Search Results (27)

Heparin, a widely used polysaccharidic anticoagulant of animal origin, is associated with risks of contamination and adverse effects, notably bleeding and thrombocytopenia. These limitations have prompted interest in alternative sulfated polysaccharides with anticoagulant properties and improved safety profiles. This study explored the anticoagulant potential of two marine bacterial exopolysaccharides (EPS), infernan and diabolican. It assessed whether chemical modifications (depolymerization, oversulfation) could enhance their anticoagulant properties compared to unfractionated and low molecular weight heparins. Native EPS were depolymerized to generate different molecular weights and then chemically oversulfated to increase negative charge density. Anticoagulant activities were evaluated using clotting and thrombin generation assays (TGA). Molecular docking was performed to model interactions with antithrombin and heparin cofactor II. Only highly sulfated derivatives significantly prolonged activated partial thromboplastin time while showing negligible effect on thrombin time and anti-factor Xa activity. They present different structures, and their binding to antithrombin is not achieved via the classic pentasaccharide motif. In TGA, these derivatives inhibited thrombin formation at higher doses than heparin but induced a marked delay in clot generation. Docking analyses supported their ability to bind serpins, albeit with lower specificity than heparin. Their limited anti-Xa activity and non-animal origin position them as promising anticoagulant candidates. Full article

Background: Laboratory monitoring of the effect of low-molecular-weight heparins (LMWHs) is generally not necessary. However, prompt evaluation of heparin inhibitory effects (i.e., anti-Xa activity) is important in cases of life-threatening bleeding, need for urgent surgery or acute thromboembolism under LMWH treatment. We aimed to establish a simple and reliable point-of-care method for the detection of enoxaparin. Methods: Eighty patients under enoxaparin therapy and ten healthy volunteers without any anticoagulant treatment were enrolled. Simultaneous measurements of anti-Xa activity using the chromogenic method and clotting times in the absence and presence of polybrene using viscoelastometric assays containing Russell’s viper venom (RVV-test) were performed on the ClotPro device. Results: Among the measured and derived RVV-test parameters, the ratio of the RVV clotting times (RVV CT) detected in the absence and presence of polybrene showed the best statistically significant correlation with anti-Xa activity (r = 0.774, p < 0.001). Based on ROC analysis, we designated RVV CT ratios of 1.02, 1.23 and 1.6 as the best cut-off values for separating anti-Xa ranges below and above 0.3 and 0.6 IU/mL, respectively. If the RVV CT ratio is below or above 1.23, the anti-Xa activity is suggested to be below 0.6 IU/mL or above 0.3 IU/mL with high certainty, respectively. Further differentiation is possible if the RVV CT ratio is measured below 1.02 or above 1.6. In these cases, the measured anti-Xa values are below 0.3 IU/mL or above 0.6 IU/mL, respectively, with high probability and good predictive values. Conclusions: Our method can provide semiquantitative information on the effect of enoxaparin and the expected anti-Xa activity within 10 min in real clinical situations. Full article

Introduction: A drug-specific chromogenic assay is not immediately available, so it hampers the treatment of patients who present in a clinical emergency. In this pilot study, we aimed to create a formula to predict a plasma edoxaban level based on the international normalized ratio (INR) and heparin-calibrated anti-Xa activity and derive a novel workflow for routine laboratory diagnosis. Method: Forty-two patients prescribed edoxaban were recruited and randomized to a testing or validation cohort. Plasma levels from the testing cohort were used to create a prediction formula that was then validated in a validation cohort and real-world clinical requests. Results: The INR-derived formula had high sensitivity (95.8–100%) to predict the plasma edoxaban level > 50 ng/mL and >100 ng/mL but with low specificity. However, the specificity of predicting the plasma edoxaban level of ≥100 ng/mL was 100% by using an INR ≥ 1.5 as cut-off. Heparin-calibrated anti-Xa-derived formula had a high sensitivity (90.9–100%) and specificity (93.8–100%) in real clinical situations. A two-tier approach of combining INR-derived and heparin-calibrated anti-Xa-derived formulae can overcome the low specificity and utilize the advantages of wide availability and a short turnaround time of the INR-derived formula. Conclusions: Both INR-derived and heparin-calibrated anti-Xa-derived formulae can be applied to calculate the plasma edoxaban level. A two-tier workflow of combining these two formulae greatly helps streamline the treatment of patients prescribed edoxaban who present in a clinical emergency. Adoption of this framework is feasible for routine diagnostic laboratories. Full article

We here sought to assess thrombotic and hemorrhagic complications and associated risk factors during pregnancy, delivery, and postpartum in women with prosthetic heart valves (PHV). Methods: The retrospective cohort study covered January 2011 to December 2022. The objective of the study was to assess the risk factors and frequency of thrombotic and hemorrhagic complications during pregnancy, delivery, and the postpartum period in women with PHV based on the experience of one perinatal center. We included 88 pregnancies with 77 prosthetic heart valves (PHV), which were divided into two groups, mechanical valve prostheses (MVP) (n = 64) and biological valve prosthesis (BVP) (n = 24). In the study we analyzed pregnancy outcomes, as well as thrombotic and hemorrhagic complication frequencies. Results: Of 88 pregnancies, 79 resulted in live births. In the MVP group, there were six miscarriages (9.4%) and two medical abortions (3.1%), including one due to Warfarin’s teratogenic effects. No miscarriages were reported in the BVP group, but one fetal mortality case (4.2%) occurred. During pregnancy, 11 MVP cases (17.2%) experienced thrombotic complications. In the BVP group, one patient (4.2%) had transient ischemic attack (TIA). Two MVP cases required surgical valve repair during pregnancy, and one in the post-delivery stage was caused by thrombotic complications. Postpartum, two MVP cases had strokes, and in one MVP patient, pulmonary embolism was registered, while no thrombotic complications occurred in the BVP group. Hemorrhagic complications affected 15 MVP cases (17.9%) in the postpartum period. There were no registered cases of maternal mortality. Conclusions: The effective control of anti-factor Xa activity reduced thrombotic events. However, the persistently high incidence of postpartum hemorrhagic complications suggests a need to reassess anticoagulant therapy regimens, lower target levels of anti-Xa, and reduce INR levels for discontinuing heparin bridge therapy. Despite the heightened mortality risk in MVP patients, our study cohort did not have any mortality cases, which contrasts with findings from other registries. Full article

Background. Unfractionated heparin is administered in patients undergoing veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Anticoagulation monitoring is recommended, with an anti-activated factor X (anti-Xa) targeting 0.3 to 0.7 IU/mL. Owing to heparin’s heterogeneous pharmacokinetic properties, anti-Xa is unpredictable, generating a challenge in anticoagulation practices. The aim of this study was to build a pharmacokinetic model of heparin accounting for potential confounders, and derive an optimized dosing regimen for a given anti-Xa target. Methods. Adult patients undergoing VA-ECMO were included between January 2020 and June 2021. Anticoagulation was managed with an initial 100 IU/kg heparin loading dose followed by a continuous infusion targeting 0.2 to 0.7 IU/mL anti-Xa. The data were split into model development and model validation cohorts. Statistical analysis was performed using a nonlinear mixed effects modeling population approach. Model-based simulations were performed to develop an optimized dosing regimen targeting the desired anti-Xa. Results. A total of 74 patients were included, with 1703 anti-Xa observations. A single-compartment model best fitted the data. Interpatient variability for distribution volume was best explained by body weight, C-reactive protein and ECMO indication (post-cardiotomy shock or medical cardiogenic shock), and interpatient variability for elimination clearance was best explained by serum creatinine and C-reactive protein. Simulations using the optimized regimen according to these covariates showed accurate anti-Xa target attainment. Conclusion. In adult patients on VA-ECMO, heparin’s effect increased with serum creatinine and medical indication, whereas it decreased with body weight and systemic inflammation. We propose an optimized dosing regimen accounting for key covariates, capable of accurately predicting a given anti-Xa target. Full article

Anticoagulant and antiplatelet therapies are used to prevent life-threatening complications associated with thrombosis. While there are numerous clinical guidelines for antithrombotic medications, there is an incomplete understanding of whether these interventions yield similar effects in preclinical models, potentially impacting their predictive value for translational studies on the development of medical devices, therapies, and surgical techniques. Due to their close physiologic similarities to humans, we employed nonhuman primates (NHPs) using a reverse translational approach to analyze the response to clinical regimens of unfractionated heparin, low-molecular-weight heparin (LMWH) and aspirin to assess concordance with typical human responses and evaluate the predictive validity of this model. We evaluate activated clotting time (ACT) in nine rhesus and six cynomolgus macaques following the intraoperative administration of intravenous unfractionated heparin (100–300 U/kg) reflecting the clinical dose range. We observed a significant dose-dependent effect of heparin on ACT (low-dose average = 114.1 s; high-dose average = 148.3 s; p = 0.0011). LMWH and aspirin, common clinical antithrombotic prophylactics, were evaluated in three rhesus macaques. NHPs achieved therapeutic Anti-Xa levels (mean = 0.64 U/mL) and ARU (mean = 459) via VerifyNow, adhering to clinical guidance using 1.0 mg/kg enoxaparin and 81 mg aspirin. Clinical dosing strategies for unfractionated heparin, LMWH, and aspirin were safe and effective in NHPs, with no development of thrombosis or bleeding complications intraoperatively, postoperatively, or for prophylaxis. Our findings suggest that coagulation studies, performed as an integrative part of studies on biologics, bioengineered devices, or transplantation in NHPs, can be extrapolated to the clinical situation with high predictive validity. Full article

For coagulation to be initiated, anticoagulant glycosaminoglycans (GAGs) such as heparins need to be neutralised to allow fibrin clot formation. Platelet activation triggers the release of several proteins that bind GAGs, including histidine-rich glycoprotein (HRG), fibrinogen, and fibronectin. Zn²⁺ ions are also released and have been shown to enhance the binding of HRG to heparins of a high molecular weight (HMWH) but not to those of low molecular weight (LMWH). The effect of Zn²⁺ on fibrinogen and fibronectin binding to GAGs is unknown. Here, chromogenic assays were used to measure the anti-factor Xa and anti-thrombin activities of heparins of different molecular weights and to assess the effects of HRG, fibrinogen, fibronectin, and Zn²⁺. Surface plasmon resonance was also used to examine the influence of Zn²⁺ on the binding of fibrinogen to heparins of different molecular weights. Zn²⁺ had no effect on the neutralisation of anti-factor Xa (FXa) or anti-thrombin activities of heparin by fibronectin, whereas it enhanced the neutralisation of unfractionated heparin (UFH) and HMWH by both fibrinogen and HRG. Zn²⁺ also increased neutralisation of the anti-FXa activity of LMWH by fibrinogen but not HRG. SPR showed that Zn²⁺ increased fibrinogen binding to both UFH and LMWH in a concentration-dependent manner. The presented results reveal that an increase in Zn²⁺ concentration has differential effects upon anticoagulant GAG neutralisation by HRG and fibrinogen, with implications for modulating anti-coagulant activity in plasma. Full article

(1) Background: Direct oral anticoagulants (DOACs) require monitoring in some critical clinical situations. The specific tests for DOAC monitoring are not yet available in all labs. The aim of this study was to evaluate if a unique, more widespread heparin-calibrated anti-Xa assay could be suitable to estimate the concentrations of apixaban and rivaroxaban in order to establish an algorithm helping our clinicians in their therapeutic decision for patients treated with DOACs in emergencies. (2) Methods: A first retrospective part allowed us to determine of a conversion factor between the measured DOAC concentration and the deducted anti-Xa heparin activity based on optic density. During the second prospective part, both DOAC concentration (ng/mL) and anti-Xa activity heparin (UI/mL) were measured on the same sample, and the previously determined conversion factor was applied to each UI/mL value. We then compared the calculated and measured DOAC concentration values. (3) Results: The analysis of the derivation cohort confirmed a good correlation, especially between the anti-Xa heparin activity and the apixaban concentrations (r = 0.97). Additionally, we determined heparin-calibrated anti-Xa assay cut-offs for invasive procedures at 0.3 UI/mL and for intravenous thrombolysis at 0.51 UI/mL using ROC curves with a sensitivity at 98% and specificity at 95% for 0.3 UI/mL and a sensitivity at 97.7% and specificity at 88.2% for the cut-off of 0.51 UI/mL. In the validation cohort, we confirmed the agreement between measured and calculated DOAC concentrations for the low values, especially around cut-offs with an excellent negative predictive value for 0.51 UI/mL (94% for apixaban and 100% for rivaroxaban) and a good negative predictive value for 0.3 UI/mL (83.3% for apixaban and 85.7% for rivaroxaban). (4) Conclusions: Our results confirm that it is possible to correctly predict or exclude the presence of apixaban/rivaroxaban in emergency situations when specific tests are not readily available. Full article

Activated clotting time (ACT) is used in cardiac surgery for monitoring unfractionated heparin (UFH). In endovascular radiology, ACT use is less established. We aimed to test the validity of ACT in UFH monitoring in endovascular radiology. We recruited 15 patients undergoing endovascular radiologic procedure. ACT was measured with ICT Hemochron^® device as point-of-care (1) before standard UFH bolus, (2) immediately after the bolus, and in some cases (3) 1 h into the procedure or a combination thereof (altogether 32 measurements). A total of two different cuvettes, ACT-LR and ACT+ were tested. A reference method of chromogenic anti-Xa was used. Blood count, APTT, thrombin time and antithrombin activity were also measured. UFH levels (anti-Xa) varied between 0.3–2.1 IU/mL (median 0.8) and correlated with ACT-LR moderately (R² = 0.73). The corresponding ACT-LR values were 146–337 s (median 214). ACT-LR and ACT+ measurements correlated only modestly with one another at this lower UFH level, with ACT-LR being more sensitive. Thrombin time and APTT were unmeasurably high after the UFH dose, rendering them of limited use in this indication. We adopted an ACT target of >200–250 s in endovascular radiology based on this study. While ACT correlation with anti-Xa is suboptimal, the readily available point-of-care nature increases its suitability. Full article

Background: Unfractionated heparin (UFH) is used as an anticoagulant during the atrial fibrillation (AF) ablation procedure to prevent the occurrence of thromboembolic events. Guidelines recommend an activated clotting time (ACT) greater than 300 s (s) based on studies of patients treated with vitamin K antagonist (VKA) for their AF. However, direct oral anticoagulants (DOACs) have supplanted VKAs in AF and are now used as first-line therapy. It is recommended not to interrupt them during the procedure, which could interfere with the ACT measures. Objective: To assess the real-life relationship between ACT, DOAC concentrations, and UFH anti-Xa activity in patients treated by uninterrupted DOAC therapy. Methods: We conducted a single-center retrospective study. We analyzed consecutive patients with AF who underwent catheter ablation under DOAC therapy. Results: In total, 40 patients were included, including 15 (37.5%), 20 (50.0%), and 5 (12.5%) on rivaroxaban, apixaban, and dabigatran, respectively. Baseline ACT was significantly lower in the apixaban group. ACT was linearly correlated with the residual concentration of apixaban and dabigatran but not with rivaroxaban. After UFH injection, ACT was linearly correlated with the anti-Xa activity, regardless of DOAC. Patients in the apixaban group received a higher total dose of UFH during the procedure to achieve a target ACT > 300 s, which resulted in significantly higher anti-Xa activity during the procedure. Conclusion: Our results raise the question of optimal management of intra-procedural heparin therapy and highlight the limitations of the ACT test, particularly in patients on apixaban. Full article

The correction of blood coagulation impairments of a bleeding or thrombotic nature employs standard protocols where the type of drug, its dose and the administration regime are stated. However, for a group of patients, such an approach may be ineffective, and personalized therapy adjustment is needed. Laboratory hemostasis tests are used to control the efficacy of therapy, which is expensive and time-consuming. Computer simulations may become an inexpensive and fast alternative to real blood tests. In this work, we propose a procedure to numerically define the individual hemostasis profile of a patient and estimate the anticoagulant efficacy of low-molecular-weight heparin (LMWH) based on the computer simulation of global hemostasis assays. We enrolled a group of 12 patients receiving LMWH therapy and performed routine coagulation assays (activated partial thromboplastin time and prothrombin time) and global hemostasis assays (thrombodynamics and thrombodynamics-4d) and measured anti-Xa activity, fibrinogen, prothrombin and antithrombin levels, creatinine clearance, lipid profiles and clinical blood counts. Blood samples were acquired 3, 6 and 12 h after LMWH administration. We developed a personalized pharmacokinetic model of LMWH and coupled it with the mechanism-driven blood coagulation model, which described the spatial dynamics of fibrin and thrombin propagation. We found that LMWH clearance was significantly lower in the group with high total cholesterol levels. We generated an individual patient’s hemostasis profile based on the results of routine coagulation assays. We propose a method to simulate the results of global hemostasis assays in the case of an individual response to LMWH therapy, which can potentially help with hemostasis corrections based on the output of global tests. Full article

Current guidelines recommend monitoring the anticoagulant effect of unfractionated heparin (UFH) by measuring anti-Xa activity rather than activated partial thromboplastin time (aPTT) in intensive care unit (ICU) patients. The primary objective of this study was to evaluate the correlation of aPTT, anti-Xa activity, and thrombin generation in UFH-treated ICU patients. A prospective observational pilot study was conducted in adult surgical ICU patients treated with UFH. aPTT and anti-Xa activity were monitored daily. The therapeutic target was aPTT between 50 s and 84 s, and/or anti-Xa between 0.3 and 0.7 U/mL. Correlation among aPTT, anti-Xa activity, and thrombin generation was determined by measuring endogenous thrombin potential (ETP), with the inflammatory response evaluated. C-reactive protein (CRP) was used as a marker of inflammatory response. The plasma of 107 samples from 30 ICU patients was analyzed. The correlation between aPTT and anti-Xa activity was 0.66, CI_95% [0.54;0.76] (p < 0.0001). Although thrombin generation, aPTT, and anti-Xa were correlated with inflammatory responses, the correlation was higher with thrombin generation and anti-Xa activity compared to aPTT. When aPTT was in a therapeutic range, a low thrombin generation was observed but was 50% inhibited when anti-Xa was in a therapeutic range. Coagulation testing with aPTT, anti-Xa correlated with thrombin generation. A 50% decrease in thrombin generation was observed when anti-Xa was within a therapeutic range. Further work is needed to evaluate coagulation biomarker responses and clinical outcomes in specific ICU populations. Full article

Induction of a hypocoagulable state is imperative in the treatment of feline arterial thromboembolism. Publications in human medicine report the use of enoxaparin intravenously in selected cases. The aim of our retrospective study was to report the regain of perfusion, short-term outcome, and complications of cats treated with a novel intravenous enoxaparin protocol (1 mg/kg bolus injection followed by 3 mg/kg/day continuous infusion) combined with oral clopidogrel administration. The secondary aim was to report the monitoring of enoxaparin with anti-Xa activity. There were 36 cats included. The probability of reaching limb reperfusion was significantly (p = 0.0148) higher with anti-Xa activity within or above the target range compared to results below the target range (19/21, 90% versus 11/20, 55%). The complications observed were acute kidney injury (15/36, 42%), hemorrhage (2/36, 6%), and neurological signs (6/36, 17%). The most common causes of death/euthanasia were cardiac instability, acute kidney injury, neurological abnormalities, and limb necrosis. The hospital discharge rate was 83% (10/12) for single limb and 29% (7/24) for dual limb thrombosis; the difference was significant (p = 0.0039). The median hospitalization time for the survivors was 119.5 (95–480) h. Our study supports the use of intravenous continuous rate infusion of enoxaparin in combination with oral clopidogrel for cats with aortic thromboembolism. We report similar discharge rates and lower hemorrhage rates than previously reported with thrombolytic treatment. Full article

Background. Fixed-dose ultrasound-assisted catheter-directed thrombolysis (USAT) rapidly improves hemodynamic parameters and reverses right ventricular dysfunction caused by acute pulmonary embolism (PE). The effectiveness of USAT for acute PE associated with coronavirus disease 2019 (COVID-19) is unknown. Methods and results. The study population of this cohort study consisted of 36 patients with an intermediate-high- or high-risk acute PE treated with a fixed low-dose USAT protocol (r-tPA 10–20 mg/15 h). Of these, 9 patients tested positive for COVID-19 and were age–sex-matched to 27 patients without COVID-19. The USAT protocol included, beyond the infusion of recombinant tissue plasminogen activator, anti-Xa-activity-adjusted unfractionated heparin therapy (target 0.3–0.7 U/mL). The study outcomes were the invasively measured mean pulmonary arterial pressure (mPAP) before and at completion of USAT, and the National Early Warning Score (NEWS), according to which more points indicate more severe hemodynamic impairment. Twenty-four (66.7%) patients were men; the mean age was 67 ± 14 years. Mean ± standard deviation mPAP decreased from 32.3 ± 8.3 to 22.4 ± 7.0 mmHg among COVID-19 patients and from 35.4 ± 9.7 to 24.6 ± 7.0 mmHg among unexposed, with no difference in the relative improvement between groups (p = 0.84). Within 12 h of USAT start, the median NEWS decreased from six (Q1–Q3: 4–8) to three (Q1–Q3: 2–4) points among COVID-19 patients and from four (Q1–Q3: 2–6) to two (Q1–Q3: 2–3) points among unexposed (p = 0.29). One COVID-19 patient died due to COVID-19-related complications 14 days after acute PE. No major bleeding events occurred. Conclusions. Among patients with COVID-19-associated acute PE, mPAP rapidly decreased during USAT with a concomitant progressive improvement of the NEWS. The magnitude of mPAP reduction was similar in patients with and without COVID-19. Full article

The routine monitoring of direct oral anticoagulants (DOACs) may be considered in patients with renal impairment, patients who are heavily obese, or patients requiring elective surgery. Using the heparin-binding copolymer (HBC) and polybrene, we aimed to develop a solution for monitoring the anticoagulant activity of DOACs in human plasma in the interfering presence of unfractionated heparin (UFH) and enoxaparin. The thrombin time (TT) and anti-factor Xa activity were monitored in pooled plasma from healthy volunteers. In these tests, plasma with dabigatran or rivaroxaban was mixed with UFH or enoxaparin and then incubated with HBC or polybrene, respectively. HBC and polybrene neutralized heparins and enabled monitoring of anticoagulant activity of dabigatran in the TT test. Both agents allowed for accurate measurement of anti-factor Xa activity in the plasma containing rivaroxaban and heparins in the concentration range reached in patients’ blood. Here, we present diagnostic tools that may improve the control of anticoagulation by eliminating the contamination of blood samples with heparins and enabling the monitoring of DOACs’ activity. Full article