Low-dose and high-dose acetylsalicylic acid for patients undergoing carotid endarterectomy: a randomised controlled trial. ASA and Carotid Endarterectomy (ACE) Trial Collaborators

Aspirin use, dose, and clinical outcomes in postmenopausal women with stable cardiovascular disease: the Women's Health Initiative Observational Study

BACKGROUND

Despite compelling evidence that aspirin reduces fatal and nonfatal vascular events among the overall population in various settings, women have frequently been underrepresented and their data underreported. We sought to evaluate the relationship between aspirin use, dose (81 or 325 mg), and clinical outcomes among postmenopausal women with stable cardiovascular disease (CVD).

METHODS AND RESULTS

Women with CVD (n=8928) enrolled in the Women's Health Initiative Observational Study were used for this analysis. The primary outcome was the incidence of all-cause mortality and cardiovascular events (myocardial infarction, stroke, and cardiovascular death). Among 8928 women with stable CVD, 4101 (46%) reported taking aspirin, of whom 30% were on 81 mg and 70% were on 325 mg. At 6.5 years of follow-up, no significant association was noted for aspirin use and all-cause mortality or cardiovascular events. However, after multivariate adjustment, aspirin use was associated with a significantly lower all-cause (adjusted hazard ratio, 0.86 [0.75 to 0.99]; P=0.04) and cardiovascular-related mortality (adjusted hazard ratio, 0.75 [0.60 to 0.95]; P=0.01) compared with no aspirin. Aspirin use was associated with a lower risk of cardiovascular events (adjusted hazard ratio, 0.90 [0.78 to 1.04]; P=0.14), which did not meet statistical significance. Compared with 325 mg, use of 81 mg was not significantly different for all-cause mortality, cardiovascular events, or any individual end point.

CONCLUSIONS

After multivariate adjustment, aspirin use was associated with significantly lower risk of all-cause mortality, specifically, cardiovascular mortality, among postmenopausal women with stable CVD. No significant difference was noted between 81 mg and 325 mg of aspirin. Overall, aspirin use was low in this cohort of women with stable CVD.

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.

The 2008 William M. Feinberg lecture: prioritizing stroke research

Stroke is a tremendous burden to health worldwide both in the developed and developing world. Current levels of research funding do not adequately reflect this burden, particularly when expected increases in stroke rates are considered. Of course, an investment in stroke research is only justified if a return can be expected. The ultimate goal of stroke research is to reduce the burden of disease, and clinical trials are the clearest expression of the value of research because their results can directly impact health. In a review of stroke trials funded by the US National Institute of Neurological Disorders and Stroke, we found that the overall impact of the trials was dramatically positive and justified the entire research budget of the Institute. Nonetheless, there were obvious opportunities for improvement.

METHODS

meta--research--on topics not just relevant to stroke, but to the study of all disease.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Blood pressure declines and less favorable outcomes in the NINDS tPA stroke study

BACKGROUND AND PURPOSE

Hypertension is the most important modifiable risk factor for secondary stroke prevention but the immediate management of blood pressure after stroke is uncertain. We evaluated outcomes in the NINDS tPA stroke study in relation to blood pressure declines during the first 24 h after randomization.

METHODS

Declines in blood pressure compared to baseline and preceding time points were analyzed in relationship to favorable outcomes (by a global test), poor outcomes (Rankin scale >3) and death at 3 months.

RESULTS

551 patients did not receive immediate pre-randomization anti-hypertensive treatment and had available blood pressures. Multivariate analysis showed significantly and progressively reducing likelihoods of a favorable outcome with each 10 mmHg decline in systolic blood pressure (SBP) >50 mmHg compared to any preceding measurement. Poor outcomes were significantly more likely in patients with >50 mmHg SBP reduction (or >30 mmHg compared to any immediately preceding measurement). There was an increased risk of death with blood pressure declines >60 mmHg. tPA treatment still produced favorable outcomes compared with placebo even with blood pressure declines. The median largest SBP reduction from baseline in patients treated with tPA was 35 mmHg compared to 30 mmHg in placebo-treated patients (p<0.01).

CONCLUSIONS

In this post hoc analysis, progressively reducing likelihoods of a favorable outcome were seen with increasing declines in SBP. Despite a greater likelihood of favorable outcomes, tPA treatment was associated with a greater reduction in blood pressure than placebo. Randomized trials of blood pressure management are needed.

Aspirin: Promise and Resistance in the New Millennium

Although conceived at the end of the 19th century, aspirin remains the gold standard of antiplatelet therapy. Approximately 100 randomized clinical trials have established its efficacy and safety in the prevention of myocardial infarction, ischemic stroke, and vascular death among high-risk patients treated for a few weeks, at one end of the spectrum, and in low-risk subjects treated up to 10 years at the other. Despite this wealth of data, several issues continue to be debated concerning the use of aspirin as an antiplatelet agent, and novel opportunities appear on the horizon for this 110-year-old drug. These issues include: (1) the optimal dose for cardiovascular prophylaxis; (2) the uncertain threshold of cardiovascular risk for its use in primary prevention; (3) the apparent gender-related difference in its cardioprotective effects; (4) the increasingly popular theme of aspirin “resistance”; (5) the opportunities of chemoprevention in colorectal cancer; and (6) the renewed interest in aspirin as an analgesic agent in osteoarthritic patients at high cardiovascular risk. The aim of this review is to address these issues by integrating our current understanding of the molecular mechanism of action of the drug with the results of clinical trials and epidemiological studies of aspirin as an antiplatelet drug.

The effect of high-dose aspirin pre-treatment on the incidence of myonecrosis following elective coronary stenting

BACKGROUND

Inadequate platelet response to aspirin is associated with increased incidence of peri-procedural myonecrosis. Antiplatelet activity of aspirin can be improved by increasing the dose. High-dose aspirin pre-treatment, therefore, may reduce the incidence of myonecrosis post stenting.

METHODS AND RESULTS

Two-hundred patients taking 75-325 mg daily doses of aspirin for at least 2 weeks were randomized for addition or no addition of 500 mg aspirin before elective coronary stenting (aspirin 500 group, n=100 and control group, n=100). Primary endpoint was the occurrence of peri-procedural myonecrosis defined as creatine kinase-myocardial band (CK-MB) elevation of >1x upper limits of normal (ULN). Aspirin 500 patients were significantly younger and more likely to have family history of coronary artery disease, but less likely to have received statins than controls. Elevation of CK-MB was observed in 29% of aspirin 500 patients and 15% of controls (p=0.017). The incidence of non-Q wave myocardial infarction (CK-MB elevation of >3xULN) tended to be higher in the aspirin 500 group than in the control group (5% versus 0%, p=0.059). Multivariate analysis identified baseline aspirin dose (OR: 1.006; 95% CI: 1.002-1.010; p=0.004), aspirin 500 mg treatment (OR: 2.5; 95% CI: 1.2-5.5; p=0.021) and baseline CK-MB level (OR: 1.4; 95% CI: 1.1-1.7; p=0.012) as independent predictors of CK-MB elevation after coronary stenting.

CONCLUSION

For patients taking daily low-dose aspirin therapy, supplementation with high-dose aspirin before elective coronary stenting does not reduce, but may increase the incidence of peri-procedural myonecrosis.

Endarterectomy or carotid artery stenting: the quest continues

BACKGROUND

Carotid endarterectomy (CEA) is still considered the "gold-standard" of the treatment of patients with significant carotid stenosis and has proven its value during past decades. However, endovascular techniques have recently been evolving. Carotid artery stenting (CAS) is challenging CEA for the best treatment in patients with carotid stenosis. This review presents the development of CAS according to early reports, results of recent randomized trials, and future perspectives regarding CAS.

METHODS

A literature search using the PubMed and Cochrane databases identified articles focusing on the key issues of CEA and CAS.

RESULTS

Early nonrandomized reports of CAS showed variable results, and the Stenting and Angioplasty With Protection in Patients at High Risk for Endarterectomy trial led to United States Food and Drug Administration approval of CAS for the treatment of patients with symptomatic carotid stenosis. In contrast, recent trials, such as the Stent-Protected Angioplasty Versus Carotid Endarterectomy trial and the Endarterectomy Versus Stenting in Patients with Symptomatic Severe Carotid Stenosis trial, (re)fuelled the debate between CAS and CEA. In the Stent-Protected Angioplasty Versus Carotid Endarterectomy trial, the complication rate of ipsilateral stroke or death at 30 days was 6.8% for CAS versus 6.3% for CEA and showed that CAS failed the noninferiority test. Analysis of the Endarterectomy Versus Stenting in Patients With Symptomatic Severe Carotid Stenosis trial showed a significant higher risk for death or any stroke at 30 days for endovascular treatment (9.6%) compared with CEA (3.9%). Other aspects-such as evolving best medical treatment, timely intervention, interventionalists' experience, and analysis of plaque composition-may have important influences on the future treatment of patients with carotid artery stenosis.

CONCLUSIONS

CAS performed with or without embolic-protection devices can be an effective treatment for patients with carotid artery stenosis. However, presently there is no evidence that CAS provides better results in the prevention of stroke compared with CEA.

Aspirin "resistance" and risk of cardiovascular morbidity: systematic review and meta-analysis

OBJECTIVE

To determine if there is a relation between aspirin "resistance" and clinical outcomes in patients with cardiovascular disease.

DESIGN

Systematic review and meta-analysis.

DATA SOURCE

Electronic literature search without language restrictions of four databases and hand search of bibliographies for other relevant articles.

REVIEW METHODS

Inclusion criteria included a test for platelet responsiveness and clinical outcomes. Aspirin resistance was assessed, using a variety of platelet function assays.

RESULTS

20 studies totalling 2930 patients with cardiovascular disease were identified. Most studies used aspirin regimens, ranging from 75-325 mg daily, and six studies included adjunct antiplatelet therapy. Compliance was confirmed directly in 14 studies and by telephone or interviews in three. Information was insufficient to assess compliance in three studies. Overall, 810 patients (28%) were classified as aspirin resistant. A cardiovascular related event occurred in 41% of patients (odds ratio 3.85, 95% confidence interval 3.08 to 4.80), death in 5.7% (5.99, 2.28 to 15.72), and an acute coronary syndrome in 39.4% (4.06, 2.96 to 5.56). Aspirin resistant patients did not benefit from other antiplatelet treatment.

CONCLUSION

Patients who are resistant to aspirin are at a greater risk of clinically important cardiovascular morbidity long term than patients who are sensitive to aspirin.

Initial Aspirin Dose and Outcome Among ST-Elevation Myocardial Infarction Patients Treated With Fibrinolytic Therapy

Background— Although treatment with immediate aspirin reduces morbidity and mortality in ST-elevation myocardial infarction, the optimal dose is unclear. We therefore compared the acute mortality and bleeding risks associated with the initial use of 162 versus 325 mg aspirin in fibrinolytic-treated ST-elevation myocardial infarction patients.

Methods and Results— Using combined data from the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO I) and Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO III) trials (n=48 422 ST-elevation myocardial infarction patients), we compared the association between initial aspirin dose of 162 versus 325 mg and 24-hour and 7-day mortality, as well as rates of in-hospital moderate/severe bleeding. Results were adjusted for previously identified mortality and bleeding risk factors. Overall, 24.4% of patients (n=11 828) received an initial aspirin dose of 325 mg, and 75.6% (n=36 594) received 162 mg. The 24-hour mortality rates were 2.9% versus 2.8% ( P =0.894) for those receiving an initial aspirin dose of 325 versus 162 mg. Mortality rates at 7 and 30 days were 5.2% versus 4.9% ( P =0.118) and 7.1% versus 6.5% ( P =0.017) among patients receiving the 325 versus 162 mg aspirin. After adjustment, aspirin dose was not associated with 24-hour (odds ratio [OR], 1.01; 95% CI, 0.82 to 1.25), 7-day (OR, 1.00; 95% CI, 0.87 to 1.17), or 30-day (OR, 0.99; 95% CI, 0.87 to 1.12) mortality rates. No significant difference was noted for myocardial infarction or the composite of death or myocardial infarction between groups. In-hospital moderate/severe bleeding occurred in 9.3% of those treated with 325 mg versus 12.2% among those receiving 162 mg ( P <0.001). After adjustment, 325 mg was associated with a significant increase in moderate/severe bleeding (OR, 1.14; 95% CI, 1.05 to 1.24; P =0.003).

Conclusion— These data suggest that an initial dose of 162 mg aspirin may be as effective as and perhaps safer than 325 mg for the acute treatment of ST-elevation myocardial infarction.

Antiplatelet agents for stroke prevention following transient ischemic attack

Regardless of extent or duration of acute effects, transient ischemic attack (TIA) is a marker for cerebrovascular ischemia and carries risk for secondary stroke comparable to that associated with ischemic stroke. Pharmacologic and nonpharmacologic interventions aimed at reducing risk of secondary stroke should be implemented as soon as possible after characterization of the initial event. Medical strategies for secondary prevention include modifying general cardiovascular risk factors but are centered on the specific reduction of stroke risk by antiplatelet agents. Aspirin and clopidogrel have each demonstrated efficacy in reducing secondary event risk; however, clopidogrel has not been shown specifically to prevent secondary events in patients who have had a TIA or stroke. Combination therapy using aspirin plus dipyridamole is the only combination approach to demonstrate additive benefit that is significantly greater than that conferred by aspirin. In contrast, the combination of clopidogrel plus aspirin has not demonstrated significant benefit over monotherapy with either agent and has been associated with increased risk of bleeding episodes.

Is there a role for combinations of antiplatelet agents in stroke prevention?

Antiplatelet medications are the agents of choice for secondary prevention of noncardioembolic ischemic strokes. Multiple clinical trials have proven their reliable albeit modest clinical benefits and relatively good safety profile. The most commonly recommended antiplatelet agents for secondary stroke prevention in North America and Europe are aspirin, clopidogrel, and the combination of aspirin and extended-release dipyridamole. Because of the multiple pharmacologic mechanisms available for platelet inhibition, combination antiplatelet agents have the potential for synergistic effects. However, combinations of antithrombotic agents do not necessarily improve clinical efficacy and are typically associated with increased toxicity. Clopidogrel and aspirin have been used in combination in patients with diverse arterial vascular diseases. Combination antiplatelet therapy with clopidogrel and aspirin has established clinical benefits, particularly in coronary disease and in patients who have undergone coronary stenting. Although it is tempting to extrapolate the benefits of clopidogrel and aspirin to the setting of secondary stroke prevention, recent clinical trials have failed to document significant clinical benefits in cerebrovascular patients. This failure has occurred because of a lack of significant efficacy for prevention of vascular events and a substantial increase in bleeding risk. Therefore, the clopidogrel and aspirin combination is not recommended for recurrent stroke prevention. In general, when clopidogrel is used for cerebrovascular patients, the addition of aspirin should be avoided unless there is a specific cardiac indication such as recent acute coronary syndrome or a coronary stent. The combination of aspirin and extended-release dipyridamole is supported by Class I data from two large studies demonstrating superiority over aspirin alone for recurrent stroke prevention. Although dual antiplatelet therapy with clopidogrel and aspirin has never been directly compared with the combination of aspirin and extended-release dipyridamole, clinical trial results favor the latter for secondary stroke prevention. Currently, there are no data for primary stroke prevention with dual antiplatelet agents regarding aspirin and extended-release dipyridamole. Limited data from the recent Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization Management and Avoidance (CHARISMA) trial indicate that the combination of clopidogrel and aspirin may be harmful, compared with aspirin alone.

Surgery Insight: carotid endarterectomy--which patients to treat and when?

Over the past 15 years, we have witnessed a resurgence of surgery for prevention of ischemic stroke. Landmark trials including the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial have explored the role of carotid endarterectomy in this context, comparing the procedure with best medical treatment in patients with high-grade stenosis of the internal carotid artery and transient ischemic attack or minor nondisabling stroke in the same territory. Here, we discuss the lessons learnt from these trials, and review the Asymptomatic Carotid Atherosclerosis Study and the Asymptomatic Carotid Surgery Trial, which attempted to resolve the rather vexing issue of surgical treatment for patients with asymptomatic internal carotid artery stenosis. We also review the best medical treatment for patients undergoing carotid endarterectomy in the perioperative period, and examine the risk of ischemic stroke after CABG surgery, both when this procedure is performed alongside endarterectomy and when CABG surgery and endarterectomy are performed as a two-staged procedure.

NINDS clinical trials in stroke: lessons learned and future directions

Since 1977 the National Institute of Neurological Disorders and Stroke (NINDS) at the National Institutes of Health (NIH) has sponsored 28 phase 3 trials to evaluate treatments of stroke, which when all completed will have randomized a total of 44 862 patients in the United States and other countries. NINDS stroke clinical trials have been successful in finding beneficial and cost-effective treatments for cerebrovascular disease. Future trials are likely to be larger and have simpler designs which allow for the inclusion of more patients and which collect less data for each patient. In addition, measures of cognitive outcomes, particularly timed tests of executive function, disability scales, and quality-of-life outcomes will become more common. The stroke research community can take pride in the solid base of evidence that has been built over the past 2 decades. If we continue to follow the discoveries of science, continue to create new trial methodology, and increase participation in clinical trials, significant advances in the treatment of cerebrovascular disease will continue.

Stroke prevention in the high-risk patient

Strokes are increasing in number due to an ageing population and are largely preventable. In the highest risk patients, a 90% relative risk reduction for stroke is attainable by appropriately using all the measures proven to reduce stroke: smoking cessation, a Mediterranean diet, control of hypertension, anticoagulants or antiplatelet agents, lipid lowering drugs and appropriate carotid endarterectomy. Vitamin therapy to lower homocysteine and carotid stenting are additional measures that may yet prove beneficial. Diet, smoking cessation and appropriate carotid endarterectomy reduce stroke by more than do pharmacotherapies. Blood pressure control depends more on selecting appropriate therapy individualised for the patient, than on using any particular drug class. This review, therefore, places pharmacotherapy in perspective as part of, but not all of, stroke prevention.

Cyclo-oxygenase-2 selective inhibitors and nonsteroidal anti-inflammatory drugs: balancing gastrointestinal and cardiovascular risk

Background

Differences between gastrointestinal and cardiovascular effects of traditional NSAID or cyclooxygenase-2 selective inhibitor (coxib) are affected by drug, dose, duration, outcome definition, and patient gastrointestinal and cardiovascular risk factors. We calculated the absolute risk for each effect.

Methods

We sought studies with large amounts of information to calculate annualised rates for clearly defined gastrointestinal (complicated upper gastrointestinal perforations, ulcers, or bleeds, but not symptomatic or endoscopic ulcers) and serious cardiovascular outcomes (antiplatelet trial collaborators – APTC – outcome of fatal or nonfatal myocardial infarction or stroke, or vascular death).

Results

Meta-analyses and large randomised trials specifically analysing serious gastrointestinal bleeding or cardiovascular events occurring with five different coxibs had appropriate data. In total there were 439 complicated upper gastrointestinal events in 49,006 patient years of exposure and 948 serious cardiovascular events in 99,400 patient years of exposure. Complicated gastrointestinal events occurred less frequently with coxibs than NSAIDs; serious cardiovascular events occurred at approximately equal rates. For each coxib, the reduction in complicated upper gastrointestinal events was numerically greater than any increase in APTC events. In the overall comparison, for every 1000 patients treated for a year with coxib rather than NSAID, there would be eight fewer complicated upper gastrointestinal events, but one more fatal or nonfatal heart attack or stroke. Three coxib-NSAID comparisons had sufficient numbers of events for individual comparisons. For every 1000 patients treated for a year with celecoxib rather than an NSAID there would be 12 fewer upper gastrointestinal complications, and two fewer fatal or nonfatal heart attacks or strokes. For rofecoxib there would be six fewer upper gastrointestinal complications, but three more fatal or nonfatal heart attacks or strokes. For lumiracoxib there would be eight fewer upper gastrointestinal complications, but one more fatal or nonfatal heart attack or stroke.

Conclusion

Calculating annualised event rates for gastrointestinal and cardiovascular harm shows that while complicated gastrointestinal events occur more frequently with NSAIDs than coxibs, serious cardiovascular events occur at approximately equal rates. For each coxib, the reduction in complicated upper gastrointestinal events was numerically greater than any increase in APTC events.

Carotid endarterectomy

Carotid endarterectomy (CEA) is performed to prevent embolic stroke in patients with atheromatous disease at the carotid bifurcation. There is now substantial evidence to support early operation in symptomatic patients, ideally within 2 weeks of the last neurological symptoms. Thus, the anaesthetist may be faced with a high risk patient in whom there has been limited time for preoperative preparation. The operation may be performed under local or general anaesthesia. The advantages and disadvantages of both are explored in this review. Carotid shunting may offer a degree of cerebral protection, but carries its own risks and has not been proved to reduce morbidity and mortality. The use of carotid shunts is based on clinical judgement, awake neurological monitoring, and the use of monitors of cerebral perfusion. There is no ideal monitor of cerebral perfusion in the patient receiving general anaesthesia. Both the intraoperative and postoperative periods may be witness to dramatic haemodynamic changes that may compromise the cerebral or myocardial circulations. In particular, postoperative hypotension may compromise both myocardial and cerebral perfusion, and severe hypertension can cause cerebral hyperperfusion. There is as yet limited evidence to guide the management of these problems. In summary, CEA can yield significant benefit, but those with the most to gain from the operation also present the greatest challenge to the anaesthetist.

Intensive management of risk factors for accelerated atherosclerosis: the role of multiple interventions

Patients at high risk of vascular events can reduce their risk by 75% to 80% through a combination of lifestyle changes and medical therapy. These include smoking cessation, a Mediterranean diet, daily exercise, maintaining a fit weight, moderate consumption of alcohol, effective control of blood pressure and diabetes, intensive treatment with lipid-lowering drugs and antiplatelet agents, and perhaps treatment with vitamins to lower homocysteine. Much of this is achieved primarily by the patient; physicians need to become better at assisting their patients in making lifestyle changes. Effective control of treatment-resistant hypertension can be improved by individualizing medical therapy to the underlying cause, based on measurement of plasma renin and aldosterone. Measurement of carotid plaque may be useful by providing feedback on the success of therapy.

Cyclooxygenase inhibition: what should we do to resolve the confusion? An American perspective

Recent placebo-controlled clinical trials suggest excessive adverse cardiovascular (CV) events associated with cyclooxygenase (COX)-2 selective nonsteroidal anti-inflammatory drugs (NSAIDs), developed to reduce gastrointestinal irritation associated with nonselective NSAIDs. Subsequent retrospective analyses of observational series and non-CV clinical trials suggest that CV events may occur with modest excess with all NSAIDs, nonselective and COX-2 selective, compared with nonuse of these drugs, may be dose related, and do not differ substantially in frequency among various NSAIDs. However, inadequacy of study designs, controls, and events has precluded definition of the risk-benefit relationship of COX-2 selective and nonselective NSAIDs. Resolution of this problem requires several different types of studies, necessarily including appropriately designed randomized, controlled trials comparing commonly employed nonselective and COX-2 selective NSAIDs in patients expected to benefit (ie, those with symptomatically severe arthritis) who also have coronary occlusive disease so that achievable noninferiority trial size has power sufficient to resolve relatively small differences in adverse CV (and gastrointestinal) event rates. This article explores the goals and possible designs of trials appropriate for defining risk-benefit relationship that must be known for optimal application of NSAID therapy.

The PGH-synthase system and isozyme-selective inhibition

Virtually all human cell types can express both cyclooxygenase (COX)-1 and COX-2 under appropriate circumstances. Both isoforms can subserve physiologic and pathophysiologic roles when coupled with the appropriate stimuli and downstream prostaglandin (PG)H2-isomerases and prostanoid receptors. Although the ratio of maximal biosynthetic capacity of human platelets to the basal rate of production of thromboxane A2 is approximately 5000, this ratio is much lower in the case of PGI2, thus dictating quite different requirements for the extent and duration of COX inhibition in human platelets and vascular endothelial cells to detect functional and clinical effects. The development of low-dose aspirin as an antiplatelet agent has been instrumental in characterizing the role of platelet COX-1 in atherothrombosis. Similarly, though quite unexpectedly, the development of coxibs as anti-inflammatory agents has been instrumental in elucidating the role of endothelial COX-2 in vascular occlusion. Because of differential requirements for the inhibition of thromboxane A2 versus PGI2 biosynthesis in vivo, most traditional nonsteroidal anti-inflammatory drugs tend to mimic the effects of coxibs, rather than aspirin, on prostanoid-dependent cardiovascular homeostasis.

Aspirin resistance or variable response or both?

Numerous clinical trials have demonstrated that aspirin is effective in secondary prevention and in high-risk primary prevention of adverse cardiovascular events. However, a constellation of clinical and laboratory evidence exists that demonstrates diminished or absent response to aspirin in some patients. This has led to the concept of "aspirin resistance," which is a poorly defined, somewhat misleading term. The mechanism for aspirin resistance has not been fully established, but it is almost certainly due to a combination of clinical, biological, and genetic properties affecting platelet function. There are no criteria for distinguishing true resistance from treatment failure, and there is no consensus on whether the definition of aspirin resistance should be based on clinical outcomes, laboratory evidence, or both. Studies in large populations are needed to define antiplatelet resistance using consistent and reproducible assays and correlate the measurements with clinical outcomes. One such prospective randomized trial is completed, and 2 others are under way: the Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management, and Avoidance (CHARISMA) trial compared clopidogrel and aspirin with placebo and aspirin for high-risk primary or secondary prevention, and the Aspirin Nonresponsiveness and Clopidogrel Endpoint Trial (ASCET) is evaluating whether switching to clopidogrel will be superior to continued aspirin therapy in improving clinical outcomes in aspirin-resistant patients with angiographically documented coronary artery disease. The Research Evaluation to Study Individuals Who Show Thromboxane or P2Y(12) Receptor Resistance (RESISTOR) trial is investigating whether modifying antiplatelet regimens could prevent myonecrosis after percutaneous coronary intervention in patients with aspirin and clopidogrel resistance.

Discontinuation of perioperative antiplatelet and anticoagulant therapy in stroke patients

Growing evidence suggests that perioperative withdrawal of ASA for secondary stroke prevention increases thromboembolic risk without the associated benefit of decreased bleeding complications. ASA maintenance is acceptable in many procedures, including invasive ones. Many procedures, in particular ophthalmologic, dermatologic, and dental surgeries, also are safe while continuing oral AC. Warfarin has been continued successfully even in some surgeries that have high bleeding risk. When the risk is too high, temporary bridging therapy with LWMH is safe in many populations. Although the exact thromboembolic risks associated with temporary cessation of AP and AC are unknown and likely low, morbidity and mortality associated with thromboembolism are high. Further studies investigating the risks and benefits of maintaining AP and AC during procedures, particularly invasive ones, are needed. Meanwhile, it is critical that physicians understand the risks and benefits of perioperative AP and AC and the variety of procedures in which these agents can be safely continued.

Low-dose aspirin before intracranial surgery--results of a survey among neurosurgeons in Germany

BACKGROUND

Increasing numbers of patients presenting for intracranial surgery are receiving concurrent medication with low-dose aspirin, leading to dysfunctional circulating platelets, which might increase the peri-operative risk of bleeding.

OBJECTIVE

To survey the opinions and working practices of neurosurgical facilities in Germany regarding patients who present with low-dose aspirin medication before elective intracranial surgery. Methods. Questionnaires were sent to 210 neurosurgical facilities asking five main questions: (1) the adherence of any policy of stopping aspirin pre-operatively, (2) the personal risk assessment for patients with brain surgery under low-dose aspirin medication, (3) the preferred method of treatment for excessive bleeding in this context, (4) personal knowledge of haemorrhagic complications in this group of patients, and (5) the characteristics of the neurosurgical units concerned.

RESULTS

There were 138 (65.7%) valid responses. Of the respondents, 111 (80.4%) had a departmental policy for the discontinuation of pre-operative aspirin treatment. The mean time for discontinuation of aspirin pre-operatively was 7.3 days (range: 0-21 days). 107 respondents (77.5%) considered that patients taking low-dose aspirin were at increased risk for excessive peri-operative haemorrhage, and 80 (58%) reported having personal experience of such problems. Ninety-seven respondents (70.3%) would use special medical therapy, preferably desmopressin, if haemorrhagic complications developed intra-operatively. The mean amount of intracranial operations per year in each neurosurgical facility was 494 (range: 50-1700).

CONCLUSIONS

The majority of neurosurgical facilities in Germany have distinct departmental policies concerning the discontinuation of low-dose aspirin pre-operatively, with an average of 7.3 days. Three-quarter of the respondents felt that aspirin was a risk factor for haemorrhagic complications associated with intracranial procedures, and more than half of the interviewees reported having personal experience of such problems. Various medicamentous methods of counteracting aspirin-induced platelet dysfunction and excessive bleeding in this context are discussed and evaluated.

Warfarin versus aspirin in patients with reduced cardiac ejection fraction (WARCEF): rationale, objectives, and design

BACKGROUND

Warfarin is widely prescribed for patients with heart failure without level 1 evidence, and an adequately powered randomized study is needed.

METHODS AND RESULTS

The Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction study is a National Institutes of Health-funded, randomized, double-blind clinical trial with a target enrollment of 2860 patients. It is designed to test with 90% power the 2-sided primary null hypothesis of no difference between warfarin (International Normalized Ratio 2.5-3) and aspirin (325 mg) in 3- to 5-year event-free survival for the composite endpoint of death, or stroke (ischemic or hemorrhagic) among patients with cardiac ejection fraction < or =35% who do not have atrial fibrillation or mechanical prosthetic heart valves. Secondary analyses will compare warfarin and aspirin for reduction of all-cause mortality, ischemic stroke, and myocardial infarction (MI), balanced against the risk of intracerebral hemorrhage, among women and African Americans; and compare warfarin and aspirin for prevention of stroke alone. Randomization is stratified by site, New York Heart Association (NYHA) heart class (I vs II-IV), and stroke or transient ischemic attack (TIA) within 1 year before randomization versus no stroke or TIA in that period. NYHA class I patients will not exceed 20%, and the study has a target of 20% (or more) patients with stroke or TIA within 12 months. Randomized patients receive active warfarin plus placebo or active aspirin plus placebo, double-blind.

CONCLUSION

The results should help guide the selection of optimum antithrombotic therapy for patients with left ventricular dysfunction.

Pharmacotherapy for patients undergoing carotid stenting

Stroke is the second most common cause of death worldwide [Murray CJ, Lopez AD. Mortality by cause for eight regions of the World: Global Burden of Disease Study, Lancet 1997;349:1269-76. [1]] and remains one of the most common and disabling neurological disorders, particularly in the elderly. Survivors of stroke remain at high risk for developing further vascular events including recurrent strokes, myocardial infarction and vascular deaths. Treatment modalities for such patients include life style modifications, drug therapy and where applicable, surgical or endovascular intervention. Carotid artery disease is implicated in 20-30% of the population as the aetiology for stroke [De Bakey ME. Carotid endarterectomy revisited, J Endovasc Surg 1996;3:4. [2]]. This article examines the pharmacotherapy for patients undergoing carotid stenting. This will be divided into best medical therapy for these patients, and is the same as that that should be given to all patients following transient ischaemic attack (TIA) or stroke. It will provide a concise description of the safety profile, dosage, indications and contraindications of the various drugs that are currently available to reduce the risk of further TIA or stroke. Then the specific drugs used in the peri-procedural period during carotid stenting will be described, along with the evidence supporting their use.

Review article: gastrointestinal bleeding with low-dose aspirin - what's the risk?

This review examines ulcers and gastrointestinal bleeding with low-dose aspirin, focusing on randomized placebo-controlled trials. The single endoscopic trial assessing ulcers showed no significant difference in 12-week ulcer incidence: 6% of 381 given placebo vs. 7% of 387 given 81 mg enteric-coated aspirin. The relative risk of major gastrointestinal bleeding with low-dose aspirin in a meta-analysis of placebo-controlled trials of vascular protection was 2.07 (95% CI: 1.61-2.66). The absolute rate increase with aspirin above placebo was 0.12% per year (95% CI: 0.07-0.19%) with a number-needed-to-harm of 833 patients (95% CI: 526-1429). A meta-analysis of aspirin 50-1500 mg daily reported an odds ratio for any gastrointestinal bleeding of 1.68 (95% CI: 1.51-1.88) with an number-needed-to-harm at 1 year of 247. The relative risk of hospitalization for upper gastrointestinal bleeding with low-dose aspirin in a large Danish cohort study was 2.6 (95% CI: 2.2-2.9) with an absolute annual incidence of 0.6%. Factors that may increase the risk of gastrointestinal bleeding include prior history of ulcers or gastrointestinal bleeding, corticosteroid use, anticoagulant therapy and addition of a non-aspirin non-steroidal anti-inflammatory drug. When determining whether low-dose aspirin is appropriate for an individual patient, the cardiovascular benefit must be weighed against the potential for clinical events such as gastrointestinal bleeding.

Adjunctive pharmacologic use in carotid endarterectomy: a review

Although carotid endarterectomy (CEA) is now widely accepted as the surgical therapy for carotid stenosis, the role of and indications and evidence for many pharmacologic agents that are used adjunctively in the perioperative setting have not been conclusively established. Aspirin (acetylsalicylic acid) is the pharmaceutical agent that has been studied most extensively in conjunction with CEA; other than aspirin and dextran, the use of many agents before, during, and after CEA has not been standardized. Prospective randomized trials are still needed to demonstrate efficacy, predict outcome, and determine the optimal use of these medications in their adjunctive use during CEA to improve patient care and obtain optimal surgical outcomes.