Specific antidotes against direct oral anticoagulants: A comprehensive review of clinical trials data

Thromboembolic prevention in athletes: management of anticoagulation in sports players affected by atrial fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia that poses a significant risk of stroke and thromboembolic events. Anticoagulation therapy is essential for preventing stroke in patients with AF. An increasing number of people of all ages, including cardiac patients, approach physical activity as both a leisure-time exercise and a competitive sport. Therefore, patients at risk of AF are increasingly allowed to practice sports activities. Management of oral anticoagulant therapy (OAT) in these patients is extremely challenging because of the need to balance the risks and benefits of medications, considering both hemorrhagic (in case of trauma) and ischemic complications when the drugs are avoided. Official recommendations are limited for these patients and forbid sports that increase the risk of trauma and consequent bleeding in most cases. These recommendations are strongly influenced by the "traditional" management of OAT, which mainly involves coumarin derivatives. Non-vitamin K antagonist direct oral anticoagulants (DOACs), with their more favorable pharmacokinetic-pharmacodynamic profile than that of coumarin derivatives, may represent an opportunity to modify the approach to sports activity in patients with AF and indications for OAT. This study aimed to review the use of anticoagulants in athletes with AF, highlight their efficacy and safety, and provide practical considerations regarding their management.

Being precise with anticoagulation to reduce adverse drug reactions: are we there yet?

Anticoagulants are potent therapeutics widely used in medical and surgical settings, and the amount spent on anticoagulation is rising. Although warfarin remains a widely prescribed oral anticoagulant, prescriptions of direct oral anticoagulants (DOACs) have increased rapidly. Heparin-based parenteral anticoagulants include both unfractionated and low molecular weight heparins (LMWHs). In clinical practice, anticoagulants are generally well tolerated, although interindividual variability in response is apparent. This variability in anticoagulant response can lead to serious incident thrombosis, haemorrhage and off-target adverse reactions such as heparin-induced thrombocytopaenia (HIT). This review seeks to highlight the genetic, environmental and clinical factors associated with variability in anticoagulant response, and review the current evidence base for tailoring the drug, dose, and/or monitoring decisions to identified patient subgroups to improve anticoagulant safety. Areas that would benefit from further research are also identified. Validated variants in VKORC1, CYP2C9 and CYP4F2 constitute biomarkers for differential warfarin response and genotype-informed warfarin dosing has been shown to reduce adverse clinical events. Polymorphisms in CES1 appear relevant to dabigatran exposure but the genetic studies focusing on clinical outcomes such as bleeding are sparse. The influence of body weight on LMWH response merits further attention, as does the relationship between anti-Xa levels and clinical outcomes. Ultimately, safe and effective anticoagulation requires both a deeper parsing of factors contributing to variable response, and further prospective studies to determine optimal therapeutic strategies in identified higher risk subgroups.

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

Systematic Review and Meta-Analysis of Oral Anticoagulant Therapy in Atrial Fibrillation Cancer Patients

(1) Introduction: Cancer and atrial fibrillation (AF) are increasingly coexisting medical challenges. These two conditions share an increased thrombotic and bleeding risk. Although optimal regimens of the most suitable anti-thrombotic therapy are now affirmed in the general population, cancer patients are still particularly understudied on the matter; (2) Aims And Methodology: This metanalysis (11 studies (incl. 266,865 patients)) aims at evaluating the ischemic-hemorrhagic risk profile of oncologic patients with AF treated with oral anticoagulants (vitamin K antagonists vs. direct oral anticoagulants); (3) Results: In the oncological population, DOACs confer a benefit in terms of the reduction in ischemic, hemorrhagic and venous thromboembolic events. However, ischemic prevention has a non-insignificant bleeding risk, lower than Warfarin but significant and higher than the non-oncological patients; (4) Conclusions: Anticoagulation with DOACs provides a higher safety profile with respect to VKAs in terms of stroke reduction and a relative bleeding reduction risk. Further studies are needed to better assess the optimal anticoagulation strategy in cancer patients with AF.

Anti-Strychnine Immunoconjugate Reduces the Effects of Strychnine-Induced Toxicity in Mice

Strychnine poisoning induces seizures that result in loss of control of airway muscles, leading to asphyxiation and subsequent death. Current treatment options are limited, requiring hands-on medical care and isolation to low-stimulus environments. Anticonvulsants and muscle relaxants have shown limited success in cases of severe toxicity. Furthermore, nonfatal strychnine poisoning is likely to result in long-term muscular and cognitive damage. Due to its potency, accessibility, and lack of effective antidotes, strychnine poses a unique threat for mass casualty incidents. As a first step toward developing an anti-strychnine immunotherapy to reduce or prevent strychnine-induced seizures, a strychnine vaccine was synthesized using subunit keyhole limpet hemocyanin. Mice were vaccinated with the strychnine immunoconjugate and then given a 0.75 mg/kg IP challenge of strychnine and observed for seizures for 30 min. Vaccination reduced strychnine-induced events, and serum strychnine levels were increased while brain strychnine levels were decreased in vaccinated animals compared to the control. These data demonstrate that strychnine-specific antibodies can block the seizure-inducing effects of strychnine and could be used to develop a therapeutic for strychnine poisoning.

Present Knowledge on Direct Oral Anticoagulant and Novel Oral Anti Coagulants and Their Specific Antidotes: A Comprehensive Review Article

Thromboembolic diseases are one of the leading causes of morbidity and mortality worldwide. For a long time, heparin and Vitamin K antagonist (VKA) drugs were used for treatment and prophylaxis of the thromboembolic diseases. The development of newer direct and novel oral anticoagulant medications (DOACs/NOACs) has changed clinical practice significantly. Lesser monitoring, ease with dosing, less drug interactions have made these drugs useful to the providers and the patients. But these drugs have bleeding as a side effect. There is ongoing research on the specific antidotes of these anticoagulants in case of life-threatening bleeding. Though the use of the DOACs and NOACs have increased, there is still not enough clinical evidence about the specific antidotes of these medications. Unlike heparin or VKA, reversal of life-threatening bleeding in the setting of DOAC use is still a clinical challenge. We need more data on the dose, pharmacokinetics, and clinical efficacy of those antidotes. Authors have reviewed articles on DOACs and their antidotes in Pubmed and also in the clinical trial website. Specific antidotes including Idarucizumab for Dabigatran, Andexanet alfa for factor Xa inhibitors are being used to reverse the actions of the anticoagulants. Ciraparantag is a universal antidote for the DOACs, which is still under investigation. FXaI16L is currently being investigated as a potential universal antidote for multiple anticoagulants, including dabigatran and rivaroxaban. Though mostly safe, the use of DOACs can still carry a risk of severe bleeding in patients. More data on the use of the antidotes is required to reverse the side effect of DOACs if clinically indicated.

Alternatives for Vitamin K Antagonists as Thromboprophylaxis for Mechanical Heart Valves and Mechanical Circulatory Support Devices: A Systematic Review

The holy grail of anticoagulation in patients with intracardiac devices, such as mechanical heart valves (MHVs) and left ventricular assist devices (LVADs), comprises safe prevention of thrombosis without interrupting normal hemostasis. Device-induced thrombosis and anticoagulant-related bleeding problems are dreaded complications that may cause a significantly reduced quality of life and increased morbidity and mortality. Vitamin K antagonists are the current standard for oral anticoagulation therapy in patients with MHVs and LVADs. Even within the therapeutic range, hemorrhage is the primary complication of these drugs, which emphasizes the need for safer anticoagulants for the prevention of device-induced thrombosis. Device-induced thrombosis is a complex multifactorial phenomenon that likely requires anticoagulant therapy targeting multiple pathways. Here, we review the preclinical and clinical data describing the efficacy of a variety of anticoagulants as thromboprophylaxis after implantation of intracardiac devices.

Direct oral anticoagulants in point-of-care monitoring: an ex-vivo study

BACKGROUND

Anticoagulatory activity of direct oral anticoagulants (DOACs) is not routinely measurable by point-of-care monitoring. Thus, the aim of this study was to evaluate the influence of dabigatran/rivaroxaban on point-of-care testing.

METHODS

Samples from 34 participants under DOAC therapy were drawn at two time points. Before ingestion and two-to-three hours afterwards. Thrombelastometric (ROTEM) and aggregometric (Multiplate) measurements were performed. Dabigatran and rivaroxaban plasma levels were determined.

RESULTS

Dabigatran and rivaroxaban plasma levels showed significant correlations with clotting time (CT) in EXTEM (r=0.765, P<0.0001; r=0.689, P<0.0001) and INTEM (r=0.792, P<0.0001; r=0.595, P<0.001). A positive correlation was identified between dabigatran ingestion and maximum-clot-firmness (MCF) (r=0.354, P<0.05) in the EXTEM test, pronounced in the absence of concomitant antiplatelet therapy (r=0.709, P<0.05). EXTEM-MCF positively correlated with the TRAP test in aggregometry (0.662, P<0.05), an effect not observed in patients treated with antiplatelet therapy.

CONCLUSIONS

Prolongation of CT-EXTEM and CT-INTEM indicates delayed initiation of clot formation. The CT-EXTEM seems to facilitate qualitative monitoring of dabigatran. In contrast, qualitative monitoring of rivaroxaban by CT-EXTEM may be limited as rivaroxaban may affect the measurement at therapeutic plasma levels. It seems that clot formation is faster/firmer in the presence of increased dabigatran plasma levels. This can be attributed to a non-dose-dependent effect via increased fibrin polymerization and second to a dose-dependent effect via increased platelet sensitivity to thrombin.

Dabigatran Reversal With Idarucizumab in 2 Patients With Portal Vein Thrombosis Undergoing Orthotopic Liver Transplantation

There are limited data to guide the use of anticoagulation in cirrhotic patients prior to liver transplantation especially when using direct oral anticoagulants. In this article, we present 2 cases. The first is a 42-year-old male with cirrhosis complicated by portal vein thrombosis (PVT) treated with dabigatran who underwent orthotopic liver transplantation without complication. The second case is a 65-year-old man with alcoholic cirrhosis complicated by PVT treated with dabigatran who underwent orthotopic liver transplantation and required reoperation for surgical bleeding. Both patients were treated with dabigatran’s reversal agent idarucizumab prior to incision. In this case series, we discuss the treatment of cirrhotic patients with various anticoagulants, considerations for anticoagulant selection and reversal prior to liver transplant, and questions for future investigation.

What is the role of andexanet alfa in the reversal of anticoagulant effects?

ABSTRACT

Although using direct oral anticoagulants increases patient risk for hemorrhagic events, FDA-approved options for reversing anticoagulant effects are limited. This article discusses one of the more recent FDA-approved antidotes, andexanet alfa, and provides guidelines for its safe and effective use.

Direct oral anticoagulants: a review on the current role and scope of reversal agents

New guideline recommendations prefer direct oral anticoagulants (DOACs) over warfarin in DOAC-eligible patients with atrial fibrillation and patients with venous thromboembolism. As expected with all antithrombotic agents, there is an associated increased risk of bleeding complications in patients receiving DOACs that can be attributed to the DOAC itself, or other issues such as acute trauma, invasive procedures, or underlying comorbidities. For the majority of severe bleeding events, the widespread approach is to withdraw the DOAC, then provide supportive measures and "watchful waiting" with the expectation that the bleeding event will resolve with time. However, urgent reversal of anticoagulation may be advantageous in patients with serious or life-threatening bleeding or in those requiring urgent surgery or procedures. Until recently, the lack of specific reversal agents, has affected the uptake of these agents in clinical practice despite a safer profile compared to warfarin in clinical trials. In cases of life-threatening or uncontrolled bleeding or when patients require emergency surgery or urgent procedures, idarucizumab has been recently approved for reversal of anticoagulation in dabigatran-treated patients and andexanet alfa for factor Xa inhibitor-treated treated patients. The current review summarizes the current clinical evidence and scope of these agents with the potential impact on DOAC use in clinical practice.

National Physician Survey for Nonvalvular Atrial Fibrillation (NVAF) Anticoagulation Comparing Knowledge, Attitudes and Practice of Cardiologist to PCPs

Introduction:

NVAF is estimated to affect between 6.4 and 7.4 million Americans in 2018, and increases the risk of stroke 5-fold. To mitigate this risk, guidelines recommend anticoagulating AF patients unless their stroke risk is very low. Despite these recommendations, 30.0-60.0% of NVAF patients do not receive indicated anticoagulation. To better understand why this may be, we surveyed PCPs and cardiologists nationwide on their attitudes, knowledge and practices toward managing NVAF with warfarin and direct-acting oral anticoagulants (DOACs).

Methods:

We surveyed 1,000 PCPs and 500 cardiologists selected randomly from a master list of the American Medical Association, using a paper based, anonymous, self-administered, mailed scannable survey. The survey contained questions on key demographics and data concerning attitudes, knowledge and practices related to prescribing DOACs. The surveys went out in the fall/winter of 2017-8 with a $10 incentive gift card. Survey responses were scanned into an Excel database and analyzed using SAS 9.3 (Cary, NC) for descriptive and inferential statistics.

Results:

Two hundred and forty-nine providers (167 PCPs, 82 cardiologists) participated in the study with a response rate of 18.8% (249/1320). Respondent mean years ±SD of experience since completing residency was 23.2 ± 13.8. Relative to cardiologists, less PCPs use CHADsVASC (36.8% vs. 74.4%) (p < 0.0001); more have never used HAS-BLED, HEMORR2HAGES, or ATRIA (38.5% vs. 9.8%) (p < .0001); more felt that their lack of knowledge/experience with DOACs was a barrier to prescribing the agents (p = 0.005); and more reported that they could use additional education on DOACs (87.0% vs. 47.0%) (p < 0.0001). Overall, cardiologists were more concerned about ischemic stroke outcomes, while PCPs were more concerned with GI bleeding. Cardiologists also felt that clinical trial data were most helpful in choosing the most appropriate DOAC for their patients, while PCPs felt that Real World Data was most useful.

Conclusions:

Cardiologists were more concerned with ischemic stroke while anticoagulating patients and utilized screening instruments like CHADsVASC in a majority of their patients. PCPs were concerned with GI bleeds when anticoagulating but nearly 40.0% utilized no screening tools to assess bleeding risk. Our findings show that future education about DOACs would be warranted especially with PCPs.

Update and Review of Bleeding Considerations in Dermatologic Surgery: Anticoagulants and Antiplatelets

BACKGROUND

Bleeding is an unavoidable risk of dermatologic surgery. The risk may be higher in patients taking agents that affect hemostasis.

OBJECTIVE

The aim of this study was to provide an updated review of current anticoagulant and antiplatelet therapy available in the market and their associated risk of bleeding complications in cutaneous surgery.

MATERIALS AND METHODS

A review of PubMed and MEDLINE was performed to review the English-language medical literature.

RESULTS

Many anticoagulant and antiplatelet therapies exist. Several studies recommend the continued use of antiplatelet and anticoagulant medications in the perioperative period. Combination regimens and novel oral anticoagulants may be associated with an increased risk of bleeding.

CONCLUSION

An updated understanding of antiplatelet and anticoagulant agents is critical for the surgeon. Current evidence does not support the discontinuation of antiplatelet and anticoagulant agents in the perioperative period under most circumstances. However, relevant data on novel oral anticoagulant agents are still sparse, suggesting that a precautionary approach is warranted.

Andexanet alfa for reversal of factor Xa inhibitor-associated anticoagulation

Background:

Review of clinical data on andexanet alfa for the reversal of factor Xa (FXa) inhibitor associated anticoagulation.

Data sources:

In the present review, we identified articles via PubMed using the combined keywords andexanet alfa, apixaban, enoxaparin, edoxaban, and rivaroxaban. Additional online searches via PubMed, Google Scholar, and Lexicomp were conducted for both prescribing and cost information. Portola Pharmaceuticals was contacted for information used for United States Food and Drug Administration approval of andexanet alfa.

Study selection and data extraction:

English-language clinical trials and reviews published between January 2008 and April 2019 were included for review. Bibliographies of selected articles were reviewed manually for relevant publications, focusing on reversal strategies for apixaban, enoxaparin, edoxaban, or rivaroxaban associated anticoagulation using andexanet alfa. Review articles were excluded.

Data synthesis:

The safety and tolerability of andexanet alfa were evaluated in one phase I, two phase II, and one phase III clinical trials. The use of andexanet alfa for reversing FXa inhibitor-associated anticoagulation were evaluated in the phase III ANNEXA-4 study.

Conclusions:

Studies evaluating laboratory parameters for coagulation show that andexanet alfa rapidly neutralizes the anticoagulant effects of apixaban, enoxaparin, edoxaban, and rivaroxaban. Clinical studies show that andexanet alfa improves markers related to coagulation, and reverses major bleeding in healthy volunteers and patients with life-threatening bleeding. Interruption of anticoagulation may result in thromboembolic and ischemic events. The use of andexanet alfa requires close monitoring for signs and symptoms of thromboembolic events, ischemic events, and cardiac arrest. Furthermore, anticoagulation should be resumed following the administration of andexanet alfa as soon as medically appropriate.

Management of Hemorrhage Related to Direct Action Oral Anticoagulant Medication

Introduction: Direct Oral Anticoagulant – DOACs) are a new class of anticoagulant that directly inhibit the trombine (dabigatran) or Xa factor (rivaroxabane , edoxabane and apixabane) in the coagulation cascade. These medications are being more frequently used for the treatment and prevention of thrombolytic events, mainly in patients with atrial fibrillation, in substitute to varfrine or other vitamin K antagonists (VKAs). Although the incidence of hemorrhage is higher in AVKs than in DOACs, these events may also occur in this group, even in the form of intracranial hemorrhage (ICH), with risk of death. Nowadays, DOACs indications have progressively enhanced and the availability of their specific reverse agents certainly will enhance the safety of their usage. Idarucizumab, reverse agent of dabigatrane, and alpha andexanet, reverse agent of Xa factor, have been approved by the Food and Drug Administration in the United States and ciraparantag may be approved in a near future. Objective: To review the literature on the manage of hemorrhage related to the use of DOACs. Methods: Review of literature that used articles from 1998 to 2017, from several platforms and journals. Conclusion: DOACs constitute a great advance in prophylaxis and treatment of thrombolytic diseases, which presents elevated morbidymortality, and hemorrhages are the main adverse events related to their usage, being rarely necessary the immediate reverse of the anticoagulation. However, the existence of DOACs specific reverse agents enhance the safety of patients, whose anticoagulation may be rapidly reversed if necessary.

Manejo das Hemorragias Relacionadas aos Anticoagulantes Orais de Ação Direta

Introdução: Os anticoagulantes orais diretos (direct oral anticoagulant – DOACs) são uma nova classe de anticoagulantes que inibem diretamente a trombina (dabigatrana) ou o fator Xa (rivaroxabana, edoxabana e apixabana) na cascata da coagulação. Esses estão sendo cada vez mais utilizados para tratamento e prevenção de eventos tromboembólicos, principalmente em pacientes com fibrilação atrial, em substituição à varfarina ou outros antagonistas de vitamina K (AVKs). Embora a incidência de hemorragias seja maior nos AVKs do que nos DOACs, elas também podem ocorrer nesse grupo, até mesmo na forma de hemorragia intracraniana (HIC) com risco de morte. Atualmente as indicações dos DOACs vêm aumentando progressivamente, e a disponibilização de seus agentes reversores específicos certamente aumentará a segurança e, consequentemente, sua utilização. O idarucizumab, reversor da dabigatrana, e o andexanet alfa, reversor dos inibidores do fator Xa, foram aprovados pelo Food and Drug Administration (FDA) dos Estados Unidos e o ciraparantag poderá ser aprovado em um futuro próximo. Objetivo: Revisar a literatura sobre o manejo da hemorragia relacionada ao uso dos DOACs. Métodos: Revisão da literatura que utilizou artigos de 1998 a 2017, de diversas plataformas e revistas. Conclusão: Os DOACs constituem um grande avanço na profilaxia e tratamento da doença tromboembólica, que cursa com elevada morbimortalidade, e as hemorragias são os principais eventos adversos relacionados ao seu uso, sendo raramente necessária a reversão imediata da anticoagulação. No entanto, a existência dos reversores específicos dos DOAcs aumenta a segurança dos pacientes, que poderão ter sua anticoagulação revertida rapidamente, se necessário.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Reversal agents for oral anticoagulants

For more than half a century, warfarin, a vitamin K antagonist, has been the anticoagulant of choice. However, direct oral anticoagulants are rapidly gaining in popularity, which poses the need for efficacious reversal agents. This review article summarizes the strategies and agents used to reverse oral anticoagulants.

Perioperative management of patients with atrial fibrillation receiving anticoagulant therapy

The number of patients with atrial fibrillation (AF) and the number of patients indicated for anticoagulant therapy have been increasing because AF would affect patient survival due to thromboembolism. Once AF develops, following the disappearance of pulsation, the circumstances within the atrium become prothrombotic and thrombus formation within the left atrium occurs in patients with AF. In recent years, not only warfarin but also new oral anticoagulants were introduced clinically and have become used as oral anticoagulants. In the perioperative period, the risk of major hemorrhage needs to be reduced. On the other hand, the suspension of anticoagulant therapy and neutralization of anticoagulant effects elevate the risk of thrombosis. The perioperative management of patients receiving anticoagulant therapy is different from that of scheduled surgery and emergency surgery. In addition, knowledge of the characteristics of each oral anticoagulant is required at drug cessation and resumption. Unlike warfarin, which has been used in the past five decades, direct oral anticoagulants (DOACs) do not have sensitive indicators such as prothrombin time-international normalized ratio. To avoid major hemorrhages and thromboembolism, quantitative assays can be implemented for DOAC monitoring and for reversal therapies in perioperative settings.

Effects of Oral Anticoagulant Therapy on Gene Expression in Crosstalk between Osteogenic Progenitor Cells and Endothelial Cells

Direct oral anti-coagulants (DOACs) are employed in clinical practice for the prevention and treatment of recurrent venous thromboembolism and for the prevention of stroke in non-valvular atrial fibrillation. DOACs directly and reversibly inhibit activated factor X or thrombin and can interfere with other pathophysiological processes such as inflammation, lipid metabolism, and bone turnover. We aimed to evaluate the possible effects of DOACs on osteogenesis and angiogenesis. We treated 34 patients affected by cardiovascular disorders with DOACs; biochemical and molecular analyses were performed before and after three months of treatment. Circulating progenitors (CPs; CD34⁻, CD45⁻, CD14⁻, CD73⁺, CD105⁺), which share typical bone marrow stem cell (MSCs) features, were harvested from peripheral blood of the study subjects to monitor the expression of osteogenesis-related genes RUNX2 and SPARC. Human umbilical vein endothelial cells (HUVECs) were used to probe angiogenesis-related VEGF, CD31, and CD105 gene expression. We performed co-culture experiments using a commercial human mesenchymal stem cells line (hMSCs) obtained from bone marrow and HUVECs. Clinical parameters related to bone metabolism, coagulation, renal and liver function, and the lipid profile were evaluated. Values of the C-terminal telopeptide type I collagen (CTX) increased after the treatment. We found a significant increase in osteogenesis marker gene expression in CPs after three months of anticoagulant therapy. An increase in the RUNX2 expression determinant alone was detected instead in hMSCs co-cultured with HUVECs in the presence of treated patients’ sera. The VEGF, CD31, and CD105 marker genes appeared to be significantly upregulated in HUVECs co-cultured with hMSCs in the presence of treated patients’ sera. Under these conditions, new vessel formation increased as well. Our results highlight an unexpected influence of DOAC therapy on osteogenic commitment and vascular endothelial function promotion.

Reversal of dabigatran using idarucizumab: single center experience in four acute stroke patients

Dabigatran is a direct thrombin inhibitor and a non-vitamin-K-antagonizing oral anticoagulant, approved for the prevention of stroke and systemic embolization in atrial fibrillation. Idarucizumab is a humanized monoclonal antibody that was recently approved for antagonizing the anticoagulant effects of dabigatran. Here, we report the use of idarucizumab in four acute stroke patients treated with dabigatran in order to enable intravenous thrombolysis in three patients and emergent trepanation in one patient with space occupying subdural hematoma. Since experience on the optimal management of acute stroke patients under medication with dabigatran and on the use of idarucizumab is currently limited, we propose an approach for laboratory testing and fast administration of intravenous thrombolysis and neurosurgery based on our experience.

The Reversal of Bleeding Caused by New Oral Anticoagulants (NOACs): A Systematic Review and Meta-Analysis

New oral anticoagulants (NOACs; ie, direct thrombin inhibitor [DTI] and factor Xa [FXa] inhibitors) were used as alternatives to warfarin. Specific antidotes (idarucizumab for dabigatran and andexanet alfa for FXa inhibitors) and hemostatic reversal agents were used for lowering bleeding, but their efficacies were still uncertain. The objectives of this study were to estimate and compare the efficacy of NOAC antidotes on bleeding reversal and death. Studies were identified from MEDLINE and Scopus databases until May 2018. Case reports/series and cohorts were selected if they assessed reversal or death rates. Data were independently extracted by 2 reviewers. Individual patient data and aggregated data of outcomes were extracted from case reports/series and cohorts. Binary regression was used to estimate outcome rates, risk ratio (RR) along with 95% confidence interval (CI). Interventions were NOACs and reversal agents (ie, DTI-specific, DTI-standard, FXa-specific, and FXa-standard). Among 220 patients of 93 case reports/series, reversal rates were 95.9%, 77.6%, and 71.5% for DTI-specific, FXa-standard, and DTI-standard. Pooled RRs for DTI-specific and FXa-standard versus DTI-standard, respectively, were 1.34 (CI: 1.13-1.60) and 1.09 (CI: 0.84-1.40). Death rate was 0.18 (CI: 0.06-0.57) times lower in DTI-specific versus DTI-standard. For pooling 10 subcohorts, pooled RRs were 1.08 (CI: 1.00-1.16), 1.29 (CI: 1.20-1.39), and 1.13 (CI: 1.01-1.25) for DTI-specific, FXa-specific, and FXa-standard versus DTI-standard. In conclusion, specific reversal agents might be useful for reversal of bleeding and lowering the risk of death than standard reversal agents. Our findings were based on case reports/series and selected cohorts, further comparative studies are thus needed.

Practical perspectives on the use of non-vitamin K antagonist oral anticoagulants for stroke prevention in patients with nonvalvular atrial fibrillation: A view from the Middle East and North Africa

Clinical guidelines for the prevention of stroke in patients with nonvalvular atrial fibrillation (NVAF) are available from several international cardiology associations. Patients with NVAF in the Middle East and North Africa (MENA) region present unique challenges and opportunities related to differences in geography, practice patterns, and patient demographics that are as yet unaddressed in practice guidelines. This review aims to offer a practical perspective on the management of NVAF in patients in MENA and draws on evidence-based guidelines as well as real-world evidence and expert opinion. The literature was searched for relevant original research articles, systematic reviews, meta-analyses, and guideline recommendations addressing the prevention of stroke in patients with NVAF with a focus on issues relevant to the MENA region. Guideline recommendations, best practices, and expert opinion were discussed and agreed on by a working group consisting of cardiologists from across the MENA region. The incidence of stroke secondary to atrial fibrillation in patients across the MENA region is higher than rates reported globally, and this might be attributed to a higher incidence of vascular risk factors and underuse of anticoagulants in patients in the MENA. The available evidence supports the established role of non-vitamin K antagonist oral anticoagulants (NOACs) in the prevention of stroke in patients with NVAF. There is a consistent body of clinical trial and real-world evidence supporting their efficacy for stroke prevention in NVAF, with more favorable bleeding risk profiles relative to vitamin K antagonists, such that guidelines now recommend the use of NOACs in preference over vitamin K antagonists. There are important opportunities to improve the management of NVAF outcomes for patients with NVAF by applying evidence-based guidelines for stroke prevention. Growing experience with NOACs in the MENA region will help guide patient selection and elucidate optimal dosing strategies to maximize the clinical benefits of the NOACs.

The Evaluation of Pharmacodynamics and Pharmacokinetics of Anti-thrombin DNA Aptamer RA-36

Anticoagulants are a vital class of drugs, which are applied for short-term surgical procedures, and for long-term treatments for thrombosis prevention in high risk groups. Several anticoagulant drugs are commercially available, but all have intrinsic disadvantages, e.g., bleeding risks, as well as specific ones, e.g., immune response to peptide/protein drugs. Therefore, the search for novel, efficient and safe anticoagulants is essential. Nucleic acid aptamers are an emerging class of contemporary pharmaceuticals which are fully biocompatible and biodegradable; they have low toxicity, and are as efficient as many protein-based drugs. The anti-thrombin DNA aptamer RA-36 has been created using a combination of rational design and molecular dynamics, showing several extra-features over existing aptamers. Aptamer RA-36 has a bimodular structure; the first G-quadruplex binds and inhibits thrombin, whereas the second G-quadruplex varies the properties of the first. This bimodular structure provides a favorable dose-effect dependence allowing the risk of bleeding to be potentially decreased. Here, the results of efficiency trials of the aptamer are presented. The aptamer RA-36 has a distinctive species specificity; therefore, the careful selection of experimental animals was required. The anticoagulant activity was characterized in rats and monkeys in vivo. Antithrombotic activity was evaluated in the live murine model of the induced thrombosis. Pharmacokinetics was estimated by tracking radionuclide labeled aptamer in rats. The aptamer was thoroughly characterized using bivalirudin as a reference drug. Despite the different profiles of anticoagulant activity, these two compounds could refer to each other, and the corresponding doses could be estimated. Bivalirudin turned out to have 10-fold higher anticoagulant and antithrombotic activity. The difference in activity is easy to explain due to the pharmacokinetic profiles of the substances: the aptamer RA-36 has 20-fold faster elimination from blood with a half-life of 1 min. The entire dataset revealed that the non-modified DNA aptamer could be an alternative to the currently used bivalent peptide inhibitor; the dosage profile could be improved by manipulating aptamer pharmacokinetics. The study has revealed aptamer RA-36 to be one of the most promising candidates for further development as a new generation of anticoagulants.

An update on the bleeding risks associated with DOACs

The direct oral anticoagulants (DOACs), also referred to as novel (or non-vitamin K antagonist) oral anticoagulants (NOACs), represent a major development in anticoagulation therapy due to their rapid onset of action, predictable dose-response with fixed doses and limited interactions with food and drugs.^1,2 However, these agents have been in widespread clinical use for less than a decade and, compared with extensive experience with warfarin, there is uncertainty relating to optimal laboratory monitoring of anticoagulation, perioperative management and treatment of bleeding.3 In addition, there is currently only one drug licensed in the UK for rapid reversal of the anticoagulant effect of a DOAC. Here, we review DOAC-related bleeding and the role of drugs to reverse the anticoagulant action of DOACs.

Indications and Methods of Anticoagulation Reversal

The use of anticoagulation in the prevention of strokes due to atrial fibrillation or the treatment of venous thromboembolic disease has been on the rise. With the advent and proliferation of direct oral anticoagulation medications, the management of anticoagulation reversal has become increasingly complex, especially when urgent or emergent reversal is required. This review details the commonly used parenteral and oral anticoagulants, the treatment strategies necessary for their reversal, and therapies still in development.

Ischaemic stroke

There are about 25.7 million stroke survivors worldwide. Ischaemic stroke remains the most common type of stroke. Numerous modifiable risk factors have been identified, including behaviors such as cigarette smoking and sedentary lifestyle and treatable medical comorbidities such as hypertension, hyperlipidemia and atrial fibrillation. Once considered irreversible, acute ischaemic stroke is now amenable to acute medical and endovascular therapies to reduce infarct volume. Many advances are expected in the years to come, particularly in the areas of prevention and recovery.

Transfusion Practice in Trauma Resuscitation

Recognition of the acute coagulopathy of trauma and the limits of reconstituting whole blood with conventional blood components has led to a radical change in the way trauma patients with severe injuries are resuscitated. Massive transfusion protocols (MTP) have evolved toward the administration of conventional blood components in fixed ratios. Administration of a 1:1:1 unit ratio of fresh frozen plasma to whole-blood-derived platelets to packed red blood cells is now the most common strategy and the stated goal of directors of >80% of the level I trauma centers in the United States. Various physiologic scoring systems exist to guide early activation of an MTP. After activation of an MTP, more goal-directed therapy follows as soon as laboratory results are available. Hemostatic resuscitation using defined blood component ratios modified by early laboratory results can lead to more efficient blood product usage and improved patient outcomes.

The representativeness of direct oral anticoagulant clinical trials to hospitalized patients with atrial fibrillation

PURPOSE

Trials of the direct oral anticoagulants (DOACs) dabigatran, rivaroxaban and apixaban provide the basis for prescribing for the prevention of stroke and systemic embolism in atrial fibrillation (AF). The objective of this study was to assess the representativeness of the three pivotal DOAC randomized controlled trials of dabigatran, rivaroxaban and apixaban for unselected hospitalized patients with AF.

METHODS

A cross-sectional study was undertaken. All patients discharged with AF between 2012 and 2015 from a large public hospital network in Melbourne, Australia, were identified. Inclusion and exclusion criteria from the DOAC trials were applied. The proportions of hospitalized patients with AF who would have been eligible for the dabigatran (RE-LY), rivaroxaban (ROCKET-AF) and apixaban (ARISTOTLE) trials were estimated, as was pooled eligibility for all three trials. Characteristics of eligible and ineligible patients were compared.

RESULTS

For the 4734 patients, application of the inclusion and exclusion criteria resulted in 60.5, 52.6 and 35.8% eligibility for the trials of apixaban, dabigatran and rivaroxaban, respectively. Pooled eligibility across all three trials demonstrated that 33.4% of the patients would have been eligible for all three trials but 36.7% ineligible for any trial. Ineligible patients who met exclusion criteria were older and experienced more comorbidities.

CONCLUSIONS

The apixaban and dabigatran trials may be the most representative of hospitalized patients with AF. The DOAC trial results can readily be extrapolated to, and guide prescribing for, at least two thirds of patients discharged from a large metropolitan health service in Australia.

Prothrombin Complex Concentrates in Pediatric Cardiac Surgery: The Current State and the Future

BACKGROUND

After decades of practice of pediatric cardiac surgery, postoperative bleeding due to the immaturity of hemostasis, hemodilution, and hypothermia remains a concern. Recently, a new approach for adult coagulopathy after bypass has emerged. Prothrombin complex concentrates (PCCs), designed to treat bleeding in hemophilia patients, are safely and efficiently used off label for hemorrhage after bypass. However, optimal dosing, indications and contraindications, and laboratory tests to assess the efficacy of PCC use in children have not yet been established. This literature review outlines the challenges of bypass-related coagulopathy, the pharmacology, and the experience in use of PCCs, with a focus on their potential in pediatric cardiac surgery.

METHODS

After a thorough literature search of MEDLINE, Scopus, and Ovid databases using the term "prothrombin complex concentrate AND pediatric," 23 relevant articles were selected.

RESULTS

The data supporting successful use of PCCs in acquired coagulopathy after cardiac surgery in adults have been increasing. Although small volume, low immunogenicity, efficiency, and speed in correcting coagulopathy are attractive qualities of PCCs for pediatric practice, current evidence is only anecdotal. The main concerns are unknown dosing regimens, the inability to closely monitor the effects of PCCs in real time, and a possibility of thrombotic complications, which can be particularly devastating in young congenital cardiac patients whose lives frequently depend upon the patency of artificial shunts.

CONCLUSIONS

Extensive, high-quality research is warranted to fill in the gaps of knowledge regarding using PCCs in pediatric cardiac practice.

The Nonvitamin K Antagonist Oral Anticoagulants and Atrial Fibrillation: Challenges and Considerations

The nonvitamin K antagonist oral anticoagulants (NOACs) dabigatran, rivaroxaban, apixaban, and edoxaban are used for the reduction of the risk of stroke or systemic embolism (SEE) in patients with nonvalvular atrial fibrillation (NVAF). The purpose of this review is to highlight the safety and efficacy results of the pivotal NOAC clinical trials for use in NVAF, discuss some of the unique management challenges in the use of NOACs in special populations, summarize data on emerging and novel indications, and address potential future directions.

METHODS

A literature search was conducted and to identify relevant clinical trials and studies regarding the use of NOACs for the prevention of stroke or SEE in patients with atrial fibrillation.

RESULTS

Relative to warfarin, NOACs are as effective or superior in the prevention of stroke or SEE, and are associated with similar or lower rates of major bleeding and significantly decreased rates of intracranial bleeding, but may be associated with a slightly increased risk of gastrointestinal bleeding in patients with AF. The NOACs are not indicated for use and have not been widely tested in AF patients with other cardiovascular conditions. Additional ongoing and planned clinical trials will provide additional information regarding the use of NOACs in these patients. In situations requiring rapid reversal of anticoagulation, the availability of specific antidotes will improve safety and facilitate NOAC use.

CONCLUSIONS

Use of NOACs in clinical practice requires consideration of patient characteristics as well as potentially required procedures.