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Why Do Patients With Atrial Fibrillation Not Receive Warfarin?
Tammy J. Bungard, BSP, PharmD;
William A. Ghali, MD, MPH, FRCPC;
Koon K. Teo, MB, PhD, FRCPC;
Finlay A. McAlister, MD, FRCPC;
Ross T. Tsuyuki, PharmD, MSc, FCSHP
Arch Intern Med. 2000;160:41-46.
ABSTRACT
Atrial fibrillation (AF) is a growing public health problem associated with significant morbidity and mortality. Numerous randomized controlled trials of warfarin have conclusively demonstrated that long-term anticoagulation therapy can reduce the risk for stroke by approximately 68% per year in patients with nonvalvular AF, and even more in patients with valvular AF. However, available data show that of those patients with AF and no contraindication to warfarin therapy, only 15% to 44% are prescribed warfarin. Our literature review has identified patient-, physician-, and health care system–related barriers to warfarin prescription. However, the relative importance of these specific barriers remains unknown. Further work is needed to understand the discrepancy between the randomized controlled trial evidence and clinical practice patterns.
INTRODUCTION
Atrial fibrillation (AF) is a growing public health problem associated with significant morbidity and mortality.1 Patients with AF have an increased risk for ischemic stroke; those with nonvalvular AF have at least a 5-fold increased risk,2-4 whereas those with valvular AF have an estimated 17-fold increased risk.4 The initial stroke occurring with AF is often severe; in 1 series, 71% of patients died or had severe permanent neurologic deficits.5 Approximately 15% of all strokes are associated with this dysrhythmia, and the association increases steadily with age, from 6.7% of all strokes for patients aged 50 through 59 years to 36.2% of all strokes for patients aged 80 through 89 years.5
Numerous randomized controlled trials of warfarin therapy have conclusively demonstrated that long-term anticoagulation therapy can reduce the risk for ischemic stroke by approximately 68% in patients with nonvalvular AF,6-11 and even more in patients with valvular AF. Despite this conclusive evidence of efficacy, several studies have shown that "real-world" use of warfarin in patients with AF is suboptimal.12-27 The reasons for this low use are unclear, despite the availability of multiple physician surveys investigating the barriers to the prescription of warfarin.15, 17, 28-34 Our purpose is to review the evidence of the widespread underuse of warfarin therapy in AF as well as the proposed reasons (barriers) for underuse.
MATERIALS AND METHODS
Articles published in English from January 1, 1966, through December 31, 1998, were identified through MEDLINE by using the following keywords and Medical Subject Headings: atrial fibrillation, prophylaxis, anticoagulation, warfarin, barrier, survey, questionnaire, and underutilization. The reference lists of the articles were reviewed for additional relevant articles, and experts within the field were contacted to identify other articles. All articles assessing practice patterns and barriers to using warfarin in AF were reviewed and are included herein.
EVIDENCE OF THE UNDERUSE OF WARFARIN IN AF
Despite conclusive evidence demonstrating benefit from the use of thromboembolic prophylaxis,6-11 practice pattern evaluations consistently identify suboptimal use (Table 1).12-27 In a study of 12 Canadian hospitals and 3575 patients, the Clinical Quality Improvement Network reviewed the medical records of consecutive patients admitted to the participating hospitals during 1993 and 1994 with the primary, most responsible, or complicating diagnosis of AF.26 Only 23.8% of the patients were prescribed warfarin during their hospital stay or at discharge, 29.8% received aspirin, 8.0% received both, and 33.2% received no thromboembolic prophylaxis.26 Although these rates improved during hospitalization (16.4% received warfarin on admission, compared with 32.0% at discharge), these findings indicate suboptimal care in light of the aforementioned randomized controlled trial evidence.6-11 A repeated pattern of practice analysis comparing 1993-1994 with 1995-1996 admissions at an institution within the Clinical Quality Improvement Network showed little change in warfarin use.35
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Reported Rates of Warfarin Use in Patients Without Contraindications*
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There are several other studies confirming the underuse of anticoagulant therapy.12-25,27 In those patients with no contraindications to warfarin therapy, studies report that anywhere from 15% to 79% of patients actually receive this therapy.12-25 Excluding a study that looked at warfarin use in a center that had participated in one of the large randomized controlled trials of anticoagulation for AF,17 warfarin was prescribed for only 15% to 44% of patients.12-16,18-27 A national survey of randomly selected office-based physician visits found a significant increase (from 7% in 1980-1981 to 32% in 1992-1993) in warfarin use, although use still remained low.24 In fact, the low rate likely overestimates actual use, as individuals were captured on a per-visit basis (not a per-patient basis), and patients receiving warfarin were more likely to see physicians.24 In another study, physicians reported prescribing warfarin to 51% of their patients on a survey, but an audit of their practices revealed only 24% had received a prescription.15 Despite evidence that informed patients want to receive warfarin therapy36 and that warfarin therapy is highly cost-effective in the prevention of stroke,37 warfarin still is not prescribed to most patients with AF.
BARRIERS TO THE USE OF WARFARIN
Several physician surveys have been performed to examine the barriers to prescribing anticoagulant therapy.15, 28-34 With a single exception,34 these surveys have used vignettes (case scenarios) to depict various clinical situations.15, 28-33 Central to these depictions are factors believed to influence the clinician's decision to prescribe anticoagulants. The decision to implement therapy with warfarin necessitates close follow-up because of the narrow therapeutic index that is influenced by multiple factors (eg, drugs, diet, patient health status). Our review of the studies evaluating barriers to the prescription of warfarin demonstrates 3 general categories of barriers (Figure 1), ie, patient-, physician-, and health care system–related factors.
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Schematic model of factors influencing the decision to prescribe warfarin.
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Barriers Pertaining to the Patient
Patient-related factors such as age,13, 15, 20, 24-27,30, 32-33 perceived embolic risk, and perceived risk for hemorrhage13, 15, 29-33 are consistently identified as influencing the decision of prescribing anticoagulation in vignettes. For example, increasing age has been identified consistently as a barrier to anticoagulation therapy,15-16,20, 22, 24, 27, 30, 32, 38 and even those physicians who are willing to prescribe anticoagulation for elderly patients aim for a lower intensity than that supported by the randomized controlled trial evidence.15-16,28, 39 In contrast, physicians are more enthusiastic about15, 22, 30, 32 and more aggressive32 with anticoagulation therapy in patients with a history of stroke. A strong relationship has been documented between physician estimates of the patient's relative risk for embolism compared with that for hemorrhage and the decision to implement anticoagulation therapy.29-33 Surveyed physicians have reported withholding warfarin based on the belief that patients would refuse therapy22, 32 or be noncompliant.30 More detailed explanations are not available.
When given the choice of warfarin prophylaxis, patients in 1 study decided to take warfarin 93% of the time.17 These data originate from a site that was actively involved in recruiting patients for the Boston Area Anticoagulation Trial for Atrial Fibrillation,11 and thus adopted the practice of recommending anticoagulation therapy in almost all patients. Although these data may not be representative of other settings, they demonstrate patient willingness to undergo anticoagulation therapy with warfarin. Patients presented with visual aids depicting the risks and benefits of warfarin therapy elected to take warfarin at a lower level of stroke risk than their physicians preferred to prescribe it.36 Very few physicians (approximately 10%) believed that the patient's quality of life would be significantly impaired if warfarin was administered.32
Overall, the vignettes are targeted at assessing patient clinical characteristics that may influence the prescribing of warfarin. Although consistently identifying age, embolic risk, and risk for hemorrhage as major determinants of the decision to prescribe anticoagulation therapy, the surveys undertaken are highly variable in assessing any other factors influencing warfarin use. In evaluating studies analyzing patient-related barriers, it is not possible to determine how these barriers relate to the numerous potential obstacles in daily practice (ie, whether identified barriers actually prevent the prescription of warfarin).
Barriers Pertaining to the Physician
Although most surveys have made inferences about the barriers to the prescription of anticoagulants based on physicians' treatment decisions in vignettes,15, 28-29,31, 33 few have directly questioned physicians regarding their perceived barriers to anticoagulation.30, 32, 34 Surveys suggest15, 17, 28-32,34 the primary determinant of the use of anticoagulants to be a weighting of the benefit vs risk in each individual patient. In an evaluation by Chang and colleagues,29 cardiologists believed the risk for embolism relative to hemorrhage to be lower than did general practitioners, and therefore cardiologists were less likely to prescribe warfarin. In fact, the physician's perception of the benefit vs risk of therapy appears to be the only consistent finding influencing the implementation of warfarin therapy. This perception, in part, likely is derived from the physician's previous experience with the use of warfarin. Physicians with good or excellent experiences with warfarin were more likely to prescribe it, but nonetheless still did not prescribe warfarin for half of their patients.15
Clinical uncertainty, although commonly reported,15, 27-30,33-34,40 is not defined clearly within surveys, and it ranges in relative importance. In these evaluations, clinical uncertainty has been interpreted to mean that physicians were not aware of the current literature,29 were aware of the literature but did not accept the results,29-30 or believed the clinical vignette had features not addressed by previous studies.29 The relative importance of clinical uncertainty as a barrier ranges from being uncommon15, 30, 32 to being common enough to justify most surveyed physicians to request practice guidelines pertaining to candidacy for anticoagulation therapy.34 However, guidelines may vary markedly in their recommendations. For example, a study evaluating AF guidelines available in Great Britain found that the variation among the guidelines would result in vastly different prescribing practices, with 13% to 100% of patients being prescribed warfarin.41
This widespread lack of consensus may contribute to the varying practice patterns observed, although the precise reasons for this are unknown. Perhaps physicians are unaware of how infrequently they prescribe warfarin, as the rates they report are often greater than those used in clinical practice.15 Rarely reported, and infrequently investigated, is the fear of litigation by physicians.34 One survey reported that 79% of physicians cited a lack of patient reliability as a contraindication to therapy, and greater than 90% of the same group did not prescribe warfarin to patients with a history of chronic alcoholism.29 In a clinical scenario depicting a patient with a history of falls, 71% of physicians believed anticoagulation therapy was contraindicated.33 Another survey specifically questioned physicians regarding the cost-effectiveness of warfarin, and most recognized that it was cost-effective.32 Some physicians reported difficulty in maintaining therapy within the therapeutic range,15, 30, 34 stating that further training, the availability of consultant advice, or guidelines on managing anticoagulation therapy would increase willingness to use it34; whereas a few physicians (17%) believed patient noncompliance was responsible for the difficulty in monitoring the prothrombin ratio.30
Of those physicians aware of clinical practice guidelines, several believed the guidelines were not applicable to their patients.14-15,29, 38, 40, 42 In an evaluation of anticoagulation therapy within a health maintenance organization, Gottlieb and Salem-Schatz17 found patients to have a significantly greater prevalence of angina, previous myocardial infarction, congestive heart failure, and diabetes than patients in clinical trials. In this analysis, patients were not monitored as closely as those in clinical trials, and control of anticoagulation was found to be inferior, with prothrombin time ratios being in the target range on only 50% of the days compared with 68% of days in clinical trials. In another evaluation of warfarin therapy, patients were reported to be within the therapeutic range only 40% of the time.18 In assessing patients being admitted to the hospital with the diagnosis of acute stroke and AF, Albers et al12 found that half of the patients with no contraindication to anticoagulation therapy were not receiving any antithrombotic agent on admission. Of those having an international normalized ratio performed on admission, 72% were below the therapeutic range of 2.0 to 3.0.12
Barriers Pertaining to the Health Care System
To expect the same reduction in stroke and rates of hemorrhage as that seen in clinical trials, it is logical to require an equivalent level of anticoagulation to that achieved in clinical trials.24, 43 Of those patients admitted to hospital with a stroke while receiving warfarin therapy, most have subtherapeutic international normalized ratios.12, 16 Clinical trials contain the expertise and resources dedicated to delivering therapeutic interventions in an efficient, controlled setting. In clinical practice, however, there are numerous potential barriers related to the health care system. The surveys performed largely focus on clinical characteristics of patients, with many reports only indirectly assessing barriers outside of a patient's candidacy for warfarin prophylaxis.
Surveys of these barriers to warfarin therapy have produced highly variable results. This reported variance may be due to regional differences or could be a result of the method in which surveys elicited responses from physicians (which range from a ranking system to creation of a list). Many physicians surveyed believed that monitoring therapy was inconvenient30, 32, 34 because of a lack of time, delay in laboratory result reporting, or space constraints. Some physicians believed there was a need for further remuneration, whereas some believed the availability of consultant advice would increase physician willingness to use anticoagulant prophylaxis.34 Most physicians surveyed in Great Britain (94%) reported a desire for someone else to manage an anticoagulation clinic.44 Given these logistical concerns, there may be a lack of resources and experienced personnel in the community to adopt practice recommendations and to provide anticoagulation therapy at rates similar to those of controlled clinical trials.17
Despite the potential scarcity of resources, physicians surveyed in Great Britain appear to believe that the management of anticoagulation should be undertaken in the community or primary care setting.34 When comparing primary with secondary care, British physicians agree that primary care offers improved access for patients and continuity of care.34 Given the expectation of managing anticoagulation at the level reported in clinical trials, it seems prudent to ensure that services are carefully planned, that appropriate resources are available to meet patient demand, and that measures are in place to ensure quality control in the primary care setting.43, 45
Surveys performed to date offer little information about barriers pertaining to the health care system, particularly in the North American setting. In assessing the barriers to warfarin use, such information is crucial because of the complexities of warfarin therapy and the necessity to arrange frequent laboratory tests to ensure an appropriate level of anticoagulation.
LIMITATIONS OF PREVIOUS RESEARCH ON PRESCRIBING BARRIERS
Available data evaluating the barriers to the prescription of warfarin in patients with AF have several important limitations. With the exception of 1 survey,34 all evaluations have used case vignettes, which have several methodological limitations.15, 28-33 First, vignettes attempt, but often are not successful in, mimicking a clinical scenario for the physician. Their use rests on the assumption that responses in hypothetical situations reflect actual clinical practice patterns. Comparative data indicate that physician responses to vignettes may not be representative of their clinical practice patterns, and thus this type of analysis may not identify the true barriers present in clinical practice.15, 46-53 In fact, only a few studies (11 of 74) using written case simulations assess validity.47 Attempts at validating vignettes have not been successful,47, 49-50 and reliability testing has produced disappointing results.49 Second, the identification of prescribing barriers is inferred or measured indirectly from vignettes. On interpreting the decision to prescribe anticoagulation therapy, assumptions must be made regarding factors triggering the physician's decision. These assumptions may be factors in the vignette, eg, patient age or type of AF. However, there may be circumstances outside of the case that may influence this decision (eg, health care system factors). This information cannot be captured in this format. Third, use of the vignette format does not allow for the assessment of the relative importance of each of the barriers in prescribing warfarin. For example, several factors required when using warfarin (eg, arrangement of laboratory testing, dosage modification) may be identified as barriers to prescribing warfarin, but may not be inconvenient enough to prevent prescription. To identify this information, a rating scale of barrier importance directly eliciting physician responses would be required. Finally, no single study has evaluated the complete spectrum of prescribing barriers for anticoagulation therapy. In general, instruments typically assess patient-related barriers while not assessing physician- and health care system–related barriers. In the only study not using case vignettes, only a partial list of possible barriers is assessed.34 As a result of variability in content in any given survey, certain barriers may be recognized only because they were highlighted, whereas the same barrier may have gone unrecognized in another survey.
FUTURE DIRECTIONS
To understand more completely the problem of warfarin underuse in AF, all aspects pertaining to the provision of health care must be evaluated. A direct and systematic analysis of the importance of patient-, physician-, and health care system–related barriers is warranted. This might be accomplished by listing potential barriers with a rating scale to indicate the importance of these barriers in relation to one another. By clarifying the relative importance of barriers representing different aspects of patient care, an in-depth understanding of the mechanisms of this problem would be facilitated. Once important barriers are identified, future interventions can be developed to address the current limitations in practice. Through targeting interventions toward the identified barriers, positive changes in behavior are more likely to occur.54
CONCLUSIONS
With an aging population, AF is a growing public health problem with significant clinical consequences. Despite conclusive evidence from randomized controlled clinical trials, the use of warfarin for the prevention of ischemic stroke in AF is suboptimal. Physician surveys assessing the barriers to warfarin use have numerous limitations. As a result, more research is needed to identify and to clarify the relative importance of patient-, physician-, and health care system–related barriers. Thus, future interventions can be targeted to make an impact on prescribing patterns, with the ultimate goal of improved outcomes for patients with AF.54
AUTHOR INFORMATION
Accepted for publication April 13, 1999.
Supported by a grant from the Alberta Heritage Foundation for Medical Research, Edmonton (Drs Bungard, Ghali, Teo, and McAlister), the Medical Research Council of Canada, Ottawa, Ontario (Dr McAlister), and by the University Hospital Foundation, Edmondton (Dr Tsuyuki).
Reprints: Ross T. Tsuyuki, PharmD, Msc, FCSHP, Division of Cardiology, 213 Heritage Medical Research Centre, Edmonton, Alberta, Canada T6G 2S2 (e-mail: rtsuyuki{at}cha.ab.ca).
From the Division of Cardiology, University of Alberta, Edmonton (Drs Bungard, Teo, and Tsuyuki); the Department of Medicine and Community Health Sciences, University of Calgary, Calgary (Dr Ghali), Alberta; and the Centre for Evidence-Based Medicine, Oxford, England (Dr McAlister).
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Serum lipid profile on admission for ischemic stroke: Failure to meet National Cholesterol Education Program Adult Treatment Panel (NCEP-ATPIII) guidelines
Smith et al.
Neurology 2007;68:660-665.
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Reduced Poststroke Mortality in Patients With Stroke and Atrial Fibrillation Treated With Anticoagulants: Results From a Danish Quality-Control Registry of 22 179 Patients With Ischemic Stroke
Andersen and Olsen
Stroke 2007;38:259-263.
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Bleeding risk stratification models in deciding on anticoagulation in patients with atrial fibrillation: a useful complement to stroke risk stratification schema.
Kakar et al.
Chest 2006;130:1296-1299.
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Eligibility for Anticoagulation in Elderly Patients With Atrial Fibrillation
Ono et al.
Stroke 2006;37:2205-2205.
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Trends in the prevalence of diagnosed atrial fibrillation, its treatment with anticoagulation and predictors of such treatment in UK primary care
DeWilde et al.
Heart 2006;92:1064-1070.
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Atrial Fibrillation and Stroke in the General Medicare Population: A 10-Year Perspective (1992 to 2002)
Lakshminarayan et al.
Stroke 2006;37:1969-1974.
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Not All Patients With Atrial Fibrillation-Associated Ischemic Stroke Can Be Started on Anticoagulant Therapy
Somerfield et al.
Stroke 2006;37:1217-1220.
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Statin treatment and adherence to national cholesterol guidelines after ischemic stroke
Ovbiagele et al.
Neurology 2006;66:1164-1170.
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Translating the Results of Randomized Trials into Clinical Practice: The Challenge of Warfarin Candidacy Among Hospitalized Elderly Patients With Atrial Fibrillation
Hylek et al.
Stroke 2006;37:1075-1080.
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Impact of adverse events on prescribing warfarin in patients with atrial fibrillation: matched pair analysis
Choudhry et al.
BMJ 2006;332:141-145.
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Search for Predictors of Nontherapeutic INR Results with Warfarin Therapy
McGriff-Lee et al.
The Annals of Pharmacotherapy 2005;39:1996-2002.
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Monitored Atrial Fibrillation Duration Predicts Arterial Embolic Events in Patients Suffering From Bradycardia and Atrial Fibrillation Implanted With Antitachycardia Pacemakers
Capucci et al.
J Am Coll Cardiol 2005;46:1913-1920.
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Impact of Age, CYP2C9 Genotype and Concomitant Medication on the Rate of Rise for Prothrombin Time During the First 30 Days of Warfarin Therapy
Wilke et al.
Clin Med Res 2005;3:207-213.
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Impact of a patient decision aid on care among patients with nonvalvular atrial fibrillation: a cluster randomized trial
McAlister et al.
CMAJ 2005;173:496-501.
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Should a patient with primary intracerebral haemorrhage receive antiplatelet or anticoagulant therapy?
Wani et al.
BMJ 2005;331:439-442.
FULL TEXT
Uncertain times for oral anticoagulation therapy
Nutescu et al.
Am J Health Syst Pharm 2005;62:1449-1449.
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Antithrombotic Therapy Practices in US Hospitals in an Era of Practice Guidelines
Tapson et al.
Arch Intern Med 2005;165:1458-1464.
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Percutaneous Left Atrial Appendage Transcatheter Occlusion (PLAATO System) to Prevent Stroke in High-Risk Patients With Non-Rheumatic Atrial Fibrillation: Results From the International Multi-Center Feasibility Trials
Ostermayer et al.
J Am Coll Cardiol 2005;46:9-14.
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Differences in quality of care among patients hospitalized with atrial fibrillation as primary or secondary cause for admission
Lim et al.
Int J Qual Health Care 2005;17:255-258.
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Direct thrombin inhibitors: novel antithrombotics on the horizon in the thromboprophylactic management of atrial fibrillation
Katira et al.
Postgrad. Med. J. 2005;81:370-375.
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Letter Regarding Article by Masoudi et al, "National Patterns of Use and Effectiveness of Angiotensin-Converting Enzyme Inhibitors in Older Patients With Heart Failure and Left Ventricular Systolic Dysfunction" * Response
Sabatini et al.
Circulation 2005;111:e276-e277.
FULL TEXT
Risk of bleeding with long-term antithrombotic therapy in atrial fibrillation
Schulman and Beyth
Eur Heart J Suppl 2005;7:C34-C40.
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Economic factors associated with antithrombotic treatments for stroke prevention in patients with atrial fibrillation
Miller et al.
Eur Heart J Suppl 2005;7:C41-C54.
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Ximelagatran vs Warfarin for Stroke Prevention in Patients With Nonvalvular Atrial Fibrillation: A Randomized Trial
SPORTIF Executive Steering Committee for the SPORT
JAMA 2005;293:690-698.
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Costs and Effectiveness of Ximelagatran for Stroke Prophylaxis in Chronic Atrial Fibrillation
O'Brien and Gage
JAMA 2005;293:699-706.
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Emerging Role of Direct Thrombin Inhibitors in Nonvalvular Atrial Fibrillation: Potential and Peril
Kim and Arora
J CARDIOVASC PHARMACOL THER 2005;10:11-21.
ABSTRACT
Anticoagulation in atrial fibrillation and flutter
Scholten et al.
Europace 2005;7:492-499.
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Advanced Age, Anticoagulation Intensity, and Risk for Intracranial Hemorrhage among Patients Taking Warfarin for Atrial Fibrillation
Fang et al.
ANN INTERN MED 2004;141:745-752.
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A Community-Based Educational Intervention to Improve Antithrombotic Drug Use in Atrial Fibrillation
Jackson et al.
The Annals of Pharmacotherapy 2004;38:1794-1799.
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PROTECT: A coordinated stroke treatment program to prevent recurrent thromboembolic events
Ovbiagele et al.
Neurology 2004;63:1217-1222.
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Stroke patients with atrial fibrillation have a worse prognosis than patients without: data from the Austrian Stroke registry
Steger et al.
Eur Heart J 2004;25:1734-1740.
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Presidential Reflections on the 25th Anniversary of the Society for Medical Decision Making
Elstein et al.
Med Decis Making 2004;24:408-420.
The Increasing Need for Anticoagulant Therapy to Prevent Stroke in Patients With Atrial Fibrillation
Ezekowitz and Falk
Mayo Clin Proc. 2004;79:904-913.
ABSTRACT
How research-conscious GPs make decisions about anticoagulation in patients with atrial fibrillation: a qualitative study
Lipman et al.
Fam Pract 2004;21:290-298.
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Elimination of the Left Atrial Appendage To Prevent Stroke or Embolism?: Anatomic, Physiologic, and Pathophysiologic Considerations
Stollberger et al.
Chest 2003;124:2356-2362.
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Predictors of Warfarin Use Among Ohio Medicaid Patients With New-Onset Nonvalvular Atrial Fibrillation
Johnston et al.
Arch Intern Med 2003;163:1705-1710.
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Ximelagatran versus warfarin forstroke prevention in patientswith nonvalvular atrial fibrillation: SPORTIF ii: a dose-guiding, tolerability, and safety study
Petersen et al.
J Am Coll Cardiol 2003;41:1445-1451.
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Rhythm or Rate Control in Atrial Fibrillation: Insights from the Randomized Controlled Trials
Gronefeld and Hohnloser
J CARDIOVASC PHARMACOL THER 2003;8:S39-S44.
ABSTRACT
Is treatment of atrial fibrillation in primary care based on thromboembolic risk assessment?
Rutten et al.
Fam Pract 2003;20:16-21.
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Ethnic Differences in Patient Perceptions of Atrial Fibrillation and Anticoagulation Therapy: The West Birmingham Atrial Fibrillation Project * Editorial Comment: The West Birmingham Atrial Fibrillation Project
Lip et al.
Stroke 2002;33:238-242.
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Diurnal Variation in the Intensity of Anticoagulation in Atrial Fibrillation
Garcia et al.
Stroke 2002;33:322-324.
FULL TEXT
Should Stroke Subtype Influence Anticoagulation Decisions to Prevent Recurrence in Stroke Patients With Atrial Fibrillation?
Evans et al.
Stroke 2001;32:2828-2832.
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Clinical Inertia
Phillips et al.
ANN INTERN MED 2001;135:825-834.
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Evaluation of Risk Factors for Stroke/Embolism and of Complications Due to Anticoagulant Therapy in Atrial Fibrillation
Wehinger et al.
Stroke 2001;32:2246-2252.
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Keynote address
Fieschi and Falcou
Neurology 2001;57:S82-86.
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Physicians' perceptions of the benefits and risks of warfarin for patients with nonvalvular atrial fibrillation
Bungard et al.
CMAJ 2001;165:301-302.
FULL TEXT
Prevention of Glucocorticoid-Induced Osteoporosis: Experience in a Managed Care Setting
Yood et al.
Arch Intern Med 2001;161:1322-1327.
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Characteristics, Outcome, and Care of Stroke Associated With Atrial Fibrillation in Europe : Data From a Multicenter Multinational Hospital-Based Registry (The European Community Stroke Project)
Lamassa et al.
Stroke 2001;32:392-398.
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The Use of Practitioner Education and a Warfarin Monitoring Service to Improve Anticoagulation Practices
Gaughan
Arch Intern Med 2000;160:2401-2402.
FULL TEXT
Geriatric Assessment and Anticoagulation in Elderly Patients With Chronic Atrial Fibrillation
Bellelli et al.
Arch Intern Med 2000;160:2402-2403.
FULL TEXT
Warfarin Therapy for Atrial Fibrillation: The Patient's Preference Is Important
Fahey et al.
Arch Intern Med 2000;160:2403-2403.
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The impact of patients' preferences on the treatment of atrial fibrillation: observational study of patient based decision analysis Commentary: patients, preferences, and evidence
Protheroe et al.
BMJ 2000;320:1380-1384.
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Quality of Anticoagulation Management Among Patients With Atrial Fibrillation: Results of a Review of Medical Records From 2 Communities
Samsa et al.
Arch Intern Med 2000;160:967-973.
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Stroke prevention practices in patients with atrial fibrillation and pacemaker therapy: Evidence for under-use of anticoagulation
Carlsson et al.
Europace 2000;2:115-118.
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