Dabigatran versus warfarin in patients with mechanical heart valves

Anticoagulation in atrial fibrillation

Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin's shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment.

Left Atrial Appendage Closure with Transcatheter-Delivered Devices

Left atrial appendage (LAA) closure with transcatheter-delivered devices is an evolving story of compelling randomized data and the potential to dramatically reduce the incidence of stroke and improve the quality of life among patients with atrial fibrillation. Oral anticoagulation is the standard of care for stroke prevention in atrial fibrillation but falls short of providing an adequate solution to this common threat when considered from efficacy and safety perspectives. The robust series of Watchman device trials has demonstrated the Watchman device to provide stroke prevention efficacy similar to that of warfarin and by extension provides proof of concept of LAA closure.

Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively: protocol

Background

Warfarin and similar vitamin K antagonists have been the standard therapy for patients with mechanical or biological valve prosthesis and atrial fibrillation (AF). Even with the appropriate use of therapy, some studies have reported that there is a high incidence of thromboembolic events, 1%-4% per year. Furthermore, a bleeding risk is significant, ranging from 2% to 9% per year, according to some studies.

Objective

The objective of our study was to examine the effect of dabigatran etexilate versus dose-adjusted warfarin for the prevention of intracardiac thrombus in persistent or permanent AF at least 3 months after aortic and/or mitral bioprosthesis replacement.

Methods

Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively (DAWA) is a phase 2, prospective, open label, randomized exploratory pilot study. The main variable to be observed in this study is intracardiac thrombus. From August 2013 to April 2015, 100 patients, at least 3 months after aortic and/or mitral bioprosthesis replacement and permanent or persistent AF postoperatively, who match eligibility criteria will be selected from Ana Nery Hospital in Salvador-Bahia with a follow-up of three months. Patients were randomly assigned in a 1:1 ratio to receive either dabigatran etexilate or warfarin.

Results

Although the present study has no statistic power to proof non-inferiority, it is expected that the dabigatran etexilate group will be protected as well as the warfarin group from intracardiac thrombus, without increasing the bleeding rates, since we are using safer doses (110 mg bid). The lack of necessity of monitoring INR is also another factor that contributes to a better adherence to the new drug and it can make all the difference in the manner of doing anticoagulation for patients with similar clinical characteristics.

Conclusions

The study is in the recruitment phase. It is possible that dabigatran etexilate is as effective as warfarin in preventing the emergence of intracardiac thrombus in patients with AF and mitral and/or aortic bioprosthesis.

Trial Registration

Clinicaltrials.gov NCT01868243; http://clinicaltrials.gov/ct2/show/NCT01868243 (Archived by WebCite at http://www.webcitation/6OABiuasd).

Thromboembolism in pregnancy: challenges and controversies in the prevention of pregnancy-associated venous thromboembolism and management of anticoagulation in women with mechanical prosthetic heart valves

Thromboembolism in pregnancy is an important clinical issue. Despite identification of maternal and pregnancy-specific risk factors for development of pregnancy-associated venous thromboembolism, limited data are available to inform on optimal approaches for prevention. The relatively low overall prevalence of pregnancy-associated venous thromboembolism has prompted debate about the validity of recommendations, which are mainly based on expert opinion, and have resulted in an increased use of pharmacological thromboprophylaxis in pregnancy and postpartum. A pragmatic approach is required in the absence of more robust data. Anticoagulation management of pregnant women with mechanical prosthetic heart valves is particularly challenging. Continuation of therapeutic anticoagulation during pregnancy is essential to prevent valve thrombosis. Warfarin, the most effective anticoagulant, is associated with adverse fetal outcomes, including embryopathy and stillbirth. Fetal outcome is improved with therapeutic-dose low-molecular-weight heparin, but there may be more thromboembolic complications. More intensive anticoagulation, targeting higher trough anti-Xa levels, may reduce the risk of valve thrombosis.

Direct thrombin inhibitors versus vitamin K antagonists for preventing cerebral or systemic embolism in people with non-valvular atrial fibrillation

BACKGROUND

Chronic anticoagulation with vitamin K antagonists (VKAs) prevents ischaemic stroke and systemic embolism in people with non-valvular atrial fibrillation (AF) but dose adjustment, coagulation monitoring and bleeding limits its use. Direct thrombin inhibitors (DTIs) are under investigation as potential alternatives.

OBJECTIVES

To assess (1) the comparative efficacy of long-term anticoagulation using DTIs versus VKAs on vascular deaths and ischaemic events in people with non-valvular AF, and (2) the comparative safety of chronic anticoagulation using DTIs versus VKAs on (a) fatal and non-fatal major bleeding events including haemorrhagic strokes, (b) adverse events other than bleeding and ischaemic events that lead to treatment discontinuation and (c) all-cause mortality in people with non-valvular AF.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library, May 2013), MEDLINE (1950 to July 2013), EMBASE (1980 to October 2013), LILACS (1982 to October 2013) and trials registers (September 2013). We also searched the websites of clinical trials and pharmaceutical companies and handsearched the reference lists of articles and conference proceedings.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing DTIs versus VKAs for prevention of stroke and systemic embolism in people with non-valvular AF.

DATA COLLECTION AND ANALYSIS

All three review authors independently performed data extraction and assessment of risk of bias. Primary analyses compared all DTIs combined versus warfarin. We performed post hoc analyses excluding ximelagatran because this drug was withdrawn from the market owing to safety concerns.

MAIN RESULTS

We included eight studies involving a total of 27,557 participants with non-valvular AF and one or more risk factors for stroke; 26,601 of them were assigned to standard doses groups and included in the primary analysis. The DTIs: dabigatran 110 mg twice daily and 150 mg twice daily (three studies, 12,355 participants), AZD0837 300 mg once per day (two studies, 233 participants) and ximelagatran 36 mg twice per day (three studies, 3726 participants) were compared with the VKA warfarin (10,287 participants). Overall risk of bias and statistical heterogeneity of the studies included were low.The odds of vascular death and ischaemic events were not significantly different between all DTIs and warfarin (odds ratio (OR) 0.94, 95% confidence interval (CI) 0.85 to 1.05). Sensitivity analysis by dose of dabigatran on reduction in ischaemic events and vascular mortality indicated that dabigatran 150 mg twice daily was superior to warfarin although the effect estimate was of borderline statistical significance (OR 0.86, 95% CI 0.75 to 0.99). Sensitivity analyses by other factors did not alter the results. Fatal and non-fatal major bleeding events, including haemorrhagic strokes, were less frequent with the DTIs (OR 0.87, 95% CI 0.78 to 0.97). Adverse events that led to discontinuation of treatment were significantly more frequent with the DTIs (OR 2.18, 95% CI 1.82 to 2.61). All-cause mortality was similar between DTIs and warfarin (OR 0.91, 95% CI 0.83 to 1.01).

AUTHORS' CONCLUSIONS

DTIs were as efficacious as VKAs for the composite outcome of vascular death and ischaemic events and only the dose of dabigatran 150 mg twice daily was found to be superior to warfarin. DTIs were associated with fewer major haemorrhagic events, including haemorrhagic strokes. Adverse events that led to discontinuation of treatment occurred more frequently with the DTIs. We detected no difference in death from all causes.

Evaluation of dabigatran bleeding adverse reaction reports in the FDA adverse event reporting system during the first year of approval

STUDY OBJECTIVE

Evaluate dabigatran adverse event reports with a reported bleeding event and/or reported fatal outcome compared with warfarin.

DESIGN

Retrospective analysis of the FDA Adverse Event Reporting System (FAERS) database.

MEASUREMENTS AND MAIN RESULTS

We identified reports from October 1, 2010, through December 31, 2011, in the United States listing dabigatran or warfarin as the primary suspected agent. Bleeding events and related outcomes were determined. A bleeding-related mortality rate was calculated based on national dabigatran treatment data.

RESULTS

Dabigatran was the primary suspected agent in 9029 adverse reports. Of these, 2347 (26%) were bleeding events; a fatal outcome was reported in 348 (15%) of the bleeding events. In comparison, warfarin was the suspected agent in 2038 reports, of which 647 (32%) were reported as bleeding events. Among the warfarin bleeding reports, 46 (7.1%) reported a fatal outcome. Based on national dabigatran use and adverse bleed reports with fatal outcomes, we estimate a lower bound of 150 bleeding-related fatalities per 100,000 dabigatran patient-years. Because of underreporting bias, these estimates represent a lower bound on the population bleeding mortality rates.

CONCLUSION

Reports from FAERS are subject to significant bias but suggest that fatal outcomes among dabigatran reports are higher in clinical practice than they were in controlled clinical trials.

The new direct oral anticoagulants in special indications: rationale and preliminary data in cancer, mechanical heart valves, anti-phospholipid syndrome, and heparin-induced thrombocytopenia and beyond

The present review will briefly summarize the interplay between coagulation and inflammation, highlighting possible effects of direct inhibition of factor Xa and thrombin beyond anticoagulation. Additionally, the rationale for the use of the new direct oral anticoagulants (DOACs) for indications such as cancer-associated venous thromboembolism (CAT), mechanical heart valves, thrombotic anti-phospholipid syndrome (APS), and heparin-induced thrombocytopenia (HIT) will be explored. Published data on patients with cancer or mechanical heart valves treated with DOAC will be discussed, as well as planned studies in APS and HIT. Although at the present time published evidence is insufficient for recommending DOAC in the above-mentioned indications, there are good arguments in favor of clinical trials investigating their efficacy in these contexts. Direct inhibition of factor Xa or thrombin may reveal interesting effects beyond anticoagulation as well.

Common Questions in Anticoagulation Management in Atrial Fibrillation

The limitations of the vitamin K antagonists (VKAs) have promoted the development of novel oral anticoagulants (NOACs) to benefit patients with poor predicted anticoagulation control. To assess the probability of good or poor anticoagulation control with VKAs, the SAMe-TT2R2 score has been developed. Trials of stroke prevention have shown a significant reduction in hemorrhagic stroke and intracranial bleeding with the NOACs. Clinicians need to be prepared to manage bleeding complications and patients requiring urgent surgery, systemic thrombolysis for ischemic stroke, or ST elevation myocardial infarction. This article addresses some of these management issues.

Drug Therapies for Stroke Prevention in Atrial Fibrillation: An Historical Perspective

Oral anticoagulants are effective in minimizing stroke and systemic embolism in patients with atrial fibrillation at risk. All have a high degree of efficacy and acceptable safety records. Drug selection should be made on an individual basis. The most important thing is to make the selection. There are many factors to consider in the selection of oral anticoagulants. The new oral anticoagulants offer a measure of improvement over the many limits of warfarin; however, well-managed warfarin is an acceptable and inexpensive option. The efficacy of aspirin is questionable at best, deserving its almost complete disappearance from the guidelines.

Self-management of oral anticoagulation

BACKGROUND

Properly dosed oral anticoagulation effectively prevents thromboembolic events. It is unclear whether adult patients with an indication for long-term oral anticoagulation can benefit from self-management in terms of patient-oriented endpoints and improved coagulation values.

METHOD

We selectively searched the Medline database for high-quality systematic reviews based on randomized controlled trials of self-measurement or self-management of oral anticoagulation, compared to standard treatment.

RESULTS

We identified eight review articles based on overlapping sets of ran - domized clinical trials. In all of these systematic reviews, patients who performed self-measurement or self-management had a 40% to 50% lower rate of thromboembolic events; in six of them, the mortality was also significantly lower, by 30% to 50%. Subgroup analysis revealed that these effects were present exclusively in patients who performed self-management, and not in those who only performed self-measurement. None of the review articles revealed any difference in the frequency of severe hemorrhagic events. Quality of life and patient satisfaction were rated in five reviews, which, however, used different instruments, with the result that no clear conclusions could be drawn. All of the review articles documented an improvement in coagulation values, but information on statistical significance was mostly lacking.

CONCLUSION

Adults with an indication for long-term oral anticoagulation benefit from self-management, as compared to standard treatment with management of dosing by a physician. A limitation of this study is that the multiple review articles on which it is based were largely analyses of the same group of clinical trials.

New oral anticoagulants: are coagulation units still required?

Chronic antithrombotic therapy involves the use of anticoagulants, antiplatelets given either as monotherapy or in combination for the prevention of thrombotic complications. The most feared and sometimes fatal complication with this therapy is bleeding. It should be considered a "golden rule" that a drug or combination of drugs that maximizes efficiency (decreased thromboembolic risk) will probably be less safe (increased risk of bleeding), and this holds true either for single therapy or during combined therapy. The chances of bleeding indicated by risk tables can be useful but show only a snapshot, and the biological, social, environmental, and drug changes and therapeutic adherence also determine changes in the risk of thrombosis and bleeding. Bleeding is an eventuality that occurs in places of "locus minoris resistentiae," and the results of careful phase 3 studies thus cannot be completely predictive of outcomes when a medication is introduced on the pharmaceutical market. With the use of warfarin, the International Normalized Ratio (INR) that has been established to indicate adequately balanced therapy is between 2.0 and 3.0. With the new oral anticoagulants, the pharmaceutical companies emphasize that it is not necessary to monitor anticoagulant effects. In studies with different doses of new oral anticoagulants, however, incidence of clinically significant bleeding complications have been directly related to the doses. Therefore, therapeutic excesses can condition bleeding risk and therapeutic limitation can increase thrombotic risk, especially when short-acting drugs such as the new oral anticoagulants are used. Hence, it is imperative to establish an appropriate method for monitoring new oral anticoagulants, setting levels of safety and effectiveness through periodic dosage and monitoring of their anticoagulant effects. Therefore, we still recommend the use of anticoagulation units for monitoring during treatment with the new oral anticoagulants.

Novel oral anticoagulants for stroke prevention in the geriatric population

Prior to the availability of several newer anticoagulant medications, there had been no new advances in anticoagulation management for stroke prevention since the advent of warfarin in the 1950s. The availability of the novel oral anticoagulants (NOACs) dabigatran, rivaroxaban,and apixaban represent improvements over warfarin in many respects, including the elimination of the need for therapeutic drug monitoring, fewer drug and food interactions,and favorable efficacy; however, these agents are not without risk. Specifically, the use of the NOACs in the geriatric population, who are more likely to have an increased risk of stroke due to atrial fibrillation and other medical comorbidities, is not without risk. The objective of this review is to update the clinician on the use of the NOACs in the geriatric population and introduce the controversies and risks surrounding these newer therapies.

14th International Congress on Antiphospholipid Antibodies: task force report on antiphospholipid syndrome treatment trends

Antiphospholipid Syndrome (APS) is characterized by vascular thrombosis and/or pregnancy morbidity occurring in patients with persistent antiphospholipid antibodies (aPL). The primary objective of the APS Treatment Trends Task Force, created as part of the 14th International Congress on aPL, was to systematically review the potential future treatment strategies for aPL-positive patients. The task force chose as future clinical research directions: a) determining the necessity for controlled clinical trials in venous thromboembolism with the new oral direct thrombin or anti-factor Xa inhibitors pending the results of the ongoing rivaroxaban in APS (RAPS) trial, and designing controlled clinical trials in other forms of thrombotic APS; b) systematically analyzing the literature as well as aPL/APS registries, and creating specific registries for non-warfarin/heparin anticoagulants; c) increasing recruitment for an ongoing primary thrombosis prevention trial, and designing secondary thrombosis and pregnancy morbidity prevention trials with hydroxychloroquine; d) determining surrogate markers to select patients for statin trials; e) designing controlled studies with rituximab and other anti-B-cell agents; f) designing mechanistic and clinical studies with eculizumab and other complement inhibitors; and g) chemically modifying peptide therapy to improve the half-life and minimize immunogenicity. The report also includes recommendations for clinicians who consider using these agents in difficult-to-manage aPL-positive patients.

The Year in Cardiology 2013: valvular heart disease (focus on catheter-based interventions)

2013 was the year of transcatheter heart valve interventions. Not least because of the 2012 European guidelines on the management of valvular heart disease (VHD), the multidisciplinary heart team approach became an established concept. Decision-making, when a patient is too 'sick' for surgery and too 'healthy' for catheter-based interventions, is complex, since VHD is often seen at an older age and, as a consequence, there is a higher frequency of co-morbidity and frailty. However, before TAVI and other transcatheter heart valve interventions can be expanded to intermediate-risk patients, evidence in favour of this less invasive treatment has to be provided by upcoming randomized clinical trials.

Prediction of optimal warfarin maintenance dose using advanced artificial neural networks

BACKGROUND

In recent years, pharmacogenetic algorithms were developed for estimating the appropriate dose of vitamin K antagonists.

AIM

To evaluate the performance of new generation artificial neural networks (ANNs) to predict the warfarin maintenance dose.

METHODS

Demographic, clinical and genetic data (CYP2C9 and VKORC1 polymorphisms) from 377 patients treated with warfarin were used. The final prediction model was based on 23 variables selected by TWIST® system within a bipartite division of the data set (training and testing) protocol.

RESULTS

The ANN algorithm reached high accuracy, with an average absolute error of 5.7 mg of the warfarin maintenance dose. In the subset of patients requiring ≤21 mg and 21-49 mg (45 and 51% of the cohort, respectively) the absolute error was 3.86 mg and 5.45 with a high percentage of subjects being correctly identified (71 and 73%, respectively).

CONCLUSION

ANN appears to be a promising tool for vitamin K antagonist maintenance dose prediction.

Atrial fibrillation: a review of recent studies with a focus on those from the duke clinical research institute

Atrial fibrillation is the most common arrhythmia and accounts for one-third of hospitalizations for rhythm disorders in the United States. The prevalence of atrial fibrillation averages 1% and increases with age. With the aging of the population, the number of patients with atrial fibrillation is expected to increase 150% by 2050, with more than 50% of atrial fibrillation patients being over the age of 80. This increasing burden of atrial fibrillation will lead to a higher incidence of stroke, as patients with atrial fibrillation have a five- to sevenfold greater risk of stroke than the general population. Strokes secondary to atrial fibrillation have a worse prognosis than in patients without atrial fibrillation. Vitamin K antagonists (e.g., warfarin), direct thrombin inhibitors (dabigatran), and factor Xa inhibitors (rivaroxaban and apixaban) are all oral anticoagulants that have been FDA approved for the prevention of stroke in atrial fibrillation. This review will summarize the experience of anticoagulants in patients with atrial fibrillation with a focus on the experience at the Duke Clinic Research Institute.

Neurologic complications of valvular heart disease

Valvular heart disease (VHD) is frequently associated with neurologic complications; cerebral embolism is the most common of these since thrombus formation results from the abnormalities in the valvular surfaces or from the anatomic and physiologic changes associated with valve dysfunction, such as atrial or ventricular enlargement, intracardiac thrombi, and cardiac dysrhythmias. Prosthetic heart valves, particularly mechanical valves, are very thrombogenic, which explains the high risk of thromboembolism and the need for anticoagulation for the prevention of embolism. Infective endocarditis is a disease process with protean manifestations that include not only cerebral embolism but also intracranial hemorrhage, mycotic aneurysms, and systemic manifestations such as fever and encephalopathy. Other neurologic complications include nonbacterial thrombotic endocarditis, a process associated with systemic diseases such as cancer and systemic lupus erythematosus. For many of these conditions, anticoagulation is the mainstay of treatment to prevent cerebral embolism, therefore it is the potential complications of anticoagulation that can explain other neurologic complications in patients with VHD. The prevention and management of these complications requires an understanding of their natural history in order to balance the risks posed by valvular disease itself against the risks and benefits associated with treatment.

Dabigatran use in mechanical heart valve patients

Current guidelines have no recommendations on the utilization of novel oral anticoagulants, such as dabigatran, for the prevention of thromboembolic events in patients with mechanical heart valves. However, recent studies on the use of dabigatran in patients with atrial fibrillation and animal studies have suggested a new potential role for dabigatran in patients with mechanical heart valves. The study by Eikelboom et al. investigates this important clinical question in a prospective, randomized controlled Phase II clinical trial. The authors randomly assigned 252 patients from 39 centers in ten countries to receive dabigatran or warfarin in a 2:1 ratio. The objective of the study was to validate a dosing regimen for use of dabigatran in patients with mechanical heart valves. The trial was prematurely terminated after a recommendation by the data and safety monitoring board. The composite of stroke, systemic embolism, myocardial infarction and death was 8% in the dabigatran group and 2% in the warfarin group (hazard ratio: 3.37; 95% CI: 0.76–14.95; p = 0.11). There were significantly higher bleeding rates of any type in the dabigatran group (27%) compared with the warfarin group (12%; hazard ratio: 2.45; 95% CI: 1.23–4.86; p = 0.01). These results demonstrated a higher risk and no additional benefits in using dabigatran compared with warfarin in patients with mechanical heart valves.

Mitral valve prosthesis choice for patients aged 65 years and over in the UK. Are the guidelines being followed and does it matter?

OBJECTIVE

Current guidelines recommend that most patients aged ≥65 years should undergo mitral valve replacement (MVR) using a biological prosthesis. The objectives of this study were to assess whether these guidelines are being followed in UK practice, and to investigate whether the guidelines are appropriate based on in-hospital mortality and mid-term survival.

METHODS

Data from the National Institute for Cardiovascular Outcomes Research Adult Cardiac Surgery Audit database from all National Health Service (NHS) hospitals and some private hospitals performing adult cardiac surgery in the UK between April 2001 and March 2011 were analysed. The overall cohort included 3862 patients aged ≥65 years who underwent first-time MVR. Propensity score matching and regression adjustment were used to compare outcomes between prosthesis groups.

RESULTS

The mean age was 73.0 years (SD 4.9) with 50% of patients having surgery with a mechanical prosthesis. This proportion decreased over the study period and with increasing patient age with marked variation between hospitals. In the propensity-matched cohort, in-hospital mortality in the biological group was 6.9%, and in the mechanical group it was 5.9% giving an unadjusted OR of 1.17 (95% CI 0.84 to 1.63). There was no significant difference in mid-term survival between the matched groups with an unadjusted HR for biological prosthesis of 1.08 (95% CI 0.93 to 1.24). Similar results were found when using regression adjustment on unmatched data.

CONCLUSIONS

Current guidelines concerning age and mitral valve prosthesis choice are not being followed for patients aged ≥65 years. With regards to in-hospital and mid-term mortality, this study demonstrates that there is no difference between prosthesis types.

The vexing problem of thrombosis in long-term mechanical circulatory support

Durable left ventricular assist devices (LVADs) have not only enhanced longevity but also conferred sustained improvements in quality of life, symptom control, and functional capacity in patients with medically refractory advanced heart failure. Problems with device-related infection, bleeding, neurologic events, right-sided heart failure, and device malfunction have dominated the clinical care of patients living on mechanical support. Even as adoption of durable LVADs accelerated globally, we began to encounter a growing dilemma of pump malfunction caused by thrombosis. In early 2011, clinicians began to notice a spike in the incidence of pump thrombosis with the HeartMate II (Thoratec Corp, Pleasanton, CA) LVAD. By 2012, the problem of thrombosis in LVADs began to consume most of the scientific direction as centers and collaborative groups began to dissect this nascent phenomenon. In this perspective, we describe the magnitude and implications of pump thrombosis, discuss secular and management trends in this unique population, attempt to dissect the problem at its root, offer guidance on surveillance and therapeutic principles, and outline issues that deserve our immediate and collaborative attention.

New oral anticoagulants and the cancer patient

Indications for anticoagulation are common in patients with malignancy. Cancer patients have an increased risk of developing venous thromboembolic events or may have other indications for anticoagulation, such as atrial fibrillation. New oral anticoagulants (NOACs) are now available that offer increased options for anticoagulation beyond the traditional vitamin K antagonists and low molecular weight heparins that have long been the cornerstone of treatment. This review will focus on the three NOACs that are currently approved for use in the U.S.: the direct thrombin inhibitor, dabigatran, and the factor Xa inhibitors, apixaban and rivaroxaban. Oncologists are likely to encounter an increasing number of patients taking these agents at the time of their cancer diagnosis or to have patients who develop indications for anticoagulation during the course of their disease. The basic pharmacology, current clinical indications, and approach to the use of NOACs in the cancer patient will be reviewed.

Vitamin K antagonists in heart disease: current status and perspectives (Section III). Position paper of the ESC Working Group on Thrombosis--Task Force on Anticoagulants in Heart Disease

Oral anticoagulants are a mainstay of cardiovascular therapy, and for over 60 years vitamin K antagonists (VKAs) were the only available agents for long-term use. VKAs interfere with the cyclic inter-conversion of vitamin K and its 2,3 epoxide, thus inhibiting γ-carboxylation of glutamate residues at the amino-termini of vitamin K-dependent proteins, including the coagulation factors (F) II (prothrombin), VII, IX and X, as well as of the anticoagulant proteins C, S and Z. The overall effect of such interference is a dose-dependent anticoagulant effect, which has been therapeutically exploited in heart disease since the early 1950s. In this position paper, we review the mechanisms of action, pharmacological properties and side effects of VKAs, which are used in the management of cardiovascular diseases, including coronary heart disease (where their use is limited), stroke prevention in atrial fibrillation, heart valves and/or chronic heart failure. Using an evidence-based approach, we describe the results of completed clinical trials, highlight areas of uncertainty, and recommend therapeutic options for specific disorders. Although VKAs are being increasingly replaced in most patients with non-valvular atrial fibrillation by the new oral anticoagulants, which target either thrombin or FXa, the VKAs remain the agents of choice for patients with atrial fibrillation in the setting of rheumatic valvular disease and for those with mechanical heart valves.

Anticoagulation for prosthetic valves

Implantation of prosthetic valve requires consideration for anticoagulation. The current guideline recommends warfarin on all mechanical valves. Dabigatran is the new generation anticoagulation medication which is taken orally and does not require frequent monitoring. This drug is approved for treatment for atrial fibrillation and venous thromboembolism, but the latest large trial showed that this drug increases adverse events when used for mechanical valve anticoagulation. On-X valve is the new generation mechanical valve which is considered to require less anticoagulation due to its flow dynamics. The latest study showed that lower anticoagulation level lowers the incidence of bleeding, while the risk of thromboembolism and thrombosis remained the same. Anticoagulation poses dilemma in cases such as pregnancy and major bleeding event. During pregnancy, warfarin can be continued throughout pregnancy and switched to heparin derivative during 6-12 weeks and >36 weeks of gestation. Warfarin can be safely started after 1-2 weeks of discontinuation following major bleeding episode.

A new era of stroke prevention in atrial fibrillation: comparing a new generation of oral anticoagulants with warfarin

Traditionally, warfarin has been used to prevent stroke in patients with atrial fibrillation (AF), but data from large, multinational, prospective, randomized studies suggest that novel oral anticoagulants (NOACs) may be suitable alternatives. These include the direct thrombin inhibitor dabigatran and the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban. These data showed that dabigatran 150 mg twice daily was more effective at preventing stroke than warfarin, with similar rates of major bleeding, while rivaroxaban 20 mg once daily was noninferior to warfarin, with no difference in major bleeding rates. In addition, apixaban 5 mg twice daily was shown to be superior to warfarin for preventing stroke, with lower bleeding rates. Currently, edoxaban is still in clinical trials. NOACs offer more predictable anticoagulant effects than warfarin and do not require regular monitoring; however, different NOACs are associated with varied drug interactions and limitations related to use in certain patient populations. Overall, the clinical data suggest that these novel agents will offer new options for stroke prevention in patients with AF.

Mid-term results of self-testing of the international normalized ratio in adults with a mechanical heart valve

BACKGROUND

Commonly the frequency of international normalized ratio (INR) monitoring with a conventional laboratory test in stable patients is once a month. When using a dedicated personal device for INR assessment, the frequency may be increased to two or more times a month.

OBJECTIVE

To show that INR assessed by self-measurement at home is reliable and feasible in the mid-term and improves medical care.

PATIENTS AND METHODS

All patients in the study on INR self-measurement (clinical trial.gov: NCT00925197), conducted between 2004 and 2007, were re-contacted for mid-term follow-up. One hundred and seventy eight out of 192 patients who participated in the study answered a questionnaire. The average follow-up time was 4.2 years (±1) for the self-measurement group and 4.9 years (±1) for the laboratory-analyzed control group.

RESULTS

Only 26 patients (group A) continued to use INR self-measurement to monitor treatment with vitamin K antagonists (VKA). The main reasons to stop INR self-measurement were its high cost and difficulty in obtaining strips. There were significantly fewer bleeding complications (p=0.04) and complications related to VKA (p=0.01) in self-measured patients compared to the control group. Feelings of security and quality of life were also significantly better (p=0.002) for self-measured patients.

CONCLUSION

Many patients with a mechanical heart valve, who self-measured INR, continue to use this method for their follow-up because of its positive effects on their health and quality of life.