Diet as prophylaxis and treatment for venous thromboembolism?

Background

Both prophylaxis and treatment of venous thromboembolism (VTE: deep venous thrombosis (DVT) and pulmonary emboli (PE)) with anticoagulants are associated with significant risks of major and fatal hemorrhage. Anticoagulation treatment of VTE has been the standard of care in the USA since before 1962 when the U.S. Food and Drug Administration began requiring randomized controlled clinical trials (RCTs) showing efficacy, so efficacy trials were never required for FDA approval. In clinical trials of 'high VTE risk' surgical patients before the 1980s, anticoagulant prophylaxis was clearly beneficial (fatal pulmonary emboli (FPE) without anticoagulants = 0.99%, FPE with anticoagulants = 0.31%). However, observational studies and RCTs of 'high VTE risk' surgical patients from the 1980s until 2010 show that FPE deaths without anticoagulants are about one-fourth the rate that occurs during prophylaxis with anticoagulants (FPE without anticoagulants = 0.023%, FPE while receiving anticoagulant prophylaxis = 0.10%). Additionally, an FPE rate of about 0.012% (35/28,400) in patients receiving prophylactic anticoagulants can be attributed to 'rebound hypercoagulation' in the two months after stopping anticoagulants. Alternatives to anticoagulant prophylaxis should be explored.

Methods and Findings

The literature concerning dietary influences on VTE incidence was reviewed. Hypotheses concerning the etiology of VTE were critiqued in relationship to the rationale for dietary versus anticoagulant approaches to prophylaxis and treatment. Epidemiological evidence suggests that a diet with ample fruits and vegetables and little meat may substantially reduce the risk of VTE; vegetarian, vegan, or Mediterranean diets favorably affect serum markers of hemostasis and inflammation. The valve cusp hypoxia hypothesis of DVT/VTE etiology is consistent with the development of VTE being affected directly or indirectly by diet. However, it is less consistent with the rationale of using anticoagulants as VTE prophylaxis. For both prophylaxis and treatment of VTE, we propose RCTs comparing standard anticoagulation with low VTE risk diets, and we discuss the statistical considerations for an example of such a trial.

Conclusions

Because of (a) the risks of biochemical anticoagulation as anti-VTE prophylaxis or treatment, (b) the lack of placebo-controlled efficacy data supporting anticoagulant treatment of VTE, (c) dramatically reduced hospital-acquired FPE incidence in surgical patients without anticoagulant prophylaxis from 1980 - 2010 relative to the 1960s and 1970s, and (d) evidence that VTE incidence and outcomes may be influenced by diet, randomized controlled non-inferiority clinical trials are proposed to compare standard anticoagulant treatment with potentially low VTE risk diets. We call upon the U. S. National Institutes of Health and the U.K. National Institute for Health and Clinical Excellence to design and fund those trials.     

Anticoagulation for non-valvular atrial aibrillation - towards a new beginning with ximelagatran

OBJECTIVES: Ximelagatran is a novel oral direct thrombin inhibitor. It has favorable pharmacodynamic properties, with a broad therapeutic range without the need for anticoagulation monitoring. We aimed to discover whether ximelagatran offers a genuine future replacement to warfarin for patients in persistent atrial fibrillation (AF). MATERIALS AND METHODS: We provide an evidence-based review of the relative merits and disadvantages of warfarin and aspirin. We subsequently present an overview of the evidence for the utility of ximelagatran in the treatment of AF. RESULTS: Adjusted dose warfarin is recommended over aspirin for patients in AF at high risk of future stroke. Some of this benefit is partially offset by the higher bleeding risks associated with warfarin therapy. The SPORTIF III and V studies have shown that ximelagatran is not inferior to warfarin in the prevention of all strokes in patients with AF (both persistent and paroxysmal). This benefit was partially offset by the finding of a significant elevation of liver transaminases (>3 x normal) in 6% of patients. CONCLUSIONS: Current data would suggest that ximelagatran might represent a future alternative to warfarin. The lack of need for anticoagulant monitoring has been partially offset by a need for regular monitoring of liver function. Further data from randomized clinical trials is clearly needed.     

Increased tissue plasminogen activator levels in patients with nonvalvular atrial fibrillation

OBJECTIVE: To determine whether plasma tissue plasminogen activator (tPA) levels (a) are higher in patients with novalvular atrial fibrillation (NVAF) than in control subjects in sinus rhythm; (b) differ between NVAF patients with and without a history of an embolic event (transient ischemic attack or embolic stroke); and (c) differ in control subjects with and without a history of thrombotic stroke. DESIGN: Cross-sectional study. SETTING: Internal medicine outpatient group practice and anticoagulation clinic in 2 teaching hospitals. PATIENTS: Seventy-four NVAF patients (24 with and 50 without a history of an embolic event), separated into 3 groups: no prior embolic event and no warfarin use (group 1), no prior embolic event and warfarin use (group 2), and prior embolic event and warfarin use (group 3). Forty control subjects in sinus rhythm (29 without and 11 with prior thrombotic stroke). OUTCOME MEASURES: Plasma tPA levels. RESULTS: The age-adjusted mean tPA levels exceeded the upper limit of normal in all 3 NVAF groups but not in the control groups. The NVAF patients had significantly higher mean tPA levels than the control subjects (p = 0.015). The levels did not differ significantly between the NVAF patients with a history of an embolic event and those without such a history. The control subjects with a history of thrombotic stroke had significantly higher mean tPA levels than the other control subjects (p = 0.03). CONCLUSIONS: NVAF patients, regardless of their history of embolic events, and control patients with a history of thrombotic stroke have higher tPA levels than subjects in sinus rhythm without a history of stroke. A prospective, longitudinal study involving NVAF patients is required to determine whether high baseline tPA levels are associated with, and perhaps causally related to, an increased risk of stroke.     

Equivalence and noninferiority trials – are they viable alternatives for registration of new drugs? (III)

Objectives

Ximelagatran is a novel oral direct thrombin inhibitor. It has favorable pharmacodynamic properties, with a broad therapeutic range without the need for anticoagulation monitoring. We aimed to discover whether ximelagatran offers a genuine future replacement to warfarin for patients in persistent atrial fibrillation (AF).

Materials and methods

We provide an evidence-based review of the relative merits and disadvantages of warfarin and aspirin. We subsequently present an overview of the evidence for the utility of ximelagatran in the treatment of AF.

Results

Adjusted dose warfarin is recommended over aspirin for patients in AF at high risk of future stroke. Some of this benefit is partially offset by the higher bleeding risks associated with warfarin therapy. The SPORTIF III and V studies have shown that ximelagatran is not inferior to warfarin in the prevention of all strokes in patients with AF (both persistent and paroxysmal). This benefit was partially offset by the finding of a significant elevation of liver transaminases (>3 × normal) in 6% of patients.

Conclusions

Current data would suggest that ximelagatran might represent a future alternative to warfarin. The lack of need for anticoagulant monitoring has been partially offset by a need for regular monitoring of liver function. Further data from randomized clinical trials is clearly needed.     

Cost-effectiveness of enoxaparin versus warfarin prophylaxis against deep-vein thrombosis after total hip replacement.

OBJECTIVE: To compare the efficacy and cost-effectiveness of enoxaparin, a low-molecular-weight heparin derivative, with that of low-dose warfarin in the prevention of deep-vein thrombosis (DVT) after total hip replacement. DATA SOURCES: English-language articles on enoxaparin and warfarin prophylaxis is patients undergoing total hip replacement published from January 1982 to December 1992. STUDY SELECTION: Four trials of enoxaparin (involving 567 patients) and six trials of warfarin (involving 630) met the following criteria: randomized controlled trial, prophylaxis started no later than 24 hours after surgery and continued for at least 7 days, warfarin dose monitored and adjusted appropriately, enoxaparin dosage 30 mg twice daily, and DVT confirmed by bilateral venography. DATA EXTRACTION: Rates of DVT, cost of prophylaxis, diagnosis and treatment per patient, rate of pulmonary embolism (PE), number of deaths and incremental cost-effectiveness (cost per life-year gained). DATA SYNTHESIS: The pooled rate of DVT was 13.6% with enoxaparin (95% confidence interval [CI] 10.9% to 16.3%) and 20.6% with warfarin (95% CI 17.4% to 23.8%). At a cost of $19.55 per day for enoxaparin the total cost per patient, including prophylaxis and management of DVT, exceeded that per patient receiving warfarin by about $121. For every 10,000 patients treated the use of enoxaparin will prevent 47 cases of DVT, 3 cases of PE and 4 deaths. Thus, the estimated incremental cost-effectiveness of enoxaparin is $29 120 per life-year gained. CONCLUSION: On the basis of current Canadian cost-effectiveness guidelines the results of this study would be considered moderate to strong evidence to adopt enoxaparin prophylaxis against DVT after total hip replacement. However, because of the limited data the estimates are uncertain. Future trials should compare enoxaparin and warfarin and incorporate a prospective economic appraisal.     

Wearable defibrillator use in heart failure (WIF): results of a prospective registry

Background

In patients with non-valvular atrial fibrillation (NVAF) at high risk for stroke guidelines consistently recommend long-term oral anticoagulation (OAC) with a vitamin K antagonist. However recommendations remain ambiguous in respect to the precise OAC initiation regimens. Based on the clinical observation, that the initiation of OAC for NVAF varies considerably in daily practice, we aimed to assess the current practice in Switzerland.

Methods

Cross-sectional survey of randomly selected general practitioners, internists and cardiologists from different health care settings in an urban Swiss region that covers 1.4 million inhabitants. The main outcome measures were the preferred antithrombotic initiation regimen and long-term treatment in patients with newly diagnosed NVAF at high risk for stroke.

Results

We received 226 out of 388 (58.2%) surveys. Compared to physicians working in a hospital setting (33.6% of respondents) physicians in ambulatory care reported more years of experience and claimed lower-use (never or seldom) of guidelines in general (47.6 vs. 12.2%). Regarding long-term thromboembolic prophylaxis 93.7% of all responders followed current recommendation by choosing an OAC. When focussing on guideline-consistent correct OAC initiation (either low-dose initial OAC or a combination of LMWH and OAC) adherence dropped to 60.6% with hospital physicians demonstrating a significantly higher use of guideline-conform OAC regimens (79.7 vs. 51.0%). Medical speciality in non-hospital physicians was not related to correct guideline-use. Hospital setting remained independently associated with a guideline-conform OAC initiation regimen (OR 2.8, p = 0.023) when controlled for medical speciality, physicians' characteristics and clinical experience. Problems when starting an anticoagulation treatment were seldom reported (never or seldom accounting for 94.1% of all responses).

Conclusions

The guideline adherence with respect to OAC initiation regimens in NVAF was significantly lower when compared to long-term treatment and health care setting rather than medical speciality explained guideline-conform OAC initiation. The majority of the physicians did not consider the initiation of anticoagulation to be a major obstacle in outpatient care.     

Treatment of nonvalvular atrial fibrillation.

Nonvalvular atrial fibrillation is an increasingly common condition. It may cause disabling symptoms and is an important risk factor for stroke. The goals of treatment include the relief and prevention of rate- and rhythm-related symptoms and the prevention of stroke and systemic emboli. Three principal treatments should be considered: pharmacologic rate control, cardioversion and antiarrhythmic therapy to restore and maintain sinus rhythm, and prophylactic anticoagulation or antiplatelet therapy to reduce the risk of stroke. The risks and benefits of each of these therapies have been reviewed. Symptoms, if present, can often be managed safely with rate-directed therapy alone. Until issues regarding safety and long-term efficacy are resolved, cardioversion and antiarrhythmic therapy should be limited to those patients whose symptoms cannot otherwise be controlled. The benefits of warfarin anticoagulation for the primary and secondary prevention of stroke in nonvalvular atrial fibrillation have been demonstrated convincingly by several randomized clinical trials. These benefits must be weighed against the real risk of major hemorrhage. For patients at low risk of stroke, the use of aspirin may be an acceptable alternative to warfarin sodium therapy.     

ABC of atrial fibrillation. Antithrombotic treatment for atrial fibrillation.

Antithrombotic prophylaxis with long term warfarin or aspirin reduces thromboembolic risk in atrial fibrillation. Identification, risk assessment, and regular review of all patients with atrial fibrillation should be routine in general and hospital practice. Risk stratification is easily performed on clinical grounds--echocardiography may refine it.     

关节置换术后抗凝药物预防深静脉血栓及相关并发症的临床研究进展

抗凝药物有助于预防全髋关节置换术和全膝关节置换术后深静脉血栓形成,临床上最常使用的传统抗凝药物如低分子肝素、华法林等可以起到很好的预防效果。目前有一类新的口服抗凝药物已经用于临床,为关节置换术后患者带来了一种更方便、安全和有效预防血栓的治疗选择。本篇综述主要针对传统抗凝药物低分子肝素及维生素K拮抗剂,直接凝血酶抑制剂达比加群,以及选择性Xa因子抑制剂利伐沙班和阿哌沙班,对迄今为止传统抗凝药物在全髋关节置换术和全膝关节置换术患者中的临床使用经验、优缺点、以及新型口服抗凝药物最新临床用药进展进行综述,为关节置换术后患者预防深静脉血栓提供用药参考。     

Also the very elderly benefit from warfarin in atrial fibrillation

Warfarin therapy is the cornerstone in the prevention of thromboembolism in patients with atrial fibrillation. It reduces the risk of stroke by two thirds in comparison with no anticoagulation. 1 A weak alternative to warfarin is aspirin, which is also effective over placebo in the prevention of stroke in atrial fibrillation. 1 Aspirin is safer than warfarin in general use. The incidence of atrial fibrillation sharply increases with age, but also the risk of bleeding from warfarin shows the same pattern.     

Comparison of the Non-VKA Oral Anticoagulants Apixaban,Dabigatran, and Rivaroxaban in the Extended Treatment and Prevention of Venous Thromboembolism: Systematic Review and Network Meta-Analysis

BackgroundHistorically, warfarin or aspirin have been the recommended therapeutic options for the extended treatment (>3 months) of VTE. Data from Phase III randomised controlled trials (RCTs) are now available for non-VKA oral anticoagulants (NOACs) in this indication. The current systematic review and network meta-analysis (NMA) were conducted to compare the efficacy and safety of anticoagulants for the extended treatment of VTE.MethodsElectronic databases (accessed July 2014 and updated April 2016) were systematically searched to identify RCTs evaluating apixaban, aspirin, dabigatran, edoxaban, rivaroxaban, and warfarin for the extended treatment of VTE. Eligible studies included adults with an objectively confirmed deep vein thrombosis, pulmonary embolism or both. A fixed-effect Bayesian NMA was conducted, and results were presented as relative risks (RRs). Sensitivity analyses examining (i) the dataset employed according to the time frame for outcome assessment (ii) the model used for the NMA were conducted.ResultsEleven Phase III RCTs (examining apixaban, aspirin, dabigatran, rivaroxaban, warfarin and placebo) were included. The risk of the composite efficacy outcome (VTE and VTE-related death) was statistically significantly lower with the NOACs and warfarin INR 2.0–3.0 compared with aspirin, with no significant differences between the NOACs. Treatment with apixaban (RR 0.23, 95% CrI 0.10, 0.55) or dabigatran (RR 0.55, 95% Crl 0.43, 0.71) was associated with a statistically significantly reduced risk of ‘major or clinically relevant non-major bleed’ compared with warfarin INR 2.0–3.0. Apixaban also showed a significantly reduced risk compared with dabigatran (RR 0.42, 95% Crl 0.18, 0.97) and rivaroxaban (RR 0.23, 95% Crl 0.09, 0.59). Sensitivity analyses indicate that results were dependent on the dataset, but not on the type of NMA model employed.ConclusionsResults from the NMA indicate that NOACs are an effective treatment for prevention of VTE or VTE-related death) in the extended treatment setting. However, bleeding risk differs between potential treatments, with apixaban reporting the most favourable profile compared with other NOACs, warfarin INR 2.0–3.0, and aspirin.     

A comparison of aspirin and anticoagulation following thrombolysis for myocardial infarction (the AFTER study): a multicentre unblinded randomised clinical trial.

OBJECTIVE: To compare aspirin with anticoagulation with regard to risk of cardiac death and reinfarction in patients who received anistreplase thrombolysis for myocardial infarction. DESIGN: A multicentre unblinded randomised clinical trial. SETTING: 38 hospitals in six countries. SUBJECTS: 1036 patients who had been treated with anistreplase for myocardial infarction were randomly assigned to either aspirin (150 mg daily) or anticoagulation (intravenous heparin followed by warfarin or other oral anticoagulant). The trial was stopped earlier than originally intended because of the slowing rate of recruitment. MAIN OUTCOME MEASURE: Cardiac death or recurrent myocardial infarction at 30 days. RESULTS: After 30 days cardiac death or reinfarction, occurred in 11.0% (57/517) of the patients treated with anticoagulation and 11.2% (58/519) of the patients treated with aspirin (odds ratio 1.02, 95% confidence interval 0.69 to 1.50, P = 0.92). Corresponding findings at three months were 13.2% (68/517) and 12.1% (63/519) (0.91, 0.63 to 1.32, P = 0.67). Patients receiving anticoagulation were more likely than patients receiving aspirin to have had severe bleeding or a stroke by three months (3.9% v 1.7% (0.44, 0.20 to 0.97, P = 0.04)). CONCLUSION: No evidence of a difference in the incidence of cardiac events was found between the two treatment groups, though the trial is too small to claim treatment equivalence confidently. A higher incidence of severe bleeding events and strokes was detected in the group receiving anticoagulation, suggesting that aspirin may be the drug of choice for most patients in this context.     

Fixed minidose warfarin: a new approach to prophylaxis against venous thrombosis after major surgery.

A prospective study was carried out to see whether a small fixed dose of warfarin (1 mg daily) given before operation (mean 20 days) would prevent deep vein thrombosis in patients having major gynaecological surgery. One hundred and four patients were randomised into three groups: fixed minidose warfarin; full dose oral anticoagulation; and no treatment (controls). There was a significantly lower incidence of deep vein thrombosis in the minidose warfarin and full dose anticoagulant treatment groups (9% (3/32) and 3% (1/35) respectively) than in the controls (30%; 11/37) but no significant difference between the two anticoagulant treatment groups. Prothrombin time and the activated partial thromboplastin time were normal on the day of surgery in the warfarin treatment group, whereas times were prolonged in the group given full dose anticoagulation. Mean haemoglobin concentrations fell in all three groups after operation but the fall was significantly less in the minidose warfarin treatment group than after full dose anticoagulation. The benefit from full dose oral anticoagulant prophylaxis, based on a preoperative international normalised ratio of 1.5-2.5 with rabbit brain Manchester reagent, was similar to the protection achieved in an oral anticoagulant treatment group controlled with human brain Manchester comparative reagent at a similar level of anticoagulation. The lack of disturbance of normal haemostasis at the time of operation together with a significant reduction in deep vein thrombosis may encourage surgeons to introduce minidose prophylaxis with warfarin.     

Novel Anticoagulants for Stroke Prevention in Atrial Fibrillation: A Systematic Review of Cost-Effectiveness Models

Objective

To conduct a systematic review of economic models of newer anticoagulants for stroke prevention in atrial fibrillation (SPAF).

Patients and Methods

We searched Medline, Embase, NHSEED and HTA databases and the Tuft’s Registry from January 1, 2008 through October 10, 2012 to identify economic (Markov or discrete event simulation) models of newer agents for SPAF.

Results

Eighteen models were identified. Each was based on a lone randomized trial/new agent, and these trials were clinically and methodologically heterogeneous. Dabigatran 150 mg, 110 mg and sequentially-dosed were assessed in 9, 8, and 9 models, rivaroxaban in 4 and apixaban in 4. Warfarin was a first-line comparator in 94% of models. Models were conducted from United States (44%), European (39%) and Canadian (17%) perspectives. Models typically assumed patients between 65–73 years old at moderate-risk of stroke initiated anticoagulation for/near a lifetime. All models reported cost/quality-adjusted life-year, 22% reported using a societal perspective, but none included indirect costs. Four models reported an incremental cost-effectiveness ratio (ICER) for a newer anticoagulant (dabigatran 110 mg (n = 4)/150 mg (n = 2); rivaroxaban (n = 1)) vs. warfarin above commonly reported willingness-to-pay thresholds. ICERs vs. warfarin ranged from $3,547–$86,000 for dabigatran 150 mg, $20,713–$150,000 for dabigatran 110 mg, $4,084–$21,466 for sequentially-dosed dabigatran and $23,065–$57,470 for rivaroxaban. Apixaban was found economically-dominant to aspirin, and dominant or cost-effective ($11,400–$25,059) vs. warfarin. Indirect comparisons from 3 models suggested conflicting comparative cost-effectiveness results.

Conclusions

Cost-effectiveness models frequently found newer anticoagulants cost-effective, but the lack of head-to-head trials and the heterogeneous characteristics of underlying trials and modeling methods make it difficult to determine the most cost-effective agent.     

Occurrence and quality of anticoagulant treatment of chronic atrial fibrillation in primary health care in Sweden: a retrospective study on electronic patient records

Background  

Chronic atrial fibrillation is a prevalent cardiac disorder. The literature indicates varying proportions of those treated with anticoagulants, and varying intensity of anticoagulation. Electronic patient records are providing us with clinical data concerning management of anticoagulant treatment in real-life practice that is useful for audits. We aimed to assess warfarin treatment for chronic atrial fibrillation in primary health care with regard to prevalence, incidence, the proportion treated and the quality of anticoagulation control.     

Target Specific Anticoagulant Peptides: A Review

Anticoagulant drugs are of crucial importance for the treatment and prophylaxis of thrombotic disorders. The use of traditional anticoagulants like heparin and warfarin is majorly associated with bleeding complications. In the quest for safer anticoagulation therapy, the interest for the isolation of novel anticoagulant compounds has shifted towards natural sources. Peptides can be considered as better alternative due to their therapeutic potential in the treatment of diseases. Peptides from hematophagous (blood-feeding) and venomous organisms have been recognized as potential anticoagulant agents. Of late, peptides derived from the hydrolysis of food proteins, including edible seaweeds, milk and seed proteins, have also shown to possess promising in vitro anticoagulant activity. To overcome the problems associated with regular anticoagulants, peptides targeting vital steps in the clotting cascade have been studied. This review focuses on anticoagulant peptides with known targets, inhibiting crucial factors in the coagulation cascade such as FXa, FXIa, FXIIa and FVIIa/TF complex, as well as peptides with unknown targets.     

Antithrombotic therapy in heart failure

Patients with congestive heart failure have a significant risk of stroke due to thromboembolism from the dilated left ventricle. Two relatively small trials suggest that oral anticoagulation with vitamin-K antagonists may reduce this risk when compared with placebo, aspirin or clopidogrel. However, more studies are eagerly awaited. So far, physicians seeing patients with heart failure should decide who needs antithrombotic prophylaxis on a case-by-case basis, especially since most heart failure patients have significant comorbidity precluding the use of oral anticoagulant.     

Cost effectiveness of primary stroke prevention in atrial fibrillation: Swedish national perspective.

OBJECTIVE--To assess the potential effects of primary prevention with anticoagulants or aspirin in atrial fibrillation on Swedish population. DESIGN--Analysis of cost effectiveness based on the following assumptions: about 83,000 people have atrial fibrillation in Sweden, of whom 22,000 would be potential candidates for treatment with anticoagulants and 55,000 for aspirin treatment; the annual 5% stroke rate is reduced by 64% (with anticoagulants) and 25% (with aspirin); incidence of intracranial haemorrhage of 0.3%, 1.3%, or 2.0% per year; direct and indirect costs of a stroke of Kr180,000 and Kr90,000; estimated annual cost of treatment is Kr5030 for anticoagulants and Kr100 for aspirin. SETTING--Total Swedish population. MAIN OUTCOME MEASURES--Direct and indirect costs of stroke saved, number of strokes prevented, and cost of preventive treatment. RESULTS--Depending on the rate of haemorrhagic complications 34 to 83 patients would need to be treated annually with anticoagulants to prevent one stroke; 83 patients would need to be treated with aspirin. Giving anticoagulant treatment only would reduce costs by Kr60 million if the incidence of intracranial haemorrhage were 0.3% but would imply a net expense if the complication rate exceeded 1.3%. The total savings from giving anticoagulant (22,000 patients) and aspirin (55,000 patients) treatment would be Kr175 million per year corresponding to 2 million pounds per million inhabitants each year. CONCLUSIONS--Treatment with anticoagulants and, if contraindications exist, with aspirin is cost effective provided that the risk of serious haemorrhage complications due to anticoagulants is kept low.