Antiplatelet agents in the secondary prevention of stroke: meta-analysis of the randomized control trials

Antiplatelet versus anticoagulation treatment for patients with heart failure in sinus rhythm

BACKGROUND

Morbidity in patients with chronic heart failure is high, and this predisposes them to thrombotic complications, including stroke and thromboembolism, which in turn contribute to high mortality. Oral anticoagulants (e.g. warfarin) and antiplatelet agents (e.g. aspirin) are the principle oral antithrombotic agents. Many heart failure patients with sinus rhythm take aspirin because coronary artery disease is the leading cause of heart failure. Oral anticoagulants have become a standard in the management of heart failure with atrial fibrillation. However, a question remains regarding the appropriateness of oral anticoagulants in heart failure with sinus rhythm. This update of a review previously published in 2012 aims to address this question.

OBJECTIVES

To assess the effects of oral anticoagulant therapy versus antiplatelet agents for all-cause mortality, non-fatal cardiovascular events and risk of major bleeding in adults with heart failure (either with reduced or preserved ejection fraction) who are in sinus rhythm.

SEARCH METHODS

We updated the searches in September 2015 on CENTRAL (The Cochrane Library), MEDLINE and Embase. We searched reference lists of papers and abstracts from cardiology meetings and contacted study authors for further information. We did not apply any language restrictions. Additionally, we searched two clinical trials registers: ClinicalTrials.gov (www.ClinicalTrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) Search Portal apps.who.int/trialsearch/) (searched in July 2016).

SELECTION CRITERIA

We included randomised controlled trials comparing antiplatelet therapy versus oral anticoagulation in adults with chronic heart failure in sinus rhythm. Treatment had to last at least one month. We compared orally administered antiplatelet agents (aspirin, ticlopidine, clopidogrel, prasugrel, ticagrelor, dipyridamole) versus anticoagulant agents (coumarins, warfarin, non-vitamin K oral anticoagulants).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed the risks and benefits of antithrombotic versus antiplatelet therapy using relative measures of effects, such as risk ratios (RR), accompanied with 95% confidence intervals (CI). The data extracted included data relating to the study design, patient characteristics, study eligibility, quality, and outcomes. We used GRADE criteria to assess the quality of the evidence.

MAIN RESULTS

This update identified one additional study for inclusion, adding data for 2305 participants. This addition more than doubled the overall number of patients eligible for the review. In total, we included four randomised controlled trials (RCTs) with a total of 4187 eligible participants. All studies compared warfarin with aspirin. One RCT additionally compared warfarin with clopidogrel. All included RCTs studied patients with heart failure with reduced ejection fraction.Analysis of all outcomes for warfarin versus aspirin was based on 3663 patients from four RCTs. All-cause mortality was similar for warfarin and aspirin (RR 1.00, 95% CI 0.89 to 1.13; 4 studies; 3663 participants; moderate quality evidence). Oral anticoagulation was associated with a reduction in non-fatal cardiovascular events, which included non-fatal stroke, myocardial infarction, pulmonary embolism, peripheral arterial embolism (RR 0.79, 95% CI 0.63 to 1.00; 4 studies; 3663 participants; moderate quality evidence). The rate of major bleeding events was twice as high in the warfarin groups (RR 2.00, 95% CI 1.44 to 2.78; 4 studies; 3663 participants; moderate quality evidence). We generally considered the risk of bias of the included studies to be low.Analysis of warfarin versus clopidogrel was based on a single RCT (N = 1064). All-cause mortality was similar for warfarin and clopidogrel (RR 0.93, 95% CI 0.72 to 1.21; 1 study; 1064 participants; low quality evidence). There were similar rates of non-fatal cardiovascular events (RR 0.85, 95% CI 0.50 to 1.45; 1 study; 1064 participants; low quality evidence). The rate of major bleeding events was 2.5 times higher in the warfarin group (RR 2.47, 95% CI 1.24 to 4.91; 1 study; 1064 participants; low quality evidence). Risk of bias for this study can be summarised as low.

AUTHORS' CONCLUSIONS

There is evidence from RCTs to suggest that neither oral anticoagulation with warfarin or platelet inhibition with aspirin is better for mortality in systolic heart failure with sinus rhythm (high quality of the evidence for all-cause mortality and moderate quality of the evidence for non-fatal cardiovascular events and major bleeding events). Treatment with warfarin was associated with a 20% reduction in non-fatal cardiovascular events but a twofold higher risk of major bleeding complications (high quality of the evidence). We saw a similar pattern of results for the warfarin versus clopidogrel comparison (low quality of the evidence). At present, there are no data on the role of oral anticoagulation versus antiplatelet agents in heart failure with preserved ejection fraction with sinus rhythm. Also, there were no data from RCTs on the utility of non-vitamin K antagonist oral anticoagulants compared to antiplatelet agents in heart failure with sinus rhythm.

Selection of Treatment for Patients with Carotid Artery Disease: Medication, Carotid Endarterectomy, or Carotid Artery Stenting

Patients presenting with atherosclerosis of the extracranial carotid arteries may be offered carotid endarterectomy (CEA), carotid artery stenting (CAS), or medical therapy to reduce their risk of stroke. In many cases, the choice between treatment modalities remains controversial.

An algorithm based on patients' neurologic symptoms, comorbidities, limiting factors for CAS and CEA, and personal preferences was developed to determine the optimal treatment in each case. This algorithm was then employed to determine therapy in 308 consecutive patients presenting to a single institution during one calendar year.

Ninety-five (30.8%) patients presented with an asymptomatic carotid stenosis of more than 80% and 213 (69.2%) with a symptomatic stenosis of more than 50%. According to our algorithm, 59 (62.1%) of the 95 asymptomatic patients received CAS, 20 (21.1%) received CEA, and 16 (16.8%) received medical therapy. All symptomatic patients underwent intervention; 153 (71.8%) were treated with CAS and 60 (28.2%) with CEA. Combined 30-day stroke and death rates after CAS were 1.7% in asymptomatic patients and 2.6% in symptomatic patients. After CEA, these rates were 0% and 3.3%, respectively.

Careful selection of treatment modality according to predetermined criteria can result in improved outcomes.

Carotid Endarterectomy: The Gold Standard

Carotid endarterectomy has been firmly established as the gold standard of therapy for symptomatic and asymptomatic patients with severe carotid stenosis, provided surgical complication rates are within prescribed limits. The procedure-related risk of stroke/death should be < 3% in asymptomatic patients and < 6% in symptomatic patients. New investigational therapies such as balloon angioplasty and stenting for carotid stenosis should be evaluated against the same standard.

Comparison of proton pump inhibitor and histamine-2 receptor antagonist in the prevention of recurrent peptic ulcers/erosions in long-term low-dose aspirin users: a retrospective cohort study

Background. Proton pump inhibitor and histamine-2 receptor antagonist can prevent aspirin-related ulcers/erosions but few studies compare the efficacy of these two agents. Aims. We evaluated the efficacy of omeprazole and famotidine in preventing recurrent ulcers/erosions in low-dose aspirin users. Methods. The 24-week clinical outcomes of the patients using low-dose aspirin for cardiovascular protection with a history of ulcers/erosions and cotherapy of omeprazole or famotidine were retrospectively reviewed. The incidence of gastrointestinal symptoms, recurrent ulcers/erosions, erosive esophagitis, gastrointestinal bleeding, and thromboembolic events was analyzed. Results. A total of 104 patients (famotidine group, 49 patients; omeprazole group, 55 patients) were evaluated. Famotidine group had more gastrointestinal symptoms episodes than omeprazole group (46.9% versus 23.6%, P = 0.01). Fifteen famotidine group patients and 5 omeprazole group patients had recurrent ulcers/erosions (30.6% versus 9.1%, P = 0.005). Lanza scale was significantly lower in omeprazole group than in famotidine group (1.2 ± 0.7 versus 1.7 ± 1.1, P = 0.008). Only 1 famotidine group patient had ulcer bleeding. The incidences of erosive esophagitis and thromboembolic events were comparable between both groups. Conclusions. Omeprazole was superior to famotidine with less gastrointestinal symptoms and recurrent ulcers/erosions in patients using 24-week low-dose aspirin. The risk of erosive esophagitis, gastrointestinal bleeding, and thromboembolic events was similar between both groups.

European Stroke Prevention Study 2: A study of low-dose acetylsalicylic acid and of high dose dipyridamole in secondary prevention of cerebro-vascular accidents

In spite of some data being added to our knowledge of the effect of antiplatelets in secondary prevention of brain ischemic lesion in recent years, the main reasons to perform a second European Stroke Prevention Study (ESPS 2), which started in 1987-1988, were: (a) clarify the relative roles of aspirin (ASA) and dipyridamole (DP) alone or in combination; (b) confirm the efficacy of small doses of ASA and, so doing, decrease the number of drop-outs due to ASA side effects; (c) join information to the effect of antiplatelets in complete stroke. General characteristics of the sample of 6602 patients are presented and compared with other major trials and series. The patients in the four treatment arms (aspirin, dipyridamole, aspirin + dipyridamole and placebo) are compared. The more relevant features and risk factors known to influence long term prognosis are described and discussed. The small proportion of patients included with TIA (23.7%) and the comparability among treatment groups are stressed. No relevant differences have been found, among groups, on the sex or age distribution, prevalence of hypertension, diabetes, previous vascular events or atrial fibrillation, nor in the characteristics of the accident leading to the inclusion in trial.

Platelet antiaggregants in stroke prevention

Antiplatelet agents are one of the main interventions for recurrent ischemic stroke prevention. Their time of use, dosage, and combination of therapy have different effects in terms of stroke risk reduction and adverse effects. This review provides an evidence-based update of the latest on antiplatelet therapy for stroke prevention.

Design and data analysis 1 study design

This article is intended to give the reader guidance in evaluating different study designs used in medical research for better scientific quality, reliability and validity of their research. This article explains three main types of study designs with understanding examples. Care and caution with skills and experience needed to design suitable studies and appropriate design coupled with reliable sampling techniques and appropriate statistical analysis, supported by clear objectives with decent communication of the findings, are essential for good research.

Optimization of antiplatelet/antithrombotic therapy for secondary stroke prevention

Role of antiplatelet therapy in secondary stroke prevention is of major significance. Antiplatelet agents predominantly in use are aspirin, clopidogrel, and combination regimes. The review focuses on the optimization of antiplatelet regimen based on evidence obtained from randomized-controlled trials, on different antiplatelet regimes and the risk assessment that may be unique to each patient.

Current status of antiplatelet agents to prevent stroke

Stroke is one of the leading causes of disability; most are due to atherothrombotic mechanisms. About one third of ischemic strokes are preceded by other stroke or transient ischemic attacks. Stroke survivors are at high risk for vascular events (i.e., cerebrovascular and cardiovascular). Prevention of recurrent stroke and other major vascular events can be accomplished by control of risk factors. Nonetheless, the use of antiplatelet agents remains the fundamental component of secondary stroke prevention strategy in patients with noncardioembolic disease. Currently, the uses of aspirin, clopidogrel, or aspirin plus extended-release dipyridamole are valid alternatives for stroke or transient ischemic attack patients. To maximize the beneficial effects of these agents, the treatment should be initiated as early as possible and continue on a lifelong basis.

Secondary prevention of atherothrombotic events after ischemic stroke

Atherosclerotic vascular disease is the leading cause of ischemic stroke, resulting in occlusive or severely stenotic lesions of major intracranial or extracranial arteries and narrowing of small penetrating arteries of the brain. Atherosclerosis of the coronary arteries (ie, coronary artery disease) is an indirect cause of cardioembolic stroke secondary to myocardial infarction. Ischemic heart disease may also be complicated by atrial fibrillation and cardioembolic stroke. Prevention of recurrent stroke and other ischemic events, including myocardial infarction, is a key component of treatment for patients with symptomatic ischemic cerebrovascular disease. Prevention of recurrent stroke involves controlling those factors that promote the course of atherosclerosis, including hypertension, hyperlipidemia, diabetes mellitus, and smoking, as well as such local interventions as carotid endarterectomy and endovascular treatment. Nevertheless, administration of antiplatelet agents remains the core of management for preventing recurrent stroke and other cardiovascular events in at-risk patients.

Secondary prevention of atherothrombotic events after ischemic stroke

Atherosclerotic vascular disease is the leading cause of ischemic stroke, resulting in occlusive or severely stenotic lesions of major intracranial or extracranial arteries and narrowing of small penetrating arteries of the brain. Atherosclerosis of the coronary arteries (ie, coronary artery disease) is an indirect cause of cardioembolic stroke secondary to myocardial infarction. Ischemic heart disease may also be complicated by atrial fibrillation and cardioembolic stroke. Prevention of recurrent stroke and other ischemic events, including myocardial infarction, is a key component of treatment for patients with symptomatic ischemic cerebrovascular disease. Prevention of recurrent stroke involves controlling those factors that promote the course of atherosclerosis, including hypertension, hyperlipidemia, diabetes mellitus, and smoking, as well as such local interventions as carotid endarterectomy and endovascular treatment. Nevertheless, administration of antiplatelet agents remains the core of management for preventing recurrent stroke and other cardiovascular events in at-risk patients.

Use of antiplatelet agents for prevention of ischemic stroke

Overall management to lower risk for ischemic stroke is multifaceted. Management includes measures to treat risk factors for accelerated atherosclerosis and stroke, antithrombotic therapies to lower the risk for thromboembolism, and surgery to treat a defined arterial or cardiac lesion. Treatment decisions are made on a case-by-case basis, with most patients receiving some combination of medication and recommendations for lifestyle modification. Some patients will also undergo surgical or endovascular interventions. This article discusses antithrombotic treatment for ischemic stroke prevention, placing major emphasis on the indications for and administration of antiplatelet therapy.

Aspirin in the prophylaxis of coronary artery disease

Aspirin has been used for more than 100 years, but its mechanisms of action have only been understood in the past 20 years. Aspirin interferes with arachidonic acid metabolism in platelets and endothelial cells and thereby reduces thromboxane A2 and prostacyclin. It also has other mechanisms of action, including anti-inflammatory roles, protection from oxidative stress, enhancement of fibrinolysis, and suppression of plasma coagulation and platelet-dependent inhibition of thrombin generation. It has been used for primary and secondary prevention of myocardial ischemia, and for primary and secondary prevention of cerebrovascular ischemia. We review the 5 pivotal studies relating to primary prevention for cardiovascular risk and the many studies relating to secondary prevention of myocardial ischemia. We also review the utility of aspirin in primary prevention of myocardial infarction and stroke. We conclude that aspirin is one of the most potent drugs ever discovered and that its effects extend well beyond those of cycloxoxygenase enzyme inhibition. Aspirin treatment does not preclude control of underlying and comorbid conditions such as diabetes mellitus, hypertension, and dyslipidemia. For most patients, a daily dose of 325 mg is optimal. Patients must understand the potential for gastrointestinal upset and hemorrhagic complications. The utility of aspirin is greater in coronary artery disease prevention than in cerebrovascular prevention.

Antiplatelet agents versus control or anticoagulation for heart failure in sinus rhythm

BACKGROUND

Morbidity and mortality in patients with symptomatic chronic heart failure is high, it predisposes to stroke and thromboembolism which in turn contribute to high mortality in heart failure.

OBJECTIVES

To determine effect of antiplatelet agents when compared to placebo or anticoagulant therapy on death and/or major thromboembolic events in adults with heart failure who are in sinus rhythm.

SEARCH STRATEGY

Systematic search of electronic databases (MEDLINE, EMBASE, DARE). Abstracts from cardiology meetings and reference lists of relevant papers were searched. Authors of studies were contacted for further information.

SELECTION CRITERIA

Randomised parallel group placebo or controlled trials comparing antiplatelet therapy with control or anticoagulation in adults with chronic heart failure in sinus rhythm. Treatment for at least 1 month. To assess any adverse effects cohort study & non-randomised controlled studies were assessed. Orally administered antiplatelet agents e.g. non-steroidal anti-inflammatory agents, TICLOPIDINE, CLOPIDOGREL, DIPYRIDAMOLE, ASPIRIN compared with anticoagulant agents e.g. COUMARINS, WARFARIN or placebo.

DATA COLLECTION AND ANALYSIS

Data were extracted by two reviewers independently. No meta-analyses were performed as no data were available from randomised comparisons. The data extracted included data relating to the complexities of the topic area, such as patient characteristics and concomitant treatments, as well as data relating to study eligibility, quality, and outcomes. Non-randomised studies were used to identify side-effects caused by anticoagulants.

MAIN RESULTS

One RCT of warfarin, aspirin versus no antithrombotic therapy was found but no definitive data have yet been published. Three retrospective, non-randomised cohort studies from the V-HeFT, SOLVD and SAVE trials examining the role of ACE inhibitors have examined the role of aspirin therapy +/- anticoagulant therapy in patients with heart failure and/or left ventricular systolic dysfunction. The results from these trials were conflicting.

REVIEWER'S CONCLUSIONS

At present there is no evidence from long term RCTs to recommend use of aspirin to prevent thromboembolism in patients with heart failure in sinus rhythm. A possible interaction with ACE inhibitors may reduce the efficacy of aspirin, although this evidence is from retrospective analyses of trial cohorts. There is also no evidence to indicate superior effects from oral anticoagulation, when compared to aspirin, in patients with heart failure in sinus rhythm.

Antiplatelet therapy for secondary stroke prevention

The precise role of antiplatelet therapy in secondary stroke prevention remains a matter of some debate. Although specific antiplatelet agents (notably aspirin, ticlopidine, dipyridamole, and clopidogrel) have been shown to be active in the prevention of secondary stroke, questions remain about the effective dose of these agents and their potential efficacy in combined therapeutic regimens. In addition, haematological and gastrointestinal side-effects of antiplatelet agents remain a significant clinical concern for patients and prescribing physicians. This review article examines research on both monotherapy and combination antiplatelet therapy for secondary stroke prevention, with an emphasis on lessons learned about dosage schedules, treatment protocols, and side-effect profiles.

Consensus among experts and research synthesis. A comparison of methods

A comparison of two assessment methods, consensus among experts and research synthesis of the scientific literature, was performed using a surgical procedure, carotid endarterectomy (CE), as an example. These two methods have been widely advocated as being scientifically valid. While the comparison revealed a number of areas of general agreement, important differences between the two methods emerged. For example, 30-day mortality for asymptomatic patients was considered an effective outcome (ranked first) by the synthesis, but only "equivocal" (ranked third) of six major indicators reported by the consensus method. The synthesis results are also consistent with other literature reviews as well as with recent large-scale randomized trial results. A number of factors that could account for differences between the two methods were examined. Overall, use of consensus panels may be appropriate early in the development of an intervention where the evidence is sparse, while quantitative research synthesis is preferable when a number of high-quality studies have been performed.

Carotid endarterectomy: the gold standard

Carotid endarterectomy has been firmly established as the gold standard of therapy for symptomatic and asymptomatic patients with severe carotid stenosis, provided surgical complication rates are within prescribed limits. The procedure-related risk of stroke/death should be < 3% in asymptomatic patients and < 6% in symptomatic patients. New investigational therapies such as balloon angioplasty and stenting for carotid stenosis should be evaluated against the same standard.

Acute stroke

Disruption of cerebral blood flow may influence brain energy metabolism to produce reversible or irreversible neurologic deficits. The emergency physician is in a unique position to provide timely treatment during the first few hours of an acute stroke. He or she must be facile with unique pharmacologic and non-pharmacologic treatment designed for the stroke patient concerning ventilation, blood pressure, and circulation.

Efficacy of dipyridamole as prophylaxis for stroke and the added value of dipyridamole in combination with aspirin

Although dipyridamole was identified as a potential antithrombotic agent many years ago,(1) its effectiveness as a single agent in secondary prevention of arterial thrombosis in man has never been proven in properly conducted clinical trials with sufficient power. In many clinical trials it has been tested in combination with aspirin, and until recently meta-analyses have failed to show any significant benefit of the combination of aspirin and dipyridamole beyond that shown with aspirin alone.(2,3).

Pharmacological prophylaxis against postoperative graft occlusion after peripheral vascular surgery: a world-wide survey

OBJECTIVES

To define current practice regarding the use of pharmacological prophylaxis to prevent postoperative graft occlusion.

DESIGN

Prospective open questionnaire.

MATERIALS AND METHODS

Questionnaires regarding this subject were sent to vascular surgeons throughout the world to analyse current practice.

RESULTS

651 questionnaires were returned with a response rate of 62% and form the basis for this report. Data from 100,334 vascular reconstructions were reported in this survey. Prophylaxis against postoperative graft occlusions was common. Treatment periods were usually greater than 1 year. Among carotid surgery patients, 82% received prophylaxis, consisting mainly of low-dose acetysalicylic acid (ASA). In Mid-Europe the use of oral anticoagulation was more common than in other regions (p < 0.001). Among aneurysm surgery patients, 38% received prophylaxis. For infrainguinal bypass, ASA in low dose was the most commonly used agent worldwide. However, oral anticoagulation was more frequent in Mid-Europe, in contrast to South America where the combination of ASA and dipyridamole was most common. Considerable geographical differences regarding patient selection, the frequency of specific procedures and operative techniques existed.

CONCLUSIONS

Important world-wide differences exist regarding prophylaxis for postoperative graft occlusion.

Pyrazolopyridine derivative acts as a novel cyclooxygenase inhibitor: antiplatelet effect in aged patients with ischemic stroke

OBJECTIVE

To examine the antiplatelet effect of a novel pyrazolopyridine derivative (KC-764) in geriatric patients with ischemic stroke.

DESIGN

Randomized clinical trial of three graded dose levels.

SETTING

A geriatric clinic attached to a nursing home.

PATIENTS

Fifteen patients with a history of cerebral infarction with a mean age of 75 +/- 5 years (range, 65-83). Patients were divided into three groups and administered 10, 20, or 40 mg/day KC-764 for 8 weeks.

MEASUREMENTS

Platelet aggregation induced by arachidonate, ADP, collagen and platelet-activating factor. Plasma or serum levels of thromboxane B2 and 6-ketoprostaglandin F1 alpha.

MAIN RESULTS

Platelet aggregation was inhibited by KC-764 administration and returned to the control level after discontinuation. Although plasma thromboxane B2 levels were markedly decreased, plasma 6-ketoprostaglandin F1 alpha was not affected. However, the dose of 10 mg/day was not sufficient to maintain an effective plasma level of KC-764. There were no side effects or changes in laboratory findings.

CONCLUSIONS

We confirmed that KC-764 at a dose of 20 to 40 mg/day is an effective antiplatelet agent and a good candidate for a trial to see if it is feasible for long-term use for the prevention of ischemic stroke in high-risk patients.

Archie Cochrane's challenge: can periodically updated reviews of all randomised controlled trials relevant to neurology and neurosurgery be produced?

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Vascular disease in the elderly patient

At a time of potentially dramatic changes in health care policy in this country, and in view of the necessity for health care cost containment, physicians are expected to exercise serious introspection in the selection of treatment for the elderly patient with peripheral arterial disease. These decisions should be made while acknowledging that it is the goal of the health-care provider "to postpone chronic illness, to maintain vigor, and to slow social and psychological involution." For the elderly patient with an abdominal aortic aneurysm, with significant carotid disease, or with limb-threatening peripheral ischemia, the evidence is compelling that timely surgical intervention in properly selected patients is well tolerated and will satisfy this goal.

Anticoagulants, antiaggregants or nothing following carotid endarterectomy?

Carotid endarterectomy (TEA) has proven to be beneficial for symptomatic patients. Anticoagulation (AC) and antiplatelet therapy (ASA) have been shown to prolong life following vascular surgery in patients with occlusive arterial disease (PAOD). To determine whether ASA or AC prolong life after TEA, retrospective analysis was undertaken, since cerebral haemorrhage is associated with the use of both drugs, especially AC. Between 1979-1986, 328 patients with stenotic lesions of the carotid bifurcation were operated upon electively. Patient survival and causes of death were the primary end points of the analysis. Recent data were obtained from the Austrian Central Bureau of Statistics. Cumulative survival rates were calculated by Kaplan-Meier estimation and differences determined by Breslow and Mantel tests. 36 patients were on AC, 157 on ASA and 135 remained without medication (0-group). Since the common risk factors in PAOD were unevenly distributed between groups, a stepwise Cox regression model was applied which revealed age (p < 0.01), cardiac pathology (p < 0.01) and diabetes (p < 0.05) as relevant for survival. Therefore, ASA patients and 0-group patients were selected and matched, employing the aforementioned prognostic criteria, and compared to the patients on long-term AC for various indications (vein bypass surgery, myocardial infarction, pulmonary embolism; i.e. data-matching). The median postoperative survival was 7.72 years for ASA and 8.48 years for AC, compared to 6.07 years for the 0-group (p = 0.0095 Breslow, p = 0.477 Mantel). There was no significant difference between AC and ASA treated patients. Irrespective of medication, the causes of death were well balanced, and no higher incidence of intracerebral haemorrhage was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Stroke prophylaxis: hypertension management and antithrombotic therapy

OBJECTIVE

To review trials involving risk factor management and pharmacologic therapy for the prevention of stroke.

DATA SOURCES

English-language literature published between 1966 and 1992 was analyzed; pertinent literature is reviewed.

STUDY SELECTION

Studies that evaluated the impact of risk factor management on prevention of vascular events were selected. In addition, trials assessing the safety and efficacy of pharmacologic intervention in primary and secondary stroke prevention were evaluated.

DATA EXTRACTION

Trials were evaluated for their ability to demonstrate a decrease in stroke occurrence.

DATA SYNTHESIS

Various trials were analyzed in several categories. Studies evaluating risk factor management of hypertension and cardiogenic cerebral emboli were reviewed and recommendations made based on a consensus of these trials. The use of antiplatelet agents in stroke prevention was addressed by a review of pertinent trials and meta-analyses.

CONCLUSIONS

The control of risk factors and the use of antiplatelet agents significantly reduces the risk of vascular events. Benefit from different therapies may be specific to certain patient populations and recommendations are made for these patients.

Evaluation of the clinical utility of platelet aggregation studies in the long-term follow-up of patients with atherosclerotic vascular disease

The present study was designed to evaluate the usefulness of laboratory monitoring of antiplatelet therapy by means of a multiparametric evaluation of in vitro platelet aggregation tests in the attempt to individually optimize a given therapeutic regimen. The presence of a condition of hyperaggregability was shown in approximately 80% of patients with different forms of atherosclerotic vascular disease not undergoing any therapeutic regimen with antiplatelet agents. Conversely, a significant decrease in platelet activity was observed in patients undergoing different therapies based on acetylsalicylic acid (ASA), ticlopidine, or indobufen. The similar antiaggregatory effect of low-dose vs. high-dose ASA therapies was also shown. Dipyridamole alone showed no antiaggregatory effect, which, in turn, was reached only by the addition of ASA. Nevertheless, the association of ASA plus dipyridamole did not show any stronger antiplatelet effect than ASA alone. The evaluation of in vitro platelet activity in a group of patients treated with picotamide failed to show any significant change in comparison with the untreated group, probably due to the short half-life of picotamide in man and/or to its capability of reversibly antagonizing the action of thromboxane at receptor level. The evaluation of a long-term follow-up of 90 patients treated with different antiplatelet agents supports the idea that a multiparametric analysis of in vitro platelet aggregation may provide valuable help in monitoring and optimizing a given therapeutic regimen.

An empirical study of the possible relation of treatment differences to quality scores in controlled randomized clinical trials

Meta-analytic investigations sometimes use assessments of research quality according to a formal protocol as a tool for improving research synthesis. We asked whether a particular quality scoring system could have a direct use in adjusting the summary estimates of a treatment difference. In an empirical study of the relation of quality scores to treatment differences in published meta-analyses of 7 groups of controlled randomized clinical trials comprising 107 primary studies, we found no relation between treatment difference and overall quality score. We also found no relation between quality score and variation in treatment difference. The level of quality scores has increased at a rate of 9% per decade for three decades, averaging 0.51 on a scale of 0 to 1 for the 1980s, and leaving much room for improvement. Nevertheless, attention to quality of studies by editors, reviewers, and authors may be raising both the level of research done and quality of the reports.

Secondary prevention of myocardial infarction in the first European Stroke Prevention Study

The first European Stroke Prevention Study (ESPS 1) showed that a statistically significant degree of secondary ischemic lesions could be prevented by combined therapy with aspirin (330 mg) and dipyridamole (75 mg) t.i.d. The risk of both central and myocardial secondary ischemic lesions was reduced by more than 30%. Similar results were seen after both transient ischemic attacks and stroke, and in both men and women.

Issues in planning and interpreting active control equivalence studies

Active control equivalence studies, with the goal of demonstrating therapeutic equivalence between a new and an active control treatment, are becoming more widespread due to current therapies that reflect previous successes in the development of new treatments. Because ethical requirements preclude the use of a placebo or no-treatment control for internal study validation, certain methodologic issues arise in active control equivalence trials that require special attention. We emphasize a special feature of this alternative study design, namely, its reliance on an implicit "historical control assumption". To conclude that a new drug is efficacious on the basis of an active control equivalence study (ACES) requires a fundamental assumption that the active control drug would have performed better than a placebo, had a placebo been used in the trial. In designing an ACES, one needs some assurance that historical estimates of the active control drug's efficacy relative to placebo are applicable to the new experimental setting. Steps that can be taken to compile such evidence and to justify the use of an active control equivalence design are described. These issues are illustrated in the context of a planned study to evaluate the efficacy of a new drug for the prevention of stroke, using aspirin as an active control.