telephone. Secondary outcomes include vascular events, functional measures (disability, mood, cognition, quality of life), and safety (bleeding, death, serious adverse events).

DISCUSSION

The trial has recruited more than 50% of its target sample size (latest number: 2399) and is running in 104 sites in 4 countries. One-third of patients presented with a transient ischemic attack.

Antiplatelet strategies for secondary prevention of stroke and TIA

Stroke is a major public health issue, and stroke recurrence accounts for a quarter of all events. Antiplatelet therapy has been extensively studied for secondary stroke prevention and is established as effective in this high-risk population. Several agents have been evaluated in this setting, both in isolation and combination. The most widely used antiplatelet medications are aspirin, clopidogrel, and aspirin plus extended-release dipyridamole. However, new agents and combinations continue to be evaluated. A detailed review of the evidence supporting various antiplatelet regimens for secondary stroke prevention is outlined with special focus on recent developments that may impact clinical management of patients with stroke or TIA.

Testing devices for the prevention and treatment of stroke and its complications

We are entering a challenging but exciting period when many new interventions may appear for stroke based on the use of devices. Hopefully these will lead to improved outcomes at a cost that can be afforded in most parts of the world. Nevertheless, it is vital that lessons are learnt from failures in the development of pharmacological interventions (and from some early device studies), including inadequate preclinical testing, suboptimal trial design and analysis, and underpowered studies. The device industry is far more disparate than that seen for pharmaceuticals; companies are very variable in size and experience in stroke, and are developing interventions across a wide range of stroke treatment and prevention. It is vital that companies work together where sales and marketing are not involved, including in understanding basic stroke mechanisms, prospective systematic reviews, and education of physicians. Where possible, industry and academics should also work closely together to ensure trials are designed to be relevant to patient care and outcomes. Additionally, regulation of the device industry lags behind that for pharmaceuticals, and it is critical that new interventions are shown to be safe and effective rather than just feasible. Phase IV postmarketing surveillance studies will also be needed to ensure that devices are safe when used in the 'real-world' and to pick up uncommon adverse events.

Post-stroke cognitive decline: an update and perspectives for clinical research

The close relationship between stroke and dementia is an important health issue. Ischaemic stroke can facilitate the onset of vascular dementia as well as aggravate pre-existing cognitive decline. The onset of cognitive decline may become manifest immediately following the onset of ischaemic stroke, but often there is a delay in the development of cognitive decline after a stroke. This delay can be seen as a therapeutic time window allowing interventions to be applied to preserve cognition following stroke. Both neurodegenerative and vascular mechanisms are activated and probably result in overlapping processes within the neurovascular unit. This review focuses on the incidence and prevalence of cognitive decline following stroke, predisposing stroke aetiologies, pre-stroke decline, imaging factors and biomarkers. Outcomes are discussed in relation to timing of assessment and neuropsychological tests used for evaluation of cognitive decline in ischaemic stroke patients. Including such tests in routine evaluations of stroke patients after some weeks or months is recommended. Finally, an outlook on ongoing and planned intervention trials is added and some recommendations for future research are proposed.

Stroke in patients with occlusion of the internal carotid artery: options for treatment

Ischemic stroke may occur in patients in whom vascular imaging shows the ipsilateral internal carotid artery (ICA) to be occluded. In younger patients this is often due to carotid artery dissection, while in older people this most likely results from cardiac embolism or thrombosis secondary to high-grade stenosis at the carotid bifurcation. Interventional techniques aim at recanalization of the carotid artery for early restoration of cerebral blood flow and secondary prevention of future strokes. In chronic ICA occlusion the ischemic infarct may be related to hemodynamic compromise. In this situation, extracranial-intracranial bypass surgery was introduced, but its role remains still unclear. Ischemic stroke may also occur in patients with a chronic occlusion of the contralateral ICA. This situation demands the usual stroke treatment, but surgical and neuroradiological interventions face a higher risk than unilateral vascular pathology. Medical treatment supports stroke prevention in carotid artery occlusion.

Longitudinal assessment of von Willebrand factor antigen and von Willebrand factor propeptide in response to alteration of antiplatelet therapy after TIA or ischaemic stroke

The impact of commencing or changing antiplatelet therapy on von Willebrand factor antigen (VWF:Ag) and von Willebrand factor propeptide (VWF:Ag II) levels has not been comprehensively assessed following TIA or ischaemic stroke. In this pilot, longitudinal, observational analytical study, VWF:Ag and VWF:Ag II levels were simultaneously quantified in platelet poor plasma by ELISA in patients within 4 weeks of TIA or ischaemic stroke (baseline), and then 14 days (14d) and >90 days (90d) after altering antiplatelet therapy. Ninety-one patients were recruited. Eighteen were initially assessed on no antiplatelet therapy, and then after 14d (N = 17) and 90d (N = 8) on aspirin monotherapy; 21 patients were assessed on aspirin and after 14d and 90d on clopidogrel; 52 were assessed on aspirin monotherapy, and after 14d and 90d on aspirin and dipyridamole combination therapy. VWF:Ag, VWF:Ag II levels and VWF:Ag/VWF:Ag II ratio were unchanged at 14d and 90d in the overall study population (p ≥ 0.1). VWF:Ag and VWF:Ag II levels remained stable at 14d and 90d after commencing aspirin (p ≥ 0.054), and after changing from aspirin to clopidogrel (p ≥ 0.2). Following the addition of dipyridamole MR to aspirin, there was a significant reduction in VWF:Ag levels at 14d (p = 0.03) and 90d (p = 0.005), but not in VWF:Ag II levels (p ≥ 0.3). The addition of dipyridamole to aspirin led to a persistent reduction in VWF:Ag but not in VWF:Ag II levels, suggesting that dipyridamole may inhibit release of platelet-derived VWF:Ag following TIA or ischaemic stroke.

What’s new in stroke prevention and treatment

This review summarizes the latest results and developments in stroke prevention and acute treatment studies published in 2004 and 2005. In contrast to primary prevention in men, aspirin did not significantly reduce the risk of myocardial infarction or death from cardiovascular causes in women over 45 years of age. Patients with symptomatic intracranial stenosis do not benefit from secondary prevention with oral anticoagulation. Magnetic resonance-based acute stroke studies with recombinant tissue plasminogen activator (rtPA) or with desmoteplase, a new thrombolytic agent, showed similar safety and potential benefit beyond the 3-h time window, as with the established inclusion criteria of rtPA. The surgical trial in intracerebral hemorrhage (STICH) failed to demonstrate any benefit for early operative evacuation of hematoma. The authors aim to provide a wide overview of stroke prevention and acute treatment studies published in 2004 and 2005. Relevant journals were hand-searched to compile a broad, but not comprehensive, summary of innovative and clinically relevant findings. A short critical evaluation at the end of selected reviews should encourage the reader to further reading of studies of interest.

Is there an alternative to systemic anticoagulation, as related to interventional biomedical devices?

To reduce the toxic effects, related clinical problems and complications such as bleeding disorders associated with systemic anticoagulation, it has been hypothesized that by coating the surfaces of medical devices, such as stents, bypass grafts, extracorporeal circuits, guide wires and catheters, there will be a significant reduction in the requirement for systemic anticoagulation or, ideally, it will no longer be necessary. However, current coating processes, even covalent ones, still result in leaching followed by reduced functionality. Alternative anticoagulants and related antiplatelet agents have been used for improvement in terms of reduced restenosis, intimal hyperphasia and device failure. This review focuses on existing heparinization processes, their application in clinical devices and the updated list of alternatives to heparinization in order to obtain a broad overview, it then highlights, in particular, the future possibilities of using heparin and related moieties to tissue engineer scaffolds.

Comparative evaluation of treatment with low-dose aspirin plus dipyridamole versus aspirin only in patients with acute ischaemic stroke

BACKGROUND

Previous studies have suggested that pre-stroke treatment with low-dose aspirin (A) could reduce the severity of acute ischaemic stroke, but less is known on the effect of pre-stroke treatment with a combination of aspirin and dipyridamole (A + D) and post-stroke effects of these drugs. The aim of the present study was to evaluate the effect of this drug combination on acute and long-term prognosis of ischaemic stroke.

METHODS

Patients without atrial fibrillation admitted to the stroke unit with acute ischaemic stroke (n = 554) or TIA (n = 108) were studied during acute hospital care and up to 12 months after discharge from hospital.

RESULTS

Prior to acute stroke 62 patients were treated with A + D while 247 patients were treated with A only. No beneficial effects of the combination A + D compared to A only were noted on stroke severity and/or acute in-hospital mortality. However, survival analysis by Cox-proportional hazard model demonstrated lower 12-months all-cause mortality in patients discharged with A + D (n = 275) compared with patients on A only (HR, 0.52; CI, 0.32-0.86; p = 0.011; n = 262) after adjusting for age, baseline NIHSS, previous stroke, previous myocardial infarction and type 2 diabetes. We also noted a tendency towards lower all-cause mortality at 3 months with use of A + D, but this was not statistically significant (p = 0.12).

CONCLUSIONS

Pre-stroke treatment with a combination of low-dose A + D does not reduce the severity of acute stroke, nor does it reduce the acute in-hospital mortality. However, treatment with A + D at discharge from hospital is seemingly associated with lower long-term mortality compared with A only, contrary to the results from previous randomised studies. However, our results must be interpreted with extreme caution considering the non-randomised study design.

Dual or mono antiplatelet therapy for patients with acute ischemic stroke or transient ischemic attack: systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND PURPOSE

Antiplatelets are recommended for patients with acute noncardioembolic stroke or transient ischemic attack. We compared the safety and efficacy of dual versus mono antiplatelet therapy in patients with acute ischemic stroke or transient ischemic attack.

METHODS

Completed randomized controlled trials of dual versus mono antiplatelet therapy in patients with acute (≤3 days) ischemic stroke/transient ischemic attack were identified using electronic bibliographic searches. The primary outcome was recurrent stroke (ischemic, hemorrhagic, unknown; fatal, nonfatal). Comparison of binary outcomes between treatment groups was analyzed with random effect models and described using risk ratios (95% CI).

RESULTS

Twelve completed randomized trials involving 3766 patients were included. In comparison with mono antiplatelet therapy, dual therapy (aspirin+dipyridamole and aspirin+clopidogrel) significantly reduced stroke recurrence, dual 58 (3.3%) versus mono 91 (5.0%; risk ratio, 0.67; 95% CI, 0.49-0.93); composite vascular event (stroke, myocardial infarction, vascular death), dual 74 (4.4%) versus mono 106 (6%; risk ratio, 0.75; 95% CI, 0.56-0.99); and the combination of stroke, transient ischemic attack, acute coronary syndrome, and all death, dual 100 (1.7%) versus mono 136 (9.1%; risk ratio, 0.71; 95% CI, 0.56-0.91); dual therapy was also associated with a nonsignificant trend to increase major bleeding, dual 15 (0.9%) versus mono 6 (0.4%; risk ratio, 2.09; 95% CI, 0.86-5.06).

CONCLUSIONS

Dual antiplatelet therapy appears to be safe and effective in reducing stroke recurrence and combined vascular events in patients with acute ischemic stroke or transient ischemic attack as compared with mono therapy. These results need to be tested in prospective studies.

Preventing recurrent cerebrovascular events in patients with stroke or transient ischemic attack: the current data

PURPOSE

To describe recurrent stroke in relation to the current data, treatment guidelines, diagnostic considerations, risk prevention, and management for the nurse practitioner (NP).

DATA SOURCES

An extensive review of the scientific literature, clinical trials, and clinical guidelines.

CONCLUSIONS

Recurrent stroke is a major health concern. A first ischemic cerebrovascular event or transient ischemic attack (TIA) is a risk factor for future strokes.

IMPLICATIONS FOR PRACTICE

The risk of recurring stroke has been demonstrated in multiple studies, yet only approximately 5% of stroke patients receive appropriate therapy in a timely manner. The stroke or TIA workup should be completed quickly so that the appropriate treatments and interventions can be initiated to reduce the risk of an additional event. The etiology of the stroke and identification of personal risk factors are important because treatment depends on the specific stroke mechanism. A variety of antiplatelet trials have specific implications for stroke and recurrent stroke. Present treatments include aspirin, aspirin plus extended-release dipyridamole and clopidogrel. The NP plays an important role in ongoing patient education about symptoms, the long-term management of the patient, and reduction of future stroke risk.

Atherothrombosis and the role of antiplatelet therapy

Atherothrombosis remains a major global public health problem. Chronic atherosclerotic disease is often clinically silent and coexists across vascular beds, but when complicated by thrombosis can result in acute coronary syndrome, stroke, transient ischaemic attack and critical limb ischaemia. Platelets play a role in the development of chronic atherosclerotic disease and are a key mediator of clinical events in atherothrombosis. Numerous trials have examined the role of antiplatelet agents in primary and secondary prevention and several new antiplatelet drugs are under development. In secondary prevention, there is evidence of clear benefit of single and in some cases dual antiplatelet therapy in the prevention of recurrent cerebro-vascular complications. Dual antiplatelet therapy has emerged as the standard of care in acute coronary syndromes, with aspirin typically being used in combination with clopidogrel or one of the newer more potent antiplatelet agents. Conversely, in chronic stable coronary disease, no benefit has yet been convincingly demonstrated from dual antiplatelet therapy. In cerebro-vascular disease, aspirin monotherapy remains the cornerstone of prevention of recurrent events, with clopidogrel or the combination of aspirin and dipyridamole being only modestly more efficacious. In primary prevention, the evidence for the routine use of aspirin or any other antiplatelet agent is mixed and suggests this should only be considered on an individual basis in high-risk groups where the thrombotic risk outweighs the risk of major bleeding complications.

Antiplatelet therapy in secondary stroke prevention--state of the art

Our objective is to provide the reader with an overview as well as an update on current antiplatelet therapy for secondary stroke prevention. Relevant journals were hand-searched by the authors to compile a broad but by far not comprehensive summary of innovative and clinically relevant studies. Aspirin, clopidogrel and the combination of dipyridamole plus aspirin are the cornerstone therapy in secondary prevention after non-cardio-embolic stroke or transient ischaemic attack. A head-to-head comparison showed no difference in the prevention of recurrent stroke between dipyridamole plus aspirin and clopidogrel. More potent antiplatelet drugs or the combination of aspirin and clopidogrel prevent more ischaemic events, but also lead to more bleeding complications. For secondary stroke prevention in patients with atrial fibrillation, oral anticoagulation is more effective than aspirin or the combination of aspirin and clopidogrel.

Calculation of Numbers-Needed-To-Treat in Parallel Group Trials Assessing Ordinal Outcomes: Case Examples from Acute Stroke and Stroke Prevention

Background

Number-needed-to-treat describes the magnitude of the effect of an intervention, underpins health economic analyses, and is typically calculated for binary events. Ordered categorical outcomes provide more clinical information and their analysis using ordinal approaches is usually more efficient statistically. However, to date, techniques to calculate number-needed-to-treat based on ordinal outcomes for parallel group trials have had important limitations.

Aims

Numbers-needed-to-treat may be calculated for ordinal data from parallel group trials by using an unmatched comparison of all subjects or by generating matched pairs of patients nested within the study.

Methods

The above approaches were assessed and compared with numbers-needed-to-treat calculated for binary outcomes using individual patient data from acute and prevention stroke trials testing the effect of interventions of varying utility and efficacy.

Results

Numbers-needed-to-treat were generally lower numerically for ordinal vs. binary, and matched vs. unmatched analyses, and the lowest in highly efficacious interventions: hemicraniectomy, ordinal matched 2·4 vs. ordinal unmatched 2·5 vs. binary matched 12 vs. binary unmatched 9 (one trial, 12 month outcome); alteplase, 4·5 vs. 6·6 vs. 8·4 vs. 8·4 (one trial with two parts, three-months); aspirin, 42 vs. 58 vs. 76 vs. 80 (one trial, six-months); and stroke units, 3·6–5·3 vs. 6·2 vs. 4·7–5·9 vs. 6·3–7·0 (two trials, three- to 60 months). Similar trends were seen for aspirin/dipyridamole vs. aspirin in secondary prevention, 22 vs. 20 vs. 31 vs. 31 (one trial, 24 months).

Conclusions

Number-needed-to-treat may be calculated for ordinal outcome data derived from parallel group stroke trials; such numbers-needed-to-treat are lower than those calculated for binary outcomes. Their use complements the use of ordinal statistical approaches in the analysis of ordered categorical data.

[Myocardial infarction after voluntary intoxication by drug interaction between dipyridamole and aspirin]

A 60-year-old male presented a myocardial infarction after a voluntary overdose of Asasantine(®) started after strokes. He took chronically this association and some psychotropic drugs with vasodilator effects. After an intake of 40 tablets, he presented a cardiogenic shock with a myocardial infarction confirmed by biological samples, EKG, echocardiography and angiocoronarographie. No recent change of his treatment was found and symptoms regressed when dipyridamole was stopped while other vasodilators drugs were continued. Chronological analysis of events led us to suspect dipyridamole as a starter of the myocardial infarction secondary to a coronary artery steal reinforced by the vasodilator effect of combined treatments, in a patient at risk of ischemia. This case shows that, in such particular conditions, a change in dipyridamole dosage can induce a myocardial infarction even if its blood level remains in the therapeutic range.

Emulating multicentre clinical stroke trials: a new paradigm for studying novel interventions in experimental models of stroke

The recent meta-analysis of NXY-059 in experimental stroke models using individual animal data found the drug to be an effective neuroprotective agent. However, the failure of translation of both this compound and many others from preclinical studies to the clinic indicates that new approaches must be used in drug discovery so that animal models become more reflective of the clinical situation, and studies using animal models of stroke mimic the design of studies performed in humans, as far as possible. In this review, we suggest that a fundamental paradigm shift is needed away from performing preclinical studies in individual laboratories to performing them in an organised group of independent laboratories. Studies should be run by a steering committee and should be supported by a coordinating centre, external data monitoring committee and outcome adjudication committee. This structure will mimic the practice of multicentre clinical trials. By doing so, future studies will minimise potential sources of bias including randomisation, concealment of allocation, blinding of surgery and outcome assessment and ensure publication of all data. It is likely that individual studies will involve increased heterogeneity and therefore will need to be larger. However, regular independent monitoring of data will allow development of interventions to be ceased immediately if neutral or negative data are obtained. The additional costs involved should be seen as reasonable when compared with the resources that would have been expended in running a clinical trial that subsequently proved negative.

Effect of aspirin, clopidogrel and dipyridamole on soluble markers of vascular function in normal volunteers and patients with prior ischaemic stroke

Although the mechanisms of action by which aspirin, clopidogrel and dipyridamole inhibit platelets are well characterised, their effects on soluble modulators of thrombosis, inflammation, and endothelial function have yet to assessed systematically. In this investigation aspirin (A), clopidogrel (C), and dipyridamole (D) were administered singly and in combination (A, C, D, AC, AD, CD, ACD) in random order for 2 weeks (without washout) to 11 healthy subjects and 11 patients with previous ischaemic stroke. At the end of each treatment period plasma cyclic guanosine monophosphate (cGMP), monocyte chemoattractant pertide-1 (MCP-1), nitric oxide metabolites (NO(x)), plasminogen activator inhibitor-1 (PAI-1) and von Willebrand factor (vWf); and serum C-reactive protein (CRP) and platelet derived growth factor (PDGF); were measured blinded to treatment. Dipyridamole reduced plasma vWf levels (%) in both volunteers, -10.0 (4.95), and patients, -10.11 (4.34) (p < 0.05). Dipyridamole also lowered CRP (mg/l) in patients, -0.96 (0.47), but not volunteers. Clopidogrel reduced PAI-1 (ng/ml) in volunteers, -5.30 (2.20) (p < 0.05), and patients, -3.61 (2.75) (non-significant trend). Aspirin lowered PDGF (ng/ml) in volunteers, -3.46 (1.55), but not patients. Triple antiplatelet therapy was superior to dual and mono therapy in reducing vWf levels. In conclusion, antiplatelet agents have non-platelet-related effects on soluble modulators of thrombosis, inflammation, and endothelial function. In particular, dipyridamole reduces plasma vWf and clopidogrel lowers plasma PAI-1 levels. These effects may explain, in part, their roles in preventing atherothrombogenesis.

Clinical trials in heart valve disease

PURPOSE OF REVIEW

To summarize evidence from clinical trials of heart valve disease and identify areas where further trials are needed.

RECENT FINDINGS

Recent randomized studies suggest that statins do not influence progression of aortic stenosis. Other medical therapies with the potential to reduce progression of valve disease or decrease myocardial dysfunction include vasodilators in aortic regurgitation, angiotensin II receptor antagonists or beta-blockers in mitral regurgitation and angiotensin-converting enzyme inhibitors in aortic stenosis. However, these treatments have not been evaluated or have been evaluated only in small studies. Meta-analysis of randomized studies of antithrombotic strategies in patients with mechanical valves suggests overall risk is lower with the combination of warfarin with a lower target international normalized ratio and an antiplatelet drug. Novel anticoagulants have the potential to replace warfarin but have not yet been evaluated for this indication. Clinical trials are also needed to reliably evaluate different surgical strategies and novel percutaneous technology.

SUMMARY

Clinical trials in heart valve disease have important limitations, including the small number of trials undertaken and the small size of most studies. Many trials were undertaken more than 10-20 years ago in patients with earlier generation valve prostheses. To improve outcomes for patients with heart valve disease more clinical trials of contemporary approaches are needed.

Systematic reviews as a tool for planning and interpreting trials

BACKGROUND

Systematic reviews followed by a meta-analysis are carried out in medical research to combine the results of two or more related studies. Stroke trials have struggled to show beneficial effects and meta-analysis should be used more widely throughout the research process to either speed up the development of useful interventions, or halt more quickly research with hazardous or ineffective interventions.

SUMMARY OF REVIEW

This review summarises the clinical research process and illustrates how and when systematic reviews may be used throughout the development programme. Meta-analyses should be performed after observational studies, preclinical studies in experimental stroke, and after phase I, II, and III clinical trials and phase IV clinical surveillance studies. Although meta-analyses most commonly work with summary data, they may be performed to assess relationships between variables (meta-regression) and, ideally, should utilise individual patient data. Meta-analysis techniques may also work with ordered categorical outcome data (ordinal meta-analysis) and be used to perform indirect comparisons where original trial data do not exist.

CONCLUSION

Systematic review/meta-analyses are powerful tools in medical research and should be used throughout the development of all stroke and other interventions.