Review of atrial fibrillation outcome trials of oral anticoagulant and antiplatelet agents

In-thrombus thrombin secretion: a new diagnostic marker of atrial fibrillation in cryptogenic stroke

BACKGROUND

Endovascularly retrieved clots are a potential resource for diagnosing stroke etiology, which may influence secondary prevention treatment. In this study we measured thrombin activity eluted by serially washing clots.

METHODS

Clots were retrieved from 68 patients with acute ischemic stroke, freshly frozen and classified by standard criteria into proven atrial fibrillation (AF, 18 patients), atherosclerotic origin (AS, 15 patients), cryptogenic stroke (Cr, 17 patients) and other known causes (18 patients). Thawed clot samples were washed by transferring them into 1 mL buffer in seven hourly cycles and a fluorescent substrate assay was used to measure secreted thrombin activity. The clots were also examined histologically. Artificial fibrin and red blood cell-rich clots were similarly assayed for wash-eluted thrombin activity as an external control.

RESULTS

Thrombin activity eluted from clots of AF origin decreased significantly with time in contrast to steady levels eluted from AS origin thrombi (P<0.0001 by repeated measures ANOVA). The Cr stroke group was indistinguishable from the AF group and differed statistically from the AS group (P=0.017 by repeated measures ANOVA). In artificial clots we found a biphasic activity pattern, with initially decreasing levels of eluted thrombin (AF pattern) and then, with continuing washes, steady eluted thrombin levels (AS pattern).

CONCLUSIONS

An assay measuring the change in thrombin in clots retrieved during acute stroke endovascular thrombectomy procedures may serve as a diagnostic marker of the origin of the clot. The suggested mechanism for these differences may be the clot location before its retrieval, with high blood flow causing thrombin washout in atherosclerotic clots, in contrast to atrium appendage low blood flow retaining high thrombin levels.

Atrial fibrillation in patients with first-ever stroke: Incidence trends and antithrombotic therapy before the event

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia among adults. Despite the proven advantages in primary and secondary stroke prevention in patients with AF, oral anticoagulation (OAC) therapy is still underused in many countries. In this study, we investigated the incidence of AF-related ischemic stroke over the past decade in South Korea and trends of preventive antithrombotic therapy use before stroke in a nationwide cohort.

Methods and findings

The data source for this study was a nationwide sample cohort comprising 1,025,340 individuals that was established by the nationwide health insurance system in 2002. A total of 10,215 patients with acute ischemic stroke (AIS) were selected from the cohort between 2004 and 2013. AF was identified in 1,662 patients, and 979 patients had preexisting AF before AIS. The annual proportion of patients with AIS with AF gradually increased from 13.4% to 22.6% over the study period (p for trends <0.001). Only 14.0% of patients with high risk AF were receiving OAC before the stroke, and this proportion remained relatively constant during the study period. However, the proportion of patients treated with antiplatelet agents had increased from 18.8% in 2004 to 45.3% in 2013, while that of patients receiving no antithrombotic agent decreased from 64.6% in 2004 to 43.9% in 2013. As a limitation, no information was available about non-vitamin K antagonist oral anticoagulants, because they were widely used since late 2014 in Korea.

Conclusions

The number of patients with AIS and AF has steadily increased over the last 10 years in Korea. However, a small portion of patients with AF were receiving OAC therapy before the stroke and about half of the patients did not receive any antithrombotic medication. Our study demonstrates that there is huge gap between clinical practice and treatment guidelines for patients with AF in Korea.

Management of dental extractions in patients on warfarin and antiplatelet therapy

BACKGROUND/PURPOSE

Planning dental extractions for Taiwanese patients on antithrombotic therapy remains controversial. This study aimed to examine management of dental extraction in patients on warfarin and antiplatelet therapy.

METHODS

Subjects comprised 1331 patients, with (1) 60 on warfarin with intentional normalized ratio (INR) below 4.0 (warfarin continued: 28 patients/33 occasions; warfarin stopped and switched to heparin under hospitalization: 32 patients/37 occasions); (2) 183 on antiplatelet therapy (aspirin: 125 patients/185 occasions; clopidogrel: 42 patients/65 occasions; dual therapy: 16 patients/24 occasions); and (3) a control group of 1088 patients/1472 occasions without any antithrombotic therapy. The patient's clinico-demographic parameters, warfarin effectiveness (dose and INR levels) and antiplatelet therapy, number and type of dental extraction and incidence of postoperative bleeding were investigated.

RESULTS

Incidence of postoperative bleeding in the warfarinized group (warfarin continued: 9.1%; warfarin stopped: 8.1%) was higher than in the antiplatelet group (aspirin: 1.1%; clopidogrel: 3.1%; dual antiplatelet: 4.2%), and the control group (0.7%), but these differences were not significant and unrelated to INR or number and type of dental extraction. Postoperative hemorrhage was managed successfully by repacking with Gelfoam impregnated with tranexamic acid powder in most patients.

CONCLUSION

The study indicated that there is no need to interrupt warfarin (INR<4.0) and antiplatelet therapy before dental extractions in Taiwanese patients. A sufficient hemostasis could be obtained using local measures. This approach can save these individuals from becoming exposed to the risk of thromboembolism and the inconvenience of bridging anticoagulation with heparin.

Synthesis and evaluation of anthranilamide-based derivatives as FXa inhibitors

Factor Xa (FXa) plays a significant role in the blood coagulation cascade and is a promising target for anticoagulation drugs. Three oral FXa inhibitors have been approved by FDA for treating thrombotic diseases. In this study, 43 novel compounds were synthesized anthranilamide-based FXa inhibitors aiming to ameliorate the toxicity of traditional FXa inhibitors in clinic. The data indicated that the compounds 6a, 6a-b, 6a-e, 6k, 6k-a and 6k-b showed remarkable FXa inhibitory activity and excellent selectivity over thrombin in vitro. Selected compounds also exhibited anticoagulant activities in vitro consequently and were potent novel anti-coagulators in further.

Real world adherence to oral anticoagulant in non-valvular atrial fibrillation patients in China

BACKGROUND AND OBJECTIVE

Adherence to oral anticoagulants is crucial for the prevention of ischemic stroke in atrial fibrillation patients; however, evidence of oral-anticoagulant adherence from developing countries is still lacking. This study aimed to evaluate the current situation and predictors of oral-anticoagulant adherence in non-valvular atrial fibrillation (NVAF) patients in China.

METHODS

Records of NVAF patients were obtained from a regional claims database. Both initiation and adherence to oral anticoagulants were calculated from linked records. Factors of oral-anticoagulant initiation were identified using Cox regression.

RESULTS

Among 33,463 NVAF patients, only 13.9% initialized warfarin treatment after the indexed hospital visit. Stratified by CHA₂DS₂-VASc scores, 20.9% of patients in the low-risk group were on warfarin, followed by 15.3% and 10.7% from the middle and high-risk groups, respectively. Among patients who initialized warfarin, only 40.4% filled the first repeat prescription within 3 months. Concurrent statin use, hypertension and heart failure were associated with higher warfarin initiation rate. Factors such as age above 75, female sex, manufacture workers, discharge from the primary-care center, antiplatelet use, and diabetes, ischemic and hemorrhagic stroke were associated with lower rate of warfarin initiation. Additionally, initiating warfarin treatment reduced risk of ischemic stroke in middle and high-risk patients.

CONCLUSION

Oral anticoagulation was significantly under-used in NVAF patients in China. Age, sex, concurrent drug usage, and disease history were associated factors. Improving warfarin adherence was promising to reduce ischemic stroke risk of NVAF patients.

Minimizing bleeding risk in patients receiving direct oral anticoagulants for stroke prevention

Many primary care physicians are wary about using direct oral anticoagulants (DOACs) in patients with nonvalvular atrial fibrillation (AF). Factors such as comorbidities, concomitant medications, and alcohol misuse increase concerns over bleeding risk, especially in elderly and frail patients with AF. This article discusses strategies to minimize the risk of major bleeding events in patients with AF who may benefit from oral anticoagulant therapy for stroke prevention. The potential benefits of the DOACs compared with vitamin K antagonists, in terms of a lower risk of intracranial hemorrhage, are discussed, together with the identification of reversible risk factors for bleeding and correct dose selection of the DOACs based on a patient’s characteristics and concomitant medications. Current bleeding management strategies, including the new reversal agents for the DOACs and the prevention of bleeding during preoperative anticoagulation treatment, in addition to health care resource use associated with anticoagulation treatment and bleeding, are also discussed. Implementing a structured approach at an individual patient level will minimize the overall risk of bleeding and should increase physician confidence in using the DOACs for stroke prevention in their patients with nonvalvular AF.

Discovery of 5-Phenyl-N-(pyridin-2-ylmethyl)-2-(pyrimidin-5-yl)quinazolin-4-amine as a Potent I Kur Inhibitor

A new series of phenylquinazoline inhibitors of Kv 1.5 is disclosed. The series was optimized for Kv 1.5 potency, selectivity versus hERG, pharmacokinetic exposure, and pharmacodynamic potency. 5-Phenyl-N-(pyridin-2-ylmethyl)-2-(pyrimidin-5-yl)quinazolin-4-amine (13k) was identified as a potent and ion channel selective inhibitor with robust efficacy in the preclinical rat ventricular effective refractory period (VERP) model and the rabbit atrial effective refractory period (AERP) model.

Suboptimal Use of Oral Anticoagulants in Atrial Fibrillation: Has the Introduction of Direct Oral Anticoagulants Improved Prescribing Practices?

BACKGROUND AND OBJECTIVES

Atrial fibrillation (AF) and the associated risk of stroke are emerging epidemics throughout the world. Suboptimal use of oral anticoagulants for stroke prevention has been widely reported from observational studies. In recent years, direct oral anticoagulants (DOACs) have been introduced for thromboprophylaxis. We conducted a systematic literature review to evaluate current practices of anticoagulation in AF, pharmacologic features and adoption patterns of DOACs, their impacts on proportion of eligible patients with AF who receive oral anticoagulants, persisting challenges and future prospects for optimal anticoagulation.

LITERATURE SOURCE AND SELECTION CRITERIA

In conducting this review, we considered the results of relevant prospective and retrospective observational studies from real-world practice settings. PubMed (MEDLINE), Scopus (RIS), Google Scholar, EMBASE and Web of Science were used to source relevant literature. There were no date limitations, while language was limited to English. Selection was limited to articles from peer reviewed journals and related to our topic.

RESULTS

Most studies identified in this review indicated suboptimal use of anticoagulants is a persisting challenge despite the availability of DOACs. Underuse of oral anticoagulants is apparent particularly in patients with a high risk of stroke. DOAC adoption trends are quite variable, with slow integration into clinical practice reported in most countries; there has been limited impact to date on prescribing practice.

CONCLUSION

Available data from clinical practice suggest that suboptimal oral anticoagulant use in patients with AF and poor compliance with guidelines still remain commonplace despite transition to a new era of anticoagulation featuring DOACs.

Novel Anthranilamide-Based FXa Inhibitors: Drug Design, Synthesis and Biological Evaluation

Factor Xa (FXa) plays a significant role in the blood coagulation cascade and it has become a promising target for anticoagulation drugs. Three oral direct FXa inhibitors have been approved by the FDA for treating thrombotic diseases. By structure-activity relationship (SAR) analysis upon these FXa inhibitors, a series of novel anthranilamide-based FXa inhibitors were designed and synthesized. According to our study, compounds 1a, 1g and 1s displayed evident FXa inhibitory activity and excellent selectivity over thrombin in in vitro inhibition activities studies. Compounds 1g and 1s also exhibited pronounced anticoagulant activities in in vitro anticoagulant activity studies.

Dental extraction without stopping single or dual antiplatelet therapy: results of a retrospective cohort study

The aim of this study was to investigate the incidence of bleeding after dental extraction without stopping antiplatelet therapy. Postoperative bleeding was assessed in a total of 1271 patients who were divided into two groups: a study group comprising 183 patients on antiplatelet therapy (aspirin 125 patients/185 occasions; clopidogrel 42 patients/65 occasions; dual therapy 16 patients/24 occasions) who underwent 548 dental extractions on 274 occasions, and a control group comprising 1088 patients who were not receiving any antiplatelet or anticoagulant therapy and underwent 2487 dental extractions on 1472 occasions. The incidence of postoperative bleeding was higher in the study group (5/274, 1.8%) than in the control group (10/1472, 0.7%), and also in the dual antiplatelet subgroup (1/24, 4.2%) than in the single antiplatelet subgroups (clopidogrel: 2/65, 3.1%; aspirin: 2/185, 1.1%); however, these differences were not significant. Postoperative bleeding was managed successfully by repacking with Gelfoam impregnated with tranexamic acid powder in 12 patients and by resuturing in three of the control patients undergoing extraction of impacted teeth with flap elevation. These findings indicate that there is no need to interrupt antiplatelet drugs before dental extraction.

Atrial fibrillation, CHA2DS2-VASc score, antithrombotics and risk of traffic accidents: A population-based cohort study

BACKGROUND

Traffic accidents account for a substantial proportion of premature disabilities and deaths. Whether atrial fibrillation (AF) provokes while antithrombotics prevent from such events remains un-investigated.

METHODS

All patients ≥40years with newly diagnosed AF in 2005 were scrutinized from the "Longitudinal Health Insurance Database 2005" (1 million beneficiaries) of Taiwan's National Health Insurance Institute as the AF group. Four-fold number of age-, gender-, and comorbidity-matched patients but without AF served as the Non-AF controls. Patients were followed till occurrence of hospitalization-requiring traffic injury, death, withdrawal from insurance, or the end of 2010. Cumulative incidence of traffic accidents was compared between groups, and predictors and preventive role of antithrombotics for these accidents were identified by Cox regression analysis.

RESULTS

Within a mean follow-up of 4.3years, traffic injury occurred significantly more often in patients with AF (N=1724) than those without it (N=6896) (5.4 vs. 4.9 per 1000 person-years, log-rank p=0.012, HR 1.110, 95% CI 1.013-1.572). Cox models identified age ≧65years, hypertension, coronary artery disease, stroke, liver cirrhosis and CHADS2VASC score≧1 as risk factors for traffic injury in AF patients, whereas oral anticoagulants (HR 0.576, 95% CI 0.285-0.791, p=0.002) used in patients with CHADS2VASC score ≧1 but not antiplatelet therapy (p=0.197) as negative predictors.

CONCLUSION

Patients with AF are more vulnerable to traffic accidents especially when with higher CHADS2VASC scores and other comorbidities. This tendency to traffic accidents, however, could be ameliorated by oral anticoagulation in specialized cases but not by antiplatelet therapy.

Desmopressin acetate in intracranial haemorrhage

Introduction. The secondary increase in the size of intracranial haematomas as a result of spontaneous haemorrhage or trauma is of particular relevance in the event of prior intake of platelet aggregation inhibitors. We describe the effect of desmopressin acetate as a means of temporarily stabilising the platelet function. Patients and Methods. The platelet function was analysed in 10 patients who had received single (N = 4) or multiple (N = 6) doses of acetylsalicylic acid and 3 patients (control group) who had not taken acetylsalicylic acid. All subjects had suffered intracranial haemorrhage. Analysis was performed before, half an hour and three hours after administration of desmopressin acetate. Statistical analysis was performed by applying a level of significance of P ≤ 0.05. Results. (1) Platelet function returned to normal 30 minutes after administration of desmopressin acetate. (2) The platelet function worsened again after three hours. (3) There were no complications related to electrolytes or fluid balance. Conclusion. Desmopressin acetate can stabilise the platelet function in neurosurgical patients who have received acetylsalicylic acid prior to surgery without causing transfusion-related side effects or a loss of time. The effect is, however, limited and influenced by the frequency of drug intake. Further controls are needed in neurosurgical patients.

Determination of dabigatran, rivaroxaban and apixaban by ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) and coagulation assays for therapy monitoring of novel direct oral anticoagulants

BACKGROUND

Three novel direct oral anticoagulants (DOACs) have recently been registered by the Food and Drug Administration and European Medicines Agency Commission: dabigatran, rivaroxaban, and apixaban. To quantify DOACs in plasma, various dedicated coagulation assays have been developed.

OBJECTIVE

To develop and validate a reference ultra-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) method and to evaluate the analytical performance of several coagulation assays for quantification of dabigatran, rivaroxaban, and apixaban.

METHODS

The developed UPLC-MS/MS method was validated by determination of precision, accuracy, specificity, matrix effects, lower limits of detection, carry-over, recovery, stability, and robustness. The following coagulation assays were evaluated for accuracy and precision: laboratory-developed (LD) diluted thrombin time (dTT), Hemoclot dTT, Pefakit PiCT, ECA, Liquid anti-Xa, Biophen Heparin (LRT), and Biophen DiXal anti-Xa. Agreement between the various coagulation assays and UPLC-MS/MS was determined with random samples from patients using dabigatran or rivaroxaban.

RESULTS

The UPLC-MS/MS method was shown to be accurate, precise, sensitive, stable, and robust. The dabigatran coagulation assay showing the best precision, accuracy and agreement with the UPLC-MS/MS method was the LD dTT test. For rivaroxaban, the anti-factor Xa assays were superior to the PiCT-Xa assay with regard to precision, accuracy, and agreement with the reference method. For apixaban, the Liquid anti-Xa assay was superior to the PiCT-Xa assay.

CONCLUSIONS

Statistically significant differences were observed between the various coagulation assays as compared with the UPLC-MS/MS reference method. It is currently unknown whether these differences are clinically relevant. When DOACs are quantified with coagulation assays, comparison with a reference method as part of proficiency testing is therefore pivotal.

Circulating Endothelial Cells and Platelet Microparticles in Mitral Valve Disease With and Without Atrial Fibrillation

Hypercoagulability in mitral valve disease (MVD), a cause of atrial fibrillation (AF) and stroke, is potentially due to endothelial damage/dysfunction (marked by circulating endothelial cells [CECs]), platelet activation (soluble P-selectin [sPsel], platelet microparticles [PMPs], and soluble CD40 [sCD40]), and oxidized low-density lipoprotein (oxLDL) cholesterol. We measured these variables in 24 patients with MVD as well as in 21 with MVD + AF and compared them with 20 healthy controls (HCs). The CECs and PMPs were measured by flow cytometry; sPsel, oxLDL, and CD40 by enzyme-linked immunosorbent assay. Compared with HCs, sPsel and PMPs were equally higher in MVD and MVD + AF; sCD40 and oxLDL were higher in MVD + AF than in HCs and MVD; and CECs were higher in MVD than in the HCs, with further increases in MVD + AF (all P < .001). We conclude that excess platelet activation is present in MVD regardless of AF, and that increased endothelial damage in MVD is greater when compounded by AF.

Stroke prevention in patients with atrial fibrillation in France: comparative cost-effectiveness of new oral anticoagulants (apixaban, dabigatran, and rivaroxaban), warfarin, and aspirin

OBJECTIVES

To conduct an economic evaluation of the currently prescribed treatments for stroke prevention in patients with non-valvular atrial fibrillation (NVAF) including warfarin, aspirin, and novel oral anticoagulants (NOACs) from a French payer perspective.

METHODS

A previously published Markov model was adapted in accordance to the new French guidelines of the Commission for Economic Evaluation and Public Health (CEESP), to adopt the recommended efficiency frontier approach. A cohort of patients with NVAF eligible for stroke preventive treatment was simulated over lifetime. Clinical events modeled included strokes, systemic embolism, intracranial hemorrhage, other major bleeds, clinically relevant non-major bleeds, and myocardial infarction. Efficacy and bleeding data for warfarin, apixaban, and aspirin were obtained from ARISTOTLE and AVERROES trials, whilst efficacy data for other NOACs were from published indirect comparisons. Acute medical costs were obtained from a dedicated analysis of the French national hospitalization database (PMSI). Long-term medical costs and utility data were derived from the literature. Univariate and probabilistic sensitivity analyses were performed to assess the robustness of the model projections.

RESULTS

Warfarin and apixaban were the two optimal treatment choices, as the other five treatment strategies including aspirin, dabigatran 110 mg, dabigatran in sequential dosages, dabigatran 150 mg, and rivaroxaban were strictly dominated on the efficiency frontier. Further, apixaban was a cost-effective alternative vs warfarin with an incremental cost of €2314 and an incremental quality-adjusted life year (QALY) of 0.189, corresponding to an incremental cost-effectiveness ratio (ICER) of €12,227/QALY.

CONCLUSIONS

Apixaban may be the most economically efficient alternative to warfarin in NVAF patients eligible for stroke prevention in France. All other strategies were dominated, yielding apixaban as a less costly yet more effective treatment alternative. As formally requested by the CEESP, these results need to be verified in a French clinical setting using stroke reduction and bleeding safety observed in real-life patient cohorts using these anticoagulants.

Sex differences in stroke prevention in atrial fibrillation in French primary care. Results of the AFIGP (Atrial Fibrillation In General Practice) database

BACKGROUND AND OBJECTIVES

Most of the French patients diagnosed with atrial fibrillation (AF) are managed by general practitioners (GPs). The objective was to evaluate stroke prevention in AF patients ahead of the arrival of the non vitamin K oral anticoagulant in France.

METHODS

A cross-sectional study using a French GPs database of all patients with a diagnosis of AF consulting their GP between July-2010 and June-2011. Multivariate analyses were used to identify determinants of prevention prescription.

RESULTS

Among 15,623 AF patients, 42.5 % were ≥75 years and 40.5 % women, 59.2 % had hypertension, 17.2 % diabetes, 11.4 % heart failure, 4.9 % stroke history. CHADS2 score was ≥1 for 83.1 % and ≥2 for 50.9 % of patients (CHA2DS2-VASc score ≥1 for 93.7 % and ≥2 for 82.3 %). Antithrombotic therapies were vitamin K antagonists (VKA) for 50.7 % of patients, followed by aspirin for 19.9 %, clopidogrel ± aspirin for 4.3 % and none for 25.1 %. For patients with CHADS2 scores ≥1, 73.3 % received an antithrombotic and for those with CHADS2 scores ≥2, 54.9 % were treated by a VKA. An age-stratified multivariate analysis showed that women had an odds ratio to be treated with VKA compared to 0.83 (95 % CI: 0.72-0.95) and 0.66 (95 % CI: 0.59-0.74) when aged <75 years and ≥75 years, respectively.

CONCLUSIONS

Most AF patients followed by French GPs required stroke prevention according to European guidelines, but many of them did not receive the recommended antithrombotic treatment. Women over 75 were a third less likely to be treated with recommended anticoagulants than men of similar age.

Latest developments in anticoagulant drug discovery

Thromboembolic diseases have increased in number over the past years. Oral anticoagulants impair the formation and progression of thrombotic processes and are therefore of great importance in the treatment of these diseases. Until recently, vitamin K antagonists were used to block the coagulation system. But these agents display a lot of interactions besides their narrow therapeutic range and have potential risk of hemorrhage complications. Therefore, other factors of the coagulation cascade are currently being explored as therapeutic targets for the development of novel anticoagulants. This review will provide an overview of new drugs promising more effectiveness in the treatment of arterial and venous embolism. Furthermore, pharmacodynamics and drug interactions regarding new anticoagulants will be reported.

Age as a Risk Factor for Stroke in Atrial Fibrillation Patients: Implications in Thromboprophylaxis in the Era of Novel Oral Anticoagulants

Atrial fibrillation is associated with significant morbidity and mortality. There is a strong relationship between atrial fibrillation and aging, thromboembolism, stroke, congestive heart failure and hypertension. In addition, advanced age is a powerful risk factor for stroke and thromboembolism in patients with atrial fibrillation. For many years, vitamin K antagonists were the only approved anticoagulants for the management of atrial fibrillation. Lately new anticoagulants made their appearance and large trials have already shown their superiority against vitamin K antagonists. Since the arrhythmia is encountered frequently in the elderly, it is crucial to identify the beneficial effects of the novel oral anticoagulants in this particular patient population.

Newer anticoagulants for non-valvular atrial fibrillation

Non-valvular atrial fibrillation is a recognized risk factor for stroke and systemic embolism. It has been clearly established that warfarin reduces the risk of stroke and systemic embolism in persons with atrial fibrillation and additional risk factors for stroke. The use of warfarin, however, requires frequent monitoring, and there is great variability in patient response to warfarin. Warfarin interacts with several medications and foods. In addition, warfarin use portends a significant risk of bleeding. For these reasons, warfarin is frequently not prescribed to persons for whom the drug would provide a clear benefit. Over the past decade, attempts have been made to develop drugs that are at least as safe and effective as warfarin for the treatment of atrial fibrillation that do not require monitoring nor have as many interactions. Initial studies of compounds in this regard ultimately failed due to safety concerns, but over the past two years two novel agents have been approved by the United States Food and Drug Association for anticoagulation in non-valvular atrial fibrillation, another drug is under review, and additional compounds are being studied. This article will review the use of warfarin and these new agents in the treatment of non-valvular atrial fibrillation.