Drug therapy in anticoagulation: which drug for which patient?

Fibrin-glycoprotein VI interaction increases platelet procoagulant activity and impacts clot structure

BACKGROUND

The glycoprotein VI (GPVI) signaling pathway was previously reported to direct procoagulant platelet activity through collagen binding. However, the impact of GPVI-fibrin interaction on procoagulant platelet development and how it modulates the clot structure are unknown.

OBJECTIVES

To determine the effect of GPVI-fibrin interaction on the platelet phenotype and its impact on the clot structure.

METHODS

Procoagulant platelets in platelet-rich plasma clots were determined by scanning electron microscopy (wild-type and GPVI-deficient murine samples) and confocal microscopy. Procoagulant platelet number, clot density, clot porosity, and clot retraction were determined in platelet-rich plasma or whole blood clots of healthy volunteers in the presence of tyrosine kinase inhibitors (PRT-060318, ibrutinib, and dasatinib) and eptifibatide.

RESULTS

GPVI-deficient clots showed a higher nonprocoagulant vs procoagulant platelet ratio than wild-type clots. The fiber density and the procoagulant platelet number decreased in the presence of Affimer proteins, inhibiting GPVI-fibrin(ogen) interaction and the tyrosine kinase inhibitors. The effect of GPVI signaling inhibitors on the procoagulant platelet number was exacerbated by eptifibatide. The tyrosine kinase inhibitors led to an increase in clot porosity; however, no differences were observed in the final clot weight, following clot retraction with the tyrosine kinase inhibitors, except for ibrutinib. In the presence of eptifibatide, clot retraction was impaired.

CONCLUSION

Our findings showed that GPVI-fibrin interaction significantly contributes to the development of procoagulant platelets and that inhibition of GPVI signaling increases clot porosity. Clot contractibility was impaired by the integrin αIIbβ3 and Btk pathway inhibition. Thus, inhibition of GPVI-fibrin interactions can alleviate structural characteristics that contribute to a prothrombotic clot phenotype, having potential important implications for novel antithrombotic interventions.

Effectiveness and safety of direct oral anticoagulants in patients with venous thromboembolism and creatinine clearance < 30 mL/min

The few studies that compared direct oral anticoagulants (DOAC) vs. warfarin in the setting of advanced renal insufficiency have focused on patients with atrial fibrillation. The purpose of this observational, matched, cohort study of patients was to assess the effectiveness and safety of DOAC vs. warfarin for the treatment of venous thromboembolism (VTE) among patients with a creatinine clearance (CrCl) < 30 mL/min. This observational, cohort study included patients with VTE and CrCl < 30 mL/min who were newly initiated on a DOAC or warfarin between January 1, 2016 and December 31, 2020. DOAC patients were matched up to 1:2 to warfarin patients. Primary outcome was a composite of recurrent VTE, clinically-relevant bleeding, ischemic stroke, and all-cause mortality. Adjusted conditional, multivariate Cox proportional hazards modeling was used to assess outcomes. 626 DOAC patients were matched to 1071 warfarin patients. DOAC patients had a higher mean age, higher mean baseline CrCl, and were less likely to have been receiving dialysis. There was no statistically significant difference in the composite outcome between groups (adjusted hazard ratio [aHR] 1.13, 95% confidence interval [CI] 0.87-1.47) or in the individual components of the composite (all HR 95% CI crossed 1.00). Identification of statistically non-significant rates of bleeding and thromboembolic outcomes suggest that the use of DOAC or warfarin is reasonable in patients with VTE and CrCl < 30 mL/min.

Effect of anticoagulants on fibrin clot structure: A comparison between vitamin K antagonists and factor Xa inhibitors

BACKGROUND

Abnormal clot structure has been identified in patients with thrombotic disorders. Anticoagulant therapy offers clear benefits for thrombosis prevention and treatment by reducing blood clot formation and size; nevertheless, there are limited data on the effects of different anticoagulants, where clotting is initiated with different triggers, on clot structure.

OBJECTIVES

Our aim was to investigate the effects of vitamin K antagonists and factor Xa inhibitors on clot structure.

METHODS

Clots from pooled plasma spiked with rivaroxaban, apixaban, or enoxaparin, as well as plasma from patients on warfarin, were compared to plasma without anticoagulation. The kinetic profile of polymerizing clots was obtained by turbidity, fiber density was determined by confocal microscopy, clot pore size was investigated by permeation, and fiber size was analyzed using scanning electron microscopy. Clotting agonist was either tissue factor or thrombin.

RESULTS

Following clotting with tissue factor, all anticoagulated clots had a significantly increased lag time, with the exception of enoxaparin. Rivaroxaban additionally led to significantly less dense and more permeable clots, with thicker fibers. In contrast, turbidity analysis following initiation with thrombin showed few effects of anticoagulation, with only enoxaparin leading to a prolonged lag time. Enoxaparin clots made with thrombin were less dense and more permeable.

CONCLUSION

Our results show that anticoagulants modulate clot structure particularly when induced by tissue factor, most likely due to reduction of thrombin generation. We propose that the effects of different anticoagulants could be assessed with a global clot structure measurement such as permeation or turbidity, providing information on clot phenotype.

American Society of Hematology 2020 guidelines for management of venous thromboembolism: treatment of deep vein thrombosis and pulmonary embolism

BACKGROUND

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), occurs in ∼1 to 2 individuals per 1000 each year, corresponding to ∼300 000 to 600 000 events in the United States annually.

OBJECTIVE

These evidence-based guidelines from the American Society of Hematology (ASH) intend to support patients, clinicians, and others in decisions about treatment of VTE.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and adult patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 28 recommendations for the initial management of VTE, primary treatment, secondary prevention, and treatment of recurrent VTE events.

CONCLUSIONS

Strong recommendations include the use of thrombolytic therapy for patients with PE and hemodynamic compromise, use of an international normalized ratio (INR) range of 2.0 to 3.0 over a lower INR range for patients with VTE who use a vitamin K antagonist (VKA) for secondary prevention, and use of indefinite anticoagulation for patients with recurrent unprovoked VTE. Conditional recommendations include the preference for home treatment over hospital-based treatment for uncomplicated DVT and PE at low risk for complications and a preference for direct oral anticoagulants over VKA for primary treatment of VTE.

Safety of direct oral anticoagulants in patients with hereditary hemorrhagic telangiectasia

Background

Hereditary hemorrhagic telangiectasia (HHT) is a rare vascular dysplasia resulting in visceral arteriovenous malformations and smaller mucocutaneous telangiectasia. Most patients experience recurrent nosebleeds and become anemic without iron supplementation. However, thousands may require anticoagulation for conditions such as venous thromboembolism and/or atrial fibrillation. Over decades, tolerance data has been published for almost 200 HHT-affected users of warfarin and heparins, but there are no published data for the newer direct oral anticoagulants (DOACs) in HHT.

Methods

To provide such data, a retrospective audit was conducted across the eight HHT centres of the European Reference Network for Rare Multisystemic Vascular Diseases (VASCERN), in Denmark, France, Germany, Italy, the Netherlands and the UK.

Results

Although HHT Centres had not specifically recommended the use of DOACs, 32 treatment episodes had been initiated by other clinicians in 28 patients reviewed at the Centres, at median age 65 years (range 30–84). Indications were for atrial fibrillation (16 treatment episodes) and venous thromboembolism (16 episodes). The 32 treatment episodes used Apixaban (n = 15), Rivaroxaban (n = 14), and Dabigatran (n = 3). HHT nosebleeds increased in severity in 24/32 treatment episodes (75%), leading to treatment discontinuation in 11 (34.4%). Treatment discontinuation was required for 4/15 (26.7%) Apixaban episodes and 7/14 (50%) Rivaroxaban episodes. By a 4 point scale of increasing severity, there was a trend for Rivaroxaban to be associated with a greater bleeding risk both including and excluding patients who had used more than one agent (age-adjusted coefficients 0.61 (95% confidence intervals 0.11, 1.20) and 0.74 (95% confidence intervals 0.12, 1.36) respectively. Associations were maintained after adjustment for gender and treatment indication. Extreme hemorrhagic responses, worse than anything experienced previously, with individual nosebleeds lasting hours requiring hospital admissions, blood transfusions and in all cases treatment discontinuation, occurred in 5/14 (35.7%) Rivaroxaban episodes compared to 3/15 (20%) Apixaban episodes and published rates of ~ 5% for warfarin and heparin.

Conclusions

Currently, conventional heparin and warfarin remain first choice anticoagulants in HHT. If newer anticoagulants are considered, although study numbers are small, at this stage Apixaban appears to be associated with lesser bleeding risk than Rivaroxaban.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1179-1) contains supplementary material, which is available to authorized users.

Reversal Strategies for Intracranial Hemorrhage Related to Direct Oral Anticoagulant Medications

Direct oral anticoagulants (DOACs) are a new class of anticoagulants that directly inhibit either thrombin or factor Xa in the coagulation cascade. They are being increasingly used instead of warfarin or other vitamin K antagonists (VKAs). Adverse side effects of DOACs may result in hemorrhagic complications, including life-threatening intracranial hemorrhage (ICH), though to a much lesser degree than VKAs. Currently there are relatively limited indications for DOACS but their usage is certain to expand with the availability of their respective specific reversal agents. Currently, only idarucizumab (antidote for dabigatran) has been United States Food and Drug Administration- (FDA-) approved, but others (andexanet-α and ciraparantag) may be approved in near future, and the development and availability of such reversal agents have the potential to dramatically change the current anticoagulant use by providing reversal of multiple oral anticoagulants. Until all the DOACs have FDA-approved reversal agents, the treatment of the dreaded side effects of bleeding is challenging. This article is an attempt to provide an overview of the management of hemorrhage, especially ICH, related to DOAC use.

Management of venous thromboembolism with non-vitamin K oral anticoagulants: A review for nurse practitioners and pharmacists

BACKGROUND AND PURPOSE

Venous thromboembolism (VTE), comprising deep-vein thrombosis and pulmonary embolism, is associated with significant morbidity and mortality. Non-vitamin K oral anticoagulants (NOACs), including apixaban, betrixaban, dabigatran, edoxaban, and rivaroxaban, are as effective and safe as vitamin K antagonists (VKAs) for primary prophylaxis, treatment, and/or secondary prevention of VTE and present significant advantages in convenience of use. This review provides guidance to nurse practitioners (NPs) and pharmacists on NOAC usage for the management of VTE and examines how traditional anticoagulation clinics can adapt to cater to patients on NOACs.

METHODS

A review of the scientific literature pertaining to treatment guideline recommendations, large randomized clinical trials, and real-world evidence studies related to VTE management was conducted.

CONCLUSIONS

With current data suggesting that NOACs may present as better alternatives over VKAs for the management of VTE, comprehensively educating NPs and pharmacists can help incorporate these agents in their clinical practice.

IMPLICATIONS FOR PRACTICE

Repurposing anticoagulation clinics, led by well-informed NPs and pharmacists, will allow effective integration and optimal management of patients with VTE taking NOACs as well as those taking VKAs.