Practice parameter: Stroke prevention in patients with nonvalvular atrial fibrillation. Report of the Quality Standards Subcommittee of the American Academy of Neurology

Preference-Based Antithrombotic Therapy in Atrial Fibrillation: Implications for Clinical Decision Making

Background. Patient preferences and expert-generated clinical practice guidelines regarding treatment decisions may not be identical. The authors compared the thresholds for antithrombotic treatment from studies that determined or modeled the treatment preferences of patients with atrial fibrillation with recommendations from clinical practice guidelines. Methods. Methods included MEDLINE identification, systematic review, and pooling with some reanalysis of primary data from relevant studies. Results. Eight pertinent studies, including 890 patients, were identified. These studies used 3 methods (decision analysis, probability tradeoff, and decision aids) to determine or model patient preferences. All methods highlighted that the threshold above which warfarin was preferred over aspirin was highly variable. In 6 of 8 studies, patient preferences indicated that fewer patients would take warfarin compared to the recommendations of the guidelines. In general, at a stroke rate of 1% with aspirin, half of the participants would prefer warfarin, and at a rate of 2% with aspirin, two thirds would prefer warfarin. In 3 studies, warfarin must provide at least a 0.9% to 3.0% per year absolute reduction in stroke risk for patients to be willing to take it, corresponding to a stroke rate of 2% to 6% on aspirin. Conclusions. For patients with atrial fibrillation, treatment recommendations from clinical practice guidelines often differ from patient preferences, with substantial heterogeneity in their individual preferences. Since patient preferences can have a substantial impact on the clinical decision-making process, acknowledgment of their importance should be incorporated into clinical practice guidelines. Practicing physicians need to balance the patient preferences with the treatment recommendations from clinical practice guidelines.

Summary of evidence-based guideline update: prevention of stroke in nonvalvular atrial fibrillation: report of the Guideline Development Subcommittee of the American Academy of Neurology

OBJECTIVE

To update the 1998 American Academy of Neurology practice parameter on stroke prevention in nonvalvular atrial fibrillation (NVAF). How often do various technologies identify previously undetected NVAF? Which therapies reduce ischemic stroke risk with the least risk of hemorrhage, including intracranial hemorrhage? The complete guideline on which this summary is based is available as an online data supplement to this article.

METHODS

Systematic literature review; modified Delphi process recommendation formulation.

MAJOR CONCLUSIONS

In patients with recent cryptogenic stroke, cardiac rhythm monitoring probably detects occult NVAF. In patients with NVAF, dabigatran, rivaroxaban, and apixaban are probably at least as effective as warfarin in preventing stroke and have a lower risk of intracranial hemorrhage. Triflusal plus acenocoumarol is likely more effective than acenocoumarol alone in reducing stroke risk. Clopidogrel plus aspirin is probably less effective than warfarin in preventing stroke and has a lower risk of intracranial bleeding. Clopidogrel plus aspirin as compared with aspirin alone probably reduces stroke risk but increases the risk of major hemorrhage. Apixaban is likely more effective than aspirin for decreasing stroke risk and has a bleeding risk similar to that of aspirin.

MAJOR RECOMMENDATIONS

Clinicians might obtain outpatient cardiac rhythm studies in patients with cryptogenic stroke to identify patients with occult NVAF (Level C) and should routinely offer anticoagulation to patients with NVAF and a history of TIA/stroke (Level B). Specific patient considerations will inform anticoagulant selection in patients with NVAF judged to need anticoagulation.

Heart diseases and stroke

A heterogeneous group of heart diseases, varying by cardiac anatomy and physiology, are responsible for a variety of embolic materials that result in cerebral and systemic embolism. Atrial fibrillation accounts for nearly half of all cardioembolic stroke, particularly in the elderly, but in the young congenital septal abnormalities such as patent foramen ovale play a more important role. Therapeutic strategies include stabilization or treatment of the underlying heart disease and prevention of embolism. Oral anticoagulant therapy is indicated for many but decision making on balancing the benefits versus risks can be difficult. New endovascular therapies and devices have become available and await clinical trials that allow them to be compared with existing medical therapies.

From evidence to action

Despite the availability of vast quantities of evidence from basic biomedical and clinical studies, a gap often exists between the optimal practice suggested by the evidence and actual practice. For many clinical situations, however, evidence is unavailable, of poor quality or contradictory. Out of necessity, clinicians have become accustomed to relying on non-evidence-based tools to make decisions. Out of habit, they rely on these tools even when high-quality evidence becomes available. Growing out of an increasing awareness of this problem, the evidence-based medicine (EBM) movement sought to empower clinicians to find the evidence most relevant to a specific clinical question. Various organizations have used EBM techniques to develop systematic reviews and practice guidelines to aid physicians in making evidence-based decisions. A systematic review follows a process of asking a clinical question, finding the relevant evidence, critically appraising the evidence and formulating conclusions and recommendations. Results are mixed on whether educating physicians about evidence-based recommendations is sufficient to change physician behavior. Barriers to adopting evidence-based best practice remain, including physician skepticism, patient expectations, fear of legal action, and distorted reimbursement systems. Additionally, despite enormous research efforts there remains a lack of high-quality evidence to guide care for many clinical situations.

The lowest effective intensity of prophylactic anticoagulation for patients with atrial fibrillation

BACKGROUND

Stroke prevention trials in patients with atrial fibrillation (AF) mainly studied the use of warfarin in Caucasians, and the international normalized ratio (INR) was targeted in the range of 2-4. The result may not necessarily be applicable to other ethnic groups. This study aimed to determine the optimal intensity of anticoagulation for stroke prevention in Chinese patients.

METHODS

We performed a retrospective study on all Chinese patients with AF taking warfarin for stroke prevention in our hospital from January 1, 2000, to June 30, 2002. Patients with a mechanical heart valve were excluded. We systematically studied their indication of using warfarin, duration of therapy and all INR results. Only those patients whose indications of using warfarin were consistent with the ACC/AHA/ESC Executive Summary were included. Thrombo-embolic episodes, sudden death, major bleeding, intracranial haemorrhage and the INR at the time of the event were recorded. The INR range was divided into six categories: <1.5, 1.5-1.9, 2.0-2.5, 2.6-3.0, 3.1-3.5, >3.5. The number of events was recorded for each category, and this formed the numerator. The denominator was the summation of time each patient stayed in each category of INR. The event rate was then calculated for each INR category.

RESULTS

555 patients were included in the analysis, they constituted 893 patient-years. The INR was kept below 2.6 in 84.9% of the time and between 1.5 and 1.9 in 35% of the time. The overall event rate in our patients was 6.0%, of which 3.9% were due to thrombo-embolic events and 2.1% were due to serious bleeding. The overall event rate was lowest in the INR range from 1.5 to 1.9. which is not significantly different from that of INR 2.0-2.5 and 2.6-3.0. The overall event rate was 3.6% in INR 1.5-3.0 which was significantly lower than 15.1% in INR <1.5 and 20.5% in INR >3.0 (p < 0.01).

CONCLUSIONS

Our retrospective cohort showed that a lower INR range of 1.5-3.0 was safe and effective for stroke prevention in Chinese patients treated in a single hospital.

Clinical correlation between effective anticoagulants and risk of stroke: are we using evidence-based strategies?

OBJECTIVES

Despite evidence supporting anticoagulant use in atrial fibrillation, this modality is not fully utilized.

METHODS

Retrospective chart review of 297 patients with nonvalvular atrial fibrillation between 1997 to 2000. 124 patients received warfarin and 166 did not; 91 patients suffered stroke.

RESULTS

Age (P = 0.232) and gender (P = 0.745) were not determinant factors for starting anticoagulation prophylaxis. Whites were more likely to receive anticoagulation therapy than blacks (P = 0.043). Cardiologists were 4.5 times more likely to prescribe warfarin than neurologists and internists (P = 0.035). Neurologists (P = 0.305) and internists (P = 0.770) had similar warfarin prescription patterns and often with patients experiencing the highest rates of stroke.

CONCLUSION

Lack of a uniform pattern in anticoagulant administration, despite multiple guidelines, is disturbing. Continuous physician education and community awareness by local and federal medical agencies is essential and cost-effective.

Secondary prevention strategies in ischemic stroke: identification and optimal management of modifiable risk factors

The identification and treatment of modifiable Ischemic stroke risk factors, in addition to appropriate antithrombotic therapy, can reduce the likelihood of first or recurrent stroke, prevent long-term morbidity and mortality after first stroke or transient Ischemic attack, and lower health care costs. Long-term morbidity and mortality in patients with ischemic stroke includes patients with coronary artery disease. Therefore, in patients with ischemic stroke (especially those with carotid artery disease and lacunar disease), the goal is to prevent not only recurrent stroke but also coronary artery disease. Neurologists and general practitioners must be aware of the specific risk factors and recommendations for patients with ischemic stroke and apply the information systematically. We review known risk factors for ischemic stroke and current recommendations for treatment, focusing primarily on atherosclerotic risk factors as they apply to patients with stroke. In particular, recent data on hypertension and hyperlipidemia are described. In addition, we discuss the challenges in managing these risk factors and the potential strategies for overcoming them.

The increasing need for anticoagulant therapy to prevent stroke in patients with atrial fibrillation

Ischemic stroke, a major complication of atrial fibrillation (AF), is believed to result from atrial thrombus formation caused by ineffective atrial contraction. Oral anticoagulant therapy effectively reduces the risk of ischemic stroke in patients with AF; this therapy is recommended for patients with any frequency or duration of AF and other risk factors for stroke, such as increased age (>75 years), hypertension, prior stroke, left ventricular dysfunction, diabetes, or heart failure. Recently published data comparing rate-control and rhythm-control strategies in AF emphasized the importance of maintaining an international normalized ratio higher than 2.0 during warfarin therapy and the need for continuing anticoagulant therapy to prevent stroke in high-risk patients, even if the strategy is rhythm control. Hemorrhagic complications can be minimized by stringent control of the international normalized ratio (particularly in elderly patients) and appropriate therapy for comorbidities such as hypertension, gastric ulcer, and early-stage cancers. Undertreatment of patients with AF is a continuing problem, particularly in the elderly population. Patients perceived as likely to be noncompliant, such as the functionally impaired, are less likely to receive warfarin therapy. However, stroke prevention with anticoagulants is cost-effective and improves quality of life, despite the challenges of maintaining appropriate anticoagulation with monitoring and warfarin dose titration. New medications in development with more predictable dosing and fewer drug-drug interactions may reduce the complexities of achieving optimal anticoagulation and increase the practicality of long-term anticoagulant therapy for patients with AF at risk of stroke.

Secondary prevention of stroke: a practical guide to drug treatment

Stroke is a disease of the elderly and, as a result of the expected demographic changes in many industrialised countries, its incidence is likely to increase in the future. A first-ever stroke significantly increases the likelihood of further events; thus, secondary prevention is of major importance. Only a minority of recurrent strokes can be prevented by surgical or other invasive methods, meaning that most secondary preventive measures involve drug treatment, which has become increasingly sophisticated in recent years. Ischaemic stroke constitutes the vast majority of all strokes; effective secondary prevention depends on a variety of factors, of which the correct classification in terms of subtypes and aetiological mechanisms is a pivotal prerequisite, as is the assessment of the patient's cardiovascular risk profile. In addition to the evaluation of pathomechanisms, stratification of subtypes of brain infarction is mainly based on morphology seen with brain imaging techniques, which provides additional evidence for the presumed cause of the stroke. Inhibitors of platelet function and anticoagulants are the two major groups of antithrombotic drugs used for the secondary prevention of stroke. Antiplatelet agents are still indicated in the majority of patients after ischaemic stroke, especially if an arterial origin is presumed. In addition to aspirin (acetylsalicylic acid), the position of which as the first-line antiplatelet drug is increasingly being questioned, other compounds with antiplatelet activity have been developed and have proven effective in secondary stroke prevention, including ticlopidine, clopidogrel and dipyridamole. Anticoagulants are principally indicated after cardioembolic ischaemic stroke; however, their inherent bleeding risks render their use in many cases rather difficult, in particular for elderly patients. Patient compliance with the recommended treatment is of major importance, given the somewhat limited efficacy of antithrombotic agents in stroke prevention. Since 'real world' experience does not match the circumstances under which clinical trials are conducted, this article will also deal with problems not covered by specific studies, such as risk stratification for anticoagulant treatment and how to proceed in cases of unknown stroke aetiology. The management of major cardiovascular risk factors is the other mainstay of secondary stroke prevention. Recent evidence indicates that antihypertensive treatment may be as effective as antithrombotic drugs for secondary prevention of stroke. This still needs to be proven for the treatment of other cardiovascular risk factors, such as diabetes mellitus and hypercholesterolemia. Nevertheless, the results of recent studies investigating the effect of HMG-CoA reductase inhibitors ('statins') on cardiovascular events strongly suggest a stroke-preventive effect.

Cardioembolic stroke: an update

Cardioembolic stroke accounts for approximately 15% of all strokes and is thought to be one of the more preventable types of strokes. Features that have been reported to support cardioembolism as a mechanism for ischemic stroke have included documented cardiac source of embolism, maximal neurologic deficit at onset, multiple cerebrovascular territories involved, enhanced tendency toward hemorrhagic transformation, enhanced risk of syncope or seizure associated with presentation, and lower likelihood of premonitory transient ischemic attacks. Features that tend to make cardioembolic stroke less likely include significant cerebral atherosclerosis, step-wise progression of the neurologic deficit within a finite period of time, vascular distribution such as entire internal carotid artery territory with combined middle cerebral artery and anterior cerebral artery involvement or watershed distribution, and premonitory transient ischemic attacks. A number of cardiac conditions can promote thromboembolism, and there is risk stratification reflective of the specific condition or coexistent conditions. Anticoagulant therapy generally has been found to be the most effective means of preventing cardiogenic brain embolism, but the intensity of anticoagulation needs to be optimized to reflect the risk-to-benefit ratio for the particular patient.

Risk and predictors of stroke after myocardial infarction among the elderly: results from the Cooperative Cardiovascular Project

BACKGROUND

Stroke is an important outcome after acute myocardial infarction. Studies that have examined this relationship have largely excluded older patients, even though half of stroke admissions occur among patients 75 years of age and older.

METHODS AND RESULTS

Among 111 023 medicare patients discharged with a principal diagnosis of acute myocardial infarction during an 8-month period in 1994 to 1995, we identified hospital admissions for ischemic stroke within 6 months of discharge. The rate of admission was 2.5% within 6 months. Independent predictors of ischemic stroke were age greater-than-or-equal 75 years, black race, no aspirin at discharge, frailty, prior stroke, atrial fibrillation, diabetes, hypertension, and history of peripheral vascular disease. To identify individuals at increased risk for stroke, a risk stratification score was constructed from identified factors. The 6-month stroke admission rate for patients with a score of 4 or higher (approximately 20% of the total sample) was approximately 4%.

CONCLUSIONS

The risk of stroke after myocardial infarction is substantial, with about 1 in 40 patients suffering an ischemic stroke within 6 months of discharge. Simple clinical factors can predict the risk of stroke and, based on these factors, we identified 20% of older patients who have a 1 in 25 chance of being hospitalized for a stroke within 6 months of discharge.

Primary stroke prevention

Stroke is one of the leading causes of death and disability worldwide. Although important advances in therapeutic approaches have been made, treatment is still far from satisfactory. Thus, major efforts should be made on stroke prevention. We present evidence-based recommendations for primary stroke prevention. Changes to modifiable risk factors, the role of drugs and surgery are discussed. New markers may help identification of subjects at high risk.

Stroke prevention: narrowing the evidence-practice gap

Many interventions reduce stroke risk. However, the full benefits of these interventions are not realized at current levels of utilization, as nearly all evidence-based or guideline-endorsed stroke prevention services are underused. The cause for such underuse is multifactorial and includes factors relating to both patients and providers, as well as to a health care system that has de-emphasized prevention at the expense of acute, technologically based care. Much like the evidence for stroke interventions themselves, there is a growing literature to support methods of implementing research evidence into clinical practice. There is still much to learn, however, about the effectiveness of interventions aimed at achieving changes in stroke prevention practice or the delivery of stroke prevention care. Nevertheless, there are many opportunities for providers, managed care organizations, and government to close the evidence-practice gap that exists for stroke prevention services. These opportunities exist in both the inpatient and outpatient setting, and depend on the neurologist taking a leading role in emphasizing the critical importance of risk factor identification and modification in all patients at risk for stroke.

Warfarin use among ambulatory patients with nonvalvular atrial fibrillation: the anticoagulation and risk factors in atrial fibrillation (ATRIA) study

BACKGROUND

Warfarin dramatically reduces the risk for ischemic stroke in nonvalvular atrial fibrillation, but its use among ambulatory patients with atrial fibrillation has not been widely studied.

OBJECTIVE

To assess the rates and predictors of warfarin use in ambulatory patients with nonvalvular atrial fibrillation.

DESIGN

Cross-sectional study.

SETTING

Large health maintenance organization.

PATIENTS

13428 patients with a confirmed ambulatory diagnosis of nonvalvular atrial fibrillation and known warfarin status between 1 July 1996 and 31 December 1997.

MEASUREMENTS

Data from automated pharmacy, laboratory, and clinical-administrative databases were used to determine the prevalence and determinants of warfarin use in the 3 months before or after the identified diagnosis of atrial fibrillation.

RESULTS

Of 11082 patients with nonvalvular atrial fibrillation and no known contraindications, 55% received warfarin. Warfarin use was substantially lower in patients who were younger than 55 years of age (44.3%) and those who were 85 years of age or older (35.4%). Only 59.3% of patients with one or more risk factors for stroke and no contraindications were receiving warfarin. Among a subset of "ideal" candidates to receive warfarin (persons 65 to 74 years of age who had no contraindications and had previous stroke, hypertension, or both), 62.1% had evidence of warfarin use. Among our entire cohort, the strongest predictors of receiving warfarin were previous stroke (adjusted odds ratio, 2.55 [95% CI, 2.23 to 2.92]), heart failure (odds ratio, 1.63 [CI, 1.51 to 1.77]), previous intracranial hemorrhage (odds ratio, 0.33 [CI, 0.21 to 0.52]), age 85 years or older (odds ratio, 0.35 [CI, 0.31 to 0.40]), and previous gastrointestinal hemorrhage (odds ratio, 0.47 [CI, 0.40 to 0.57]).

CONCLUSIONS

In a large, contemporary cohort of ambulatory patients with atrial fibrillation who received care within a health maintenance organization, warfarin use was considerably higher than in other reported studies. Although the reasons why physicians did not prescribe warfarin could not be elucidated, many apparently eligible patients with atrial fibrillation and at least one additional risk factor for stroke, especially hypertension, did not receive anticoagulation. Interventions are needed to increase the use of warfarin for stroke prevention among appropriate candidates.