Anticoagulation with argatroban using hemoclot™ targets is safe and effective in CARDS patients receiving venovenous extracorporeal membrane oxygenation: An exploratory bi-centric cohort study

Direct thrombin inhibitors, including argatroban, are increasingly used for anticoagulation during venovenous extracorporeal membrane oxygenation (VV ECMO). In many centers activated partial thromboplastin time (aPTT) is used for monitoring, but it can be affected by several confounders. The aim of this study was to evaluate the safety and efficacy of anticoagulation with argatroban titrated according to diluted thrombin time targets (hemoclot™ assay) compared to anti-Xa guided anticoagulation with unfractionated heparin (UFH).

METHODS

This cohort study included adults at two tertiary care centers who required VV ECMO for severe COVID-19-related acute respiratory distress syndrome (CARDS). Patients received center-dependent argatroban or UFH for anticoagulation during ECMO. Argatroban was guided following a hemoclot™ target range of 0.4-0.6 μg/ml. UFH was guided by anti-factor Xa (antiXa) levels (0.2-0.3 IU/ml). The primary outcome was safety of argatroban compared to UFH, assessed by time to first clinically relevant bleeding event or death during ECMO. Secondary outcomes included efficacy (time to thromboembolism) and feasibility (proportion of anticoagulation targets within range).

RESULTS

From 2019 to 2021 57 patients were included in the study with 27 patients (47 %) receiving argatroban and 30 patients (53 %) receiving UFH. The time to the first clinically relevant bleeding or death during ECMO was similar between groups (HR (argatroban vs. UFH): 1.012, 95 % CI 0.44-2.35, p = 0.978). Argatroban was associated with a decreased risk for thromboembolism compared to UFH (HR 0.494 (95 % CI 0.26-0.95; p = 0.034)). The overall proportion of anticoagulation within target ranges was not different between groups (46 % (23-54 %) vs. 46 % (37 %-57 %), p = 0.45).

CONCLUSION

Anticoagulation with argatroban according to hemoclot™ targets (0.4-0.6 μg/ml) compared to antiXa guided UFH (0.2-0.3 IU/ml) is safe and may prolong thromboembolism-free time in patients with severe ARDS requiring VV ECMO.

Monitoring Direct Thrombin Inhibitors With Calibrated Diluted Thrombin Time vs Activated Partial Thromboplastin Time in Pediatric Patients

OBJECTIVES

Activated partial thromboplastin time (aPTT) is the primary test used to monitor intravenous (IV) direct thrombin inhibitors (DTIs) but has many limitations. The plasma diluted thrombin time (dTT) has shown better correlation with DTI levels than aPTT. This study compared dose-response curves for dTT and aPTT in pediatric patients receiving argatroban and bivalirudin.

METHODS

A retrospective review of pediatric patients treated with argatroban (n = 45) or bivalirudin (n = 14) monitored with dTT and aPTT.

RESULTS

The dTT assay was calibrated to report DTI concentrations in µg/mL for argatroban and bivalirudin with good analytic sensitivity and specificity. The dTT was fivefold more likely to show a stable dose-response slope than the aPTT (P < .0002; odds ratio, 4.9). For patients in whom both dTT and aPTT showed a significant correlation between dose and assay results, dTT had a higher average correlation factor compared with aPTT (P = .007). Argatroban dose-response slopes showed more inter- and intrapatient variation than bivalirudin (dose-response slope coefficient of variation, 132% vs 52%).

CONCLUSIONS

The dTT assay was more likely to show a stable dose response and have a stronger correlation with DTI dose than aPTT. Argatroban shows more variation in dose response than bivalirudin.

Production and Testing of RNA Origami Anticoagulants

Nucleic acid nanotechnology provides the ability to create unprecedented nanostructures with diverse architectures and functions that can be utilized in myriad fields. A set of self-folding, single-stranded RNA origami structures bearing thrombin RNA aptamers have been demonstrated to act as anticoagulants. Here, we describe the detailed methods of producing and testing of such RNA origami anticoagulants. This method highlights the potential of RNA origami for biomedical applications.

Modified thromboelastometric tests provide improved sensitivity and specificity to direct oral anticoagulants compared to standard thromboelastometric tests in-vitro

Background

The detection of direct oral anticoagulants (DOACs) is still challenging but important in emergency patients. We recently demonstrated that modified thromboelastometry can detect rivaroxaban and dabigatran. Data on the detection rates of modified compared to standard thromboelastometric tests of apixaban and edoxaban, are missing. The aim of this in-vitro dose-effect-study was to add data on these DOACs and to evaluate thromboelastometric tests in-vitro using data of both studies.

Methods

The study was approved by the Ludwig-Maximilians-University ethics committee (No 17-525-2). Written informed consent was obtained from all individuals. Blood samples of healthy volunteers and samples of 10 volunteers for each DOAC were used. Blood samples were spiked with six different concentrations of edoxaban and apixaban (0ng/ml; 31.25ng/ml; 62.5ng/ml; 125ng/ml; 250 ng/ml; 500ng/ml). Modified tests (low-tissue-factor test TFTEM and ecarin-based test ECATEM) as well as standard tests (e.g. FIBTEM) analyzing extrinsic pathway of coagulation were used. Receiver operating characteristics analyzes were performed as well as regression analyzes.

Results

TFTEM CT correlated well with anti-Xa levels of apixaban and edoxaban (apixaban: r² = 0.8064 p < 0.0001; edoxaban: r² = 0.8603; p < 0.0001). The detection of direct FXa inhibitors (> 30 ng/mL) was successful with FIBTEM CT with a sensitivity and specificity of 81% and 90%, respectively. As expected, ECATEM CT was not prolonged by direct FXa-inhibitors due to its specificity for direct thrombin inhibitors. Again, TFTEM CT provided the highest sensitivity and specificity for the detection of direct FXa inhibitors with 96% and 95%, respectively. ECATEM test showed 100% sensitivity and 100% specificity for the detection of dabigatran.

Conclusions

Our study presents modified thromboelastometric tests with improved detection of even low DOAC concentrations > 30 ng/mL, including apixaban in-vitro. The study thus complements the previously published data on dabigatran and rivaroxaban. Validation studies must confirm the results due to the explanatory design of this study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-022-00400-3.

Intervention in COVID-19 linked hypercoaguable states characterized by circuit thrombosis utilizing a direct thrombin inhibitor

•Circuit thrombosis complicates CRRT in COVID-19 despite standard heparin-based anticoagulation regimens.•5 cases of CRRT thrombosis despite heparin-based anticoagulation resolved using a direct thrombin inhibitor, argatroban.•Changes in fibrinogen levels better reflected response to anticoagulation than did changes in D-dimer levels.•High fibrinogen levels and decreased anti-thrombin III activity may relate to argatroban superiority in these cases.

Real-world Comparisons of Direct Oral Anticoagulants for Stroke Prevention in Asian Patients with Non-valvular Atrial Fibrillation: a Systematic Review and Meta-analysis

BACKGROUND

Whether four direct oral anticoagulants (DOACs) are superior to warfarin among Asians with non-valvular atrial fibrillation (NVAF) remains unclear in the real-world setting.

METHODS

We searched PubMed and Medline + Journals@Ovid + EMBASE from September 17, 2009 to May 4, 2019 to perform a systematic review and meta-analysis of all observational real-world studies comparing four DOACs with warfarin specifically focused on Asian patients with NVAF.

RESULTS

From the original 212 results retrieved, 18 studies were included in the meta-analysis. Overall, DOACs were associated with lower risks of thromboembolism (hazard ratio; [95% confidence interval], 0.70; [0.63-0.78]), acute myocardial infarction (0.67; [0.57-0.79]), all-cause mortality (0.62; [0.56-0.69]), major bleeding (0.59; [0.50-0.69]), intracranial hemorrhage (0.50; [0.40-0.62]), gastrointestinal bleeding (0.66; [0.46-0.95]), and any bleeding (0.82; [0.73-0.92]) than warfarin. There was statistic heterogeneity between DOACs for the risks of thromboembolism (P interaction = 0.03) and acute myocardial infarction (P interaction = 0.007) when compared to warfarin. However, all DOACs showed lower risks of thromboembolism and acute myocardial infarction than warfarin when pooling studies that compared individual DOAC with warfarin. With regard to the other outcomes when compared to warfarin, there was no statistical heterogeneity between DOACs. In addition, the effectiveness and safety of four DOACs versus warfarin persisted in the subgroups of either standard-dose or low-dose DOACs.

CONCLUSIONS

The meta-analysis shows that the DOACs had greater effectiveness and safety compared to warfarin in real-world practice for stroke prevention, among Asian patients with NVAF.

VE-1902-A direct thrombin inhibitor with reversible covalent mechanism of action shows efficacy with reduced bleeding in rodent models of thrombosis

INTRODUCTION

High incidence of bleeding events remains a key risk for patients taking anticoagulants, especially those in need of long-term combination therapy with antiplatelet agents. As a consequence, patients may not receive clinically indicated combination antithrombotic therapy. Here, we report on VE-1902, a member of a novel class of precision oral anticoagulants (PROACs) that combines effective anticoagulation with reduced bleeding in preclinical testing.

METHODS AND RESULTS

Acting through covalent, reversible active-site modification of thrombin similar to a previously described molecule [1], VE-1902 shows potency and selectivity for thrombin inhibition in human plasma comparable to clinically relevant direct thrombin inhibitors (DTI) such as argatroban and dabigatran (thrombin generation assay ETP EC₅₀ = 1.3 μM compared to 0.36 μM and 0.31 μM for argatroban and dabigatran; >100-fold selectivity against related serine proteases). Unlike the current anticoagulants, VE-1902 does not significantly inhibit thrombin-mediated platelet activation in in vivo models of thrombosis. In the thrombin generation assay, the compound inhibits thrombin formation without significantly delaying the initiation phase of the clotting cascade. These features are possibly responsible for the observed reduced bleeding in tail bleeding and saphenous vein bleeding models. Consistent with this novel pharmacological profile, VE-1902 shows efficacious anticoagulation in several fibrin-driven animal models of thrombosis (arteriovenous shunt, venous stasis thrombosis, and thrombin-induced thromboembolism models), whereas it does not significantly prevent arterial occlusion in the platelet dependent FeCl₃ model.

CONCLUSIONS

By leaving platelet activation following vascular injury mostly unaffected, VE-1902, and the PROACs more generally, represent a new generation of precision anticoagulants with reduced bleeding risk.

Influence of Direct Thrombin Inhibitor and Low Molecular Weight Heparin on Platelet Function in Patients with Coronary Artery Disease: A Prospective Interventional Trial

INTRODUCTION

The interaction between anticoagulants and platelet function is complex. Previous publications showed mixed results regarding the role of heparins in platelet aggregation. On the other hand, the direct thrombin inhibitor (DTI) dabigatran might enhance the risk of myocardial infarction in patients with atrial fibrillation, which could be related to increased platelet aggregability.

METHODS

This was a prospective, interventional study of patients with chronic coronary artery disease (CAD) taking low-dose aspirin. The objective of the current study was to compare the effects of dabigatran versus enoxaparin on platelet aggregability. Subjects initially were on orally administered dabigatran for 5 days followed by subcutaneously administered enoxaparin after a 30-day washout period. Platelet function was assessed at baseline and after each intervention by multiple electrode aggregometry (MEA-ASPI) (primary endpoint), serum thromboxane B2 (TXB2), VerifyNow Aspirin™, and coagulation tests (secondary endpoints).

RESULTS

Compared to baseline MEA-ASPI values, dabigatran increased platelet aggregation while enoxaparin decreased platelet aggregation (+ 5 U ± 24.1 vs - 6 U ± 22.2, respectively, p = 0.012). The TXB2 assay showed the same pattern (+ 2 pg/ml for dabigatran vs - 13 pg/ml for enoxaparin, p = 0.011). None of the additional tests showed significant differences between the groups. Individually, compared to baseline TXB2 results, enoxaparin significantly decreased platelet activation [33 (16.5-95) pg/mL vs 20 (10-52) pg/mL, respectively, p = 0.026], but no significant differences were observed with dabigatran.

CONCLUSIONS

DTI and anti-Xa drugs exert opposite effects on platelet function. A significant decrease in platelet activation through COX1 (also known as prostaglandin G/H synthase 1) was observed with enoxaparin, but no significant differences in platelet function were observed with dabigatran.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02389582.

Comparison of polyspecific versus IgG specific ELISA in predominately cardiac patients with suspected heparin induced thrombocytopenia

A diagnosis of heparin induced thrombocytopenia (HIT) must often be made based on clinical and laboratory evidence. This was a quasi-experimental study of patients admitted from June 2016 to October 2017. The primary endpoint was the incidence of false positive results in polyspecific and IgG specific enzyme-linked immunosorbent assay (ELISA); then we compared the sensitivity and specificity of each assays in predominately cardiac patients with suspected HIT. A sensitivity/specificity analysis was conducted using serotonin release assay (SRA) as the 'gold standard'. The secondary outcome measures included length of hospital stay. We identified a total of 155 patients who met the inclusion criteria. Confirmatory tests with SRA on both groups were completed; false positive result was higher in the polyspecific group when compared to the IgG group [60% vs. 5%]. The IgG specific ELISA test yielded a sensitivity of 100% and a specificity of 95% however, the polyspecific ELISA had a low yield for specificity of 24% but maintained 100% sensitivity. In the IgG specific group with HIT-, their median length of stay was halved compared to those who were HIT + ; hospital LOS in days, IQR [30 (27-81) vs. 15 (7-33) p = 0.023] and a shorter median LOS in the ICU, IQR [24 (5-47) vs. 6 (2-14); p = 0.079]. Hospital or ICU LOS was the same in both (HIT+ and HIT-) groups managed with polyspecific ELISA. The IgG specific test had few false positive results and a high sensitivity score. Ensuring appropriate testing can bring a substantial decrease in drug expenditure, reduced length of stay and prevent unnecessary anticoagulation.

Direct Oral Anticoagulants in Addition to Antiplatelet Therapy for Secondary Prevention after Acute Coronary Syndromes: a Review

PURPOSE OF REVIEW

As the management of acute coronary syndrome (ACS) continues to evolve, many old practices proved to be of a little benefit and other approaches established the new pillars of modern medicine. Treating ACS patients with dual antiplatelet therapy (DAPT) for a year by combining aspirin and a P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) has resulted in better outcomes and is currently the standard of therapy. However, owing to the persistent activation of the coagulation cascade, patients may continue to experience recurrent ischemia and high mortality rates despite compliance with the dual antiplatelet therapy. Research is underway to establish new treatment modalities for secondary prevention post-ACS, including the use of the novel direct oral anticoagulants (DOACs).

RECENT FINDINGS

Multiple trials have been conducted to evaluate the use of DOACs for the secondary prevention after ACS. Recent emerging data showed that the addition of rivaroxaban in a very low dose of 2.5 mg twice daily to the regular DAPT regimen after ACS is beneficial in the reduction of major cardiovascular events, including recurrent myocardial infarction (MI) and strokes. On the other hand, other DOACs, including apixaban, did not show similar efficacy and did not improve the cardiovascular outcomes. Patients who experience an ACS continue to suffer long-term consequences and thromboembolic complications. Many studies have shown that after the initial ACS event, patients remain in a hypercoagulable state and are more prone to recurrent ischemic attacks including stroke, recurrent MI, or unstable angina (UA). With the objective of seeking better outcomes, it is imperative to explore more aggressive anticoagulation strategies in ACS patients. In this article, we discuss the progress that was made and the limitations we face regarding the role of different anticoagulants in this setting.

The risk of acute kidney injury in Asians treated with apixaban, rivaroxaban, dabigatran, or warfarin for non-valvular atrial fibrillation: A nationwide cohort study in Taiwan

BACKGROUND

Whether or not non-vitamin K antagonist oral anticoagulants (NOACs) are associated with a lower risk of acute kidney injury (AKI) in patients with non-valvular atrial fibrillation (NVAF) remains unknown in real world practice.

METHODS

In this nationwide retrospective cohort study, 1507, 3200, 5765 and 4227 NVAF patients with chronic kidney disease (CKD) and 4368, 16,945, 22,301, and 16,908 NVAF patients without CKD taking apixaban, dabigatran, rivaroxaban, and warfarin, respectively, from June 1, 2012 to December 31, 2016 were enrolled from the Taiwan National Health Insurance Program. Propensity-score weighted method was used to balance covariates across study groups. Patients were followed until occurrence of AKI or end date of study.

RESULTS

Three NOACs were all associated with a significantly lower risk of AKI compared with warfarin for both CKD-free (hazard ratio, [95% confidential interval]; 0.65, [0.60-0.72] for apixaban; 0.68, [0.64-0.74] for dabigatran; 0.73, [0.68-0.79] for rivaroxaban) and CKD cohorts (0.50, [0.45-0.56] for apixaban; 0.54, [0.49-0.59] for dabigatran; 0.53, [0.49-0.58] for rivaroxaban). The annual incidence of AKI for all NOACs and warfarin increased gradually as the increment of CHA₂DS₂-VASc for both CKD-free and CKD cohorts after propensity score weighting. The reduced risk of AKI for three NOACs persisted in most subgroups in either CKD-free or CKD cohort. Multivariate analysis indicated that all three NOACs were all associated with lower risk of AKI than warfarin in either CKD-free or CKD cohort.

CONCLUSIONS

All three NOACs are associated with a lower risk of AKI than warfarin among Asians with NVAF in real-world practice.

Bivalirudin for left ventricular assist device thrombosis

Pump thrombosis remains a serious complication of implantable ventricular assist device therapy and is associated with increased risk of morbidity and mortality. Optimal management strategies remain controversial and are guided largely by limited literature and expert opinion. Medical management of pump thrombosis, including the use of direct thrombin inhibitors, has been associated with mixed results. The purpose of this study is to report the outcomes associated with bivalirudin therapy in LVAD patients with suspected pump thrombosis. A single-center, retrospective observational study of 15 patients with suspected pump thrombosis that were all treated with bivalirudin therapy was conducted. The majority of subjects' initial treatment courses were unsuccessful [9/15 (60%)]; however, 6/15 (40%) achieved an initial improvement in serum lactate dehydrogenase (LDH) levels and were stabilized to be successfully discharged from the hospital. Of the subjects discharged, there was a high rate of recurrence of pump thrombosis within 6 months [5/6 (83.3%)]. Bivalirudin therapy was not associated with a consistent reduction in LDH among all subjects studied, and clinical responses to therapy appear to be associated with high rates of thrombosis recurrence. This study analyzes the largest cohort to date of LVAD patients with pump thrombosis treated with bivalirudin therapy, and suggests that alternative therapies should be considered in management.

Direct thrombin inhibition with dabigatran attenuates pressure overload-induced cardiac fibrosis and dysfunction in mice

INTRODUCTION

The multifunctional serine protease thrombin exerts proinflammatory and profibrotic cellular effects that may contribute to cardiac remodeling. This study was designed to investigate whether direct thrombin inhibition with dabigatran attenuates myocardial injury in the setting of pressure overload-induced heart failure.

MATERIAL AND METHODS

Transverse aortic constriction (TAC) surgery was performed on C57Bl/6J male mice to elicit cardiac hypertrophy. TAC, or sham, mice were randomly assigned to receive chow supplemented with the oral anticoagulant, dabigatran etexilate, or placebo.

RESULTS

Dabigatran did not affect cardiac hypertrophy, as measured by heart weight-to-body weight or the heart weight-to-tibia length, although a non-significant reduction in myocardial hypertrophic markers (ANP, BNP and MHC) occurred. Dabigatran reduced perivascular fibrosis by 25%, interstitial fibrosis by 54%, and the expression of myocardial fibrosis markers collagen I & III, MMP9, SMA, and PAR-1. These changes were associated with significant improvement in both coronary flow reserve and global left ventricular function. In cultured cardiac fibroblasts, dabigatran decreased thrombin and PAR-1-mediated collagen deposition by 30% and 37%, respectively.

CONCLUSIONS

Dabigatran attenuates cardiac fibrosis in the setting of pressure overload and improves coronary flow reserve and global cardiac function possibly by inhibiting thrombin activity and down-regulating PAR-1 expression in the absence of an effect on cardiomyocyte hypertrophy.

The Effects of Indirect- and Direct-Acting Anticoagulants on Lupus Anticoagulant Assays: A Large, Retrospective Study at a Coagulation Reference Laboratory

OBJECTIVES

To investigate the effects of indirect- and direct-acting anticoagulants on the interpretation of lupus anticoagulant (LAC) assays.

METHODS

A retrospective database review was performed to identify all LAC panels from November 2012 to November 2015. The positivity rates for three LAC tests were compared among various anticoagulant medications.

RESULTS

This analysis included 7,721 LAC panels. Direct oral anticoagulants, warfarin, and unfractionated heparin (UFH) were associated with higher LAC positivity rates compared with patients not receiving documented anticoagulation (83% for argatroban, 58% for dabigatran, 72% for rivaroxaban, 53% for apixaban, 56% for warfarin, and 36% for UFH vs 29% for no anticoagulation, P < .025). Direct thrombin inhibitors mainly affected the activated partial thromboplastin time-based assays and the tissue thromboplastin inhibition index (TTI), while direct factor Xa inhibitors mainly affected the TTI and the dilute Russell viper venom ratio.

CONCLUSIONS

Results of LAC testing performed while patients are receiving anticoagulant therapies should be interpreted with caution to avoid misdiagnosing patients with the antiphospholipid syndrome and potentially committing them to long-term anticoagulation therapy.

The use of direct oral anticoagulants in inherited thrombophilia

To review the use of the direct oral anticoagulant (DOAC) agents in inherited thrombophilia based on the literature. MEDLINE, International Pharmaceutical Abstracts, and Google Scholar searches (1970-May 2016) were conducted for case reports, case series, retrospective cohorts, or clinical trials using the key words: protein C deficiency, protein S deficiency, antithrombin deficiency, activated protein C resistance, Factor V Leiden, hypercoagulable, NOACs, dabigatran, apixaban, rivaroxaban, betrixaban, edoxaban, Xa inhibitor, direct thrombin inhibitor. Results were limited to English-only articles. Clinical studies evaluating the use of DOACs for hypercoagulable states related to inherited thrombophilia were selected and evaluated. Thrombophilia, a predisposition to thrombosis, manifests predominantly as venous thromboembolism. Causes of inherited thrombophilia include antithrombin deficiency, deficiencies of proteins C and S, and Factor V Leiden mutation. Many patients with thrombophilia receive anticoagulant therapy for primary or secondary prevention of VTE, historically either warfarin or a heparin product. DOAC's have been considered as potential alternatives to traditional agents based on their pharmacologic activity. Case reports and a post-hoc analysis of a clinical trial have indicated positive results in patients with inherited thrombophilia and VTE. Positive results have been reported for the use of DOACs in inherited thrombophilia. Further robust studies are needed for definitive decision making by clinicians.

Tissue thrombin is associated with the pathogenesis of dilated cardiomyopathy

BACKGROUND

Thrombin is a serine protease known to be the final product of the coagulation cascade. However, thrombin plays other physiological roles in processes such as gastric contractions and vessel wound healing, and a state of coagulability is increased in patients with dilated cardiomyopathy (DCM). In this study, we investigate the role of thrombin in the pathogenesis of DCM. The purpose of this study is to clarify the role of thrombin in the pathogenesis of DCM and investigate the possibility of treatment against DCM by thrombin inhibition.

METHODS

We investigated the expression of thrombin in the left ventricles of five patients with DCM who underwent the Batista operation and four patients without heart disease. Furthermore, we investigated the involvement of thrombin in the development of DCM using knock-in mice with a deletion mutation of cardiac troponin T that causes human DCM (∆K210 knock-in mouse) (B6;129-Tnnt2^tm2Mmto) and assessed the effects of a direct thrombin inhibitor, dabigatran on ∆K210 knock-in mice using echocardiographic examinations, the Kaplan-Meier method and Western blotting.

RESULTS

The immunohistochemical analysis showed a strong thrombin expression in the DCM patients compared to the patients without heart disease. In immunohistochemical analysis, a strong thrombin expression was observed in the heart tissues analysis in the ∆K210 knock-in mice. Dabigatran administration significantly improved fractional shortening according to the echocardiographic examination and the survival outcomes in ∆K210 knock-in mice.

CONCLUSION

Tissue thrombin is involved in the pathogenesis of DCM and thrombin inhibition can be beneficial for the treatment of DCM.

Resolution of a warfarin and dabigatran-resistant left atrial appendage thrombus with apixaban

The majority of embolisms associated with atrial fibrillation (AF) are from the left atrial appendage (LAA). To treat the existing thrombus, warfarin and novel anticoagulants have been used. However, there has been no clinical information regarding the difference of the effects of congealing the fibrinogenolysis system among these oral anticoagulants. Here, we report a case of persistent AF, in whom apixaban, factor Xa inhibitor resolved an LAA clot refractory to warfarin and direct thrombin inhibition. Factor Xa inhibitor, apixaban, could resolve the left appendage thrombosis refractory to warfarin and dabigatran.

Impact of dabigatran on platelet function and fibrinolysis

BACKGROUND

We sought to evaluate the potential enhanced fibrinolytic and antiplatelet activity of dabigatran etexilate (DE) due to decreased thrombin levels in patients with stroke or transient ischemic attack and non-valvular atrial fibrillation (NVAF).

METHODS

Consecutive patients with cerebrovascular diseases and NVAF that were treated with DE in a tertiary university hospital. Fibrinolysis and platelet function were assessed by thromboelastometry (ROTEM) and platelet function analyzer (PFA)-100, respectively, before and after treatment with DE. Conventional coagulation tests, endogenous thrombin potential (ETP) and hemoclot thrombin inhibitors (HTI), were also performed in order to detect any possible correlation between dabigatran plasma levels, its anticoagulant activity and the intensity of platelet dysfunction or fibrinolysis.

RESULTS

A total of nineteen patients fulfilled our inclusion criteria (mean age 62.3±7.2years; 47% males; median CHADS2-score: 3; interquartile range: 2-4). DE treatment was associated with a significant reduction of the lysis index (LI60) at 60min (p=0.036), and prolongation of the PFA-100 CEPI closure time (p=0.024). After dabigatran treatment, abnormal PFA-100 results were obtained in two patients (11%, 95% CI: 2%-33%). DE levels (determined by HTI) were strongly inversely correlated (rho=-0.85; p<0.001) with the area under the curve (AUC) values in ETP assay. Νo association was found between HTI and PFA-100 CEPI CT (p=0.64), or LI60 measurements (p=0.60).

CONCLUSIONS

Our findings indicate that DE might affect platelet function and fibrinolysis and highlight the potential role of ETP as an alternative option in DE monitoring. The intensity and clinical relevance of DE antiplatelet and fibrinolytic effects require further investigation.

The current landscape of treatment options for venous thromboembolism: a focus on novel oral anticoagulants

BACKGROUND

Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), is a major cause of morbidity, mortality, and healthcare expenditure. Anticoagulant therapy is recommended for at least 3 months in patients with acute VTE to prevent recurrence. Conventional anticoagulants are associated with inherent limitations including route of administration, required monitoring and dose adjustments, potential for food-drug and drug-drug interactions, unpredictable pharmacokinetics and pharmacodynamics, and possible severe adverse events.

SCOPE

This manuscript reviews the pharmacology of the novel oral anticoagulants (NOACs), and analyzes the differences in phase 3 clinical trial designs, outcomes, and specific patient populations investigated for the treatment of acute and prevention of secondary VTE.

METHODS

A literature search was performed in PubMed using the key words dabigatran, apixaban, rivaroxaban, edoxaban, and venous thromboembolism in PubMed. The search included all years, English language, and peer-reviewed articles relating to phase 3 clinical trials, subanalyses, and meta-analyses of these NOACs for the treatment of acute VTE and secondary prevention.

FINDINGS

NOACs have demonstrated comparable efficacy and comparable or superior safety in large, randomized clinical trials in the treatment and prevention of VTE compared with conventional therapy. New oral anticoagulants, including the direct thrombin (dabigatran etexilate) and direct factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban), have advantages over conventional agents such as oral administration at fixed doses, predictable pharmacokinetics and pharmacodynamics, minimal potential for food-drug and drug-drug interactions, and lack of required monitoring.

CONCLUSIONS

NOACs offer additional oral anticoagulation treatment options for patients with VTE.

Performance of various laboratory assays in the measurement of dabigatran in patients receiving therapeutic doses: a prospective study based on peak and trough plasma levels

OBJECTIVES

To study dabigatran etexilate, a new oral anticoagulant that functions as a direct thrombin inhibitor.

METHODS

This study evaluates four methods, one of which is performed in three different laboratories, and compares results against dabigatran levels measured by Boehringer-Ingelheim (Ingelheim, Germany) using mass spectrometry.

RESULTS

Although routine monitoring is not required, measurement of plasma concentrations may be necessary in certain clinical situations. Routine coagulation assays such as the prothrombin time, activated partial thromboplastin time, and thrombin time do not reliably determine levels of dabigatran anticoagulation. Alternative assays, when calibrated with a dabigatran standard, such as the modified dilute thrombin time, ecarin clotting time, and ecarin chromogenic assay, may be appropriate, although a comparison of these methods using samples from patients taking dabigatran has not been performed.

CONCLUSIONS

Although results using all methods in this study demonstrate adequate correlation, measured dabigatran levels varied in a statistically significant manner, even when the same method was used by different laboratories. The clinical significance of this variation in dabigatran concentrations is uncertain.

Pathology consultation on anticoagulation monitoring: factor X-related assays

OBJECTIVES

To review various anticoagulation therapies and related laboratory monitoring issues, with a focus on factor X-related chromogenic assays.

METHODS

A case-based approach is used to review pertinent published literatures and product inserts of anticoagulation drugs and to look back on clinical use of factor X-related chromogenic assays.

RESULTS

The number of anticoagulants available to clinicians has increased greatly in the past decade. Whether and how these anticoagulants should be monitored are areas of uncertainty for clinicians, which can lead to misuse of laboratory assays and suboptimal patient management. Factor X-related assays are of particular concern because of the similar and often confusing test names. Based on a common clinical case scenario and literature review regarding anticoagulant monitoring, an up-to-date discussion and review of the various factor X-related assays are provided, focusing on the differences in test designs and clinical utilities between the chromogenic anti-Xa and chromogenic factor X activity assays.

CONCLUSIONS

Anticoagulation therapy and related laboratory monitoring are rapidly evolving areas of clinical practices. A good knowledge of relevant laboratory assays and their clinical applications is necessary to help optimize patient care.

Oral thromboprophylaxis following total hip or knee replacement: review and multicentre experience with dabigatran etexilate

The risk of venous thromboembolism (VTE) in patients undergoing total knee or hip replacement surgery is high. As a result, thromboprophylaxis is highly recommended. While current thromboprophylactic agents, such as low molecular weight heparins (LMWH) and vitamin K antagonists, are safe and effective their use can be problematic. Therefore, there is a need for alternative anticoagulants that are as safe and effective as conventional agents, but are more convenient and easier to use. Dabigatran etexilate, a direct thrombin inhibitor, is one such anticoagulant. For VTE prevention following major orthopaedic surgery, dabigatran etexilate shows similar efficacy and safety to the LMWH enoxaparin, and is approved for use in more than 75 countries, including Europe and Canada. Here, we summarize and discuss the experiences of four German clinics that have recently introduced dabigatran etexilate into clinical practice. Overall, dabigatran etexilate was well received by patients, surgeons and nurses, and compared favourably with enoxaparin. Staff appreciated the oral, single-dose administration of dabigatran etexilate. Patient satisfaction was high, especially in those individuals who had previously used LMWHs. In this review, we also address a number of questions that were asked by patients or staff; this will be of relevance to orthopaedic surgeons and nurses. We conclude that, in these four German clinics, dabigatran etexilate offered an effective oral alternative to existing thromboprophylactic agents in patients undergoing major orthopaedic surgery.

Effect of a direct thrombin inhibitor compared with dalteparin and unfractionated heparin on human osteoblasts

Purpose:

Osteoporosis is a relevant problem after long term administration of unfractionated heparin (UFH) and low molecular weight heparin. Melagatran is a representative of a new group of direct thrombin inhibitors with comparable data in the prevention of thromboembolic events after orthopaedic surgery. The aim of our in vitro study was to investigate the effect of a direct thrombin inhibitor compared with dalteparin and UFH on human osteoblasts.

Materials and Methods:

Melagatran, dalteparin and UFH were added to primary osteoblast cultures in their therapeutic range and two decimal powers below and above. Cell number, protein synthesis, mitochondrial and alkaline phosphatase activity and collagen type I synthesis were evaluated.

Results:

Melagatran showed the least influence on protein synthesis and cell proliferation with a reduction of cell number to 83.5 ± 9% (p = 0.027) of the control group only in the highest investigated concentration after 15 days of incubation.

Mitochondrial and alkaline phosphatase activity and collagen type I synthesis in osteoblasts incubated with melagatran and dalteparin showed similar patterns. UFH showed the most pronounced influence on cellular metabolism.

Conclusions:

Melagatran showed less inhibitory in vitro effects on human osteoblasts than dalteparin or UFH. The presented study gives first hints that direct thrombin inhibitors may help prevent heparin-induced negative effects on bone metabolism.