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Background: Extended thromboprophylaxis has not been widely implemented in acutely ill medical patients because of bleeding concerns. The MAGELLAN (Multicenter, Randomized, Parallel Group Efficacy and Safety Study for the Prevention of Venous Thromboembolism in Hospitalized Medically Ill Patients Comparing Rivaroxaban With Enoxaparin) and MARINER (Medically Ill Patient Assessment of Rivaroxaban Versus Placebo in Reducing Post-Discharge Venous Thrombo-Embolism Risk) trials evaluated whether rivaroxaban compared with enoxaparin or placebo could prevent venous thromboembolism without increased bleeding. We hypothesized that patients with major bleeding but not those with nonmajor clinically relevant bleeding would be at an increased risk of all-cause mortality (ACM). Methods: We evaluated all bleeding events in patients taking at least 1 dose of study drug and their association with ACM in 4 mutually exclusive groups: (1) no bleeding, or first event was (2) nonmajor clinically relevant bleeding, (3) major bleeding, or (4) trivial bleeding. Using a Cox proportional hazards model adjusted for differences in baseline characteristics associated with ACM, we assessed the risk of ACM after such events. Results: Compared with patients with no bleeding, the risk of ACM for patients with nonmajor clinically relevant bleeding was not increased in MARINER (hazard ratio, 0.43; P =0.235) but was increased in MAGELLAN (hazard ratio, 1.74; P =0.021). Major bleeding was associated with a higher incidence of ACM in both studies, whereas trivial bleeding was not associated with ACM in either study. Conclusions: Patients with major bleeding had an increased risk of ACM, whereas nonmajor clinically relevant bleeding was not consistently associated with an increased risk of death. These results inform the risk-benefit calculus of extended thromboprophylaxis in medically ill patients. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: MAGELLAN, NCT00571649. URL: https://www.clinicaltrials.gov ; Unique identifier: MARINER, NCT02111564.

Although acetylsalicylic acid is of proven benefit for secondary prevention in patients with cardiovascular disease, the risk of recurrent ischemic events remains high. Intensification of antithrombotic therapy with more potent antiplatelet drugs, dual antiplatelet therapy, or vitamin K antagonists further reduces the risk of major adverse cardiovascular events compared with acetylsalicylic acid alone but increases the risk of bleeding without reducing mortality. In patients with prior coronary artery disease or peripheral arterial disease the COMPASS (Cardiovascular Outcomes for People Using Anticoagulation Strategies) trial revealed that compared with acetylsalicylic acid alone, dual pathway inhibition with low-dose rivaroxaban (2.5 mg twice-daily), an oral factor Xa inhibitor, plus acetylsalicylic acid reduced major adverse cardiovascular event by 24%, major adverse limb events by 47%, and mortality by 18%. Major bleeding was increased by 70%, but there was no increase in fatal or intracranial bleeding. This article (1) reviews the results of the COMPASS trial, (2) explains why dual pathway inhibition is superior to antiplatelet or anticoagulant therapy alone, (3) compares the results with rivaroxaban plus aspirin with those with other antithrombotic regimens, and (4) provides insight into how best to apply the COMPASS results into practice.

Recent advances in our understanding of the contribution of thrombin generation to arterial thrombosis and the role of platelets in venous thrombosis have prompted new treatment paradigms. Nonetheless, bleeding remains the major side effect of such treatments spurring the quest for new antithrombotic regimens with better benefit-risk profiles and for safer anticoagulants for existing and new indications. The aims of this article are to review the results of recent trials aimed at enhancing the benefit-risk profile of antithrombotic therapy and explain how these findings are changing our approach to the management of arterial and venous thrombosis. Focusing on these 2 aspects of thrombosis management, this article discusses 4 advances: (1) the observation that in some indications, lowering the dose of some direct oral anticoagulants reduces the risk of bleeding without compromising efficacy, (2) the recognition that aspirin is not only effective for secondary prevention of atherothrombosis but also for prevention of venous thromboembolism, (3) the finding that dual pathway inhibition with the combination of low-dose rivaroxaban to attenuate thrombin generation plus aspirin to reduce thromboxane A2-mediated platelet activation is superior to aspirin or rivaroxaban alone for prevention of atherothrombosis in patients with coronary or peripheral artery disease, and (4) the development of inhibitors of factor XI or XII as potentially safer anticoagulants.

Assessment and Management of Gastrointestinal Hemorrhage in the Setting of Direct Oral Anticoagulants: The Hematology Perspective

Four non–vitamin K antagonist oral anticoagulants (NOACs), including the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban, apixaban, and edoxaban, are currently licensed as alternatives to heparins and vitamin K antagonists for the prevention and treatment of venous thromboembolism and for the prevention of stroke in patients with nonvalvular atrial fibrillation. Dabigatran is the only NOAC that inhibits thrombin; the others inhibit factor Xa. All of the NOACs are at least as effective as vitamin K antagonists for the prevention of stroke in patients with atrial fibrillation and for the treatment of venous thromboembolism, and they are associated with less life-threatening bleeding, in particular less intracranial hemorrhage.1,2 Nonetheless, serious bleeding can occur with NOACs. In addition, patients taking NOACs may sustain trauma and may require urgent surgery or interventions. Consequently, the availability of specific reversal agents for NOACs could improve patient management during these emergency situations. Idarucizumab is a humanized monoclonal antibody fragment that has been developed as a specific reversal agent for dabigatran. In vitro and ex vivo studies have demonstrated that idarucizumab promptly restores dabigatran-prolonged coagulation parameters to baseline values,3–5 and studies in healthy volunteers and patients with life-threatening bleeding or requiring emergency surgery or invasive procedures show that it completely reverses the anticoagulant effects of dabigatran within minutes in the majority of patients. Idarucizumab was recently licensed in the United States and Europe. This article summarizes the pharmacology and clinical data on the use of idarucizumab to reverse dabigatran. The first step in the development of idarucizumab was to immunize mice with dabigatran-derived haptens coupled to carrier proteins to produce antibodies against dabigatran.3 Monoclonal antibodies exhibiting the highest affinity for dabigatran were selected, and the antigen-binding fragment (Fab) was isolated (Figure 1). Murine protein sequences were replaced …

The global burden of valvular heart disease, which currently affects more than 100 million people, is growing with the aging population.1 Severe valvular heart disease is associated with major morbidity and mortality and often necessitates surgical valve replacement with a mechanical or a tissue valve. If the risk of surgery is prohibitive, transcathether valve replacement is another option.2 See accompanying article on page 942 Although mechanical heart valves (MHV) are more durable than tissue valves, they are more thrombogenic. Consequently, patients with MHV require long-term anticoagulation with vitamin K antagonists, such as warfarin.2,3 Although effective, warfarin has well-known limitations, including multiple drug and food interactions, and the challenges of coagulation monitoring and maintaining the international normalized ratio within the therapeutic range. Indeed, variability in the international normalized ratio is a major independent predictor of reduced survival in patients with MHV.4 Consequently, there is a need for effective anticoagulants for MHV patients with better pharmacological profiles than warfarin. Direct oral anticoagulants have replaced warfarin for many indications.5 These agents include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban and edoxaban, which inhibit factor Xa. Despite the proven efficacy and safety of direct oral anticoagulants in the prevention of stroke in patients with atrial fibrillation, and in the prevention and treatment of venous thromboembolism, the unfavorable results of the RE-ALIGN (Randomized, Phase II Study to Evaluate the Safety and Pharmacokinetics of Oral Dabigatran Etexilate in Patients after Heart Valve Replacement) trial prompted the FDA to issue black-box warnings against the use …

Background: The ENGAGE AF-TIMI 48 trial (Effective Anticoagulation With Factor Xa Next Generation in Atrial Fibrillation–Thrombolysis In Myocardial Infarction) compared higher-dose edoxaban regimen (HD-ER) and lower-dose edoxaban regimen with well-managed warfarin in 21 105 patients with atrial fibrillation. The risk factors and clinical impact of gastrointestinal bleeding (GIB) in this trial have not been described in detail. Methods and Results: This analysis was undertaken to identify risk factors for major GIB (MGIB) and compare the severity and outcomes of GIB with edoxaban and warfarin. During 2.8 years mean follow-up, there were 579 MGIB (1.22% per year), of which 63 were life-threatening or fatal (0.13% per year). Male sex, increased age, prior GIB, concomitant aspirin, lower baseline hemoglobin, renal dysfunction, and higher HAS-BLED and CHADS 2 scores were independently associated with the risk of MGIB. Whereas the annual rate of MGIB was higher with HD-ER than with warfarin (1.53% and 1.25%, respectively; hazard ratio, 1.23; 95% confidence interval, 1.02–1.48; P =0.033), the annual rates of life-threatening or fatal GIB were similar (0.15% and 0.18%, respectively). Several indicators of more severe GIB, including hemodynamic instability, hospitalization, ≥ 4 U transfusion, and hemoglobin loss ≥5 g/dL, were similar with HD-ER and warfarin, whereas surgery required to manage bleeding was less frequent with HD-ER. Lower-dose edoxaban regimen, which achieved 50% lower trough edoxaban levels, was associated with significantly less MGIB than warfarin. Conclusions: MGIB occurred more frequently with HD-ER than warfarin. The rates of life-threatening or fatal GIB were low and similar with both HD-ER and warfarin. Clinical outcomes were generally favorable. The correlation between dose, trough edoxaban level, and the risk of GIB risk suggests GIB is exposure-related. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT00781391.

Sepsis is characterized by systemic activation of coagulation and inflammation in response to microbial infection. Although cell-free DNA (cfDNA) released from activated neutrophils has antimicrobial properties, it may also exert harmful effects by activating coagulation and inflammation. The authors aimed to determine whether deoxyribonuclease (DNase) administration reduces cfDNA levels, attenuates coagulation and inflammation, suppresses organ damage, and improves outcome in a cecal ligation and puncture (CLP) model of polymicrobial sepsis. Healthy C57Bl/6 mice were subjected to CLP, a surgical procedure involving two punctures of the ligated cecum, or sham surgery (no ligation/puncture). Mice were given DNase or saline by intraperitoneal injection 2, 4, or 6 h after surgery. Two hours after treatment, organs were harvested and plasma levels of cfDNA, interleukin-6 (IL-6), IL-10, thrombin-antithrombin complexes, lung myeloperoxidase, creatinine, alanine transaminase, and bacterial load were quantified. Survival studies were also performed. The CLP-operated mice had rapid time-dependent elevations in cfDNA that correlated with elevations in IL-6, IL-10, and thrombin-antithrombin complexes and had organ damage in the lungs and kidneys. Administration of DNase at 2 h after CLP resulted in increased IL-6 and IL-10 levels and organ damage in the lungs and kidneys. In contrast, DNase administration at 4 or 6 h after CLP resulted in reduced cfDNA and IL-6 levels, increased IL-10, and suppressed organ damage and bacterial dissemination. Deoxyribonuclease administration every 6 h after CLP also rescued mice from death. Our studies are the first to demonstrate that delayed but not early administration of DNase may be protective in experimental sepsis.

The non-vitamin K antagonist oral anticoagulants (NOACs) are replacing warfarin for many indications. These agents include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban, and edoxaban, which inhibit factor Xa. All 4 agents are licensed in the United States for stroke prevention in atrial fibrillation and for treatment of venous thromboembolism and rivaroxaban and apixaban are approved for thromboprophylaxis after elective hip or knee arthroplasty. The NOACs are at least as effective as warfarin, but are not only more convenient to administer because they can be given in fixed doses without routine coagulation monitoring but also are safer because they are associated with less intracranial bleeding. As part of a theme series on the NOACs, this article (1) compares the pharmacological profiles of the NOACs with that of warfarin, (2) identifies the doses of the NOACs for each approved indication, (3) provides an overview of the completed phase III trials with the NOACs, (4) briefly discusses the ongoing studies with the NOACs for new indications, (5) reviews the emerging real-world data with the NOACs, and (6) highlights the potential opportunities for the NOACs and identifies the remaining challenges.

Background— Thrombosis is the common pathology underlying ischemic heart disease, ischemic stroke, and venous thromboembolism (VTE). The Global Burden of Disease Study 2010 (GBD 2010) documented that ischemic heart disease and stroke collectively caused 1 in 4 deaths worldwide. GBD 2010 did not report data for VTE as a cause of death and disability. Objective— To review the literature on the global burden of disease caused by VTE. Approach and Results— We performed a systematic review of the literature on the global disease burden because of VTE in low-, middle-, and high-income countries. Studies from Western Europe, North America, Australia, and Southern Latin America (Argentina) yielded consistent results with annual incidences ranging from 0.75 to 2.69 per 1000 individuals in the population. The incidence increased to between 2 and 7 per 1000 among those aged ≥70 years. Although the incidence is lower in individuals of Chinese and Korean ethnicity, their disease burden is not low because of population aging. VTE associated with hospitalization was the leading cause of disability-adjusted life-years lost in low- and middle-income countries, and second in high-income countries, responsible for more disability-adjusted life-years lost than nosocomial pneumonia, catheter-related blood stream infections, and adverse drug events. Conclusions— VTE causes a major burden of disease across low-, middle-, and high-income countries. More detailed data on the global burden of VTE should be obtained to inform policy and resource allocation in health systems and to evaluate whether improved use of preventive measures will reduce the burden.

The direct oral anticoagulants (DOACs), which include dabigatran, rivaroxaban, apixaban, and edoxaban, were designed to be given in fixed doses without routine coagulation monitoring. When administered in this manner in trials that included >71 000 patients with atrial fibrillation1 and >27 000 patients with venous thromboembolism,2 the DOACs were at least as effective as vitamin K antagonists but were associated with less serious bleeding, particularly less intracranial bleeding. Eliminating coagulation monitoring simplifies anticoagulation therapy. This feature, together with their proven efficacy and safety, explains why guidelines give preference to the DOACs over vitamin K antagonists for stroke prevention in atrial fibrillation and for the treatment of venous thromboembolism. Although routine coagulation monitoring is unnecessary, there is an urgent need for readily and rapidly available tests to measure the DOACs. This need will increase with the introduction of costly reversal agents such as idarucizumab for dabigatran3 and andexanet alfa for rivaroxaban, apixaban, and edoxaban.4 Idarucizumab is already licensed, and andexanet is undergoing regulatory review and could be approved later this year. What tests are currently available, and why do we need new ones? Although currently available global tests of coagulation such as the activated partial thromboplastin time (aPTT) and prothrombin time (PT) can be useful to assess the anticoagulant effects of dabigatran and some of the oral factor Xa inhibitors, respectively, the sensitivity of these …

The thrombin-thrombomodulin (TM) complex activates thrombin-activable fibrinolysis inhibitor (TAFI) more efficiently than thrombin or plasmin alone. The exosite on TAFI required for its TM-dependent activation by thrombin has not been identified. Based on previous work by us and others, we generated TAFI variants with one or more of residues Lys 42, Lys 43, Lys 44 and Arg 12 within the activation peptide mutated to alanine. Mutation of one, two, or three Lys residues or the Arg residue alone decreased the catalytic efficiency of TAFI activation by thrombin-TM by 2.4-, 3.2-, 4.7-, and 15.0-fold, respectively, and increased the TAFI concentrations required for half-maximal prolongation of clot lysis times (K 1/2 ) by 3-, 4,- 15-, and 24-fold, respectively. Mutation of all four residues eliminated TM binding, decreased the catalytic efficiency of TAFI activation by 45.0-fold, increased the K 1/2 by 130-fold, and abolished antifibrinolytic activity in a clot lysis assay. When thrombin or plasmin was used as the activator, mutation of all four residues reduced the rate of activation by 1.1- and 4.0-fold compared with wild-type TAFI, respectively, suggesting that the mutation only impacted activation kinetics by thrombin-TM. Surface plasmon resonance data show that mutation of the four residues results in complete loss of binding, either in the presence or absence of thrombin. Together, our findings suggest that these four residues are critical for the interaction of TAFI with the thrombin-TM complex that modulates its antifibrinolytic activity.

Objective— Activation of neutrophils by microbial or inflammatory stimuli results in the release of neutrophil extracellular traps (NETs) that are composed of DNA, histones, and antimicrobial proteins. In purified systems, cell-free DNA (CFDNA) activates the intrinsic pathway of coagulation, whereas histones promote thrombin generation through platelet-dependent mechanisms. However, the overall procoagulant effects of CFDNA/histone complexes as part of intact NETs are unknown. In this study, we examined the procoagulant potential of intact NETs released from activated neutrophils. We also determined the relative contribution of CFDNA and histones to thrombin generation in plasmas from patients with sepsis. Approach and Results— NETs released from phorbyl myristate–activated neutrophils enhance thrombin generation in platelet-poor plasma. This effect was DNA dependent (confirmed by DNase treatment) and occurred via the intrinsic pathway of coagulation (confirmed with coagulation factor XII– and coagulation factor XI–depleted plasma). In platelet-rich plasma treated with corn trypsin inhibitor, addition of phorbyl myristate–activated neutrophils increased thrombin generation and shortened the lag time in a toll-like receptor-2– and toll-like receptor-4–dependent mechanism. Addition of DNase further augmented thrombin generation, suggesting that dismantling of the NET scaffold increases histone-mediated, platelet-dependent thrombin generation. In platelet-poor plasma samples from patients with sepsis, we found a positive correlation between endogenous CFDNA and thrombin generation, and addition of DNase attenuated thrombin generation. Conclusions— These studies examine the procoagulant activities of CFDNA and histones in the context of NETs. Our studies also implicate a role for the intrinsic pathway of coagulation in sepsis pathogenesis.

OBJECTIVE:: The objective of this study is to determine the relationship between inflammatory interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP)] and coagulation (D-dimer) biomarkers and the presence and type of anaemia among HIV-positive individuals. DESIGN:: A cross-sectional study. METHODS:: Combination antiretroviral therapy (cART)-treated adults participating in an international HIV trial with haemoglobin and mean corpuscular volume (MCV) measurements at entry were categorized by presence of anaemia (haemoglobin ≤14g/dl in men and ≤12g/dl in women) and, for those with anaemia, by type [microcytic (MCV 100fl)]. We analysed the association between inflammation (IL-6 and hsCRP) and coagulation (D-dimer) and haemoglobin, controlling for demographics (age, race and sex), BMI, HIV plasma RNA levels, CD4 T-cell counts (nadir and baseline), Karnofsky score, previous AIDS diagnosis, hepatitis B/C coinfection and use of zidovudine. RESULTS:: Among 1410 participants, 313 (22.2%) had anaemia. Of these, 4.1, 27.2 and 68.7% had microcytic, normocytic and macrocytic anaemia, respectively. When compared with participants with normal haemoglobin values, those with anaemia were more likely to be older, black, male and on zidovudine. They also had lower baseline CD4 T-cell counts and lower Karnofsky scores. Adjusted relative odds of anaemia per two-fold higher biomarker levels were 1.22 (P=0.007) for IL-6, 0.99 for hsCRP (P=0.86) and 1.35 (P

Supplemental Digital Content is available in the text., Objectives: To determine if a set of time-varying biological indicators can be used to: 1) predict the sepsis mortality risk over time and 2) generate mortality risk profiles. Design: Prospective observational study. Setting: Nine Canadian ICUs. Subjects: Three-hundred fifty-six septic patients. Interventions: None. Measurements and Main Results: Clinical data and plasma levels of biomarkers were collected longitudinally. We used a complementary log-log model to account for the daily mortality risk of each patient until death in ICU/hospital, discharge, or 28 days after admission. The model, which is a versatile version of the Cox model for gaining longitudinal insights, created a composite indicator (the daily hazard of dying) from the “day 1” and “change” variables of six time-varying biological indicators (cell-free DNA, protein C, platelet count, creatinine, Glasgow Coma Scale score, and lactate) and a set of contextual variables (age, presence of chronic lung disease or previous brain injury, and duration of stay), achieving a high predictive power (conventional area under the curve, 0.90; 95% CI, 0.86–0.94). Including change variables avoided misleading inferences about the effects of day 1 variables, signifying the importance of the longitudinal approach. We then generated mortality risk profiles that highlight the relative contributions among the time-varying biological indicators to overall mortality risk. The tool was validated in 28 nonseptic patients from the same ICUs who became septic later and was subject to 10-fold cross-validation, achieving similarly high area under the curve. Conclusions: Using a novel version of the Cox model, we created a prognostic tool for septic patients that yields not only a predicted probability of dying but also a mortality risk profile that reveals how six time-varying biological indicators differentially and longitudinally account for the patient’s overall daily mortality risk.

Objective— The interaction of protein C (PC) with the endothelial PC receptor (EPCR) enhances activated PC generation. We performed targeted gene sequencing of the PC gene ( PROC ) and EPCR genes ( PROCR ) in patients with unprovoked venous thromboembolism (VTE) to determine whether mutations that impair PC–EPCR interactions are associated with an increased risk of VTE. Approach and Results— We sequenced exon 3 of PROC and exons 2 and 3 of PROCR (the exons that encode the protein–protein binding domains of PC and EPCR) in 653 patients with unprovoked VTE and in 627 healthy controls. Five single nucleotide variants, each in individual patients, were identified that result in abnormal PC (Arg9Cys, Val34Met, and Arg-1Cys) or abnormal EPCR proteins (Arg96Cys and Val170Leu). We did not detect any nonsynonymous coding variants in the controls. When the PC variants were expressed in human embryonic kidney 293 cells, all exhibited decreased synthesis, and 2 of the variants had reduced capacity for activated PC generation. When expressed on the surface of human embryonic kidney 293 cells, the EPCR variants showed reduced affinity for fluorescently labeled PC. In addition, the previously reported EPCR A3 haplotype, which promotes cellular shedding of EPCR, is over-represented in the patient group ( P =0.001). Conclusions— This is the first targeted DNA sequencing analysis of PROC and PROCR in a large group of patients with unprovoked VTE. Our data suggest that mutations that impair PC–EPCR interactions may be associated with an increased risk of VTE.

Although new oral anticoagulants are replacing warfarin for stroke prevention in atrial fibrillation and for the prevention and treatment of venous thromboembolism, the lack of antidotes is a concern. Consequently, the development of a potential antidote for oral factor Xa inhibitors, such as rivaroxaban and apixaban, represents a major breakthrough. For decades, vitamin K antagonists (VKAs), such as warfarin, were the only orally available anticoagulants. This situation changed with the recent introduction of oral direct thrombin and factor Xa inhibitors. Designed to be given in fixed doses without laboratory monitoring, the new oral anticoagulants (NOACs) are more convenient to administer than warfarin. When compared with warfarin in large phase III clinical trials, NOACs were at least as effective as warfarin, but were associated with less intracranial bleeding. Despite these advantages, however, some clinicians are reluctant to use NOACs because specific antidotes are lacking. In a recent report in Nature Medicine , Lu et al have taken the first step to addressing this unmet medical need. These investigators developed a bioengineered recombinant variant of factor Xa that serves as an antidote for oral and parenteral factor Xa inhibitors. Not only does the antidote reverse the anticoagulant effect of oral factor Xa inhibitors in vitro and in animals, but it also reduces blood loss induced by these agents in rat tail transection and rabbit liver laceration bleeding models. Based on these promising results, the antidote is now undergoing phase II evaluation in humans. If the preclinical findings are confirmed in humans, this antidote has the potential to increase usage of the oral factor Xa inhibitors and streamline their management in situations where rapid reversal is needed in preparation for urgent surgery or intervention, or in patients with serious bleeding. Oral anticoagulants are used for long-term prevention and treatment of venous and arterial …

Case Presentation: A 78-year–old man with atrial fibrillation, hypertension, and a history of ischemic stroke 2 years earlier presents to the emergency department with hematemesis and melena. He is taking dabigatran (150 mg twice daily) for stroke prevention, and his last dose was taken 12 hours earlier. His hemoglobin is 5.9 g/dL, platelet count is 185×109/L, and calculated creatinine clearance is 26 mL/min. The activated partial thromboplastin time (aPTT) is 83 s and the thrombin time (TT) is >150 s. How would you manage this patient? The Randomized Evaluation of Long-Term Anticoagulant Therapy trial conducted in 18 113 patients with atrial fibrillation demonstrated that, compared with warfarin, dabigatran at a dose of 150 mg twice daily reduced the risk of stroke or systemic embolism by one third and was associated with a similar rate of major bleeding; at a dose of 110 mg twice daily, the risk of stroke or systemic embolism with dabigatran was similar to that with warfarin, but dabigatran reduced the risk of major bleeding by one fifth.1 Both doses of dabigatran reduced the risk of intracranial bleeding by two thirds compared with warfarin. The risk of stroke was consistently reduced in all of the patient subgroups, but in those over the age of 75 years, the higher dose of dabigatran was associated with an increased risk of extracranial bleeding.2 Prescribing guidelines for dabigatran vary by country and should be reviewed before starting the drug. The majority of atrial fibrillation patients with ≥1 additional risk factor for stroke are eligible for dabigatran. Absolute contraindications are uncommon, but include impaired renal function with a calculated creatinine clearance

Introduction: Dabigatran is a non-vitamin K antagonist oral anticoagulant (NOAC) licensed for stroke prevention in nonvalvular atrial fibrillation. In the RE-LY trial, both doses of dabigatran (110 mg and 150 mg bid) were associated with a significantly lower annualized rate of intracranial hemorrhage (ICH) than warfarin (0.23%, 0.32% and 0.76%, respectively). Nonetheless, the mortality rate with ICH in the context of any anticoagulation remains high, probably reflecting the effects of hematoma expansion. Whether a specific reversal agent for dabigatran will improve clinical outcomes in dabigatran-treated patients with ICH is unknown. RE-VERSE AD is an ongoing, open-label, phase 3, cohort study evaluating the extent to which idarucizumab, a humanized Fab fragment directed against dabigatran, reverses the latter’s anticoagulant effects in patients with serious bleeding or in those requiring urgent interventions. This study focuses on the results in patients with ICH. Hypothesis: Compared with historical controls, idarucizumab improves clinical outcomes in dabigatran-treated patients with ICH. Methods: Patients presenting with ICH were given intravenous idarucizumab 5 g as two 2.5 g bolus infusions administered no more than 15 minutes apart. The primary endpoint was the maximum reversal of the anticoagulant effect of dabigatran, based on central laboratory determination of the dilute thrombin time or ecarin clotting time. Results: In an interim analysis at 90 patients, 18 with ICH had been enrolled in RE-VERSE AD. Updated results on the effects of idarucizumab on coagulation parameters, imaging studies, and clinical outcomes in this patient subgroup will be presented. Conclusions: Currently, there are no specific reversal agents for the NOACs. We present the first data on the clinical outcomes for idarucizumab in dabigatran-treated patients who present with ICH.

Vitamin K antagonists, such as warfarin, have been the mainstay of oral anticoagulation for many decades. Although effective, warfarin has numerous limitations, including a variable dose requirement from patient to patient because of differences in dietary vitamin K intake, common genetic polymorphisms, and multiple drug interactions that affect its pharmacodynamics and metabolism. Consequently, warfarin requires frequent monitoring to ensure that a therapeutic anticoagulant effect has been achieved because excessive anticoagulation can lead to bleeding, and because insufficient anticoagulation can result in thrombosis. Such monitoring is burdensome for patients and physicians and is costly for the health care system. These limitations have prompted the development of new oral anticoagulants that target either factor Xa or thrombin. Although the path to the development of these drugs has been long, the new drugs are at least as effective and safe as warfarin, but they streamline clinical care because they can be administered in fixed doses without routine coagulation monitoring. This article focuses on rivaroxaban, apixaban, and edoxaban, the oral factor Xa inhibitors in the most advanced stages of development. After 20 years of discovery research, these agents are already licensed for several indications. Thus, the long path to finding replacements for warfarin has finally reached fruition. Therefore, development of the oral factor Xa inhibitors represents a translational science success story.

Background: There is more major gastrointestinal bleeding (M-GIB) with most NOACs than with warfarin. The clinical impact of this finding is poorly understood. Methods: The ENGAGE AF-TIMI 48 trial compared the efficacy and safety of higher-dose (HD-E: 60 mg/ 30mg) or lower-dose (LD-E: 30 mg/15 mg) edoxaban regimens with dose-adjusted warfarin for prevention of stroke and systemic embolism in non-valvular atrial fibrillation. ISTH definitions for major and life-threatening (LT) bleeding events were utilized. In this pre-specified analysis, we investigated the adjudicated M-GIB events utilizing pre-defined severity and outcome endpoints. Results: Although the risk of M-GIB was higher with HD-E than with warfarin, the risk of LT or fatal GIB was similar (figure), and surgery for GIB was required less frequently with HD-E than warfarin (HR 0.37; 95%CI, 0.16-0.88; p=0.03). The risk for M-GIB-related permanent drug discontinuation was similar with HD-E and warfarin (HR 0.96; 95% CI, 0.67-1.37, p=0.8), as were the risks of hospitalization (HR 1.14; 95%CI, 0.92-1.40, p=0.2) and Hgb decrease > 5 g/dL (HR 1.01; 95%CI, 0.74-1.38; p=0.9). The risks of M-GIB and of LT or fatal GIB were lower with LD-E than with warfarin (Figure), as were the risks of M-GIB-related permanent drug discontinuation (HR 0.51; 95% CI, 0.33-0.78, p=0.002), hospitalization (HR 0.67; 95%CI, 0.53-0.85; p=0.001), Hgb decrease > 5 g/dL (HR 0.58; 95%CI, 0.40-0.84; p=0.003), and M-GIB requiring transfusion of > 2 units of red cells (HR 0.66; 95%CI, 0.50-0.89; p=0.006). Fatal GIB occurred in 2, 3 and 7 patients treated with HD-E, LD-E and warfarin, respectively. Conclusions: M-GIB and LT-GIB with edoxaban are dose-dependent. Although the risk of M-GIB is higher with HD-E than warfarin, the risk of LT-GIB or fatal GIB is similar and the severity and outcomes are no worse than with warfarin. The risks of M-GIB, and of LT-GIB or fatal GIB, are lower with LD-E than warfarin.

Several new oral anticoagulants such as rivaroxaban (which targets Factor Xa) and dabigatran etexilate (which targets thrombin) are in advanced stages of clinical development and are already available for clinical use in some countries. Although these agents do not require routine coagulation monitoring, assays to assess the level of anticoagulation may be of assistance in certain circumstances such as in case of overdose, in patients with a hemorrhagic or thromboembolic event during treatment, or to assess compliance. Moreover, the influence of the new oral anticoagulants on routine coagulation tests must be recognized. The prothrombin time is not suitable for rivaroxaban measurement for several reasons, and the routinely used international normalized ratio for monitoring the vitamin K antagonists cannot be applied to rivaroxaban. Development of universal assays is challenging because the new oral anticoagulants have different targets, and even those with the same target have variable effects on routine coagulation assays. Focusing on rivaroxaban, there is emerging evidence that an anti-Factor Xa assay that uses rivaroxaban-containing plasma calibrators may provide the optimal method for determining plasma rivaroxaban concentrations.

Objective— Although stasis is important in the pathogenesis of deep vein thrombosis (DVT), how it contributes to thrombogenesis is largely unknown. To gain mechanistic insight, we used a rat model of inferior vena cava (IVC) ligation. Methods and Results— Rats were subjected to IVC ligation for 15 to 60 minutes. Ligation resulted in rapid IVC dilatation and by 60 minutes, thrombi were detected in all rats. Small thrombi were detected in the IVC of most rats after 15 minutes of ligation. Thrombi were rich in fibrin, contained aggregated platelets as well as trapped leukocytes and red cells, and most originated at sites of localized endothelial denudation. Immunohistochemical analysis revealed tissue factor (TF)-expressing leukocytes within the thrombi and adherent to the vessel wall. Despite a largely intact vessel wall, endothelial cells also stained for TF. The expression of TF colocalized with that of protein disulfide isomerase (PDI), an enzyme implicated in TF decryption. Conclusions— These findings suggest that the rapid development of DVT after IVC ligation reflects a combination of stasis-induced vein wall injury and enhanced TF expression in endothelial cells and leukocytes. Because TF expression occurs so soon after ligation, new synthesis is unlikely. Instead, stasis-induced venous dilatation with or without exposure of subendothelial TF, may be responsible for vessel wall TF expression. Colocalization of TF and PDI raises the possibility that PDI-mediated TF decryption plays a role in the pathogenesis of DVT.

Objective— The role of host-derived tissue factor (TF) in tumor growth, angiogenesis, and metastasis has hitherto been unclear and was investigated in this study. Methods and Results— We compared tumor growth, vascularity, and responses to cyclophosphamide (CTX) of tumors in wild-type (wt) mice, or in animals with TF levels reduced by 99% (low-TF mice). Global growth rate of 3 different types of transplantable tumors (LLC, B16F1, and ES teratoma) or metastasis were unchanged in low-TF mice. However, several unexpected tumor/context-specific alterations were observed in these mice, including: (1) reduced tumor blood vessel size in B16F1 tumors; (2) larger spleen size and greater tolerance to CTX toxicity in the LLC model; (3) aborted tumor growth after inoculation of TF-deficient tumor cells (ES TF −/− ) in low-TF mice. TF-deficient tumor cells grew readily in mice with normal TF levels and attracted exclusively host-related blood vessels (without vasculogenic mimicry). We postulate that this complementarity may result from tumor-vascular transfer of TF-containing microvesicles, as we observed such transfer using human cancer cells (A431) and mouse endothelial cells, both in vitro and in vivo. Conclusions— Our study points to an important but context-dependent role of host TF in tumor formation, angiogenesis and therapy.

Background— Factor Xa plays a central role in the generation of thrombin, making it a novel target for treatment of arterial thrombosis. Fondaparinux is a synthetic factor Xa inhibitor that has been shown to be superior to standard therapies for the prevention of venous thrombosis. We performed a randomized trial to determine the safety and feasibility of fondaparinux in the percutaneous coronary intervention (PCI) setting. Methods and Results— A total of 350 patients undergoing elective or urgent PCI were randomized in a blinded manner to receive unfractionated heparin (UFH), 2.5 mg fondaparinux IV, or 5.0 mg fondaparinux IV. Randomization was stratified for planned or no planned use of glycoprotein (GP) IIb/IIIa antagonists. The primary safety outcome was total bleeding, which was a combination of major and minor bleeding events. The incidence of total bleeding was 7.7% in the UFH group and 6.4% in the combined fondaparinux groups (hazard ratio, 0.81; 95% confidence interval, 0.35 to 1.84; P =0.61). Bleeding was less common in the 2.5-mg fondaparinux group compared with the 5-mg fondaparinux group (3.4% versus 9.6%, P =0.06). The composite efficacy outcome of all-cause mortality, myocardial infarction, urgent revascularization, or need for a bailout GPIIb/IIIa antagonist was 6.0% in the UFH group and 6.0% in the fondaparinux group, with no significant difference in efficacy among the fondaparinux doses compared with UFH. Coagulation marker analysis at 6 and 12 hours after PCI demonstrated that fondaparinux was superior to UFH in inducing a sustained reduction in markers of thrombin generation, as measured by prothrombin fragment F1.2 ( P =0.02). Conclusions— In this pilot study of patients undergoing contemporary PCI, factor Xa inhibition with the synthetic anticoagulant fondaparinux in doses of 2.5 and 5.0 mg was comparable to UFH for clinical safety and efficacy outcomes. These data form the basis for further evaluation of fondaparinux in arterial thrombosis.

—The limitations of traditional anticoagulants, heparin and warfarin, have prompted the development of new anticoagulant drugs for prevention and treatment of both venous and arterial thromboembolism. After a brief review of thrombogenesis and its regulation, this study focuses on new anticoagulant agents in more advanced stages of clinical testing.

Background — We studied whether aspirin resistance, defined as failure of suppression of thromboxane generation, increases the risk of cardiovascular events in a high-risk population. Methods and Results — Baseline urine samples were obtained from 5529 Canadian patients enrolled in the Heart Outcomes Prevention Evaluation (HOPE) Study. Using a nested case-control design, we measured urinary 11-dehydro thromboxane B 2 levels, a marker of in vivo thromboxane generation, in 488 cases treated with aspirin who had myocardial infarction, stroke, or cardiovascular death during 5 years of follow-up and in 488 sex- and age-matched control subjects also receiving aspirin who did not have an event. After adjustment for baseline differences, the odds for the composite outcome of myocardial infarction, stroke, or cardiovascular death increased with each increasing quartile of 11-dehydro thromboxane B 2 , with patients in the upper quartile having a 1.8-times-higher risk than those in the lower quartile (OR, 1.8; 95% CI, 1.2 to 2.7; P =0.009). Those in the upper quartile had a 2-times-higher risk of myocardial infarction (OR, 2.0; 95% CI, 1.2 to 3.4; P =0.006) and a 3.5-times-higher risk of cardiovascular death (OR, 3.5; 95% CI, 1.7 to 7.4; P Conclusions — In aspirin-treated patients, urinary concentrations of 11-dehydro thromboxane B 2 predict the future risk of myocardial infarction or cardiovascular death. These findings raise the possibility that elevated urinary 11-dehydro thromboxane B 2 levels identify patients who are relatively resistant to aspirin and who may benefit from additional antiplatelet therapies or treatments that more effectively block in vivo thromboxane production or activity.

Most acute coronary syndromes are caused by intracoronary thrombus superimposed on disrupted atherosclerotic plaque. Platelets adhere to subendothelial proteins exposed at sites of plaque disruption where they become activated, release vasoactive and procoagulant substances, and aggregate.1 Tissue factor in the lipid-rich core of the plaque initiates coagulation, which leads to thrombin generation. A potent platelet agonist, thrombin recruits additional platelets to the site of vascular injury. Thrombin also converts fibrinogen to fibrin, which serves to stabilize platelet-rich thrombi formed at sites of plaque disruption. Depending on the extent and duration of coronary artery obstruction, clinical manifestations range from unstable angina to acute myocardial infarction.1 Aspirin and heparin, the cornerstones of therapy for acute coronary syndromes, reduce the risk of myocardial infarction and death.2,3⇓ Despite the widespread use of these treatments, however, patients with unstable angina or acute myocardial infarction remain at risk for recurrent ischemic events, suggesting that intracoronary thrombus formation is incompletely attenuated by aspirin and heparin. High concentrations of thrombin are generated by tissue factor exposed at sites of arterial injury.4 When bound to fibrin,5,6⇓ fibrin degradation products,7 or subendothelial matrix,8 thrombin is resistant to inactivation by the heparin/antithrombin complex. Bound thrombin, which remains enzymatically active, triggers thrombus growth by activating factors V, VIII, and XI,9 thereby amplifying thrombin generation. Bound thrombin also activates platelets,10 at least in part, via thromboxane A2-independent pathways that are not blocked by aspirin. Because thrombin plays a central role in arterial thrombogenesis, the goal of most treatment regimens is to block thrombin generation or inhibit its activity. Direct thrombin inhibitors were developed to overcome the inability of the heparin/antithrombin complex to inactivate bound thrombin. In contrast to heparin and low-molecular-weight heparin, which catalyze the inactivation of thrombin by antithrombin, …

Adjunctive anticoagulant therapy reduces the risk of recurrent infarction and death in patients with ST-segment elevation myocardial infarction (STEMI) receiving fibrinolytic therapy.1–5 Unfractionated heparin (UFH), the first anticoagulant evaluated for this indication,1 continues to be used because of its predominantly nonrenal clearance, short half-life, reversibility, and the familiarity of clinicians with the drug. However, the anticoagulant response to UFH is unpredictable, which necessitates coagulation monitoring, and the time to achieve a therapeutic anticoagulant effect can vary from patient to patient. This is problematic because failure to achieve a therapeutic anticoagulant effect with UFH has been associated with an increased risk of recurrent ischemic events.6 Article p 1195 In this edition of Circulation , Cheng and colleagues report the results of their study exploring the clinical predictors of initial nontherapeutic anticoagulation with UFH in a subset of 6055 patients with STEMI enrolled in the Enoxaparin and Thrombolysis Reperfusion for Acute Myocardial Infarction Treatment-Thrombolysis in Myocardial Infarction (ExTRACT-TIMI)–25 trial.7 In this patient subset, UFH was given as an initial bolus dose of 60 U/kg (maximum 4000 U) followed by an intravenous infusion of 12 U/hr (maximum 1000 U/hr) according to the American College of Cardiology/American Heart Association (ACC/AHA)-recommended weight-based nomogram.8,9 Subsequent UFH dose adjustments, which were standardized via a central interactive voice response system, were based on the results of the activated partial thromboplastin time (aPTT). The trial protocol mandated continuation of UFH for a minimum of 48 hours. Patients in whom the UFH infusion was interrupted before the first aPTT measurement (4 to 8 hours …

Vitamin K antagonists (VKAs) such as warfarin are the only oral anticoagulants currently available for clinical use. Warfarin has numerous limitations, including slow onset and offset of action, a narrow therapeutic window, and a metabolism that is affected by diet, drugs, and genetic polymorphisms.1 Because of its unpredictable dose response, warfarin requires careful coagulation monitoring to ensure that a therapeutic anticoagulant effect is achieved.2 Variable dose requirements, concern about the risk of bleeding, and the need for frequent coagulation monitoring have prompted the development of new oral anticoagulants to replace warfarin. With a predictable anticoagulant response and little potential for food or drug interactions, these new agents have been designed to be administered in fixed doses without coagulation monitoring. Consequently, these drugs have the potential to simplify long-term anticoagulant therapy. Article p 180 The features of the new oral anticoagulants in the most advanced stages of clinical development are listed in the Table and are compared with those of warfarin. Unlike warfarin, which reduces the functional levels of factors II (prothrombin), VII, IX, and X, these novel agents are directed against the active site of factor Xa or thrombin, the enzymes responsible for thrombin generation and fibrin formation, respectively (see the Figure). Rivaroxaban and apixaban target factor Xa, whereas dabigatran etexilate inhibits thrombin. View this table: Comparison of Warfarin to New Oral Anticoagulants in Advanced Stages of Clinical Development Targets of new oral anticoagulant drugs. Oral factor Xa inhibitors (rivaroxaban, apixaban) bind directly to factor Xa and prevent thrombin generation. Dabigatran etexilate, an orally active direct thrombin inhibitor, undergoes metabolic activation to dabigatran, which binds to the active site of thrombin (factor IIa) and blocks its capacity to convert fibrinogen to fibrin, to activate platelets, and to amplify its own generation by activating factors V, VIII, and XI. By blocking the …

Background —Patients with acute ischemic syndromes (AIS) suffer high rates of recurrent ischemic events despite aspirin treatment. Long-term therapy with oral anticoagulants in addition to aspirin may reduce this risk. We studied the effects of long-term warfarin at 2 intensities in patients with AIS without ST elevation in 2 consecutive randomized controlled studies. Methods and Results —In phase 1, after the cessation of 3 days of intravenous antithrombotic therapy, 309 patients were randomized to receive fixed low-dose (3 mg/d) warfarin for 6 months that produced a mean international normalized ratio (INR) of 1.5±0.6 or to standard therapy. Eighty-seven percent of patients received aspirin in both groups. The rates of cardiovascular (CV) death, new myocardial infarction (MI), and refractory angina at 6 months were 6.5% in the warfarin group and 3.9% in the standard therapy group (relative risk [RR], 1.66; 95% CI, 0.62 to 4.44; P =0.31). The rates of death, new MI, and stroke were 6.5% in the warfarin group and 2.6% in the standard therapy group (RR, 2.48; 95% CI, 0.80 to 7.75; P =0.10). The overall rate of rehospitalization for unstable angina was 21% and did not differ significantly between the groups. Four patients in the warfarin group (2.6%) and none in the control group experienced a major bleed (RR, 2.48; 95% CI, 0.80 to 7.75), and there was a significant excess of minor bleeds in the warfarin group (14.2% versus 2.6%; RR, 5.46; 95% CI, 1.93 to 15.5; P =0.001). In phase 2, the protocol was modified, and 197 patients were randomized P =0.08). The rates of all death, new MI, and stroke were 5.1% in the warfarin group and 13.1% in the standard therapy group (RR, 0.39; 95% CI, 0.14 to 1.05; P =0.05). Significantly fewer patients were rehospitalized for unstable angina in the warfarin group than in the control group (7.1% and 17.2%, respectively; RR, 0.42; 95% CI, 0.18 to 0.96; P =0.03). Two patients in the warfarin group and 1 in the control group experienced a major bleed, and there was a significant excess of minor bleeds in the warfarin group (28.6% versus 12.1%; RR, 2.36; 95% CI, 1.37 to 4.36; P =0.004). Conclusions —Long-term treatment with moderate-intensity warfarin (INR, 2.0 to 2.5) plus aspirin but not low-intensity warfarin (INR, 1.5) plus aspirin appears to reduce the rate of recurrent ischemic events in patients with AIS without ST elevation.

Background —Thrombolytic therapy induces a procoagulant state characterized by elevated plasma levels of fibrinopeptide A (FPA), but the responsible mechanism is uncertain. Methods and Results —Washed plasma clots were incubated in citrated plasma in the presence or absence of tissue plasminogen activator (t-PA), and FPA generation was monitored as an index of unopposed thrombin activity. FPA levels are almost twofold higher in the presence of t-PA than in its absence. This primarily reflects the action of thrombin bound to soluble fibrin degradation products because (a) there is progressive FPA generation even after clots are removed from t-PA–containing plasma, and (b) clot lysates produce concentration-dependent FPA generation when incubated in citrated plasma. Using thrombin-agarose affinity chromatography, (DD)E and fragment E but not d -dimer were identified as the thrombin-binding fibrin fragments, indicating that the thrombin-binding site is located within the E domain. Heparin inhibits thrombin bound to fibrin degradation products less effectively than free thrombin. In contrast, D-Phe-Pro-ArgCH 2 Cl, hirudin and hirugen inhibit free thrombin and thrombin bound to fibrin degradation products equally well. Conclusions —Thrombin bound to soluble fibrin degradation products is primarily responsible for the increase in FPA levels that occurs when a clot undergoes t-PA–induced lysis. Like clot-bound thrombin, thrombin bound to fibrin derivatives is protected from inhibition by heparin but susceptible to inactivation by direct thrombin inhibitors. These findings help to explain the superiority of direct thrombin inhibitors over heparin as adjuncts to thrombolytic therapy.

An estimated 2 million people in the United States develop venous thromboembolism (VTE) annually. Anticoagulant therapy is the mainstay of VTE treatment. Once the diagnosis of VTE is established, prompt anticoagulation is necessary to prevent thrombus growth and to reduce the risk of pulmonary embolism (PE). At present, rapid anticoagulation can only be effected with parenteral agents. Low-molecular-weight heparin (LMWH) is rapidly replacing unfractionated heparin as the drug of choice for the initial treatment of most VTE patients. Because it can be given subcutaneously once or twice daily without coagulation monitoring, LMWH allows out-of-hospital management of patients with uncomplicated VTE, an approach that reduces healthcare costs and improves patient satisfaction. Extended anticoagulant treatment is necessary to prevent recurrent VTE. Vitamin K antagonists are the agents most often used for this purpose, and warfarin is the current drug of choice in North America. Recent clinical trials have provided important information regarding the optimal …

Treatment of venous thromboembolism (VTE) usually starts with concomitant administration of heparin or low-molecular-weight heparin (LMWH) and a vitamin K antagonist. The parenteral anticoagulant, which is given for at least 5 days, is stopped once the vitamin K antagonist produces a therapeutic level of anticoagulation. Although the introduction of LMWH has simplified the initial treatment of VTE, problems remain. LMWH must be given by daily subcutaneous (SC) injection and vitamin K antagonists require routine coagulation monitoring, which is inconvenient for patients and physicians. Recently, 3 new anticoagulants have been introduced in an attempt to overcome these limitations. These include fondaparinux and idraparinux, synthetic analogs of the pentasaccharide sequence that mediates the interaction of heparin and LMWH with antithrombin, and ximelagatran, an orally active inhibitor of thrombin. These agents produce a predictable anticoagulant response; thus, routine coagulation monitoring is unnecessary. Because they do not bind to platelets or platelet factor 4, fondaparinux and idraparinux do not cause heparin-induced thrombocytopenia (HIT). Unlike vitamin K antagonists, ximelagatran has a rapid onset of action, thereby obviating the need for concomitant administration of a parenteral anticoagulant when starting treatment. The lack of an antidote for these new agents is a drawback, particularly for idraparinux, which has a long half-life.

Deciphering the cryptic macromolecular messages that regulate the state of the vasculature is challenging. One of the ongoing questions is the role of heparan sulfate proteoglycans (HSPG) in such processes as hemostasis, vascular remodeling, inflammation, and angiogenesis.1 This is important because heparin preparations, the medicinal counterparts of HSPG, are cornerstones for prevention and treatment of thrombosis. Heparin preparations have evolved in recent years with the introduction of heparin fractions with reduced molecular weight. Low-molecular-weight heparin (LMWH) has a longer half-life than unfractionated heparin (UFH) and produces a more predictable anticoagulant response, properties that explain why LMWH is gradually replacing UFH for most clinical indications. What is unknown, however, is how refinements designed to improve the anticoagulant properties of heparin affect other heparin activities, such as its interaction with heparin-binding proangiogenic growth factors and their receptors. See page 2110 In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Khorana and colleagues2 provide insight into this question. This study builds on the observations that (a) meta-analyses of clinical trials comparing heparin with LMWH for treatment of venous thromboembolism indicate improved survival in cancer patients given LMWH, and (b) proangiogenic growth factors, such as basic fibroblast growth factor (bFGF) and certain isoforms of vascular endothelial growth factor (VEGF), bind heparin, a property that can modulate their bioavailability and their interactions with high-affinity receptors.1–3 Using in vitro assays of bFGF-induced angiogenesis, Khorana et al2 examined the effects of an array of heparin fractions …

After almost two decades of intensive research, low-molecular-weight heparins have established their niche as an important class of antithrombotic compounds. The demonstration that these compounds are safe and effective for the prevention and treatment of venous thromboembolism has led to the licensing of several of them in Europe and North America. In addition, danaparoid sodium, which is a mixture of dermatan sulfate, heparan sulfate, and chondroitin sulfate, is often used for the treatment of heparin-induced thrombocytopenia.1 Low-molecular-weight heparins have replaced unfractionated heparin in many parts of Europe but are only now finding their place in North America. Their use is . . .

Acquired dysfibrinogenemia was documented in a 4-year-old child with obstructive jaundice of 1-month duration, secondary to a choledochal cyst involving the distal common bile duct. It was characterized by decreased thrombin coagulable protein with elevated immunoassayable fibrinogen resulting in abnormal thrombin and reptilase times. The liver morphology was compatible with extrahepatic obstruction, without evidence of cirrhosis or hepatocyte abnormality. All the coagulation abnormalities promptly resolved after surgical correction of the obstruction. Dysfibrinogenemia has been associated with serious liver disease in adults, including tumors, chronic active hepatitis, and cirrhosis, but never with isolated obstructive jaundice. This report documents a case of acquired dysfibrinogenemia due to extra-hepatic biliary obstruction and also emphasizes the importance of the consideration of this disorder in coagulation abnormalities associated with hepatobiliary disease.