Anticoagulation Control with Acenocoumarol or Warfarin in Non-Valvular Atrial Fibrillation in Primary Care (Fantas-TIC Study)

Introduction: The use of vitamin K antagonists (VKAs) in non-valvular atrial fibrillation (NVAF) is complicated due to the narrow therapeutic margin they present and their unpredictable dose–response relationship. Most studies are based on warfarin, with the results being extrapolated to acenocoumarol. However, studies comparing the two treatments in terms of the degree of anticoagulation control are scarce, justifying the present study. Main factors associated with poor control of time in therapeutic range (TTR) of anticoagulated patients are also studied. Methods: Cross-sectional study, with real-world data from patients treated in primary care (PC). Data were obtained from the System for the Improvement of Research in PC (SIDIAP) database, covering 60,978 NVAF-anticoagulated patients from 287 PC centres in 2018. Descriptive statistics were derived, and odds ratios were estimated by multivariate logistic regression. Results: 41,430 patients were considered: 93% were being treated with acenocoumarol and 7% with warfarin. There was no difference in poor control of TTR between the two types of VKA treatment, acenocoumarol and warfarin (38.9 vs. 38.4; p = 0.610). Poor anticoagulation control was mainly associated with advanced alcoholism (OR = 1.38), liver failure (OR = 1.37) and intracranial haemorrhage (OR = 1.35) as well as female sex, age < 60 years, cardiovascular history, diabetes mellitus and other variables. Conclusions: There is no association between poor anticoagulation control and the type of VKA treatment administered. Factors associated with poor control of TTR must be considered in clinical practice to improve control and decision-making.

Cost-effectiveness of direct oral anticoagulants versus vitamin K antagonist in atrial fibrillation: A study protocol using Real-World Data from Catalonia (FantasTIC Study)

BACKGROUND

Anticoagulant therapy is used for stroke prevention and proved to be effective and safe in the long term. The study aims to analyse the cost-effectiveness relationship of using of direct-acting oral anticoagulants vs vitamin K antagonists to prevent ischaemic stroke in patients with nonvalvular atrial fibrillation, including all the active ingredients marketed in Spain, prescribed for 2 years in the Primary Care service of the Institut Català de la Salut.

METHODS

Population-based cohort study, in which the cost of the 2 treatment groups will be evaluated. Direct costs (pharmacy, primary care, emergency and hospitalization) and indirect costs (lost productivity) will be included from a social perspective. Effectiveness (assessed as the occurrence of a health event, the 1 of primary interest being stroke) will be determined, with a 2-year time horizon and a 3% discount rate. The average cost of the 2 groups of drugs will be compared using a regression model to determine the factors with the greatest influence on determining costs. We will carry out a univariate ('one-way') deterministic sensitivity analysis.

DISCUSSION

We hope to provide relevant information about direct and indirect costs of oral anticoagulants, which, together with aspects of effectiveness and safety, could help shape the consensual decision-making of evaluating bodies.

Comparison of cardiovascular response between patients on warfarin and hypertensive patients not on warfarin during dental extraction

OBJECTIVE

To evaluate cardiovascular response in patients on warfarin and hypertensive patients not on warfarin during dental extraction.

MATERIALS AND METHODS

This retrospective study included 53 patients who had undergone dental extraction while on warfarin (mean age 78.8 ± 6.3 years, 26 men) and 66 with hypertension who had undergone dental extraction but were not on warfarin (mean age 77.4 ± 6.8 years, 22 men). Vital signs were monitored in both groups during extraction.

RESULTS

The highest systolic blood pressure (SBP) values (mean 150.1 ± 21.1 mmHg) were observed in patients on warfarin before (9.0%) and after (10.3%) administration of local anesthesia (LA), during extraction (39.7%), and during (33.3%) and after (7.7%) suturing (n = 78; p < 0.01), and in hypertensive patients not receiving warfarin (160.6 ± 24.8 mmHg) before (19.2%) and after (27.3%) administration of LA, during extraction (29.3%), and during (18.2%) and after (6.1%) suturing (n = 99; p < 0.01). The highest SBP was linearly correlated with SBP before administration of LA in patients on warfarin (highest SBP = 0.9415 × SBP before LA + 23.243, R² = 0.75481) and in hypertensive patients not on warfarin (highest SBP = 1.0027 × SBP before LA + 15.789, R² = 0.60341).

CONCLUSIONS

The highest SBP was not distributed evenly between patients on warfarin and hypertensive patients not on warfarin during dental extraction and was strongly associated with SBP before LA regardless of anticoagulant status.

CLINICAL RELEVANCE

Thorough management of SBP is required in patients on warfarin to avoid thromboembolism and major hemorrhagic complications. Knowing the SBP value before dental treatment would help predict the risk of cardiovascular complications.

Direct oral anticoagulants in oral surgery: a prospective cohort

BACKGROUND

Quantitative assessment of bleeding in dental extractions is rarely reported in the literature. The assessment of bleeding might provide additional evidence to predict and minimize postoperative outcomes. The aim of this study was to evaluate the pattern of bleeding in individuals taking direct oral anticoagulants (DOACs) submitted to dental extractions.

METHODS

Intraoperative bleeding was evaluated by using total collected bleeding corrected by absorbance reading (dental bleeding score). To monitoring bleeding episodes from the day of surgery, this cohort was followed up until the seventh postoperative day.

RESULTS

Forty-five procedures were performed in three comparative groups, patients under DOACs, individuals taking vitamin K antagonists (VKAs) and without anticoagulant therapy. No bleeding events were observed in procedures carried out in individuals of the DOAC group. Additional hemostatic measures were required in two procedures in the VKA group and one in the non-anticoagulated group. The dental bleeding scores obtained for the DOAC and VKA groups were similar.

CONCLUSIONS

Our data suggest that the DOAC therapy did not result in increased bleeding outcomes in this sample.

Thromboembolic and neurologic sequelae of discontinuation of an antihyperlipidemic drug during ongoing warfarin therapy

Warfarin and antihyperlipidemics are commonly co-prescribed. Some antihyperlipidemics may inhibit warfarin deactivation via the hepatic cytochrome P450 system. Therefore, antihyperlipidemic discontinuation has been hypothesized to result in underanticoagulation, as warfarin metabolism is no longer inhibited. We quantified the risk of venous thromboembolism (VTE) and ischemic stroke (IS) due to statin and fibrate discontinuation in warfarin users, in which warfarin was initially dose-titrated during ongoing antihyperlipidemic therapy. Using 1999-2011 United States Medicaid claims among 69 million beneficiaries, we conducted a set of bidirectional self-controlled case series studies-one for each antihyperlipidemic. Outcomes were hospital admissions for VTE/IS. The risk segment was a maximum of 90 days immediately following antihyperlipidemic discontinuation, the exposure of interest. Time-varying confounders were included in conditional Poisson models. We identified 629 study eligible-persons with at least one outcome. Adjusted incidence rate ratios (IRRs) for all antihyperlipidemics studied were consistent with the null, and ranged from 0.21 (0.02, 2.82) for rosuvastatin to 2.16 (0.06, 75.0) for gemfibrozil. Despite using an underlying dataset of millions of persons, we had little precision in estimating IRRs for VTE/IS among warfarin-treated persons discontinuing individual antihyperlipidemics. Further research should investigate whether discontinuation of gemfibrozil in warfarin users results in serious underanticoagulation.

Healthcare utilization and costs for patients initiating Dabigatran or Warfarin

Background

Novel oral anticoagulants (NOAC) such as dabigatran, when compared to warfarin, have been shown to potentially reduce the risk of stroke in patients with non-valvular atrial fibrillation (NVAF) together with lower healthcare resource utilization (HCRU) and similar total costs. This study expands on previous work by comparing HCRU and costs for patients newly diagnosed with NVAF and newly initiated on dabigatran or warfarin, and is the first study specifically in a Medicare population.

Methods

A retrospective matched-cohort study was conducted using data from administrative health care claims during the study period 01/01/2010–12/31/2012. Cox regression analyses were used to compare all-cause risk of first hospitalizations and emergency room (ER) visits. Medical, pharmacy, and total costs per-patient-per-month (PPPM) were compared between dabigatran and warfarin users.

Results

A total of 1110 patients initiated on dabigatran were propensity score-matched with corresponding patients initiated on warfarin. The mean number of hospitalizations (0.92 vs. 1.13, P = 0.012), ER visits (1.32 vs. 1.56, P < 0.01), office visits (21.43 vs. 29.41; P < 0.01), and outpatient visits (10.86 vs. 22.02; P < 0.01) were lower among dabigatran compared to warfarin users. Patients initiated on dabigatran had significantly lower risk of first all-cause ER visits [hazard ratio (HR): 0.84, 95% confidence interval (CI): 0.73–0.98] compared to those initiated on warfarin. Adjusted mean pharmacy costs PPPM were significantly greater for dabigatran users ($510 vs. $250, P < 0.001); however, mean medical costs PPPM ($1912 vs. $1956, P = 0.55) and mean total costs PPPM ($2381 vs. $2183, P = 0.10) were not significantly different compared to warfarin users.

Conclusions

Dabigatran users had significantly lower HCRU compared to warfarin users. In addition, dabigatran users had lower risk of all-cause ER visits. Despite higher pharmacy costs, the two cohorts did not differ significantly in medical or total all-cause costs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12955-017-0705-x) contains supplementary material, which is available to authorized users.

Gastrointestinal bleeding and intracranial hemorrhage in concomitant users of warfarin and antihyperlipidemics

BACKGROUND

Drug interactions, particularly those involving warfarin, are a major clinical and public health problem. Minimizing serious bleeding caused by anticoagulants is a recent major focus of the United States (US) Department of Health and Human Services. This study quantified the risk of gastrointestinal bleeding (GIB) and intracranial hemorrhage (ICH) among concomitant users of warfarin and individual antihyperlipidemics.

METHODS

The authors conducted a high-dimensional propensity score-adjusted cohort study of new concomitant users of warfarin and an antihyperlipidemic, among US Medicaid beneficiaries from five states during 1999-2011. Exposure was defined by concomitant use of warfarin plus one of eight antihyperlipidemics. The primary outcome measure was a composite of GIB/ICH within the first 30days of concomitant use. As a secondary outcome measure, GIB/ICH was examined within the first 180days of concomitant use.

RESULTS

Among 236,691 persons newly-exposed to warfarin and an antihyperlipidemic, the crude incidence of GIB/ICH was 13.2 (95% confidence interval 12.7 to 13.8) per 100person-years. Users were predominantly older, female, and Caucasian. Adjusted hazard ratios (aHRs) for warfarin and individual statins were consistent with no association. Warfarin+gemfibrozil was associated with an 80% increased risk of GIB/ICH within the first month of concomitant use (aHR=1.8, 1.4 to 2.4). Warfarin+fenofibrate was associated with a similar increased risk (aHR=1.8, 1.2 to 2.7), yet with an onset during the second month of concomitant use.

CONCLUSIONS

Among warfarin-treated persons, the use of fibrates-but not statins-increases the risk of hospital presentation for GIB/ICH.

Detecting nonvalvular atrial fibrillation and anticoagulant therapy in cardioembolic ischemic stroke

Nonvalvular Atrial fibrillation (NVAF) is the most common cardiac arrhythmia associated with an increase in risk of stroke and systemic thromboembolism. Strokes related to AF are associated with higher mortality, greater disability, longer hospital stays, and lower chance of being discharged home. The present review will focus on the current status of detecting NVAF and stroke prevention when there is AF. The CHA2DS2-VASc risk stratification scheme is discussed for the identification of patients who are at risk for thromboembolic stroke related to NVAF. Patient with a CHA2DS2-VASc score of 2 or greater are candidates for warfarin or a novel oral anticoagulant, irrespective of whether the strategy is for rate or rhythm control. Finally, guidelines and landmark clinical trials in NVAF patients with primary or secondary stroke prevention are discussed.

A New Generation of Antiplatelet, and Anticoagulant Medication and the Implications for the Dental Surgeon

The management of dental patients taking either antiplatelet medication, anticoagulant medication or both has been well established in the previous literature. Recently, new generations of drugs have emerged which are becoming increasingly common, including direct thrombin inhibitors, factor X inhibitors and a new class of oral thienopyridines. The implications of these drugs for the dental surgeon are not yet fully known. Awareness remains low and there is very little information available within the literature on safe use during surgery. This review paper aims to provide some guidance for dental practitioners performing invasive procedures. CPD/CLINICAL RELEVANCE: A new generation of anticoagulant and antiplatelet drugs have serious implications for patients undergoing surgery and their use is increasing.

Cost-Effectiveness and Cost-Utility Analyses of Dabigatran Compared with Warfarin in Patients with Nonvalvular Atrial Fibrillation and Risk Factors for Stroke and Systemic Embolism within Brazilian Private and Public Health Care Systems Perspectives

OBJECTIVE

To analyze the cost-effectiveness and cost-utility of dabigatran compared with warfarin in patients with nonvalvular atrial fibrillation with moderate to high risk of ischemic stroke or systemic embolism and eligible for treatment with anticoagulants.

METHODS

Markov-based economic analysis was performed to estimate treatment costs and outcomes. Epidemiological and efficacy data were determined after a critical revision of the medical literature. Unit costs were taken from Brazilian official databases. Only direct medical costs were covered. Costs and benefits were discounted at a rate of 5% per year. Outcomes were expressed as life-year (LY) and quality-adjusted life-year (QALY).

RESULTS

Dabigatran use is cost-effective in terms of LY and QALY considering a willingness-to-pay threshold of 3 times gross domestic product per capita of 2010 (Brazilian real 57,048/US $24,275.74) per LY and QALY saved in both analyzed perspectives (private and public health care systems).

CONCLUSIONS

Dabigatran use improves patient survival and quality of life compared with warfarin. This represents the best therapeutic option in terms of cost and effectiveness in the prevention of ischemic stroke and systemic embolism in patients with nonvalvular atrial fibrillation.

Pharmacokinetic and pharmacodynamic drug interactions with new oral anticoagulants: what do they mean for patients with atrial fibrillation?

OBJECTIVE

To review pharmacokinetic and pharmacodynamic drug-drug interactions (DDIs) involving new oral anticoagulants for atrial fibrillation.

DATA SOURCES

A literature search was conducted via PubMed and the Cochrane database to identify DDI studies using the terms drug interactions, dabigatran, rivaroxaban, and apixaban. Prescribing information and Food and Drug Administration briefing documents were used to supplement published data.

STUDY SELECTION AND DATA EXTRACTION

English publications identified on Medline from 2005 up to August 2013 and US prescribing information for approved oral anticoagulants.

DATA SYNTHESIS

Articles reviewed focused on drugs affecting the permeability glycoprotein (P-gp) efflux transporter protein and/or cytochrome P (CYP) 450 3A4 enzymes, and pharmacodynamic DDIs when drugs are administered concomitantly. Phase I DDI studies have reported pharmacokinetic DDIs mediated by P-gp alone (dabigatran etexilate) or in combination with CYP3A4 enzymes (rivaroxaban and apixaban). Dabigatran etexilate should not be administered with any P-gp inhibitor in patients with severe renal impairment. Briefing documents indicate that rivaroxaban and apixaban should not be used with drugs that are strong inhibitors of both P-gp and CYP3A4. DDI studies involving rifampicin suggest that rivaroxaban and apixaban should be avoided when strong inducers of P-gp and CYP3A4 are used concurrently. Concomitant use of apixaban and strong dual inhibitors of P-gp and CYP3A4 should be avoided or the dose reduced. Five randomized clinical trials report additive effects with rivaroxaban, dabigatran, and apixaban when used concomitantly with antiplatelet agents; bleeding rates have been found to be higher, especially with dual antiplatelet therapy.

CONCLUSIONS

Awareness of drugs that alter the function of the P-gp efflux transporter protein and CYP3A4 enzymes and provide additive effects should enable prescribers to anticipate and avoid potential DDIs involving the new oral anticoagulants. To this end, briefing documents and prescribing information have applied cautionary measures for individuals treated with these newer anticoagulants.

Practical Issues to Prevent Stroke Associated with Non-valvular Atrial Fibrillation

Stroke associated with non-valvular atrial fibrillation (NVAF) is one of the most important subtypes of ischemic stroke, and its importance is becoming even more apparent in an aging population. To assess the risk of stroke associated with NVAF, the CHADS2 and CHA2DS2-VASc scores are mainly used. Such scores can be used to predict the recurrence and prognosis of ischemic stroke. In addition, new oral anticoagulants (NOACs) and devices are being evaluated in the prevention of stroke associated with NVAF in addition to treatment with the conventional oral anticoagulant, warfarin. Since clinical experience with NOACs is not globally sufficient, a cautious approach is needed.

Advances in stroke prevention in atrial fibrillation: enhanced risk stratification combined with the newer oral anticoagulants

Patients with atrial fibrillation (AF) have an increased stroke risk compared with those in sinus rhythm, although the absolute risk for individual patients is modulated by the presence of various additional risk factors. Patient selection for oral anticoagulation for stroke prevention is based on risks of stroke and bleeding. Although CHADS2 (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke or transient ischemic attack) is the most widely used scheme for evaluating stroke risk in patients with AF, several other stroke risk factors are not included; therefore, many patients' stroke risk may be underestimated, contributing to the underuse of anticoagulants. Furthermore, a substantial proportion of patients are categorized as being at moderate risk (CHADS2 = 1), and there has been some ambiguity regarding optimum thromboprophylaxis in this group. The refinement of CHADS2 , CHA2 DS2 -VASc (Congestive heart failure, Hypertension, Age 75 years [2 points], Diabetes mellitus, Stroke or transient ischemic attack [2 points], Vascular disease, Age 65 to 74 years, Sex category [female]), considers additional risk factors. Its main advantage is its ability to identify patients truly at low risk of thromboembolism (CHA2 DS2 -VASc = 0), who are unlikely to benefit from antithrombotic therapy. For all others, an oral anticoagulant may be the preferred approach, simplifying clinical decision making. Implementation of CHA2 DS2 -VASc may also result in an increased proportion of patients receiving anticoagulation. The emergence of newer oral anticoagulants that can be given without routine coagulation monitoring, with improved benefit-risk profiles vs vitamin K antagonists, promises to simplify therapy for patients with AF at risk of stroke. This, coupled with advances in stroke risk stratification, is expected to improve patient outcomes and reduce the burden of AF-related stroke.

The new oral anticoagulants in clinical practice

Vitamin K antagonists were the only class of oral anticoagulants available to clinicians for decades. However, with the US Food and Drug Administration approval of new oral anticoagulants, such as dabigatran, rivaroxaban, and apixaban, clinicians now have a broader choice. Given the recent approval and availability of these medications, several questions arise while deciding which of them would be best suited for a particular patient. This article provides a concise review for clinicians entailing the main studies that evaluated the efficacy and safety of these drugs, their pharmacokinetic and pharmacodynamic properties, and a practical approach to their clinical use. For this review, we conducted searches of PubMed and MEDLINE for articles published between January 1, 2000, and January 30, 2013, using the following search terms: oral anticoagulants, dabigatran, apixaban, rivaroxaban, novel anticoagulants, bleeding complications, management of bleeding complications, pharmacodynamics, and pharmacokinetics. Studies published in English were selected for inclusion in this review, as were additional articles identified from bibliographies.

New options for anticoagulation following total hip arthroplasty and total knee arthroplasty: new oral agents on the horizon

Patients undergoing surgery for total hip arthroplasty (THA) or total knee arthroplasty (TKA) are at particularly high risk for developing venous thromboembolism (VTE). Despite the existence of effective therapies for VTE prevention, THA/TKA patients remain at risk for developing thrombi. Furthermore, the incidence of VTE is predicted to increase as an aging and increasingly obese population experiences joint damage necessitating THA and TKA. Current guidelines recommend the use of a wide range of antithrombotic agents in patients undergoing THA and TKA. These agents include vitamin K antagonists, low-molecular-weight heparins, fondaparinux, and the new oral anticoagulants. However, adherence to guidelines in clinical practice is disappointingly low. The limitations of traditional anticoagulants present management challenges following orthopedic surgery. Vitamin K antagonists present a number of drawbacks, including a narrow therapeutic window and unpredictable pharmacokinetics and pharmacodynamics. The subcutaneous route of administration of fondaparinux and low-molecular-weight heparins may make them unacceptable to patients in the outpatient setting. The introduction of a new generation of anticoagulants promises to address many of the drawbacks associated with the traditional agents. Clinical studies have shown the new oral anticoagulants to be as effective as traditional thromboprophylaxis, with good tolerability profiles. Clinical knowledge of these new agents will be essential to ensure that patients receive appropriate care following orthopedic surgery. This article will discuss the prevention of VTE after THA and TKA based on current evidence-based practice guidelines, the limitations of conventional anticoagulants, and the promise of new therapeutics.

Practical management of anticoagulants in family medicine after orthopedic surgery

In order to prevent postoperative venous thromboembolism, prophylactic anticoagulant therapy is routinely administered to hospitalized patients after total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, after hospital discharge, anticoagulant therapy is primarily managed by a primary care physician (PCP). The agents traditionally used for this purpose are associated with certain limitations that affect anticoagulation management. The new, fixed-dose oral anticoagulants have predictable pharmacokinetic and pharmacodynamic profiles, no requirement for coagulation monitoring, and a low propensity for food and drug interactions. As a result, they have the potential to simplify and improve postoperative outcomes in patients who have undergone THA or TKA and allow for simpler management of anticoagulation in these patients. This article examines the clinical evidence for benefits of the new oral anticoagulants, discusses caveats regarding their appropriate use, and provides some guidance regarding bleeding management with these agents.

Improving long-term ACS management: is there a role for the new antiplatelets?

Acute coronary syndrome (ACS) is a major health burden, resulting in increased hospital admissions and significant morbidity and mortality. Platelet activation, which leads to thrombin generation, is highly implicated in ACS, and antiplatelet agents represent the current standard of care. Established antiplatelet agents include acetylsalicylic acid (ASA), thienopyridines (clopidogrel, ticlopidine), and glycoprotein IIb/IIIa inhibitors. Recently, antiplatelet therapy for ACS has evolved to include more potent inhibitors (e.g., prasugrel, cangrelor, and ticagrelor). During the acute phase of an acute coronary event, both anticoagulation and dual antiplatelet therapy with aspirin and a thienopyridine are guideline recommended as first-line treatment. While anticoagulation is usually limited to the acute in-patient phase, dual antiplatelet therapy is recommended for 12 months. Despite the efficacy of antiplatelet agents in ACS, in many patients the residual risk of death from cardiac events, myocardial infarction, stroke, and refractory ischemia remains high. Dual therapy (i.e., ASA or clopidogrel plus a vitamin K antagonist [VKA]), and triple therapy (two antiplatelets plus a VKA) are associated with increases in bleeding complications. New oral anticoagulants that offer a novel mechanism of action may, when added to the current standard of care, provide a more comprehensive response to thrombin generation. In this review, we examine the pathology of ACS, investigate antiplatelet therapies and describe emerging anticoagulants that may be of benefit when used as combination therapy with antiplatelet agents for secondary prevention in ACS patients.

Stroke Prevention in Atrial Fibrillation: Where are We Now?

Atrial fibrillation is the commonest arrhythmia worldwide and is a growing problem. AF is responsible for 25% of all strokes, and these patients suffer greater mortality and disability. Warfarin has traditionally been the only successful therapy for stroke prevention, but its limitations have resulted in underutilisation. Major progress has been made in AF research, leading to improved management strategies. Better risk stratification permits identification of truly low-risk patients who do not require anticoagulation and we are able to simplify ourevaluation of a patient's bleeding risk.The advent of novel anticoagulants means warfarin is no longer the only choice for stroke prophylaxis. These drugs circumvent many of warfarin's inconveniences, but onlylong-term study and use will conclusively demonstrate how they compare to warfarin. The landscape of stroke prevention in AF has changed with effective alternatives to warfarin available for the first time in 60 years-but each new option brings new considerations.

Warfarin for Venous Thromboembolism Prophylaxis After Elective Hip or Knee Arthroplasty: Exploring the Evidence, Guidelines, and Challenges Remaining

BACKGROUND:

Guidelines for the prevention of venous thromboembolism (VTE) after elective total hip or knee arthroplasty (THA/TKA) have been developed separately by the American Academy of Orthopaedic Surgeons (AAOS) and the American College of Chest Physicians (ACCP). Differences exist in approaches to preventing postoperative VTE through prophylaxis.

OBJECTIVE:

To compare trials using vitamin K antagonists (VKAs) and differences in guidelines to determine the benefits and drawbacks of warfarin for VTE prophylaxis following THA/TKA.

DATA SOURCES:

Guidelines from the AAOS published in 2009 and revised in 2011 and from the ACCP published in 2008 were compared for recommendations on the use of VKAs. A MEDLINE search from 1960 to November 2009 was conducted to identify pertinent articles on the use of warfarin or VKAs for VTE prophylaxis following THA/TKA. Search terms included warfarin, vitamin K antagonist, total hip or total knee replacement, and total hip or total knee arthroplasty.

STUDY SELECTION AND DATA EXTRACTION:

Only clinical trials in which warfarin was the primary agent for prophylaxis compared to other anticoagulants were included.

DATA SYNTHESIS:

Data on differences between guideline recommendations for the use of VKAs and the importance of a deep vein thrombosis or asymptomatic events were extracted. Thirteen comparative trials using VKAs for VTE prophylaxis and international normalized ratio (INR) targets were assessed. Overall, the incidence of bleeding tended to be lower with the use of VKAs, but thrombosis when including asymptomatic events was numerically higher when comparing INR targets. However, INR targets varied, with no comparative trials assessing the AAOS 2009 recommended INR target of 1.5-2.0. The AAOS guidelines initially recommended a longer duration of therapy and expressed stronger support for the use of aspirin for prophylaxis; however, in 2011, its guidelines were revised, with no specific recommendations as to agent, dose, or INR target goal.

CONCLUSIONS:

Warfarin is an effective agent to prevent VTE after elective THA/TKA. The most effective approach, including extended warfarin use up to 4 weeks or longer, has not been determined.

Current therapies in ischemic stroke. Part A. Recent developments in acute stroke treatment and in stroke prevention

Stroke is the third leading cause of death with an increasing prevalence. In previous years many important achievements and new therapeutic strategies have been established. This article provides an overview on recent developments and is an update to the article of Green et al. that was published in 2004. As this article is a comprehensive review we divided it in two parts. In this Part A of our review, recent developments in acute stroke treatment and in stroke prevention are described. In Part B we will reflect on neuroprotection.

Challenges of stroke prevention in patients with atrial fibrillation in clinical practice

Strokes and transient ischaemic attacks in patients with atrial fibrillation (AF) can be largely prevented. Risk stratification and appropriate prophylactic regimens help to alleviate the burden of AF-related thromboembolism. Guidelines recommend routine anticoagulation with oral vitamin K antagonists (VKAs) for patients at moderate-to-high risk of stroke, and acetylsalicylic acid (ASA) for those at low risk of stroke. ASA is less effective at reducing the risk of stroke than VKAs; however, ASA does not require monitoring or dose adjustment. Trials of anticoagulants show consistent benefits of oral VKAs for primary and secondary stroke prevention in patients with AF. Nevertheless, VKAs do require frequent coagulation monitoring and dose adjustment because of their variable dose-response profile, narrow therapeutic window, increased risk for bleeding complications and numerous food and drug interactions. This review aims to provide an overview of the clinical challenges of anticoagulant therapy for the prevention of stroke in patients with AF.

Stroke prevention in atrial fibrillation: current status and near-future directions

Prevention of atrial fibrillation-related stroke is an important part of atrial fibrillation management. However, stroke risk is not homogeneous and varies with associated morbidities and risk factors. Risk stratification schemes have been developed that categorize patients' stroke risk into classes based on a combination of risk factors. According to the calculated level of risk, guidelines recommend patients with atrial fibrillation receive antithrombotic therapy either as a vitamin K antagonist or aspirin. Despite recommendations, however, many patients with atrial fibrillation do not receive adequate thromboprophylaxis. We will discuss some of the underlying reasons, in part related to the drawbacks associated with vitamin K antagonists. These highlight the need for new anticoagulants in atrial fibrillation. The novel oral anticoagulants in development may overcome some of the limitations of vitamin K antagonists and address their underuse and safety concerns.