Inhibition of clot formation process by treatment with the lowmolecular-weight heparin nadroparin in patients with carotid artery disease undergoing angioplasty and stenting - A thromboelastography study on whole blood

"In Less than No Time": Feasibility of Rotational Thromboelastometry to Detect Anticoagulant Drugs Activity and to Guide Reversal Therapy

Anticoagulant drugs (i.e., unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and direct oral anticoagulants) are widely employed in preventing and treating venous thromboembolism (VTE), in preventing arterial thromboembolism in nonvalvular atrial fibrillation (NVAF), and in treating acute coronary diseases early. In certain situations, such as bleeding, urgent invasive procedures, and surgical settings, the evaluation of anticoagulant levels and the monitoring of reversal therapy appear essential. Standard coagulation tests (i.e., activated partial thromboplastin time (aPTT) and prothrombin time (PT)) can be normal, and the turnaround time can be long. While the role of viscoelastic hemostatic assays (VHAs), such as rotational thromboelastometry (ROTEM), has successfully increased over the years in the management of bleeding and thrombotic complications, its usefulness in detecting anticoagulants and their reversal still appears unclear.

Higher coagulation activity in hip fracture patients: A case-control study using rotational thromboelastometry

INTRODUCTION

Trauma-induced coagulopathy has been extensively investigated in the multitrauma setting, but only sparsely following moderate orthopedic trauma. The purpose of this study was to evaluate changes in the hemostatic profile of patients with hip fractures, using rotational thromboelastometry (ROTEM).

METHODS

198 patients with hip fractures who underwent surgery were included in the study. A matched group of 52 healthy individuals was also enrolled. Demographics, conventional laboratory assays, and ROTEM parameters were recorded and compared between patients and healthy adults. The preoperative and postoperative ROTEM values of fractured patients were also compared.

RESULTS

The conventional coagulation assays were similar for the 2 groups. However, several ROTEM parameters including EXTEM MCF (P < .001), EXTEM alpha angle (P < .001), INTEM MCF (P < .001), INTEM A10 (P < .001), and INTEM alpha angle (P < .001) significantly differed between the 2 groups indicating a higher coagulation potential following hip fractures. Also, fractured patients had significantly lower INTEM and EXTEM CT values (P = .008 and P = .012, respectively) and significantly lower INTEM and EXTEM CFT values (P < .001). Adjusted analysis for confounders further confirmed the direct relationship between hip fracture and higher coagulation activity. Last, INTEM CT and CFT significantly decreased (P = .008 and P < .001, respectively), while INTEM MCF, A10, and alpha angle significantly increased (P < .001) postoperatively, indicating that surgery further increases the coagulation potential.

CONCLUSION

A higher coagulation activity following hip fractures and surgical treatment can be detected by ROTEM shortly after the injury, even when this is undetectable by conventional coagulation assays.

Comparison of Coagulation Conditions in Patients With Liver Cirrhosis Due to Primary Sclerosing Cholangitis and Nonbiliary Causes of Cirrhosis Before Orthotopic Liver Transplant

OBJECTIVES

Orthotopic liver transplant can be accompanied by an obscure bleeding pattern in patients with severe hepatic malfunction. In the present study, coagulation conditions of patients with cirrhosis of the liver due to primary sclerosing cholangitis and nonbiliary causes of cirrhosis were compared using rotational thromboelastometry assays obtained before orthotopic liver transplant.

MATERIALS AND METHODS

This case control study analyzed patients who were candidates for orthotopic liver transplant from 2010 to 2016. Eighty patients with cirrhosis of the liver (40 patients with primary sclerosing cholangitis and 40 with nonbiliary causes of cirrhosis) were randomly selected and enrolled into the study. Patients received rotational thromboelastometry assays under anesthesia just before the start of the operation, and results were compared between the 2 patient groups.

RESULTS

Of 80 patients, 52 were men and 28 were women. In the assays, we found that maximum amplitudes in 10 and in 20 minutes and maximum clot firmness parameters were higher in patients with primary sclerosing cholangitis. The alpha angle and clot formation time were different in the intrinsic and extrinsic assay panels. In the intrinsic assay, we found clotting time to be shorter (P < .05). The average of all parameters in all 3 assays (intrinsic, extrinsic, and fibrinogen contribution) was lower in patients with nonbiliary causes of cirrhosis than in those with primary sclerosing cholangitis.

CONCLUSIONS

In contrast with previous studies that found that patients with primary sclerosing cholangitis are hypercoagulable, our study observed that they have normal coagulable results. Furthermore, we found that, although mean coagulation indexes in patients with primary sclerosing cholangitis were within normal ranges, in patients with nonbiliary causes of cirrhosis, these indexes were generally lower.

Comparison of antithrombin-dependent and direct inhibitors of factor Xa or thrombin on the kinetics and qualitative characteristics of blood clots

BACKGROUND

Venous thromboembolism (VTE) is associated with significant morbidity and mortality.

OBJECTIVES

We investigated the impact of direct and AT-dependent FXa or thrombin inhibitors on thrombus formation.

METHODS

Whole blood thromboelastometry and thrombin generation were assessed after triggering the TF pathway. Clinically relevant concentrations of rivaroxaban, fondaparinux, dabigatran or tinzaparin and an association of rivaroxaban and dabigatran were examined.

RESULTS

All agents delayed thrombus formation in a concentration-dependent manner, as documented by the prolongation of the clotting time (CT) and clot formation time (CFT). Rivaroxaban did not significantly alter the α-angle or maximum clot firmness (MCF). In contrast, dabigatran and fondaparinux altered the process of clot structure by decreasing the α-angle, but did not modify clot firmness. The later property was significantly affected only by tinzaparin that also reduced the MCF. The association of rivaroxaban and dabigatran did not affect the MCF, although it amplified the effect on CFT and α-angle.

CONCLUSIONS

All agents delayed thrombus formation. However, the compounds differed substantially with respect to fibrin polymerization rate and clot firmness. Comparison of the data obtained by thrombin generation assessment with those obtained by the thromboelastometric study shows that the delay in clot formation is principally associated with prolongation of the initiation phase of thrombin formation as well as a reduction of the propagation phase. Tinzaparin was much more potent than the other agents both with regard to suppression of thrombin generation and by delay in clot formation.

Impact of blood hypercoagulability on in vitro fertilization outcomes: a prospective longitudinal observational study

Background

Blood coagulation plays a crucial role in the blastocyst implantation process and its alteration may be related to in vitro fertilization (IVF) failure. We conducted a prospective observational longitudinal study in women eligible for IVF to explore the association between alterations of coagulation with the IVF outcome and to identify the biomarkers of hypercoagulability which are related with this outcome.

Methods

Thirty-eight women eligible for IVF (IVF-group) and 30 healthy, age-matched women (control group) were included. In the IVF-group, blood was collected at baseline, 5–8 days after administration of gonadotropin-releasing hormone agonist (GnRH), before and two weeks after administration of human follicular stimulating hormone (FSH). Pregnancy was monitored by measurement of βHCG performed 15 days after embryo transfer. Thrombin generation (TG), minimal tissue factor-triggered whole blood thromboelastometry (ROTEM®), procoagulant phospholipid clotting time (Procoag-PPL®), thrombomodulin (TMa), tissue factor activity (TFa), factor VIII (FVIII), factor von Willebrand (FvW), D-Dimers and fibrinogen were assessed at each time point.

Results

Positive IVF occurred in 15 women (40%). At baseline, the IVF-group showed significantly increased TG, TFa and TMa and significantly shorter Procoag-PPL versus the control group. After initiation of hormone treatment TG was significantly higher in the IVF-positive as compared to the IVF-negative group. At all studied points, the Procoag-PPL was significantly shorter and the levels of TFa were significantly higher in the IVF-negative group compared to the IVF-positive one. The D-Dimers were higher in the IVF negative as compared to IVF positive group. Multivariate analysis retained the Procoag-PPL and TG as predictors for the IVF outcome.

Conclusions

Diagnosis of women with hypercoagulability and their stratification to risk of IVF failure using a model based on the Procoag-PPL and TG is a feasible strategy for the optimization of IVF efficiency that needs to be validated in prospective trials.

Adjunctive anticoagulation during peripheral vascular intervention

Endovascular techniques for the treatment of peripheral arterial disease are becoming an increasingly common alternative to open surgery, yet the degree of anticoagulation and choice of anticoagulant to optimize outcomes in these procedures remain uncertain. To date, few randomized trials have directly compared different anticoagulants for use during peripheral vascular interventions. It is also unclear if the approach to anticoagulation should be individualized to each vascular bed or if common principles are shared among them. This has led practitioners across different specialties to use a variety of different methods for anticoagulation, with most extrapolated from techniques used in percutaneous coronary interventions. In this review, we analyze the current literature for anticoagulation used during peripheral vascular intervention of the lower extremity, renal, carotid, and aortic arteries, with special consideration to the choice of anticoagulant used to maximize safe and effective procedural outcomes.

Monitoring of unfractionated heparin with rotational thrombelastometry using the prothrombinase-induced clotting time reagent (PiCT®)

PURPOSE

To achieve sufficient and safe anticoagulation with unfractionated heparin (UFH) a close and reliable drug monitoring is necessary. In general, the activated partial thromboplastin time (APTT) is used for this purpose. In acute phase response, however, the APTT test procedure might be unreliable e.g. with false low results in the presence of elevated factor VIII. In this so called heparin resistance, measurement of anti-Xa activity is recommended over APTT to avoid potentially harmful dose escalation. A combination of anti-Xa measurement and global hemostatic testing with ROTEM® employing the anti-Xa sensitive PiCT® reagent showed high correlation with enoxaparin levels. This test modification could also be suitable for monitoring UFH. Aim of the study was to evaluate the correlation between PiCT®-ROTEM® and levels of UFH.

METHODS

In this in-vitro study blood samples from healthy volunteers were spiked with UFH and subjected to different ROTEM® tests.

RESULTS

There was a linear correlation between UFH level and clotting time (CT) in the PiCT®-ROTEM® test with an excellent correlation coefficient of 0.92. Additional endpoints showed similar results (PiCT®-ROTEM® MaxVel r = -0.85 and PiCT®-ROTEM® t_MaxVel r = 0.88).

CONCLUSIONS

As a point-of-care applicable tool ROTEM® is immediately at hand. If further clinical studies confirm sensitivity in heparin resistance, PiCT®-ROTEM® could permit rapid UFH dose adjustments especially required in critical illness with acute phase response.

Description of response to aspirin and clopidogrel in outpatients with coronary artery disease using multiple electrode impedance aggregometry

Identification of outpatients with high platelet reactivity (HPR) on antiplatelet treatment is an unmet need. The present study was conducted in healthy individuals (n = 50) and in outpatients with coronary artery disease (CAD) at a distance from the acute ischemic episode (aspirin group, n = 71; aspirin/clopidogrel group, n = 106). We studied the feasibility and the precision of whole blood multiple electrode aggregometry (MEA) after triggering platelet aggregation by arachidonic acid or adenosine diphospate (ADP). The MEA can be performed on whole blood within 2 hours after sample venipuncture. The threshold for the diagnosis of HPR is situated at 55 and 50 U for the arachidonic acid and ADP test, respectively. Frequency of HPR was 7% and 20% in aspirin and aspirin/clopidogrel groups, respectively. In 3.8% of patients in aspirin/clopidogrel group, combined HPR on aspirin and clopidogrel was found. In outpatients with CAD, use of MEA is feasible for the diagnosis of HPR.

Viscoelastic coagulation testing: technology, applications, and limitations

Use of viscoelastic point-of-care (POC) coagulation instrumentation is relatively new to veterinary medicine. In human medicine, this technology has recently undergone resurgence owing to its capacity to detect hypercoagulability. The lack of sensitive tests for detecting hypercoagulable states, along with our current understanding of in vivo coagulation, highlights the deficiencies of standard coagulation tests, such as prothrombin and partial thromboplastin times, which are performed on platelet-poor plasma. Viscoelastic coagulation analyzers can provide an assessment of global coagulation, from the beginning of clot formation to fibrinolysis, utilizing whole blood. In people, use of this technology has been reported to improve management of hemostasis during surgery and decrease usage of blood products and is being used as a rapid screen for hypercoagulability. In veterinary medicine, clinical use of viscoelastic technology has been reported in dogs, cats, foals, and adult horses. This article will provide an overview of the technology, reagents and assays, applications in human and veterinary medicine, and limitations of the 3 viscoelastic POC analyzers in clinical use.

Determination of enoxaparin with rotational thrombelastometry using the prothrombinase-induced clotting time reagent

Drug monitoring of low molecular weight heparin is generally not recommended, but could be reasonable in critically ill patients, whose risk for bleeding or thrombosis shows a high interpatient variability. Anti-Xa assays are not available around the clock even in central hospitals, whereas rotational thrombelastometry (ROTEM) becomes increasingly used at the bedside. Prothrombinase-induced clotting time (PiCT) reagent allows determination of factor Xa-inhibition in plasma. The aim of our study was to evaluate enoxaparin determination in whole blood with the ROTEM using specific test modifications, including PiCT. After ethics committee's approval, citrated whole blood obtained from overall 16 healthy volunteers was incubated with enoxaparin at 16 different anti-Xa concentrations. Main endpoint was the clotting time (CT) in ROTEM representing initial activation of clot formation. CT was determined in the new PiCT-ROTEM test, in a low-tissue factor-activated modification (LowTF-ROTEM) as well as in the commercially available heparin-sensitive ROTEM assays (HEPTEM and INTEM). In the absence of enoxaparin, CT values were 168.6 +/- 6.1 s (PiCT-ROTEM), 247.3 +/- 18.6 s (LowTF-ROTEM), and -6.2 +/- 7.9 s (INTEM-HEPTEM). A linear dependency (P < 0.01) between anti-Xa concentration and CT was found for PiCT-ROTEM, LowTF-ROTEM, and for INTEM-HEPTEM with correlation coefficients of 0.93 for PiCT-ROTEM, 0.94 for LowTF-ROTEM, and 0.81 for INTEM-HEPTEM. This in-vitro experiment demonstrates a strong correlation between enoxaparin anti-Xa concentrations and specific ROTEM tests. These promising assays should be further evaluated for monitoring anticoagulation in high-risk patients in clinical studies.