Updates on Anticoagulation and Laboratory Tools for Therapy Monitoring of Heparin, Vitamin K Antagonists and Direct Oral Anticoagulants

Thromboembolic events after major bleeding events in patients with mechanical heart valves: a 13-year analysis

Anticoagulation in patients with mechanical heart valves (MHV) is associated with a risk of major bleeding episodes (MBE). In case of MBE, anticoagulant interruption is advocated. However, there is lack of data regarding the thrombo-embolic events (TE) risk associated with anticoagulant interruption. The main objective of the study was to evaluate the rate and risk factors of 6-months of TEs in patients with MHV experiencing MBE. This observational study was conducted over a 13-year period. Adult patients with a MHV presenting with a MBE were included. The main study endpoint was 6-month TEs, defined by clinical TEs or an echocardiographic documented thrombosis, occurring during an ICU stay or within 6-months. Thromboembolic events were recorded at ICU discharge, and 6 months after discharge. Seventy-nine MBEs were analysed, the rate of TEs at 6-months was 19% CI [11-29%]. The only difference of presentation and management between 6-month TEs and free-TE patients was the time without effective anticoagulation (TWA). The Receiver Operator Characteristic curve identified the value of 122 h of TWA as a cut-off. The multivariate analysis identified early bleeding recurrences (OR 3.62, 95% CI [1.07-12.25], p = 0.039), and TWA longer than 122 h (OR 4.24, 95% CI [1.24-14.5], p = 0.021), as independent risk factors for 6-month TEs. A higher rate of TE was associated with anticoagulation interruption longer than 5 days and early bleeding recurrences. However, the management should still be personalized and discussed for each case given the heterogeneity of causes of MBE and possibilities of haemostatic procedures.

Prophylaxis of microvascular thrombosis using direct oral anticoagulants (DOAC) in microvascular free tissue transplantation - a pilot study

INTRODUCTION

We conducted this pilot study to assess direct oral anticoagulants (DOACs) in the prevention of microvascular thrombosis.

MATERIALS AND METHODS

Five patients undergoing microvascular free tissue transplantation received rivaroxaban or apixaban (depending on their home medication). We compared this group to 19 patients who received enoxaparin subcutaneously. We evaluated the rate of graft loss due to microvascular thrombosis and the number of transfusions administered intra- and postoperatively.

RESULTS

There was no graft loss due to microvascular thrombosis in either of the groups. There was no significant difference in the number of intraoperative (study group mean 1.00 (SE 0.32) vs. control group mean 1.11 (SE 0.59); p = 0.876) and postoperative (study group mean 1.2 (SE 0.37) vs. control group mean 1.74 (SE 0.34); p = 0.310) red blood cell transfusions.

CONCLUSION

Based on our results in this pilot study, DOACs can be used with microvascular flaps. Further studies with larger sample sizes should be performed to find an optimal medication regimen both for patients already taking DOACs and perhaps even for those not taking DOACs.

Understanding Antithrombotic Agents for Rehabilitation Therapy: A Comprehensive Narrative Review

In rehabilitation medicine, attention must be paid to the medication. Among them, antithrombotic drugs are used for the initial treatment and secondary prevention of stroke, so as a basic knowledge, the pharmacological actions, characteristics, indications, and precautions for the use of antithrombotic drugs should be known. Antithrombotic agents are divided into antiplatelet agents and anticoagulants, and the appropriate antithrombotic agent is selected according to the main disease or condition. Antiplatelet agents include aspirin, clopidogrel, ticlopidine, prasugrel, ticagrelor, and cilostazol. Each antiplatelet agent has a different mechanism of action, characteristics, and indications, and should be prescribed with due consideration. Anticoagulants include heparin, synthetic Xa inhibitors, direct oral anticoagulants (DOACs), synthetic antithrombin agents, and warfarin. Knowledge of the mechanism of action, characteristics, and indications of each anticoagulant is necessary, as well as monitoring and dose adjustment. With regard to ischemic cerebrovascular disease (ICD) and antithrombotic agents, the first step is to classify cerebral infarction and to determine whether antiplatelet agents or anticoagulants should be used. Bleeding and recurrence prevention are important considerations in the selection of appropriate antithrombotic agents for the pathophysiology of ICD.

Electrochemical Monitoring in Anticoagulation Therapy

The process of blood coagulation, wherein circulating blood transforms into a clot in response to an internal or external injury, is a critical physiological mechanism. Monitoring this coagulation process is vital to ensure that blood clotting neither occurs too rapidly nor too slowly. Anticoagulants, a category of medications designed to prevent and treat blood clots, require meticulous monitoring to optimise dosage, enhance clinical outcomes, and minimise adverse effects. This review article delves into the various stages of blood coagulation, explores commonly used anticoagulants and their targets within the coagulation enzyme system, and emphasises the electrochemical methods employed in anticoagulant testing. Electrochemical sensors for anticoagulant monitoring are categorised into two types. The first type focuses on assays measuring thrombin activity via electrochemical techniques. The second type involves modified electrode surfaces that either directly measure the redox behaviours of anticoagulants or monitor the responses of standard redox probes in the presence of these drugs. This review comprehensively lists different electrode compositions and their detection and quantification limits. Additionally, it discusses the potential of employing a universal calibration plot to replace individual drug-specific calibrations. The presented insights are anticipated to significantly contribute to the sensor community's efforts in this field.

Evaluation of newly-developed modified diluted prothrombin time reagent in non-valvular atrial fibrillation patients with direct oral anticoagulants: A comparative study with conventional reagents

INTRODUCTION

A single assay to assess the effect of the direct FXa inhibitor is needed clinically because prothrombin (PT) assay is not yet sensitive enough for accurate evaluation. We developed modified diluted prothrombin time (mdPT) assay showing a high reactivity to direct FXa inhibitors based on prothrombin time (PT) reagent. The purpose of this study was to evaluate the reactivity of mdPT to direct FXa inhibitors comparing to that of commercial PT reagents and diluted prothrombin time (dPT).

METHODS

The correlation and slopes of mdPT against the drug concentrations by anti-Xa assay were compared to those of the four commercial reagents of PT or dPT in 275, 257, and 243 clinical samples collected from non-valvular atrial fibrillation (NVAF) patients who are prescribed apixaban, edoxaban or rivaroxaban for stroke prevention, respectively.

RESULTS

The correlation coefficient (95% confidence interval) of mdPT against apixaban, edoxaban, and rivaroxaban was 0.818 (0.775-0.854), 0.914 (0.892-0.932), and 0.814 (0.766-0.852), respectively. The slope (95% confidence interval) of mdPT for apixaban, edoxaban, and rivaroxaban was 0.0068 (0.0063-0.0075), 0.0076 (0.0072-0.0080), and 0.0072 (0.0065-0.0078), respectively, which were higher than that of four commercial PT and dPT reagents, ranging within 0.0006-0.0023, 0.0017-0.0038, and 0.0016-0.0057 (all, p < 0.001), respectively.

CONCLUSION

Compared with other PT and dPT reagents, mdPT reagent showed sharper slope to all direct FXa inhibitors, and higher correlation to apixaban and comparable correlation to edoxaban and rivaroxaban. This new reagent is expected to be a coagulation screening assay having a consistently high response to any types of direct FXa inhibitors.

Molecularly Imprinted Nanomaterials with Stimuli Responsiveness for Applications in Biomedicine

The review aims to summarize recent reports of stimuli-responsive nanomaterials based on molecularly imprinted polymers (MIPs) and discuss their applications in biomedicine. In the past few decades, MIPs have been proven to show widespread applications as new molecular recognition materials. The development of stimuli-responsive nanomaterials has successfully endowed MIPs with not only affinity properties comparable to those of natural antibodies but also the ability to respond to external stimuli (stimuli-responsive MIPs). In this review, we will discuss the synthesis of MIPs, the classification of stimuli-responsive MIP nanomaterials (MIP-NMs), their dynamic mechanisms, and their applications in biomedicine, including bioanalysis and diagnosis, biological imaging, drug delivery, disease intervention, and others. This review mainly focuses on studies of smart MIP-NMs with biomedical perspectives after 2015. We believe that this review will be helpful for the further exploration of stimuli-responsive MIP-NMs and contribute to expanding their practical applications especially in biomedicine in the near future.

Direct oral anticoagulants versus warfarin in patients with antiphospholipid syndrome: A meta-analysis of randomized controlled trials

Objective

This study aimed to evaluate the efficacy and safety of direct oral anticoagulants (DOACs) versus warfarin in patients with antiphospholipid syndrome (APS).

Methods

We performed a literature search using MEDLINE, EMBASE, and the Cochrane Controlled Trials Register. We also performed a meta-analysis of randomized controlled trials (RCTs) investigating the effectiveness and safety of DOACs versus warfarin in patients with APS.

Results

Five RCTs involving 648 patients with APS (330 in DOAC-treated and 318 in control groups) were included in the meta-analysis. Among the patients included in the analysis, 29 (8.8%) patients experienced recurrent thrombosis in the DOAC treatment group, and 10 patients (3.1%) had thrombosis recurrence in the warfarin treatment group, resulting in a higher incidence in DOAC-treated than in the warfarin-treated groups [odds ratio (OR) = 2.163, 95% CI = 0.985–4.748, p = 0.055]. Incidence of arterial thrombosis was significantly higher in DOAC-treated patients than in warfarin-treated patients (OR = 5.168, 95% CI = 1.567–17.04, p = 0.007). Stroke and thrombosis occurrences were significantly higher in the triple positivity group than in the warfarin therapy group (OR = 12.03, 95% CI = 2.249–64.36, p = 0.004; OR = 2.940, 95% CI = 1.016–8.504, p = 0.047). However, venous thrombosis occurrences did not differ significantly between the DOAC-treated and warfarin-treated groups. There were no significant differences between the DOAC and warfarin groups in terms of any bleeding, major bleeding, minor bleeding, and all-cause mortality.

Conclusion

DOACs were associated with higher rates of arterial thrombosis than warfarin in patients with APS, especially in the triple-positive group. However, a higher risk of recurrent venous thrombosis was not found in APS patients treated with DOACs compared to those treated with warfarin.

Porous dynamic covalent polymers as promising reversal agents for heparin anticoagulants

Heparins are natural and partially degraded polyelectrolytes that consist of sulfated polysaccharide backbones. However, as clinically used anticoagulants, heparins are associated with clinical bleeding risks and thus require rapid neutralization. Protamine sulfate is the only clinically approved antidote for unfractionated heparin (UFH), which not only may cause severe adverse reactions in patients, but also is only partially effective against low molecular weight heparins (LMWHs). We here present the facile synthesis of four porous multicationic dynamic covalent polymers (DCPs) from the condensation of tritopic aldehyde and acylhydrazine precursors. We show that, as new water-soluble polymeric antidotes, the new DCPs can effectively include both UFH and LMWHs and thus reverse their anticoagulating activity, which is confirmed by the activated partial thromboplastin time and thromboelastographic assays as well as mouse tail transection assay (bleeding model). The neutralization activities of two of the DCPs were found to be overall superior to that of protamine and have wider concentration windows and good biocompatibility. This pore-inclusion neutralization strategy paves the way for the development of water-soluble polymers as universal heparin binding agents.

Vitamin K: A Simple and Efficient Add-on to the Current Treatment Regime of COVID-19

Background:

: Intravascular thrombosis and pulmonary fibrosis in COVID-19 patients with pneumonia is significantly associated with the severity of disease. Vitamin K is known to balance the coagulation mechanisms and also prevents calcification and fibrosis of the extrahepatic soft tissues. This narrative review focuses on the role of Vitamin K as a linking factor for thrombotic as well as pulmonary complications of COVID-19.

Methods and Results:

Article search was performed in databases of WHO, PubMed, Scopus and Clinical Trial Registry using appropriate key words. Original articles included very few observational studies which showed a reduced level of Vitamin K as well as activated extrahepatic Vitamin K Dependent Proteins (VKDP) in COVID-19 patients when compared to healthy controls. Chronic treatment with Vitamin K Antagonists did not reduce the risk of in-hospital death. Docking study was performed using Swiss dock and it gave a significant interaction between menaquinone and SARS-CoV-2 main Protease (SARS-CoV-2 Mpro).

Discussion:

Deficiency of Vitamin K in COVID-19 can be due to excess use of antagonists or defective ingestion or absorption. This triggers an imbalance in the normal coagulation-anticoagulation mechanism by channelling the available Vitamin K to the liver and thereby causing a deficiency of the same in extrahepatic tissues and finally leading to thrombosis. This also prevents carboxylation and activation of extrahepatic VKDP required to prevent the calcification of soft tissues and thus leading to lung fibrosis.

Conclutions:

Supplementation of Vitamin K should be considered as a potentially modifiable risk factor in severe COVID-19. Randomized control trials are highly recommended to give clearer evidence on the same.

Heparin and Its Derivatives: Challenges and Advances in Therapeutic Biomolecules

Heparin has been extensively studied as a safe medicine and biomolecule over the past few decades. Heparin derivatives, including low-molecular-weight heparins (LMWH) and heparin pentasaccharide, are effective anticoagulants currently used in clinical settings. They have also been studied as functional biomolecules or biomaterials for various therapeutic uses to treat diseases. Heparin, which has a similar molecular structure to heparan sulfate, can be used as a remarkable biomedicine due to its uniquely high safety and biocompatibility. In particular, it has recently drawn attention for use in drug-delivery systems, biomaterial-based tissue engineering, nanoformulations, and new drug-development systems through molecular formulas. A variety of new heparin-based biomolecules and conjugates have been developed in recent years and are currently being evaluated for use in clinical applications. This article reviews heparin derivatives recently studied in the field of drug development for the treatment of various diseases.

Vitamin K in COVID-19—Potential Anti-COVID-19 Properties of Fermented Milk Fortified with Bee Honey as a Natural Source of Vitamin K and Probiotics

Vitamin K deficiency is evident in severe and fatal COVID-19 patients. It is associated with the cytokine storm, thrombotic complications, multiple organ damage, and high mortality, suggesting a key role of vitamin K in the pathology of COVID-19. To support this view, we summarized findings reported from machine learning studies, molecular simulation, and human studies on the association between vitamin K and SARS-CoV-2. We also investigated the literature for the association between vitamin K antagonists (VKA) and the prognosis of COVID-19. In addition, we speculated that fermented milk fortified with bee honey as a natural source of vitamin K and probiotics may protect against COVID-19 and its severity. The results reported by several studies emphasize vitamin K deficiency in COVID-19 and related complications. However, the literature on the role of VKA and other oral anticoagulants in COVID-19 is controversial: some studies report reductions in (intensive care unit admission, mechanical ventilation, and mortality), others report no effect on mortality, while some studies report higher mortality among patients on chronic oral anticoagulants, including VKA. Supplementing fermented milk with honey increases milk peptides, bacterial vitamin K production, and compounds that act as potent antioxidants: phenols, sulforaphane, and metabolites of lactobacilli. Lactobacilli are probiotic bacteria that are suggested to interfere with various aspects of COVID-19 infection ranging from receptor binding to metabolic pathways involved in disease prognosis. Thus, fermented milk that contains natural honey may be a dietary manipulation capable of correcting nutritional and immune deficiencies that predispose to and aggravate COVID-19. Empirical studies are warranted to investigate the benefits of these compounds.