Comparison of low-intensity warfarin therapy with conventional-intensity warfarin therapy for long-term prevention of recurrent venous thromboembolism

Anticoagulants: A Review of the Pharmacology, Dosing, and Complications

Anticoagulants remain the primary strategy for the prevention and treatment of thrombosis. Unfractionated heparin, low molecular weight heparin, fondaparinux, and warfarin have been studied and employed extensively with direct thrombin inhibitors typically reserved for patients with complications or those requiring intervention. Novel oral anticoagulants have emerged from clinical development and are expected to replace older agents with their ease of use and more favorable pharmacodynamic profiles. Hemorrhage is the main concerning adverse event with all anticoagulants. With their ubiquitous use, it becomes important for clinicians to have a sound understanding of anticoagulant pharmacology, dosing, and toxicity.

Recommendations for the emergency management of complications associated with the new direct oral anticoagulants (DOACs), apixaban, dabigatran and rivaroxaban

Dabigatran, apixaban, and rivaroxaban have been approved for primary and secondary stroke prevention in patients with atrial fibrillation. However, questions have arisen about how to manage emergency situations, such as when thrombolysis would be required for acute ischemic stroke or for the managing intracranial or gastrointestinal bleedings. We summarize the current literature and provide recommendations for the management of these situations. Peak plasma levels of the direct oral anticoagulants (DOACs) apixaban, dabigatran, or rivaroxaban are observed about 2-4 h after intake. Elimination of dabigatran is mainly dependent on renal function. Consequently, if renal function is impaired, there is a risk of drug accumulation that is highest for dabigatran followed by rivaroxaban and then apixaban and thus dosing recommendations are different. To date, no bedside tests are available that reliably assess the anticoagulatory effect of DOACs, nor are specific antidotes available. We recommend performing the following tests if DOAC intake is unknown: dabigatran-associated bleeding risk is minimized or can be neglected if thrombin time, Hemoclot test, or Ecarin clotting time is normal. Apixaban and rivaroxaban effects can be ruled out if findings from the anti-factor Xa activity test are normal. High plasma levels of DOAC are also mostly excluded if PTT and PTZ are normal four or more hours after DOAC intake. However, normal values of global coagulation tests are not sufficient if thrombolysis is indicated for treating acute stroke. The decision for or against thrombolysis is an individual decision; in these cases, thrombolysis use is off-label. In case of bleeding, prothrombin complex concentrates seems to be the most plausible treatment. For severe gastrointestinal bleeding with life-threatening blood loss, the bleeding source needs to be identified and treated by invasive measures. Use of procoagulant drugs (antifibrinolytics) might also be considered. However, there is very limited clinical experience with these products in conjunction with DOAC.

Pharmacogenetics in cardiovascular disorders: an update on the principal drugs

In the coming years, genomics will impact clinical practice in multiple ways. However, one of the most important applications will be in the determination of the best treatments in personalized medicine. This is, in fact, one of the fields in which genetic variants have already been most successful and useful to clinicians. Here, we briefly review the current state of the art on pharmacogenomics and its applications to modern cardiovascular medicine.

Trial Protocol: a randomised controlled trial of extended anticoagulation treatment versus routine anticoagulation treatment for the prevention of recurrent VTE and post thrombotic syndrome in patients being treated for a first episode of unprovoked VTE (The ExACT Study)

Background

Venous thromboembolism comprising pulmonary embolism and deep vein thrombosis is a common condition with an incidence of approximately 1 per 1,000 per annum causing both mortality and serious morbidity. The principal aim of treatment of a venous thromboembolism with heparin and warfarin is to prevent extension or recurrence of clot. However, the recurrence rate following a deep vein thrombosis remains approximately 10% per annum following treatment cessation irrespective of the duration of anticoagulation therapy. Patients with raised D-dimer levels after discontinuing oral anticoagulation treatment have also been shown to be at high risk of recurrence.

Post thrombotic syndrome is a complication of a deep vein thrombosis which can lead to chronic venous insufficiency and ulceration. It has a cumulative incidence after 2 years of around 25% and it has been suggested that extended oral anticoagulation should be investigated as a possible preventative measure.

Methods/design

Patients with a first idiopathic venous thromboembolism will be recruited through anticoagulation clinics and randomly allocated to either continuing or discontinuing warfarin treatment for a further 2 years and followed up on a six monthly basis. At each visit D-dimer levels will be measured using a Roche Cobas h 232 POC device. In addition a venous sample will be taken for laboratory D-dimer analysis at the end of the study. Patients will be examined for signs and symptoms of PTS using the Villalta scale and complete VEINES and EQ5D quality of life questionnaires.

Discussion

The primary aim of the study is to investigate whether extending oral anticoagulation treatment (prior to discontinuing treatment) beyond 3–6 months for patients with a first unprovoked proximal deep vein thrombosis or pulmonary embolism prevents recurrence. The study will also determine the role of extending anticoagulation for patients with elevated D-dimer levels prior to discontinuing treatment and identify the potential of D-dimer point of care testing for identification of high risk patients within a primary care setting.

Trial registration

ISRCTN73819751

Prospective, multicenter validation of prediction scores for major bleeding in elderly patients with venous thromboembolism

BACKGROUND

The Outpatient Bleeding Risk Index (OBRI) and the Kuijer, RIETE and Kearon scores are clinical prognostic scores for bleeding in patients receiving oral anticoagulants for venous thromboembolism (VTE). We prospectively compared the performance of these scores in elderly patients with VTE.

METHODS

In a prospective multicenter Swiss cohort study, we studied 663 patients aged ≥ 65 years with acute VTE. The outcome was a first major bleeding at 90 days. We classified patients into three categories of bleeding risk (low, intermediate and high) according to each score and dichotomized patients as high vs. low or intermediate risk. We calculated the area under the receiver-operating characteristic (ROC) curve, positive predictive values and likelihood ratios for each score.

RESULTS

Overall, 28 out of 663 patients (4.2%, 95% confidence interval [CI] 2.8-6.0%) had a first major bleeding within 90 days. According to different scores, the rate of major bleeding varied from 1.9% to 2.1% in low-risk, from 4.2% to 5.0% in intermediate-risk and from 3.1% to 6.6% in high-risk patients. The discriminative power of the scores was poor to moderate, with areas under the ROC curve ranging from 0.49 to 0.60 (P = 0.21). The positive predictive values and positive likelihood ratios were low and varied from 3.1% to 6.6% and from 0.72 to 1.59, respectively.

CONCLUSION

In elderly patients with VTE, existing bleeding risk scores do not have sufficient accuracy and power to discriminate between patients with VTE who are at a high risk of short-term major bleeding and those who are not.

Extended use of dabigatran, warfarin, or placebo in venous thromboembolism

BACKGROUND

Dabigatran, which is administered in a fixed dose and does not require laboratory monitoring, may be suitable for extended treatment of venous thromboembolism.

METHODS

In two double-blind, randomized trials, we compared dabigatran at a dose of 150 mg twice daily with warfarin (active-control study) or with placebo (placebo-control study) in patients with venous thromboembolism who had completed at least 3 initial months of therapy.

RESULTS

In the active-control study, recurrent venous thromboembolism occurred in 26 of 1430 patients in the dabigatran group (1.8%) and 18 of 1426 patients in the warfarin group (1.3%) (hazard ratio with dabigatran, 1.44; 95% confidence interval [CI], 0.78 to 2.64; P=0.01 for noninferiority). Major bleeding occurred in 13 patients in the dabigatran group (0.9%) and 25 patients in the warfarin group (1.8%) (hazard ratio, 0.52; 95% CI, 0.27 to 1.02). Major or clinically relevant bleeding was less frequent with dabigatran (hazard ratio, 0.54; 95% CI, 0.41 to 0.71). Acute coronary syndromes occurred in 13 patients in the dabigatran group (0.9%) and 3 patients in the warfarin group (0.2%) (P=0.02). In the placebo-control study, recurrent venous thromboembolism occurred in 3 of 681 patients in the dabigatran group (0.4%) and 37 of 662 patients in the placebo group (5.6%) (hazard ratio, 0.08; 95% CI, 0.02 to 0.25; P<0.001). Major bleeding occurred in 2 patients in the dabigatran group (0.3%) and 0 patients in the placebo group. Major or clinically relevant bleeding occurred in 36 patients in the dabigatran group (5.3%) and 12 patients in the placebo group (1.8%) (hazard ratio, 2.92; 95% CI, 1.52 to 5.60). Acute coronary syndromes occurred in 1 patient each in the dabigatran and placebo groups.

CONCLUSIONS

Dabigatran was effective in the extended treatment of venous thromboembolism and carried a lower risk of major or clinically relevant bleeding than warfarin but a higher risk than placebo. (Funded by Boehringer Ingelheim; RE-MEDY and RE-SONATE ClinicalTrials.gov numbers, NCT00329238 and NCT00558259, respectively.).

Apixaban for extended treatment of venous thromboembolism

BACKGROUND

Apixaban, an oral factor Xa inhibitor that can be administered in a simple, fixed-dose regimen, may be an option for the extended treatment of venous thromboembolism.

METHODS

In this randomized, double-blind study, we compared two doses of apixaban (2.5 mg and 5 mg, twice daily) with placebo in patients with venous thromboembolism who had completed 6 to 12 months of anticoagulation therapy and for whom there was clinical equipoise regarding the continuation or cessation of anticoagulation therapy. The study drugs were administered for 12 months.

RESULTS

A total of 2486 patients underwent randomization, of whom 2482 were included in the intention-to-treat analyses. Symptomatic recurrent venous thromboembolism or death from venous thromboembolism occurred in 73 of the 829 patients (8.8%) who were receiving placebo, as compared with 14 of the 840 patients (1.7%) who were receiving 2.5 mg of apixaban (a difference of 7.2 percentage points; 95% confidence interval [CI], 5.0 to 9.3) and 14 of the 813 patients (1.7%) who were receiving 5 mg of apixaban (a difference of 7.0 percentage points; 95% CI, 4.9 to 9.1) (P<0.001 for both comparisons). The rates of major bleeding were 0.5% in the placebo group, 0.2% in the 2.5-mg apixaban group, and 0.1% in the 5-mg apixaban group. The rates of clinically relevant nonmajor bleeding were 2.3% in the placebo group, 3.0% in the 2.5-mg apixaban group, and 4.2% in the 5-mg apixaban group. The rate of death from any cause was 1.7% in the placebo group, as compared with 0.8% in the 2.5-mg apixaban group and 0.5% in the 5-mg apixaban group.

CONCLUSIONS

Extended anticoagulation with apixaban at either a treatment dose (5 mg) or a thromboprophylactic dose (2.5 mg) reduced the risk of recurrent venous thromboembolism without increasing the rate of major bleeding. (Funded by Bristol-Myers Squibb and Pfizer; AMPLIFY-EXT ClinicalTrials.gov number, NCT00633893.).

The diagnosis and treatment of venous thromboembolism

Venous thromboembolism (VTE) is a common condition that can lead to complications such as postphlebitic syndrome, chronic pulmonary artery hypertension, and death. The approach to the diagnosis of has evolved over the years and an algorithm strategy combining pretest probability, D-dimer testing, and diagnostic imaging now allows for safe, convenient, and cost-effective investigation of patients. Patients with low pretest probability and a negative D-dimer can have VTE excluded without the need for imaging. The mainstay of treatment of VTE is anticoagulation, whereas interventions such as thrombolysis and inferior vena cava filters are reserved for special situations. Low-molecular-weight heparin has allowed for outpatient management of most patients with deep vein thrombosis at a considerable cost savings to the health care system. Patients with malignancy-associated VTE benefit from decreased recurrent rates if treated with long-term low-molecular-weight heparin. The development of new oral anticoagulants further simplifies treatment. The duration of anticoagulation is primarily influenced by underlying cause of the VTE (whether provoked or not) and consideration of the risk for major hemorrhage. Testing for genetic and acquired thrombophilia may provide insight as to the cause of a first idiopathic deep vein thrombosis, but the evidence linking most thrombophilias to an increased risk of recurrent thrombosis is limited.

Confronting the chronically anticoagulated, acute care surgery patient as we evolve into the post-warfarin era

There are a growing number of new anticoagulants used as an alternative to warfarin. Surgeons will be confronted with an increasing number of patients who may be on these outpatient medications and must be familiar with their management strategies. The purpose of this review is to examine the mechanisms, monitoring and therapeutic reversal of the non-warfarin antithrombotic agents now so frequently confronting the acute care surgeon.

Genetics informatics trial (GIFT) of warfarin to prevent deep vein thrombosis (DVT): rationale and study design

The risk of venous thromboembolism (VTE) is higher after the total hip or knee replacement surgery than after almost any other surgical procedure; warfarin sodium is commonly prescribed to reduce this peri-operative risk. Warfarin has a narrow therapeutic window with high inter-individual dose variability and can cause hemorrhage. The genetics-informatics trial (GIFT) of warfarin to prevent deep vein thrombosis (DVT) is a 2 × 2 factorial-design, randomized controlled trial designed to compare the safety and effectiveness of warfarin-dosing strategies. GIFT will answer two questions: (1) does pharmacogenetic (PGx) dosing reduce the rate of adverse events in orthopedic patients; and (2) is a lower target international normalized ratio (INR) non-inferior to a higher target INR in orthopedic participants? The composite primary endpoint of the trial is symptomatic and asymptomatic VTE (identified on screening ultrasonography), major hemorrhage, INR ≥ 4, and death.

Risk of post-thrombotic syndrome after subtherapeutic warfarin anticoagulation for a first unprovoked deep vein thrombosis: results from the REVERSE study

BACKGROUND

Risk factors for post-thrombotic syndrome (PTS) remain poorly understood.

OBJECTIVES

In this multinational multicenter study, we evaluated whether subtherapeutic warfarin anticoagulation was associated with the development of PTS.

METHODS

Patients with a first unprovoked deep venous thrombosis (DVT) received standard anticoagulation for 5-7 months and were then assessed for PTS. The time in the therapeutic range was calculated from the international normalized ratio (INR) data. An INR below 2, more than 20% of the time, was considered as subtherapeutic anticoagulation.

RESULTS

Of the 349 patients enrolled, 97 (28%) developed PTS. The overall frequency of PTS in patients with subtherapeutic anticoagulation was 33.5%, compared with 21.6% in those with an INR below two for ≤ 20% of the time (P = 0.01). During the first 3 months of therapy, the odds ratio (OR) for developing PTS if a patient had subtherapeutic anticoagulation was 1.78 (95% confidence interval [CI] 1.10-2.87). After adjusting for confounding variables, the OR was 1.84 (95% CI 1.13-3.01). Corresponding ORs for the full period of anticoagulation were 1.83 (95% CI 1.14-3.00) [crude] and 1.88 (95% CI 1.15-3.07) [adjusted].

CONCLUSION

Subtherapeutic warfarin anticoagulation after a first unprovoked DVT was significantly associated with the development of PTS.

Benchmark for time in therapeutic range in venous thromboembolism: a systematic review and meta-analysis

INTRODUCTION

The percentage of time within the target INR range 2.0 to 3.0 (TTR) in patients treated with vitamin K antagonists varies considerably among efficacy-studies of novel anticoagulants. In order to properly asses the quality of anticoagulant control in upcoming cost-effectiveness studies and real life registries this systematic review reports a benchmark of TTR for different treatment durations in patients with venous thromboembolism and discusses ways to calculate TTR.

METHODS

Medline and Embase were searched for studies published between January 1990 and May 2012. Randomized controlled trials and cohort studies reporting the TTR in patients with objectively confirmed venous thromboembolism treated with vitamin K antagonists (VKA) were eligible. Duplicate reports, studies only reporting INR during initial treatment or with VKA treatment less than 3 months were excluded. Three authors assessed trials for inclusion and extracted data independently. Discrepancies were resolved by discussion between the reviewers. A meta-analysis was performed by calculating a weighted mean, based on the number of participants in each included study, for each time-period in which the TTR was measured since the confirmation of the diagnosis of VTE.

RESULTS

Forty studies were included (26064 patients). The weighted means of TTR were 54.0% in the first month since the start of treatment, 55.6% in months 1 to 3, 60.0% in months 2 to 3, 60.0% in the months 1 to 6+ and 75.2% in months 4 to 12+. Five studies reported TTR in classes. The INR in these studies was ≥ 67% of time in therapeutic range in 72.0% of the patients.

CONCLUSION

Reported quality of VKA treatment is highly dependent on the time-period since the start of treatment, with TTR ranging from approximately 56% in studies including the 1(st) month to 75% in studies excluding the first 3 months.

Duration of anticoagulation after cerebral venous sinus thrombosis

Cerebral venous sinus thrombosis (CVST) often occurs in young patients and is treated with acute and then long-term oral anticoagulation. It is important to decide when to discontinue anticoagulation, as lifelong anticoagulation exposes the patient to considerable cumulative risk. However, a lack of high quality studies makes choosing a duration of anticoagulation after CVST difficult. In this article, we review the evidence for different treatment durations in several common clinical scenarios of CVST. In addition, when no direct evidence is available, we discuss and extrapolate from the more comprehensively studied situation of systemic venous thromboembolic disease. Recommendations are graded using standard criteria for the level of evidence.

Predicting disease recurrence in patients with previous unprovoked venous thromboembolism: a proposed prediction score (DASH)

BACKGROUND

In patients with unprovoked venous thromboembolism (VTE), the optimal duration of anticoagulation is anchored on estimating the risk of disease recurrence.

OBJECTIVES

We aimed to develop a score that could predict the recurrence risk following a first episode of unprovoked VTE, pooling individual patient data from seven prospective studies.

METHODS

One thousand eight hundred and eighteen cases with unprovoked VTE treated for at least 3 months with a vitamin K antagonist were available for analysis. Optimism-corrected Cox regression coefficients were used to develop a recurrence score that was subsequently internally validated by bootstrap analysis.

RESULTS

Abnormal D-dimer after stopping anticoagulation, age <50 years, male sex and VTE not associated with hormonal therapy (in women) were the main predictors of recurrence and were used to derive a prognostic recurrence score (DASH, D-dimer, Age, Sex, Hormonal therapy) showing a satisfactory predictive capability (ROC area =0.71). The annualized recurrence risk was 3.1% (95% confidence interval [CI], 2.3-3.9) for a score ≤ 1, 6.4% (95% CI, 4.8-7.9) for a score=2 and 12.3% (95% CI, 9.9-14.7) for a score ≥ 3. By considering at low recurrence risk those patients with a score ≤ 1, life-long anticoagulation might be avoided in about half of patients with unprovoked VTE.

CONCLUSIONS

The DASH prediction rule appears to predict recurrence risk in patients with a first unprovoked VTE and may be useful to decide whether anticoagulant therapy should be continued indefinitely or stopped after an initial treatment period of at least 3 months.

Pulmonary embolism in the emergency department: a Singaporean nursing case review

INTRODUCTION

The presentation of pulmonary embolism to the emergency department (ED) can prove challenging because of the myriad of potential disease processes that mimic its signs and symptoms. The incidence of pulmonary embolism and indeed the mortality associated with it is relatively high. Early diagnosis and treatment is crucial in off-setting the potential deleterious effects associated with this condition. The aim of this article is to present a nursing case review of a patient presenting to the ED with a diagnosis of pulmonary embolism.

METHOD

We chose to use a case review to highlight the nursing and medical care that was provided for a patient who presented to the emergency department acutely with dyspnoea, chest pain and pyrexia. The use of case reviews are useful in reporting unusual or rare cases and this format is typically seen more in medicine than in nursing. They can naturally take one of two formats-a single case report or a series of case reports; in this case we opted to report on a single case.

DISCUSSION

The gentleman in question was an ambulance admission to the ED with a three day history of chest pain, shortness of breath and one episode of syncope which brought him to the ED. Over the course of his admission a variety of treatment modalities were used successfully to alleviate the problem. More notable from a nursing perspective was the use of diagnostic tools as an interpretation to guide his care and provide a platform from which a deeper understanding and appreciation of the intricacies the critically ill patient often presents.

CONCLUSION

We found the use of case review very enlightening in understanding the disease process and the decision-making that accompanies this. Whilst our patient was successfully rehabilitated home, we learnt a lot from the experience which has been most beneficial in supporting our understanding of pulmonary embolism.

Aspirin for preventing the recurrence of venous thromboembolism

BACKGROUND

About 20% of patients with unprovoked venous thromboembolism have a recurrence within 2 years after the withdrawal of oral anticoagulant therapy. Extending anticoagulation prevents recurrences but is associated with increased bleeding. The benefit of aspirin for the prevention of recurrent venous thromboembolism is unknown.

METHODS

In this multicenter, investigator-initiated, double-blind study, patients with first-ever unprovoked venous thromboembolism who had completed 6 to 18 months of oral anticoagulant treatment were randomly assigned to aspirin, 100 mg daily, or placebo for 2 years, with the option of extending the study treatment. The primary efficacy outcome was recurrence of venous thromboembolism, and major bleeding was the primary safety outcome.

RESULTS

Venous thromboembolism recurred in 28 of the 205 patients who received aspirin and in 43 of the 197 patients who received placebo (6.6% vs. 11.2% per year; hazard ratio, 0.58; 95% confidence interval [CI], 0.36 to 0.93) (median study period, 24.6 months). During a median treatment period of 23.9 months, 23 patients taking aspirin and 39 taking placebo had a recurrence (5.9% vs. 11.0% per year; hazard ratio, 0.55; 95% CI, 0.33 to 0.92). One patient in each treatment group had a major bleeding episode. Adverse events were similar in the two groups.

CONCLUSIONS

Aspirin reduced the risk of recurrence when given to patients with unprovoked venous thromboembolism who had discontinued anticoagulant treatment, with no apparent increase in the risk of major bleeding. (Funded by the University of Perugia and others; WARFASA ClinicalTrials.gov number, NCT00222677.).

Direct thrombin inhibitors for the treatment of venous thromboembolism: analysis of the Dabigatran versus Warfarin clinical trial

Vitamin-K antagonists have played a dominant role in the long-term management of patients with venous thromboembolism, and large trials from the past decade reinforced warfarin's effectiveness as an intermediate-duration and extended-duration anticoagulant. However, promising new oral direct thrombin inhibitors are proving to be at least as effective and as safe as the vitamin-K antagonists, without the associated hepatic toxicity that was seen with earlier orally administered direct thrombin inhibitors. This article reviews the recently published Dabigatran versus Warfarin in the Treatment of Acute Venous Thromboembolism clinical trial, and discusses the limitations and clinical applicability of the trial, especially in comparison with vitamin-K antagonists and the recently studied oral direct factor Xa inhibitors, rivaroxaban and apixaban.

Predicting the risk of venous thromboembolism recurrence

Venous thromboembolism (VTE) is a chronic disease with a 30% ten-year recurrence rate. The highest incidence of recurrence is in the first 6 months. Active cancer significantly increases the hazard of early recurrence, and the proportions of time on standard heparin with an APTT ≥ 0.2 anti-X(a) U/mL, and on warfarin with an INR ≥ 2.0, significantly reduce the hazard. The acute treatment duration does not affect recurrence risk after treatment is stopped. Independent predictors of late recurrence include increasing patient age and body mass index, leg paresis, active cancer and other persistent VTE risk factors, idiopathic VTE, antiphospholipid antibody syndrome, antithrombin, protein C or protein S deficiency, hyperhomocysteinemia and a persistently increased plasma fibrin D-dimer. A recommendation for secondary prophylaxis should be individualized based on the risk for recurrent VTE (especially fatal pulmonary embolism) and bleeding. The appropriateness of secondary prophylaxis should be continuously reevaluated, and the prophylaxis stopped if the benefit no longer exceeds the risk.

[Optimal duration of anticoagulation of venous thromboembolism]

The optimal duration of anticoagulation after venous thromboembolism (VTE) is determined according to the risk of recurrent VTE after stopping anticoagulant therapy and the risk of anticoagulant-related bleeding while on antivitamin K. Clinical risk factors appears to be determinant to predict the risk of recurrence whereas the influence of biochemical and morphological tests is uncertain. The risk of recurrent venous thromboembolism is low when the initial episode was provoked by a reversible major risk factor (surgery): 3 months of anticoagulation is optimal. Conversely, this risk is high when venous thromboembolism was unprovoked or associated with persistent risk factor (cancer): 6 months or more prolonged anticoagulation is warranted. After this first estimation, the duration of anticoagulation may be modulated according to the presence of additional minor risk factors (major thrombophilia, chronic pulmonary hypertension, massive pulmonary embolism): 6 months if VTE was provoked and 12 to 24 months if VTE was unprovoked. If the risk of anticoagulant related bleeding is high, the duration of anticoagulation should be shortened (3 months if VTE was provoked and 6 or 3 months if it was unprovoked). Lastly, if VTE occurred in the setting of a cancer, anticoagulation should be conducted for 6 months or more while cancer is active or on ongoing treatment. Despite an increasing knowledge of the risk factors of recurrent VTE, a number of issues remain unresolved; randomised trial comparing different duration of anticoagulation are needed.

Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

High-quality anticoagulation management is required to keep these narrow therapeutic index medications as effective and safe as possible. This article focuses on the common important management questions for which, at a minimum, low-quality published evidence is available to guide best practices.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

Most practical clinical questions regarding the management of anticoagulation, both oral and parenteral, have not been adequately addressed by randomized trials. We found sufficient evidence for summaries of recommendations for 23 questions, of which only two are strong rather than weak recommendations. Strong recommendations include targeting an international normalized ratio of 2.0 to 3.0 for patients on vitamin K antagonist therapy (Grade 1B) and not routinely using pharmacogenetic testing for guiding doses of vitamin K antagonist (Grade 1B). Weak recommendations deal with such issues as loading doses, initiation overlap, monitoring frequency, vitamin K supplementation, patient self-management, weight and renal function adjustment of doses, dosing decision support, drug interactions to avoid, and prevention and management of bleeding complications. We also address anticoagulation management services and intensive patient education.

CONCLUSIONS

We offer guidance for many common anticoagulation-related management problems. Most anticoagulation management questions have not been adequately studied.

INR targets and site-level anticoagulation control: results from the Veterans AffaiRs Study to Improve Anticoagulation (VARIA)

BACKGROUND

Not all clinicians target the same International Normalized Ratio (INR) for patients with a guideline-recommended target range of 2-3. A patient's mean INR value suggests the INR that was actually targeted. We hypothesized that sites would vary by mean INR, and that sites of care with mean values nearest to 2.5 would achieve better anticoagulation control, as measured by per cent time in therapeutic range (TTR).

OBJECTIVES

To examine variations among sites in mean INR and the relationship with anticoagulation control in an integrated system of care.

PATIENTS/METHODS

We studied 103,897 patients receiving oral anticoagulation with an expected INR target between 2 and 3 at 100 Veterans Health Administration (VA) sites from 1 October 2006 to 30 September 2008. Key site-level variables were: proportion near 2.5 (that is, percentage of patients with mean INR between 2.3 and 2.7) and mean risk-adjusted TTR.

RESULTS

Site mean INR ranged from 2.22 to 2.89; proportion near 2.5, from 30 to 64%. Sites' proportions of patients near 2.5, below 2.3 and above 2.7 were consistent from year to year. A 10 percentage point increase in the proportion near 2.5 predicted a 3.8 percentage point increase in risk-adjusted TTR (P < 0.001).

CONCLUSIONS

Proportion of patients with mean INR near 2.5 is a site-level 'signature' of care and an implicit measure of targeted INR. This proportion varies by site and is strongly associated with site-level TTR. Our study suggests that sites wishing to improve TTR, and thereby improve patient outcomes, should avoid the explicit or implicit pursuit of non-standard INR targets.

The Future of Deep Venous Thrombosis and Post-thrombotic Syndrome in 2020

This manuscript addresses six major issues involving deep venous thrombosis (DVT) and post-thrombotic syndrome. Prevention will likely see modest advances in pharmacological therapy mainly by extending prophylaxis in high-risk patients. More notable advances will be observed in mechanical means of prophylaxis, focusing on sustained application of devices that can move larger volumes of blood. Silent, large-vein thrombi continue to place patients at risk for fatal pulmonary embolism. Improved imaging techniques will permit us to identify these patients over the next eight years. In many of those patients, vena caval interruption will be required. Elimination of high-risk filters and the production of improved filters placed through low-profile systems with antithrombotic agents bound to their surface will improve the short- and long-term results for inferior vena cava filters. The long-term management of DVT will focus on establishing appropriate duration for the individual patient and will see the evolution towards direct Xa and Ha inhibitors. Patients with extensive DVT will more commonly receive treatment strategies designed to eliminate thrombus and restore patency. This will substantially reduce post-thrombotic morbidity and reduce recurrence. Post-thrombotic syndrome will see greater attention towards treating the intraluminal fibrosis, thereby eliminating post-thrombotic venous obstruction. Unfortunately, neovalves will still be searching for the appropriate application.

Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

This article addresses the treatment of VTE disease.

METHODS

We generated strong (Grade 1) and weak (Grade 2) recommendations based on high-quality (Grade A), moderate-quality (Grade B), and low-quality (Grade C) evidence.

RESULTS

For acute DVT or pulmonary embolism (PE), we recommend initial parenteral anticoagulant therapy (Grade 1B) or anticoagulation with rivaroxaban. We suggest low-molecular-weight heparin (LMWH) or fondaparinux over IV unfractionated heparin (Grade 2C) or subcutaneous unfractionated heparin (Grade 2B). We suggest thrombolytic therapy for PE with hypotension (Grade 2C). For proximal DVT or PE, we recommend treatment of 3 months over shorter periods (Grade 1B). For a first proximal DVT or PE that is provoked by surgery or by a nonsurgical transient risk factor, we recommend 3 months of therapy (Grade 1B; Grade 2B if provoked by a nonsurgical risk factor and low or moderate bleeding risk); that is unprovoked, we suggest extended therapy if bleeding risk is low or moderate (Grade 2B) and recommend 3 months of therapy if bleeding risk is high (Grade 1B); and that is associated with active cancer, we recommend extended therapy (Grade 1B; Grade 2B if high bleeding risk) and suggest LMWH over vitamin K antagonists (Grade 2B). We suggest vitamin K antagonists or LMWH over dabigatran or rivaroxaban (Grade 2B). We suggest compression stockings to prevent the postthrombotic syndrome (Grade 2B). For extensive superficial vein thrombosis, we suggest prophylactic-dose fondaparinux or LMWH over no anticoagulation (Grade 2B), and suggest fondaparinux over LMWH (Grade 2C).

CONCLUSION

Strong recommendations apply to most patients, whereas weak recommendations are sensitive to differences among patients, including their preferences.

VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The use of anticoagulant therapy during pregnancy is challenging because of the potential for both fetal and maternal complications. This guideline focuses on the management of VTE and thrombophilia as well as the use of antithrombotic agents during pregnancy.

METHODS

The methods of this guideline follow the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

We recommend low-molecular-weight heparin for the prevention and treatment of VTE in pregnant women instead of unfractionated heparin (Grade 1B). For pregnant women with acute VTE, we suggest that anticoagulants be continued for at least 6 weeks postpartum (for a minimum duration of therapy of 3 months) compared with shorter durations of treatment (Grade 2C). For women who fulfill the laboratory criteria for antiphospholipid antibody (APLA) syndrome and meet the clinical APLA criteria based on a history of three or more pregnancy losses, we recommend antepartum administration of prophylactic or intermediate-dose unfractionated heparin or prophylactic low-molecular-weight heparin combined with low-dose aspirin (75-100 mg/d) over no treatment (Grade 1B). For women with inherited thrombophilia and a history of pregnancy complications, we suggest not to use antithrombotic prophylaxis (Grade 2C). For women with two or more miscarriages but without APLA or thrombophilia, we recommend against antithrombotic prophylaxis (Grade 1B).

CONCLUSIONS

Most recommendations in this guideline are based on observational studies and extrapolation from other populations. There is an urgent need for appropriately designed studies in this population.

Oral anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The objective of this article is to summarize the published literature concerning the pharmacokinetics and pharmacodynamics of oral anticoagulant drugs that are currently available for clinical use and other aspects related to their management.

METHODS

We carried out a standard review of published articles focusing on the laboratory and clinical characteristics of the vitamin K antagonists; the direct thrombin inhibitor, dabigatran etexilate; and the direct factor Xa inhibitor, rivaroxaban

RESULTS

The antithrombotic effect of each oral anticoagulant drug, the interactions, and the monitoring of anticoagulation intensity are described in detail and discussed without providing specific recommendations. Moreover, we describe and discuss the clinical applications and optimal dosages of oral anticoagulant therapies, practical issues related to their initiation and monitoring, adverse events such as bleeding and other potential side effects, and available strategies for reversal.

CONCLUSIONS

There is a large amount of evidence on laboratory and clinical characteristics of vitamin K antagonists. A growing body of evidence is becoming available on the first new oral anticoagulant drugs available for clinical use, dabigatran and rivaroxaban.

Warfarin doses for anticoagulation therapy in elderly patients with chronic atrial fibrillation

OBJECTIVE

Anticoagulation is a challenge for the prophylaxis of thromboembolic events in elderly patients with chronic atrial fibrillation. Stable anticoagulation is defined as the time within >70% of the therapeutic range. However, the dosage required to achieve stable anticoagulation remains unknown. The aim of this study was to analyze the warfarin dose necessary for the maintenance of stable oral anticoagulation therapy in elderly patients.

METHODS

We analyzed 112 consecutive outpatients with atrial fibrillation who were >65 years of age, had received anticoagulation therapy with warfarin for more than 1 year and had a stable international normalized ratio between 2.0 and 3.0 for >6 months. The international normalized ratio was measured in the central laboratory using the traditional method.

RESULTS

The patients were stratified according to the following age groups: <75 or >75 years and <80 or >80 years. The mean daily doses of warfarin were similar for patients <75 or >75 years (3.34+1.71 versus 3.26 +1.27 mg/ day, p = 0.794) and <80 or >80 years (3.36+ 1.49 versus 3.15 + 1.23 mg/day, p = 0.433). In 88 (79%) patients, the daily warfarin dose was between 2 and 5 mg/day; in 13 (11%) patients, the daily warfarin dose was <2.0 mg/day; and in 11 (10%) patients, the daily warfarin dose was >5.0 mg/day. The correlation between the daily warfarin dose and the international normalized ratio was 0.22 (p = 0.012).

CONCLUSION

Stable anticoagulation was achieved in 80% of patients who received doses of 2 to 5 mg/day of warfarin, and the mean daily dose was similar across the age groups analyzed.

Recurrent venous thromboembolism: what is the risk and how to prevent it

Venous thromboembolism (VTE) that includes deep vein thrombosis and/or pulmonary embolism is a frequent, severe, and potentially lethal disease. After a first episode, VTE has a strong tendency to recur. While VTE is an acute disease, it may have variable outcomes in early and late phases after initial presentation. Furthermore, the incidence of late, clinically important consequences (postthrombotic syndrome and/or chronic thromboembolic pulmonary hypertension) increases in case of recurrent events. The aims of the present review are (i) to analyze the incidence and risk factors for recurrence of VTE (either those related to the type of first thrombotic event or to the patients), the risks associated with occurrence of recurrent events, and the problems linked to the diagnosis, not always easy, of recurrent events; (ii) to discuss whether or not it is possible to predict the individual risk of recurrence after a first event, by stratifying patients at high or low risk of recurrence, and how this can influence their treatment; (iii) to comment what the current guidelines and guidance suggest/recommend about anticoagulant treatment after a first VTE event and, finally, to propose practical indications on how to manage individual patients affected by VTE.

The population pharmacokinetics of R- and S-warfarin: effect of genetic and clinical factors

BACKGROUND

Warfarin is a drug with a narrow therapeutic index and large interindividual variability in daily dosing requirements. Patients commencing warfarin treatment are at risk of bleeding due to excessive anticoagulation caused by overdosing. The interindividual variability in dose requirements is influenced by a number of factors, including polymorphisms in genes mediating warfarin pharmacology, co-medication, age, sex, body size and diet.

AIMS

To develop population pharmacokinetic models of both R- and S-warfarin using clinical and genetic factors and to identify the covariates which influence the interindividual variability in the pharmacokinetic parameters of clearance and volume of distribution in patients on long-term warfarin therapy.

METHODS

Patients commencing warfarin therapy were followed up for 26 weeks. Plasma warfarin enantiomer concentrations were determined in 306 patients for S-warfarin and in 309 patients for R-warfarin at 1, 8 and 26 weeks. Patients were also genotyped for CYP2C9 variants (CYP2C9*1,*2 and *3), two single-nucleotide polymorphisms (SNPs) in CYP1A2, one SNP in CYP3A4 and six SNPs in CYP2C19. A base pharmacokinetic model was developed using NONMEM software to determine the warfarin clearance and volume of distribution. The model was extended to include covariates that influenced the between-subject variability.

RESULTS

Bodyweight, age, sex and CYP2C9 genotype significantly influenced S-warfarin clearance. The S-warfarin clearance was estimated to be 0.144 l h⁻¹ (95% confidence interval 0.131, 0.157) in a 70 kg woman aged 69.8 years with the wild-type CYP2C9 genotype, and the volume of distribution was 16.6 l (95% confidence interval 13.5, 19.7). Bodyweight and age, along with the SNPs rs3814637 (in CYP2C19) and rs2242480 (in CYP3A4), significantly influenced R-warfarin clearance. The R-warfarin clearance was estimated to be 0.125 l h⁻¹ (95% confidence interval 0.115, 0.135) in a 70 kg individual aged 69.8 years with the wild-type CYP2C19 and CYP3A4 genotypes, and the volume of distribution was 10.9 l (95% confidence interval 8.63, 13.2).

CONCLUSIONS

Our analysis, based on exposure rather than dose, provides quantitative estimates of the clinical and genetic factors impacting on the clearance of both the S- and R-enantiomers of warfarin, which can be used in developing improved dosing algorithms.

[The optimal duration of anticoagulant treatment following pulmonary embolism]

The optimal course of oral anticoagulant therapy is determined according to the risk of recurrent venous thromboembolism after stopping therapy and the risk of anticoagulant-related bleeding. Clinical risk factors appear to be important in predicting the risk of recurrence whereas the influence of biochemical and morphological tests is uncertain. The risk of recurrent venous thromboembolism is low when the initial episode was provoked by a reversible major risk factor (surgery): 3 months of anticoagulation is sufficient. Conversely, the risk is high when venous thromboembolism was unprovoked or associated with persistent risk factor (cancer): 6 months or more prolonged anticoagulation is necessary. After this first estimation, the duration of anticoagulation may be modulated according to the presence or absence of certain additional risk factors (major thrombophilia, chronic pulmonary hypertension, massive pulmonary embolism): 6 months if pulmonary embolism was provoked and 12 to 24 months if pulmonary embolism was unprovoked. If the risk of anticoagulant-related bleeding is high, the duration of anticoagulation should be shortened (3 months if pulmonary embolism was provoked and 3 to 6 months if it was unprovoked). Lastly, if pulmonary embolism occurred in association with cancer, anticoagulation should be conducted for 6 months or more if the cancer is active or treatment is on going. Despite an increasing knowledge of the risk factors for recurrent venous thromboembolism, a number of issues remain unresolved. Randomised trials comparing different durations of anticoagulation are needed.

Whole blood gene expression analyses in patients with single versus recurrent venous thromboembolism

INTRODUCTION

Venous thromboembolism may recur in up to 30% of patients with a spontaneous venous thromboembolism after a standard course of anticoagulation. Identification of patients at risk for recurrent venous thromboembolism would facilitate decisions concerning the duration of anticoagulant therapy.

OBJECTIVES

In this exploratory study, we investigated whether whole blood gene expression data could distinguish subjects with single venous thromboembolism from subjects with recurrent venous thromboembolism.

METHODS

40 adults with venous thromboembolism (23 with single event and 17 with recurrent events) on warfarin were recruited. Individuals with antiphospholipid syndrome or cancer were excluded. Plasma and serum samples were collected for biomarker testing, and PAXgene tubes were used to collect whole blood RNA samples.

RESULTS

D-dimer levels were significantly higher in patients with recurrent venous thromboembolism, but P-selectin and thrombin-antithrombin complex levels were similar in the two groups. Comparison of gene expression data from the two groups provided us with a 50 gene probe model that distinguished these two groups with good receiver operating curve characteristics (AUC 0.75). This model includes genes involved in mRNA splicing and platelet aggregation. Pathway analysis between subjects with single and recurrent venous thromboembolism revealed that the Akt pathway was up-regulated in the recurrent venous thromboembolism group compared to the single venous thromboembolism group.

CONCLUSIONS

In this exploratory study, gene expression profiles of whole blood appear to be a useful strategy to distinguish subjects with single venous thromboembolism from those with recurrent venous thromboembolism. Prospective studies with additional patients are needed to validate these results.

Splanchnic vein thrombosis in severe acute pancreatitis: a 2-year, single-institution experience

OBJECTIVES

This study aimed to determine current practice in the management and outcome of splanchnic vein thrombosis complicating acute pancreatitis (AP).

METHODS

An audit of prospectively collected data for all patients presenting with AP was conducted. Patients with splanchnic vein thrombosis were grouped according to vessel involvement and whether or not systemic anticoagulation was administered.

RESULTS

Of 127 consecutive patients admitted with AP, 20 had splanchnic venous thrombosis; in all cases the thrombosis was associated with a severe attack of AP. Involvement of the splenic vein (SV), portal vein (PV) and superior mesenteric vein (SMV) was observed in 14, 10 and three patients, respectively. Involvement of more than one vessel was observed in six patients (SV and PV in four patients; SMV and SV in one patient; all three veins in one patient). Thromboses were colocalized with collections in 19 patients. Only four patients received systemic anticoagulation. Resolution of thrombosis was observed in six patients over a median of 77 days. No significant differences were observed in recanalization rates following anticoagulation (P= 0.076). No complications associated with systemic anticoagulation occurred. One patient developed liver failure associated with progressive PV thrombosis and one patient died.

CONCLUSIONS

Splanchnic vein thrombosis is a relatively common observation in severe AP and is associated with pancreatic necrosis and peripancreatic collections. Recanalization is observed in almost a third of patients, irrespective of whether or not they receive systemic anticoagulation.

Role of cytochrome P450 genotype in the steps toward personalized drug therapy

Genetic polymorphism for cytochrome 450 (P450) enzymes leads to interindividual variability in the plasma concentrations of many drugs. In some cases, P450 genotype results in decreased enzyme activity and an increased risk for adverse drug effects. For example, individuals with the CYP2D6 loss-of-function genotype are at increased risk for ventricular arrhythmia if treated with usual does of thioridazine. In other cases, P450 genotype may influence the dose of a drug required to achieve a desired effect. This is the case with warfarin, with lower doses often necessary in carriers of a variant CYP2C9*2 or *3 allele to avoid supratherapeutic anticoagulation. When a prodrug, such as clopidogrel or codeine, must undergo hepatic biotransformation to its active form, a loss-of-function P450 genotype leads to reduced concentrations of the active drug and decreased drug efficacy. In contrast, patients with multiple CYP2D6 gene copies are at risk for opioid-related toxicity if treated with usual doses of codeine-containing analgesics. At least 25 drugs contain information in their US Food and Drug Administration-approved labeling regarding P450 genotype. The CYP2C9, CYP2C19, and CYP2D6 genes are the P450 genes most often cited. To date, integration of P450 genetic information into clinical decision making is limited. However, some institutions are beginning to embrace routine P450 genotyping to assist in the treatment of their patients. Genotyping for P450 variants may carry less risk for discrimination compared with genotyping for disease-associated variants. As such, P450 genotyping is likely to lead the way in the clinical implementation of pharmacogenomics. This review discusses variability in the CYP2C9, CYP2C19, and CYP2D6 genes and the implications of this for drug efficacy and safety.

Residual vein thrombosis for assessing duration of anticoagulation after unprovoked deep vein thrombosis of the lower limbs: the extended DACUS study

The safest duration of anticoagulation after idiopathic deep vein thrombosis (DVT) is unknown. We conducted a prospective study to assess the optimal duration of vitamin K antagonist (VKA) therapy considering the risk of recurrence of thrombosis according to residual vein thrombosis (RVT). Patients with a first unprovoked DVT were evaluated for the presence of RVT after 3 months of VKA administration; those without RVT suspended VKA, while those with RVT continued oral anticoagulation for up to 2 years. Recurrent thrombosis and/or bleeding events were recorded during treatment (RVT group) and 1 year after VKA withdrawal (both groups). Among 409 patients evaluated for unprovoked DVT, 33.2% (136 of 409 patients) did not have RVT and VKA was stopped. The remaining 273 (66.8%) patients with RVT received anticoagulants for an additional 21 months; during this period of treatment, recurrent venous thromboembolism and major bleeding occurred in 4.7% and 1.1% of patients, respectively. After VKA suspension, the rates of recurrent thrombotic events were 1.4% and 10.4% in the no-RVT and RVT groups, respectively (relative risk = 7.4; 95% confidence interval = 4.9-9.9). These results indicate that in patients without RVT, a short period of treatment with a VKA is sufficient; in those with persistent RVT, treatment extended to 2 years substantially reduces, but does not eliminate, the risk of recurrent thrombosis.

[Treatment of deep vein thrombosis and pulmonary embolism]

Deep vein thrombosis and pulmonary embolism may be considered as different manifestations of the same disease: venous thromboembolism. Under the condition of entirely stable hemodynamics, treatment follows exactly the same principles. The phase of initial therapy has a duration of 5-10 days and has remained so far a domain of parenteral anticoagulants (low molecular weight heparin, fondaparinux). The phase of early maintenance therapy is instituted with an overlap and has a duration of 3-6 months; vitamin K antagonists with a target INR of 2.0-3.0 are the standard. Patients with a high risk of recurrence and a low risk of bleeding will enter a phase of prolonged or even indefinite maintenance therapy. Again, vitamin K antagonists with a target INR of 2.0-3.0 are the standard. A target INR of 1.5-2.0 may be considered an alternative for patients in whom a very stable anticoagulation with less frequent INR testing is desirable. Clear recommendations can be made for venous thromboembolism treatment in pregnancy, in the post partum and lactation periods, as well as for patients with severe renal impairment. New anticoagulants (thrombin inhibitors, factor Xa inhibitors) have made significant progress in their clinical development and will soon become available as an alternative for all three phases of therapy.