Burden of Potentially Avoidable Anticoagulant-Associated Hemorrhagic and Thromobembolic Events in the Elderly

INR Response to Low-Dose Vitamin K in Warfarin Patients

BACKGROUND

Literature suggests that 2 mg of vitamin K intravenously (IV) provides a similar effect as 10 mg to reverse warfarin. Doses <5 mg haven't been studied in depth.

OBJECTIVE

The objective was to determine the international normalized ratio (INR) reduction effect of ultra low-dose (ULD) IV vitamin K.

METHODS

This retrospective, observational cohort study compared IV vitamin K doses of 0.25-0.5 mg (ULD) versus 1-2 mg (standard low dose [SLD]). The primary outcome assessed ΔINR at 36 hours; secondary outcomes assessed ΔINR at 12 hours and 30-day venous thromboembolism (VTE) and mortality rates.

RESULTS

Of 88 patients identified (median baseline INR [IQR], 5.1 [3.1, 7.3] vs 4.5 [2.8, 8.2], ULD vs SLD, respectively), 59 had an INR at 12 hours. The ULD had fewer 12-hour INR values <2, with no statistical difference in the ΔINR at 12 hours between the ULD and SLD cohorts (median ΔINR, 2.2 [1.1, 3.4] vs 2.2 [1.1, 6.3]; P = 0.54; median INR, 2.3 vs 1.8). A total of 41 patients had both a 12- and 36-hour INR. No significant difference in the ΔINR between the 12- and 36-hour values occurred (median ΔINR, 0.52 [0.2, 0.91] vs ΔINR, 0.46 [0.18, 0.55]; P = 0.61), suggesting no rebound or excessive reversal and no difference in 30-day rates of VTE (P > 0.99) or death (P = 0.38).

CONCLUSION AND RELEVANCE

ULD IV vitamin K reversed INR similarly to doses of 1-2 mg without rebound. A ULD strategy may be considered in patients requiring more cautious reversal.

Sustained atrial fibrillation increases the risk of anticoagulation-related bleeding in heart failure

BACKGROUND

Oral anticoagulation therapy in individuals with atrial fibrillation (AF) reduces the risk of thromboembolic events at cost of an increased bleeding risk. Whether anticoagulation-related outcomes differ between patients with paroxysmal and sustained AF receiving anticoagulation is controversially discussed.

METHODS

In the present analysis of the prospective multi-center cohort study thrombEVAL, the incidence of anticoagulation-related adverse events was analyzed according to the AF phenotype. Information on outcome was centrally recorded over 3 years, validated via medical records and adjudicated by an independent review panel. Study monitoring was provided by an independent institution.

RESULTS

Overall, the sample comprised 1089 AF individuals, of whom n = 398 had paroxysmal AF and n = 691 experienced sustained AF. In Cox regression analysis with adjustment for potential confounders, sustained AF indicated an independently elevated risk of clinically relevant bleeding compared to paroxysmal AF [hazard ratio (HR) 1.40 (1.02; 1.93); P = 0.038]. For clinically relevant bleeding, a significant interaction of the pattern of AF type with concomitant heart failure (HF) was detected: HR_HF 2.45 (1.51, 3.98) vs. HR_{no HF} 0.85 (0.55, 1.34); P_interaction = 0.003. In HF patients, sustained AF indicated also an elevated risk of major bleeding [HR 2.25 (1.26, 4.20); P = 0.006]. A simplified HAS-BLED score incorporating only information on age (> 65 years), bleeding history, and HF with sustained AF demonstrated better discriminative performance for clinically relevant bleeding than the original version: AUC_HAS-BLED: 0.583 vs. AUC_{simplifiedHAS-BLED}: 0.642 (P = 0.004).

CONCLUSIONS

In HF patients receiving oral anticoagulation, sustained AF indicates a substantially elevated risk of bleeding.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov , identifier: NCT01809015.

A multicenter, prospective study evaluating the impact of the clinical pharmacist-physician counselling on warfarin therapy management in Lebanon

Background

Health care professionals (HCP) are known key elements of effective patient’s counselling and education. For patients taking warfarin, education about the dose, side effects, and toxicity is clearly identified as a cornerstone of achieving improved health and quality of life. The study objective was to evaluate the patients’ knowledge about warfarin and assess the impact of the health care professionals’ counselling in enhancing patients’ knowledge in achieving warfarin therapeutic outcomes.

Method

A six-month prospective multicentered study was conducted in three hospitals, enrolling 300 patients admitted to the cardiac care unit and internal medicine departments. Patients’ warfarin knowledge and INR levels were assessed before and after the clinical pharmacist counselling. The main therapeutic outcome was the impact of the clinical pharmacist-physician counselling on improving patient’s education and achieving therapeutic INR level.

Results

A higher mean knowledge about warfarin score was found after counselling as compared to before counselling (4.82 vs 13.2; p < 0.001). Likewise, the drug dose (1.05 vs 1.88), drug toxicity (0.41 vs 1.92), drug-drug and food-drug interactions (0.02 vs 1.89), therapeutic INR and general drug knowledge scores (2.66 vs 4.68) were significantly higher after as compared to before counselling (p < 0.001 for all variables). The percentages of patients who achieved therapeutic INR levels pre/post counselling was 37.2% and 74.4% respectively (p < 0.001).

Conclusion

Based on the study findings, HCP play a major role in enhancing patients’ knowledge about the factors that affect warfarin therapeutic outcomes. This study highlights the need to establish and develop strategies for appropriate warfarin utilization in Lebanon.

Electronic supplementary material

The online version of this article (10.1186/s12913-018-2874-7) contains supplementary material, which is available to authorized users.

Cost-effectiveness of dabigatran etexilate for the prevention of stroke and systemic embolism in atrial fibrillation: A Canadian payer perspective

Oral dabigatran etexilate is indicated for the prevention of stroke and systemic embolism in patients with atrial fibrillation (AF) in whom anticoagulation is appropriate. Based on the RE-LY study we investigated the cost-effectiveness of Health Canada approved dabigatran etexilate dosing (150 mg bid for patients <80 years, 110 mg bid for patients ≥80 years) versus warfarin and “real-world” prescribing (i.e. warfarin, aspirin, or no treatment in a cohort of warfarin-eligible patients) from a Canadian payer perspective. A Markov model simulated AF patients at moderate to high risk of stroke while tracking clinical events [primary and recurrent ischaemic strokes, systemic embolism, transient ischaemic attack, haemorrhage (intracranial, extracranial, and minor), acute myocardial infarction and death] and resulting functional disability. Acute event costs and resulting long-term follow-up costs incurred by disabled stroke survivors were based on a Canadian prospective study, published literature, and national statistics. Clinical events, summarized as events per 100 patient-years, quality-adjusted life years (QALYs), total costs, and incremental cost effectiveness ratios (ICER) were calculated. Over a lifetime, dabigatran etexilate treated patients experienced fewer intracranial haemorrhages (0.49 dabigatran etexilate vs. 1.13 warfarin vs. 1.05 “real-world” prescribing) and fewer ischaemic strokes (4.40 dabigatran etexilate vs. 4.66 warfarin vs. 5.16 “real-world” prescribing) per 100 patient-years. The ICER of dabigatran etexilate was $10,440/QALY versus warfarin and $3,962/QALY versus “real-world” prescribing. This study demonstrates that dabigatran etexilate is a highly cost-effective alternative to current care for the prevention of stroke and systemic embolism among Canadian AF patients.

Incidence and predictors of excessive warfarin anticoagulation in patients with atrial fibrillation-The EWA study

Vitamin K antagonist warfarin is widely used in clinical practice and excessive anticoagulation is a well-known complication of this therapy. Little is known about permanent and temporary predictors for severe overanticoagulation. The aim of this study was to investigate the occurrence and predicting factors for episodes with very high (≥9) international normalized ratio (INR) values in warfarin treated patients with atrial fibrillation (AF). Excessive Warfarin Anticoagulation (EWA) study screened all patients (n = 13618) in the Turku University Hospital region with an INR ≥2 between years 2003–2015. Patients using warfarin anticoagulation for AF with very high (≥9) INR values (EWA Group) were identified (n = 412 patients) and their characteristics were compared to a control group (n = 405) of AF patients with stable INR during long-term follow-up. Over 20% (n = 92) of the EWA patients had more than one event of very high INR and in 105 (25.5%) patients EWA led to a bleeding event. Of the several temporary and permanent EWA risk factors observed, strongest were excessive alcohol consumption in 9.6% of patients (OR 24.4, 95% CI 9.9–50.4, p<0.0001) and reduced renal function (OR 15.2, 95% CI 5.67–40.7, p<0.0001). Recent antibiotic or antifungal medication, recent hospitalization or outpatient clinic visit and the first 6 months of warfarin use were the most significant temporary risk factors for EWA. Excessive warfarin anticoagulation can be predicted with several permanent and temporary clinical risk factors, many of which are modifiable.

Improving stroke prevention therapy for patients with atrial fibrillation in primary care: protocol for a pragmatic, cluster-randomized trial

Background

The prevalence of atrial fibrillation (AF) is growing as the population ages, and at least 15% of ischemic strokes are attributed to AF. However, many high-risk AF patients are not offered guideline-recommended stroke prevention therapy due to a variety of system, provider, and patient-level barriers.

Methods

We will conduct a pragmatic, cluster-randomized controlled trial randomizing primary care clinics to test a “toolkit” of quality improvement interventions in primary care. In keeping with the recommendations of the chronic care model to simultaneously activate patients and facilitate proactive care by providers, the toolkit includes provider-focused strategies (education, audit and feedback, electronic decision support, and reminders) plus patient-directed strategies (educational letters and reminders). The trial will include two feedback cycles at baseline and approximately 6 months and a final data collection at approximately 12 months. The study will be powered to show a difference of 10% in the primary outcome of proportion of patients receiving guideline-recommended stroke prevention therapy. Analysis will follow the intention-to-treat principle and will be blind to treatment allocation. Unit of analysis will be the patient; models will use generalized estimating equations to account for clustering at the clinical level.

Discussion

Stroke prevention therapy using anticoagulation in patients with AF is known to reduce strokes by two thirds or more in clinical trials, but most studies indicate under-use of this treatment in real-world practice. If the toolkit successfully improves care for patients with AF, stakeholders will be engaged to facilitate broader application to maximize the potential to improve patient outcomes. The intervention toolkit tested in this project could also provide a model to improve quality of care for other chronic cardiovascular conditions managed in primary care.

Trial registration

ClinicalTrials.gov (NCT01927445). Registered August 14, 2014 at https://clinicaltrials.gov/.

Electronic supplementary material

The online version of this article (doi:10.1186/s13012-016-0523-2) contains supplementary material, which is available to authorized users.

Alcohol misuse, genetics, and major bleeding among warfarin therapy patients in a community setting

PURPOSE

Little is known about the impact of alcohol consumption on warfarin safety, or whether demographic, clinical, or genetic factors modify risk of adverse events. We conducted a case-control study to assess the association between screening positive for moderate/severe alcohol misuse and the risk of major bleeding in a community sample of patients using warfarin.

METHODS

The study sample consisted of 570 adult patients continuously enrolled in Group Heath for at least 2 years and receiving warfarin. The main outcome was major bleeding validated through medical record review. Cases experienced major bleeding, and controls did not experience major bleeding. Exposures were Alcohol Use Disorders Identification Test Consumption Questionnaire (AUDIT-C) scores and report of heavy episodic drinking (≥5 drinks on an occasion). The odds of major bleeding were estimated with multivariate logistic regression models. The overall sample was 55% male, 94% Caucasian, and had a mean age of 70 years.

RESULTS

Among 265 cases and 305 controls, AUDIT-C scores indicative of moderate/severe alcohol misuse and heavy episodic drinking were associated with increased risk of major bleeding (OR = 2.10, 95% CI = 1.08-4.07; and OR = 2.36, 95% CI = 1.24-4.50, respectively). Stratified analyses demonstrated increased alcohol-related major bleeding risk in patients on warfarin for ≥1 year and in those with a low-dose genotype (CYP2C9*2/*3, VKORC1(1173G>A), CYP4F2*1), but not in other sub-groups evaluated.

CONCLUSIONS

Alcohol screening questionnaires, potentially coupled with genetic testing, could have clinical utility in selecting patients for warfarin therapy, as well as refining dosing and monitoring practices.

Bleeding risk factors affecting warfarin therapy in the elderly with atrial fibrillation

PURPOSE

Inadequate anticoagulation among elderly individuals with atrial fibrillation (AF) is a common problem. This synthesis of the literature review describes the pathophysiology of AF, explains the mechanism of action of warfarin (Coumadin), identifies factors that contribute to warfarin (Coumadin)-associated bleeding in the elderly population, and explores alternatives to warfarin (Coumadin) therapy. Implications for advanced practice nurse practice, education, and research will be discussed.

METHODS

A literature search was conducted using Academic Search Premier, CINAHL Plus with Full Text, and Medline from 1999 to 2012. Search terms included warfarin (Coumadin), warfarin (Coumadin) genetics, diet, interactions, bleeding, atrial fibrillation, genetics, anticoagulation clinic, dabigatran, apixaban, rivaroxaban, and elderly.

RESULTS

The literature indicates that the potential bleeding risk associated with warfarin (Coumadin) therapy limits its use in the elderly population. However, some studies have found warfarin (Coumadin) to be more effective than aspirin in preventing stroke. The safety profiles of both medications were comparable; also, effective alternatives to warfarin (Coumadin) that do not require routine testing are now available.

CONCLUSIONS

Atrial fibrillation increases the probability of an embolic stroke, especially for the elderly population. Stroke risk and bleeding risk tools, in conjunction with patient preference, determine the best stroke prevention treatment. Anticoagulant clinics manage long-term warfarin (Coumadin) therapy effectively. Newer anticoagulants offer effective alternatives to warfarin (Coumadin) therapy.

Severe non-traumatic bleeding events detected by computed tomography: do anticoagulants and antiplatelet agents have a role?

Purpose

Bleeding is the most common and most serious complication of anticoagulant (AC) and antiplatelet agents (APA) which are increasingly used in every day practice. The aim of this study was to enlist and analyze the most severe bleeding events revealed during computed tomography scanner (CT scan) examinations over a 1-year period at our University Hospital and to evaluate the role of ACs and APAs in their occurrence.

Methods

This descriptive monocentric retrospective study included all patients who benefited from an emergency CT scan with a diagnosis of severe non-traumatic bleeding. Patients were divided into two groups: those treated with ACs and/or APAs, and those not treated with ACs or APAs.

Results

After applying the inclusion criteria, 93 patients were enrolled. Sixty-one patients received an anticoagulant or antiplatelet treatment, and 32 did not receive any AC or APA therapy. Seventy nine percent presented with an intracranial hemorrhage, 17% with a rectus sheath or iliopsoas bleeding or hematoma, and 4% with a quadriceps hematoma. Only patients who received ACs or APAs suffered a muscular hematoma (p <0.0001). Among patients treated with vitamin K antagonists, 6/43 (14%), had an international normalized ratio (INR) higher than the therapeutic range (INR >3).

Conclusions

In our series, intracranial hemorrhage was preponderant and muscular hematomas occurred exclusively in patients treated with ACs and/or APAs. This study needs to be extended to evaluate the impact of new anticoagulant and antiplatelet agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13019-014-0166-9) contains supplementary material, which is available to authorized users.

Stop the clots, but at what cost? Pharmacoeconomics of dabigatran etexilate for the prevention of stroke in subjects with atrial fibrillation: a systematic literature review

Dabigatran etexilate is a newly approved agent for prophylaxis of stroke in atrial fibrillation. Through narrative review, the authors assess evidence of the efficacy of dabigatran in stroke prevention, focusing on the multicenter, randomized trial RE-LY. The authors complement this with a review of the clinical efficacy of standard treatments (antiplatelet and warfarin). Finally, the authors present a systematic review of published studies describing the economics of dabigatran. Our systematic search gave six economic reviews from a variety of healthcare systems (the USA, Canada and the UK) and utilizing different economic models. Analyses suggest economic benefit of high- or sequential-dose dabigatran, particularly when stroke risk is high; intracerebral hemorrhage risk is high or warfarin control is poor. However, questions remain around dabigatran tolerability, compliance and possible unexpected adverse events.

Clinical strategies for selecting oral anticoagulants in patients with atrial fibrillation

Atrial fibrillation is a common arrhythmia. One of the important aspects of the management of atrial fibrillation is stroke prevention. Warfarin has been the longstanding anticoagulant used for stroke prevention in patients with atrial fibrillation. There are now three novel oral anticoagulants, which have been studied in randomized controlled trials and subsequently approved by the Federal Drug Administration for stroke prevention in patients with atrial fibrillation. Special patient populations, including renal insufficiency, elderly, prior stroke, and extreme body weights, were represented to varying degrees in the clinical trials of the novel oral anticoagulants. Furthermore, there is variation in the pharmacokinetics and pharmacodynamics of each anticoagulant, which affect the patient populations differently. Patients and clinicians are faced with the task of selecting among the available anticoagulants, and this review is designed to be a tool for clinical decision-making.

Hospitalization for hemorrhage among warfarin recipients prescribed amiodarone

Amiodarone inhibits the hepatic metabolism of warfarin, potentiating its anticoagulant effect. However, the clinical consequences of this are not well established. Our objective in this study was to characterize the risk of hospitalization for a hemorrhage associated with the initiation of amiodarone within a cohort of continuous warfarin users in Ontario. We conducted a population-based retrospective cohort study among Ontario residents aged ≥66 years receiving warfarin. Among patients with at least 6 months of continuous warfarin therapy, we identified those who were newly prescribed amiodarone and an equal number who were not, matching on age, gender, year of cohort entry, and a high-dimensional propensity score. The primary outcome was hospitalization for hemorrhage within 30 days of amiodarone initiation. Between July 1, 1994, and March 31, 2009, we identified 60,497 patients with at least 6 months of continuous warfarin therapy, of whom 11,665 (19%) commenced amiodarone. For 7,124 (61%) of these, we identified a matched control subject who did not receive amiodarone. Overall, 56 (0.8%) amiodarone recipients and 23 (0.3%) control patients were hospitalized for hemorrhage within 30 days of initiating amiodarone (adjusted hazard ratio 2.45; 95% confidence interval, 1.49-4.02). Seven of 56 (12.5%) patients hospitalized for a hemorrhage after starting amiodarone died in hospital. In conclusion, initiation of amiodarone among older patients receiving warfarin is associated with a more than twofold increase in the risk of hospitalization for hemorrhage, with a relatively high fatality rate. Physicians should closely monitor patients who initiate amiodarone while receiving warfarin.

Gaps in monitoring during oral anticoagulation: insights into care transitions, monitoring barriers, and medication nonadherence

BACKGROUND

Among patients receiving oral anticoagulation, a gap of &gt; 56 days between international normalized ratio tests suggests loss to follow-up that could lead to poor anticoagulation control and serious adverse events.

METHODS

We studied long-term oral anticoagulation care for 56,490 patients aged 65 years and older at 100 sites of care in the Veterans Health Administration. We used the rate of gaps in monitoring per patient-year to predict percentage time in therapeutic range (TTR) at the 100 sites.

RESULTS

Many patients (45%) had at least one gap in monitoring during an average of 1.6 years of observation; 5% had two or more gaps per year. The median gap duration was 74 days (interquartile range, 62-107). The average TTR for patients with two or more gaps per year was 10 percentage points lower than for patients without gaps (P &lt; .001). Patient-level predictors of gaps included nonwhite race, area poverty, greater distance from care, dementia, and major depression. Site-level gaps per patient-year varied from 0.19 to 1.78; each one-unit increase was associated with a 9.2 percentage point decrease in site-level TTR (P &lt; .001).

CONCLUSIONS

Site-level gap rates varied widely within an integrated care system. Sites with more gaps per patient-year had worse anticoagulation control. Strategies to address and reduce gaps in monitoring may improve anticoagulation control.

Individual characteristics and management decisions affect outcome of anticoagulated patients with intracranial hemorrhage

BACKGROUND

Anticoagulated patients with intracranial hemorrhage represent a major management challenge. Our goal is to determine how patient characteristics and management decisions influence outcome.

METHODS

A systematic review of the literature identified relevant reported cases. Variables describing patient characteristics, management, and outcome were extracted. Statistical analyses were carried out using analysis of variance and Fisher's exact test.

RESULTS

A total of 242 patients from our updated dataset met inclusion criteria. Tissue plane of the hemorrhage (P < 0.0001), indication for anticoagulation (P < 0.0001), type of anticoagulant (P = 0.0173), and history of hypertension (P = 0.0418) were significantly associated with outcome. Older age (P < 0.0001), supratentorial index hemorrhages (P = 0.0018), failure to restart anticoagulation (P < 0.0001), and larger hematoma volume (P < 0.0001) were associated with worse outcome. Surgical evacuation was associated with improved outcome (P = 0.0011). There was a trend toward an association between the occurrence of a hemorrhagic or thromboembolic complication and risk of death (P = 0.0882). Sex and sidedness of the index hemorrhage were not significantly associated with outcome.

CONCLUSIONS

Our results provide prognostic information that may assist management of these patients. Our results also suggest that it may be unwise to withhold anticoagulation indefinitely after an index hemorrhage. As thromboembolic or hemorrhagic complications may be associated with worse outcome, efforts to avoid them may be wise. The studies that comprise our dataset have important limitations and a prospective study will be required to confirm these results.

Rates of hemorrhage during warfarin therapy for atrial fibrillation

BACKGROUND

Although warfarin has been extensively studied in clinical trials, little is known about rates of hemorrhage attributable to its use in routine clinical practice. Our objective was to examine incident hemorrhagic events in a large population-based cohort of patients with atrial fibrillation who were starting treatment with warfarin.

METHODS

We conducted a population-based cohort study involving residents of Ontario (age ≥ 66 yr) with atrial fibrillation who started taking warfarin between Apr. 1, 1997, and Mar. 31, 2008. We defined a major hemorrhage as any visit to hospital for hemorrage. We determined crude rates of hemorrhage during warfarin treatment, overall and stratified by CHADS(2) score (congestive heart failure, hypertension, age ≥ 75 yr, diabetes mellitus and prior stroke, transient ischemic attack or thromboembolism).

RESULTS

We included 125 195 patients with atrial fibrillation who started treatment with warfarin during the study period. Overall, the rate of hemorrhage was 3.8% (95% confidence interval [CI] 3.8%-3.9%) per person-year. The risk of major hemorrhage was highest during the first 30 days of treatment. During this period, rates of hemorrhage were 11.8% (95% CI 11.1%-12.5%) per person-year in all patients and 16.7% (95% CI 14.3%-19.4%) per person-year among patients with a CHADS(2) scores of 4 or greater. Over the 5-year follow-up, 10 840 patients (8.7%) visited the hospital for hemorrhage; of these patients, 1963 (18.1%) died in hospital or within 7 days of being discharged.

INTERPRETATION

In this large cohort of older patients with atrial fibrillation, we found that rates of hemorrhage are highest within the first 30 days of warfarin therapy. These rates are considerably higher than the rates of 1%-3% reported in randomized controlled trials of warfarin therapy. Our study provides timely estimates of warfarin-related adverse events that may be useful to clinicians, patients and policy-makers as new options for treatment become available.

Anticoagulation patient self-monitoring in the United States: considerations for clinical practice adoption

Systematic management models such as anticoagulation clinics have emerged in order to optimize warfarin effectiveness and to minimize related complications. Most of these models are structured so that patients come to a clinic for in-person testing and evaluation, thus making this model of care difficult to access and time consuming for many patients. The emergence of portable instruments for measuring anticoagulant effect in capillary whole blood made it possible for patients receiving warfarin to self-monitor the effect of their anticoagulant therapy. Self-monitoring empowers patients, offers the advantage of more frequent monitoring, and increases patient convenience by allowing testing at home and avoiding the need for frequent laboratory and clinic visits. Self-monitoring can entail patient self-testing (PST) and/or patient self-management (PSM). Several studies have evaluated and shown the benefit of both PST and PSM models of care when compared with either routine medical care or anticoagulation clinic management of anticoagulation therapy. Self-monitoring (PSM and/or PST) of anticoagulation results in lower thromboembolic events, lower mortality, and no increase in major bleeding when compared with standard care. Despite favorable results and enhanced patient convenience, the adoption of self-monitoring into clinical practice in the United States has been limited, especially in higher risk, disadvantaged populations. Although the emergence of a multitude of novel oral anticoagulants will permit clinicians to better individualize anticoagulant therapy options by choosing the optimum regimen based on individual patient characteristics, it is also expected that traditional agents will continue to play a role in a significant subset of patients. For those patients treated with traditional anticoagulants such as warfarin, future models of care will entail patient-centered management such as PST and PSM. The incorporation of technology (i.e., Web-based expert systems) is expected to further improve the outcomes realized by PST and PSM. Further studies are needed to explore factors that influence the adoption of self-monitoring in the United States and to evaluate the feasibility and implementation in real-life clinical settings.

Stroke prevention in elderly patients with atrial fibrillation: challenges for anticoagulation

Elderly patients with atrial fibrillation (AF), who constitute almost half of all AF patients, are at increased risk of stroke. Anticoagulant therapies, especially vitamin K antagonists (VKA), reduce the risk of stroke in all patients including the elderly but are frequently under-used in older patients. Failure to initiate VKA in elderly AF patients is related to a number of factors, including the limitations of current therapies and the increased risk for major haemorrhage associated with advanced age and anticoagulation therapy. Of particular concern is the risk of intracranial haemorrhages (ICH), which is associated with high rates of mortality and morbidity. Novel oral anticoagulant agents that are easier to use and might offer similar or better levels of stroke prevention with a similar or reduced risk of bleeding should increase the use of antithrombotic therapy in the management of elderly AF patients. Amongst these new agents, the recently approved direct thrombin inhibitor dabigatran provides effective stroke prevention with a significant reduction of ICH, and enables clinicians to tailor the dose according to age and haemorrhagic risk.

Survey of neurosurgical management of central nervous system hemorrhage in patients receiving anticoagulation therapy: current practice is highly variable and may be suboptimal

BACKGROUND

Patients with central nervous system (CNS) hemorrhage who receive anticoagulation (AC) therapy are at high risk for progressive or recurrent hemorrhagic and thromboembolic (TE) events. The authors conducted a survey at the 2010 American Association of Neurological Surgeons (AANS) annual meeting to determine how these patients are currently being managed by neurosurgeons.

METHODS

During plenary session III at the 2010 AANS annual meeting, the audience was presented with an illustrative case and surveyed with an audience response system. The number choosing each response as well as data regarding the level of training of meeting registrants were provided to the authors by the AANS.

RESULTS

Approximately 10% of all meeting registrants responded to the questions, 65% of whom were consultant neurosurgeons. The responses showed that 47.7% of respondents face dilemmas regarding AC restart time and intensity at least once per week. The most commonly selected AC restart time was 1 month after the index hemorrhage (43.5%); 8.0% indicated they would not restart AC. In making management decisions in these patients, 59.4% of respondents indicated that they relied predominantly on their own intuition or past experience.

CONCLUSIONS

This study is the first to describe how patients with CNS hemorrhage who receive AC therapy are currently being managed by clinicians. An apparent neurosurgical preference to avoid hemorrhagic complications is at odds with a suggested early risk for TE. These data suggest that the neurosurgical management of patients with CNS hemorrhage who receive AC therapy is an area that could benefit from consensus-based practice guidelines and an organized effort at knowledge translation and mobilization.

Using highly variable warfarin dosing to identify patients at risk for adverse events

BACKGROUND

Patients who receive highly variable doses of warfarin may be at risk for poor anticoagulation control and adverse events. However, we lack a system to identify patients with the highest dose variability. Our objectives were to develop a scoring system to identify patients with high dose variability, and to validate this new measure by demonstrating that patients so identified have poor anticoagulation control and higher rates of adverse events (criterion validity).

METHODS

We used a database of over 4, 000 patients who received oral anticoagulation in community practice between 2000-2002. We reviewed the charts of 168 patients with large warfarin dose variation and agreed on 18 risk factor definitions for high dose variability. We identified 109 patients with the highest dose variability (cases), as measured by coefficient of variation (CoV, SD/mean). We matched each case to two controls with low dose variability. Then, we examined all 327 charts, blinded to case/control status, to identify the presence or absence of the 18 risk factors for dose variability. We performed a multivariable analysis to identify independent predictors of high CoV. We also compared anticoagulation control, as measured by percent time in therapeutic range (TTR), and rates of adverse events between groups.

RESULTS

CoV corresponded with other measures of anticoagulation control. TTR was 53% among cases and 79% among controls (p < 0.001). CoV also predicted adverse events. Six cases experienced a major hemorrhage versus 1 control (p < 0.001) and 3 cases had a thromboembolic event versus 0 control patients (p = 0.04). Independent predictors of high dose variability included hospitalization (OR = 21.3), decreased oral intake (OR = 12.2), use of systemic steroids (OR = 6.1), acetaminophen (OR = 4.0) and antibiotics (OR = 2.7; p < 0.05 for all).

CONCLUSION

CoV can be used to identify patients at risk for poor anticoagulation control and adverse events. This new measure has the potential to identify patients at high risk before they suffer adverse events.

Quality of management of oral anticoagulation as assessed by time in therapeutic INR range in elderly and younger patients with low mean years of formal education: a prospective cohort study

BACKGROUND

despite the overwhelming evidence of its effectiveness, oral anticoagulation continues to be underused in the elderly, presumably due to physicians' misconceptions when estimating bleeding risk and ability to comply with treatment.

OBJECTIVE

to investigate the quality of anticoagulation control among deprived elderly and younger patients.

DESIGN

prospective observational study.

SETTING

a public anticoagulation clinic in a developing country.

SUBJECTS

all adult patients on intended long-term (>90 days) oral anticoagulation. We studied 171 patients (79 elderly and 92 non-elderly) with a mean follow-up of 273 ± 84.9 days.

METHODS

the main outcome measure was the quality of anticoagulation management as measured by the time in therapeutic (TTR) international normalised ratio (INR) range. Elderly patients (≥60 years) were compared with younger patients with respect to the educational level and co-morbidities.

RESULTS

the mean number of years of formal education was 4.37 ± 3.2 years. The mean TTR was 62.50 ± 17.9% in non-elderly and 62.10 ± 16.6% in elderly (P = 0.862) subjects, despite the higher prevalence of co-morbidities in the latter group: heart failure (46.3 versus 28.6%, P = 0.042), diabetes mellitus (22.8 versus 8.7%, P = 0.011), renal failure (estimated glomerular filtration rate <50 ml/min: 38.0 versus 7.1%, P < 0.001) and polypharmacy (84.8 versus 58.7%, P < 0.001). Fifty elderly and 84 non-elderly subjects require little or no assistance in taking medications. Among them, the elderly had lower educational levels (3.42 ± 2.5 versus 5.55 ± 3.4 years of formal education, P < 0.001) and higher rates of cognitive impairment (34.0 versus 13.1%, P = 0.004), but a similar mean TTR (62.46 ± 16.1 versus 63.02 ± 17.8%, P = 0.856). The oldest (≥75 years) patients did as well as those aged ≤50 years (mean TTR: 62.54 ± 16.0 versus 62.23 ± 16.4%, respectively, P = 0.98).

CONCLUSIONS

good-quality management of oral anticoagulation is achievable in deprived populations attending an anticoagulation clinic. Elderly patients may experience similar quality of anticoagulation despite having higher levels of co-morbidities and polypharmacy. These results add evidence to the safety of such therapeutic interventions in the elderly.

Prompt repeat testing after out-of-range INR values: a quality indicator for anticoagulation care

BACKGROUND

Improved control of oral anticoagulation reduces adverse events. A program of quality measurement is needed for oral anticoagulation. The interval until the next test after an out-of-range International Normalized Ratio (INR) value (the "follow-up interval") could serve as a process of care measure.

METHODS AND RESULTS

We studied 104 451 patients cared for by 100 anticoagulation clinics in the Veterans Health Administration (VA). For each site, we computed the average follow-up interval after low (≤1.5) or high (≥4.0) INR. Our outcome was each site's average anticoagulation control, measured by percent time in therapeutic range (TTR); 59 837 patients (57%) contributed to the low INR analysis, 37 697 (36%) contributed to the high INR analysis, and all patients contributed to the dependent variable (mean site TTR). After a low INR, site mean follow-up interval ranged from 10 to 24 days. Longer follow-up intervals were associated with worse site-level control (1.04% lower for each additional day, P<0.001). After a high INR, site mean follow-up interval ranged from 6 to 18 days, with longer follow-up intervals associated with worse site-level control (1.12% lower for each additional day, P<0.001). These relationships were somewhat attenuated but still highly statistically significant when the proportion of INR values in-range was used as the dependent variable rather than TTR.

CONCLUSIONS

Prompt repeat testing after out-of-range INR values is associated with better anticoagulation control at the site level and could be an important part of a quality improvement effort for oral anticoagulation.

Reexamining the recommended follow-up interval after obtaining an in-range international normalized ratio value: results from the Veterans Affairs study to improve anticoagulation

BACKGROUND

Patients receiving oral anticoagulation therapy should be tested often enough to optimize control, but excessive testing increases burden and cost. We examined the relationship between follow-up intervals after obtaining an in-range (2.0-3.0) international normalized ratio (INR) and anticoagulation control.

METHODS

We studied 104,451 patients who were receiving anticoagulation therapy from 100 anticoagulation clinics in the US Veterans Health Administration. Most patients (98,877) had at least one in-range INR followed by another INR within 56 days. For each such patient, we selected the last in-range INR and characterized the interval between this index value and the next INR. The independent variable was the site mean follow-up interval after obtaining an in-range INR. The dependent variable was the site mean risk-adjusted percentage of time in the therapeutic range (TTR).

RESULTS

The site mean follow-up interval varied from 25 to 38 days. As the site mean follow-up interval became longer, the risk-adjusted TTR was worse (-0.51% per day, P = .004). This relationship persisted when the index value was the first consecutive in-range INR (-0.63%, P < .001) or the second (-0.58%, P < .001), but not the third or greater (-0.12%, P = .46).

CONCLUSIONS

Sites varied widely regarding follow-up intervals after obtaining an in-range INR (25-38 days). Shorter intervals were generally associated with better anticoagulation control, but after obtaining a third consecutive in-range value, this relationship was greatly attenuated and no longer statistically significant. Our results suggest that a maximum interval of 28 days after obtaining the first or second in-range value and consideration of a longer interval after obtaining the third or greater consecutive in-range value may be appropriate.

Home management of oral anticoagulation via telemedicine versus conventional hospital-based treatment

BACKGROUND AND OBJECTIVE

We have developed an expert computer system for the control of oral anticoagulation therapy, accessible by the patients via their own computer. To investigate if the weekly measurement and dosing of international normalized ratio (INR) at home using the online Internet-based system was superior to conventional treatment, we performed a randomized, controlled trial.

PATIENTS AND METHODS

All 669 patients in our anticoagulation clinic were asked to participate in the trial, providing that they had Internet access and could use the CoaguChek XS system. A total of 140 patients were included and randomized to (A) once weekly measurement and report online, (B) twice weekly measurement and report online, and (C) continued conventional treatment with INR measurement in the lab every 4 weeks and dose adjustment by letter.

RESULTS

Group A had 79.7% (95% CI 79.0-80.3) of time in therapeutic range (TTR), group B 80.2% (95% CI 79.4-80.9) of TTR, and group C 72.7% (95% CI 71.9-73.4) TTR. Groups A and B perform statistically significantly better than the conventional group C, with a difference of TTR of 7% points (p < 2.2 × 10(-16)), whereas no difference was seen between A and B.

CONCLUSION

Home measurement of INR and the reporting and dosing of results online once a week increase TTR from 72% to 79% as compared to conventional computer-assisted monitoring in an anticoagulation clinic.

Risk-Adjusted Percent Time in Therapeutic Range as a Quality Indicator for Outpatient Oral Anticoagulation

Background—

Oral anticoagulation is safer and more effective when patients receive high-quality care. However, there have been no prior efforts to measure quality of oral anticoagulation care or to risk adjust it to ensure credible comparisons. Our objective was to profile site performance in the Veterans Health Administration (VA) using risk-adjusted percent time in therapeutic range (TTR).

Methods and Results—

We included 124 551 patients who received outpatient oral anticoagulation from 100 VA sites of care for indications other than valvular heart disease from October 1, 2006, to September 30, 2008. We calculated TTR for each patient and mean TTR for each site of care. Expected TTR was calculated for each patient and each site based on the variables in the risk adjustment model, which included demographics, comorbid conditions, medications, and hospitalizations. Mean TTR for the entire sample was 58%. Site-observed TTR varied from 38% to 69% or from poor to excellent. Site-expected TTR varied from 54% to 62%. Site risk-adjusted performance ranged from 18% below expected to 12% above expected. Risk adjustment did not alter performance rankings for many sites, but for other sites, it made an important difference. For example, the site ranked 27th of 100 before risk adjustment was one of the best (risk-adjusted rank, 7). Risk-adjusted site rankings were consistent from year to year (correlation between years, 0.89).

Conclusions—

Risk-adjusted TTR can be used to profile the quality of outpatient oral anticoagulation in a large, integrated health system. This measure can serve as the basis for quality measurement and quality improvement efforts.

Vitamin K1 supplementation to improve the stability of anticoagulation therapy with vitamin K antagonists: a dose-finding study

BACKGROUND

Poor anticoagulant stability in patients using vitamin K antagonists is a risk factor for both bleeding and thrombosis. In previous studies supplementation with low dose vitamin K(1) was shown to improve the stability of anticoagulant control. We set up a study to confirm earlier reports and to determine the optimal daily dose of vitamin K(1) in preparation of a large study with clinical endpoints.

DESIGN AND METHODS

Four hundred patients from two anticoagulation clinics starting with vitamin K antagonists, independently of a possible history of instable anticoagulation, were randomized to receive either placebo or 100, 150 or 200 μg of vitamin K(1) together with their treatment with vitamin K antagonists. The treatment was administered for 6 to 12 months. Anticoagulation stability, expressed as the percentage of time that the International Normalized Ratio was within the therapeutic range, was compared between the groups.

RESULTS

After adjustment for age, sex, vitamin K antagonist used, anticoagulation clinic and interacting drugs as confounding factors the difference in percentage of time with the International Normalized Ratio within the therapeutic range between the placebo group and the vitamin K(1) groups was 2.1% (95% CI: -3.2% - 7.4%) for the group taking 100 μg, 2.7% (95% CI: -2.3% -7.6%) for the group taking 150 μg and 0.9% (95% CI: -4.5% - 6.3%) for the group taking 200 μg vitamin K(1) group, in favor of the vitamin K(1) groups. The patients from both the 100 μg group and the 150 μg group had a 2-fold higher chance of reaching at least 85% of time with the International Normalized Ratio within the therapeutic range. There were no differences in thromboembolic or hemorrhagic complications between the groups.

CONCLUSIONS

In patients starting vitamin K antagonists, supplementation with low dose vitamin K(1) resulted in an improvement of time that anticoagulation was within the therapeutic range. Differences between doses were, however, small and the improvement is unlikely to be of clinical relevance. For future studies we recommend selecting only patients with instable anticoagulant control. (This study was registered at www.isrctn.org as ISRCTN37109430).

A formal risk-benefit framework for genomic tests: facilitating the appropriate translation of genomics into clinical practice

PURPOSE

Evaluation of genomic tests is often challenging because of the lack of direct evidence of clinical benefit compared with usual care and unclear evidence requirements. To address these issues, this study presents a risk-benefit framework for assessing the health-related utility of genomic tests.

METHODS

We incorporated approaches from a variety of established fields including decision science, outcomes research, and health technology assessment to develop the framework. Additionally, we considered genomic test stakeholder perspectives and case studies.

RESULTS

We developed a three-tiered framework: first, we use decision-analytic modeling techniques to synthesize data, project incidence of clinical events, and assess uncertainty. Second, we defined the health-related utility of genomic tests as improvement in health outcomes as measured by clinical event rates, life expectancy, and quality-adjusted life-years. Finally, we displayed results using a risk-benefit policy matrix to facilitate the interpretation and implementation of findings from these analyses.

CONCLUSION

A formal risk-benefit framework may accelerate the utilization and practice-based evidence development of genomic tests that pose low risk and offer plausible clinical benefit, while discouraging premature use of tests that provide little benefit or pose significant health risks compared with usual care.

Pharmacogenomic trial design: use of a PK/PD model to explore warfarin dosing interventions through clinical trial simulation

OBJECTIVE

Variants of two genes, CYP2C9 and VKORC1, explain approximately one third of variability in warfarin maintenance dose requirements. However, the clinical utility of using this information in addition to clinical and demographic data ('pharmacogenomic-guidance') is unclear, as few comparative clinical trials have been conducted to date. The objective of this study was to explore the incremental effect of pharmacogenomic-guided warfarin dosing under various conditions using clinical trial simulation.

METHODS

We used an existing pharmacokinetic/pharmacodynamic model to perform clinical trial simulations of pharmacogenomic-guided versus standard of care warfarin therapy. The primary outcome was the percentage of patient time spent in therapeutic range over the first month of therapy. We assessed the influence of the frequency of INR monitoring, and the use of a loading dose and dose increase delay in patients with CYP2C9 variants.

RESULTS

Pharmacogenomic guidance resulted in a 3-4 percentage point absolute increase in time spent in therapeutic range over the first month of therapy compared with standard of care. The improvement in time in range was greater when the frequency of INR monitoring in both arms was assumed to be lower. The absolute difference increased to 6-8 percentage points with the use of a loading dose and dose increase delay in patients with a CYP2C9 variant.

CONCLUSION

Our initial results imply that pharmacogenomic-guided warfarin dosing may be more useful in settings with less intensive patient follow-up, and when adjustments are made for slower therapeutic response in patients with a CYP2C9 variant. Further pharmacokinetic/pharmacodynamic model development may be useful for warfarin pharmacogenomic trial design.

Epidemiology of subtherapeutic anticoagulation in the United States

BACKGROUND

Low international normalized ratio (INR; <or=1.5) increases risk for thromboembolism. However, little is known about the epidemiology of low INR.

METHODS AND RESULTS

We prospectively collected data from 47 community-based clinics located throughout the United States from 2000 to 2002. We examined risk factors for low INR (<or=1.5), reasons given in the medical record for low INR, and proportion of thromboembolic events that occurred during periods of low INR. Of the 4489 patients in our database, 1540 (34%) had at least 1 low INR. Compared with men, women had an increased incidence of low INR (adjusted incidence rate ratio, 1.44; P<0.001). Compared with patients anticoagulated for atrial fibrillation, patients anticoagulated for venous thromboembolism had an increased incidence of low INR (adjusted incidence rate ratio, 1.48; P<0.001). The 5 most common reasons for low INR were nonadherence (17%), interruptions for procedures (16%), recent dose reductions (15%), no reason apparent after questioning (15%), and second or greater consecutive low INR (13%). A total of 21.8% of thromboembolic events (95% CI, 12.2 to 35.4%) occurred during periods of low INR; 58% of these events were related to an interruption of warfarin therapy.

CONCLUSIONS

In this cohort of patients receiving warfarin, more than 1 in 5 thromboembolic events occurred during a period of low INR. Women and patients anticoagulated for venous thromboembolism were particularly likely to experience low INR. Improving adherence, minimizing interruptions of therapy, and addressing low INR more promptly could reduce the risk of low INR.

Randomized controlled trial of supervised patient self-testing of warfarin therapy using an internet-based expert system

BACKGROUND

Increased frequency of prothrombin time testing, facilitated by patient self-testing (PST) of the International Normalized Ratio (INR) can improve the clinical outcomes of oral anticoagulation therapy (OAT). However, oversight of this type of management is often difficult and time-consuming for healthcare professionals. This study reports the first randomized controlled trial of an automated direct-to-patient expert system, enabling remote and effective management of patients on OAT.

METHODS

A prospective, randomized controlled cross-over study was performed to test the hypothesis that supervised PST using an internet-based, direct-to-patient expert system could provide improved anticoagulation control as compared with that provided by an anticoagulation management service (AMS). During the 6 months of supervised PST, patients measured their INR at home using a portable meter and entered this result, along with other information, onto the internet web page. Patients received instant feedback from the system as to what dose to take and when the next test was due. During the routine care arm, patients attended the AMS at least every 4-6 weeks and were dosed by the anticoagulation pharmacist or physician. The primary outcome variable was the difference in the time in therapeutic range (TTR) between both arms.

RESULTS

One hundred and sixty-two patients were enrolled (male 61.6%, mean age 58.7 years), and 132 patients (81.5%) completed both arms. TTR was significantly higher during PST management than during AMS management (median TTR 74% vs 58.6%; z=5.67, P < 0.001).

CONCLUSIONS

The use of an internet-based, direct-to-patient expert system for the management of PST improves the control of OAT as compared with AMS management.

Measuring quality of oral anticoagulation care: extending quality measurement to a new field

BACKGROUND

Oral anticoagulation with warfarin is an increasingly common medical intervention. Despite its efficacy, warfarin is difficult to manage, contributing to potential for patient harm. Efforts to measure the quality of oral anticoagulation care have focused disproportionately on the identification of ideal candidates for warfarin therapy, with comparatively little effort in measuring the quality of oral anticoagulation care once therapy has begun. To address this gap in the literature, a MEDLINE search was conducted for all papers relevant to possible quality measures in oral anticoagulation care, including measures of structure, process, and outcomes of care.

LIMITATIONS, CONCERNS, AND CHALLENGES OF QUALITY MEASUREMENT IN ORAL ANTICOAGULATION

Because they do not have intrinsic significance, measures of structure and process should be strongly related to outcomes that matter to merit our interest. Consensus guidelines may provide useful guidance to practicing clinicians but may not represent valid process measures. Outcome measures must be studied with databases that provide sufficient statistical power to reliably demonstrate real differences between providers or sites of care.

CONCLUSION

Oral anticoagulation care, a common and serious condition, is in need of a program of quality measurement. This article suggests a research agenda to begin such a program. Previous research has established the evidence for anticoagulant therapy across a broad spectrum of indications and has helped to achieve consensus on the optimal target intensity for various indications. The next task will be to use this body of evidence to develop valid measures of the structure, process, and outcomes of oral anticoagulation care. Quality indicators provide a framework for quality improvement, two goals of which are to maximize the effectiveness of therapy and to minimize harm.

Warfarin dose management affects INR control

BACKGROUND

Little is known about how patterns of warfarin dose management contribute to percentage time in the therapeutic International Normalized Ratio (INR) range (TTR).

OBJECTIVES

To quantify the contribution of warfarin dose management to TTR and to define an optimal dose management strategy.

PATIENTS/METHODS

We enrolled 3961 patients receiving warfarin from 94 community-based clinics. We derived and validated a model for the probability of a warfarin dose change under various conditions. For each patient, we computed an observed minus expected (O - E) score, comparing the number of dose changes predicted by our model to the number of changes observed. We examined the ability of O - E scores to predict TTR, and simulated various dose management strategies in the context of our model.

RESULTS

Patients were observed for a mean of 15.2 months. Patients who deviated the least from the predicted number of dose changes achieved the best INR control (mean TTR 70.1% unadjusted); patients with greater deviations had lower TTR (65.8% and 62.0% for fewer and more dose changes respectively, Bonferroni-adjusted P < 0.05/3 for both comparisons). On average, clinicians in our study changed the dose when the INR was 1.8 or lower/3.2 or higher (mean TTR: 68%); optimal management would have been to change the dose when the INR was 1.7 or lower/3.3 or higher (predicted TTR: 74%).

CONCLUSIONS

Our observational study suggests that INR control could be improved considerably by changing the warfarin dose only when the INR is 1.7 or lower/3.3 or higher. This should be confirmed in a randomized trial.

Potentially Preventable Strokes in High-Risk Patients With Atrial Fibrillation Who Are Not Adequately Anticoagulated

Background and Purpose— Warfarin is the most effective stroke prevention medication for high-risk individuals with atrial fibrillation, yet it is often underused. This study examined the magnitude of this problem in a large contemporary, prospective stroke registry.

Methods— We analyzed data from the Registry of the Canadian Stroke Network, a prospective database of consecutive patients with stroke admitted to 12 designated stroke centers in Ontario (2003 to 2007). We included patients admitted with an acute ischemic stroke who (1) had a known history of atrial fibrillation; (2) were classified as high risk for systemic emboli according to published guidelines; and (3) had no known contraindications to anticoagulation. Primary end points were the use of prestroke antithrombotic medications and admission international normalized ratio.

Results— Among patients admitted with a first ischemic stroke who had known atrial fibrillation (n=597), strokes were disabling in 60% and fatal in 20%. Preadmission medications were warfarin (40%), antiplatelet therapy (30%), and no antithrombotics (29%). Of those taking warfarin, three fourths had a subtherapeutic international normalized ratio (<2.0) at the time of stroke admission. Overall, only 10% of patients with acute stroke with known atrial fibrillation were therapeutically anticoagulated (international normalized ratio ≥2.0) at admission. In stroke patients with a history of atrial fibrillation and a previous transient ischemic attack or ischemic stroke (n=323), only 18% were taking warfarin with therapeutic international normalized ratio at the time of admission for stroke, 39% were taking warfarin with subtherapeutic international normalized ratio, and 15% were on no antithrombotic therapy.

Conclusions— In high-risk patients with atrial fibrillation admitted with a stroke, and who were candidates for anticoagulation, most were either not taking warfarin or were subtherapeutic at the time of ischemic stroke. Many were on no antithrombotic therapy. These findings should encourage greater efforts to prescribe and monitor appropriate antithrombotic therapy to prevent stroke in individuals with atrial fibrillation.