Evaluation of the profile of thrombin generation during the process of whole blood clotting as assessed by thrombelastography

Applications of Viscoelastic Testing in Breast Cancer Patients: A Systematic Review Focusing on Hypercoagulability and Free Flap Thrombosis

Viscoelastic testing is a clinically available method to assess hypercoagulability. This systematic review aims to provide a comprehensive overview of the existing literature and the potential use of such testing in patients with breast cancer. A systematic literature search for studies investigating the application of viscoelastic testing for patients with breast cancer was conducted. Studies were included as long as they were original, peer-reviewed, and in the English language. Studies were excluded if they were review articles, did not include breast cancer patients, or if the full text was unavailable. This review identified 10 articles that met the inclusion criteria. Two of the studies utilized rotational thromboelastometry, and an additional four studies used thromboelastography, to assess hypercoagulability in patients with breast cancer. Three of the identified articles discussed the use of thromboelastometry in free flap breast reconstruction for patients with breast cancer. One study was a retrospective chart review looking at thromboelastography and microsurgical breast reconstruction. Current literature regarding the application of viscoelastic testing in breast cancer and free flap breast reconstruction is limited, with no randomized trials thus far. However, some studies suggest that there may be potential utility in viscoelastic testing to assess risk for thromboembolism in breast cancer patients, and future research in this area is warranted.

Global hemostasis assays in acute myeloid leukemia: results of an observational prospective study

BACKGROUND

Acute myeloid leukemia (AML) is characterized by a complex spectrum of coagulopathy ranging from hemorrhagic to thrombotic symptoms. To date, platelet count (PLT) and conventional coagulation tests (CCTs) cannot predict hemorrhagic events and thrombotic risk. Thromboelastography (TEG) measures the viscoelastic properties of the clot, thus providing information on the entire process of blood coagulation. The primary aim of the study was to assess the hemostatic balance from AML diagnosis to the end of chemotherapy (CHT) by TEG.

MATERIAL AND METHODS

Here we present the results of a prospective study enrolling newly diagnosed AML patients treated with chemotherapy. Patients had complete blood counts (CBCs), TEG and CCTs performed at three time points: 1) diagnosis (T0); 2) during the first cycle of CHT (T1); and 3) at the end of CHT (T2). An algorithm of TEG indirectly calculated thrombin generation (TG). Patients underwent daily follow-up for bleeding and thrombotic episodes up to the time of hospital discharge or death.

RESULTS

Eighty consecutive patients were evaluated; forty were eligible for the study, and 21 completed the entire study. At T1, maximum amplitude (MA), TG and K-time were significantly shifted toward a hypocoagulability state compared to T0 (p<0.05), while a hypercoagulable state at T2 was shown by changes in α-angle, MA and TG values. Otherwise, there were no statistically significant differences in CCTs between the evaluated time points.

DISCUSSION

Overall, TEG revealed complex and dynamic coagulation abnormalities in patients with AML according to both the course of disease and therapy. Further studies are needed to investigate more fully the role of TEG in defining the hemostatic profile in patients with AML.

The Optimized Preparation Conditions of Cellulose Triacetate Hollow Fiber Reverse Osmosis Membrane with Response Surface Methodology

Reverse osmosis (RO) membrane materials play a key role in determining energy consumption. Currently, CTA is regarded as having one of the highest degrees of chlorine resistance among materials in the RO process. The hollow fiber membrane has the advantages of a large membrane surface area and a preparation process without any redundant processes. Herein, response surface methodology with Box-Behnken Design (BBD) was applied for optimizing the preparation conditions of the cellulose triacetate (CTA) hollow fiber RO membrane. There were four preparation parameters, including solid content, spinning temperature, post-treatment temperature, and post-treatment time, which could affect the permeability of the membrane significantly. In this study, the interaction between preparation parameters and permeability (permeate flux and salt rejection) was evaluated by regression equations. Regression equations can be applied to obtain the optimized preparation parameters of hollow fiber RO membranes and reasonably predict and optimize the permeability of the RO membranes. Finally, the optimized preparation conditions were solid content (44%), spinning temperature (167 °C), post-treatment temperature (79 °C), and post-treatment time (23 min), leading to a permeability of 12.029 (L·m-2·h-1) and salt rejection of 90.132%. This study of reinforced that CTA hollow fiber membrane may promote the transformation of the RO membrane industry.

Thromboelastography 6s for assessment of platelet function during coil embolization of unruptured intracranial aneurysms

OBJECTIVES

Methods for assessing platelet function in patients with neurovascular disease remain controversial and poorly studied. This study aimed to assess associations between thromboelastography 6s (TEG6s) measurements and postoperative ischemic complications in patients with unruptured intracranial aneurysms (UIAs) treated by coil embolization.

METHODS

Eighty-four patients with UIAs taking a combined aspirin and clopidogrel protocol were retrospectively reviewed from January 2021 to May 2022. Blood samples were obtained for TEG6s to assess platelet function on the day of coil embolization. To identify acute ischemic complications, diffusion-weighted imaging (DWI) was performed within 24 h after coil embolization. Multivariate logistic regression analysis was conducted to identify potential risk factors for postoperative positive DWI (DWI (+)) lesions.

RESULTS

Forty-three of the 84 patients (51%) with DWI (+) lesions were identified. Compared with patients without DWI (+) lesions, Adenosine diphosphate (ADP)-induced platelet-fibrin clot strength (MA_ADP) was significantly higher (53.6 mm [Interquartile range (IQR): 48.3-58.3 mm] vs 46.7 mm [IQR: 36.8-52.2 mm]; p=0.001) and ADP inhibition rate (ADP%) was significantly lower (19% [IQR: 11-31%] vs 31% [IQR: 21-44%]; p=0.001) in DWI (+) patients. Multivariate analysis identified MA_ADP, ADP%, and procedure time as significant independent predictors of subsequent DWI (+) lesions (odds ratios: 1.07, 0.96, and 1.02, respectively). Based on receiver operating characteristic curve analysis, MA_ADP >50.9 mm and ADP% <28.8% were associated with postoperative DWI (+) lesions in patients undergoing coil embolization for UIAs.

CONCLUSIONS

MA_ADP and ADP% as assessed by TEG6s can offer reliable parameters to predict postoperative ischemic complications after coil embolization of UIAs. Lower MA_ADP values and higher ADP% may decrease the risk of postoperative ischemic complications.

Measurement of Blood Viscoelasticity Using Thromboelastography

Thromboelastography (TEG) was the first viscoelastic test (VET), invented in Germany in 1948 by Dr. Hartert, and which evaluates the hemostatic competence of whole blood. Thromboelastography was introduced before the activated partial thromboplastin time (aPTT), which was devised in 1953. TEG was not widely used until the introduction of a cell-based model of hemostasis (1994) showing the importance of platelets and tissue factor in hemostasis. Nowadays, VET has become an essential method for assessing hemostatic competence in cardiac surgery, liver transplantation, and trauma. TEG has undergone several modifications, but the concept on which the original TEG was based (cup and pin technology) remained in up to the TEG 5000 analyzer (Haemonetics, Braintree, MA). A new generation of thromboelastography, TEG 6s (Haemonetics, Boston, MA), that assesses blood viscoelastic properties by resonance technology has recently been developed. This newer methodology represents a cartridge-based, automated assay aimed to improve on historical TEG performance and precision. In the present chapter, we will review the advantages and limitations of TEG 5000 and TEG 6s systems as well as factors that affect TEG and which must be considered when interpreting TEG tracings.

Viscoelastic Testing in the Management of Adult Patients on Mechanical Circulatory Support Devices with Focus on Extracorporeal Membrane Oxygenation

Thromboembolic and hemorrhagic complications continue to remain frequent complications that significantly impact the morbidity and mortality of patients implanted with mechanical circulatory support devices (MCSDs). The severe acute respiratory syndrome caused by coronavirus 2 (SARS-CoV-2) has resulted in a number of COVID-19 patients being supported by MCSDs, specifically extracorporeal membrane oxygenation (ECMO), which in turn has created a crucial need for rapid assessment of hemostatic status in these patients to avoid bleeding and thrombotic complications. Currently, conventional plasma-based coagulation assays such as prothrombin time and activated partial thromboplastin time (aPTT) are used to assess hemostasis, and the activated clotting time (ACT) and aPTT are the most common tests used to monitor heparin anticoagulation in patients on ECMO. Unfractionated heparin remains the mainstay anticoagulation therapy for patients on ECMO. Extracorporeal Life Support Organization (ELSO) offers little guidance on the subject but does state that each institution should create its internal anticoagulation protocols. Viscoelastic assays (VEAs) are increasingly recognized by ELSO and ECMO community for their potential to assess hemostatic derangements in patients implanted with MCSDs as well as guidance for appropriate hemostatic therapy. This review focuses on the evidence for the use of viscoelastic assays to assess overall hemostasis and to guide the treatment of adult patients connected to an ECMO circuit. Limitations of the use of conventional assays, ACT, and VEA are also discussed.

Thromboelastography and thrombin generation assessments for pediatric severe hemophilia A patients are highly variable and not predictive of clinical phenotypes

Background

Severe hemophilia A (SHA) patients vary in severity of bleeding, arthropathy, and requirements for replacement factor VIII (FVIII). Baseline hemostatic activity assays using calibrated automated thrombography (CAT) and thromboelastography (TEG) may offer insights into the physiological basis of clinical heterogeneity.

Objectives

Use CAT and TEG to measure baseline hemostatic activity in a cohort of 30 pediatric SHA patients with available clinical data. Determine effect of contact activation inhibition with corn trypsin inhibitor (CTI). Assess heterogeneity among patients for baseline hemostatic activity and examine correlations between assay results and clinical parameters including FVIII dosing regimen, von Willebrand factor level, and Pettersson arthropathy score.

Methods

SHA blood after FVIII washout was subjected to TEG, and platelet‐rich (PRP) and platelet‐poor plasma was used for CAT assays. Varying concentrations of tissue factor (TF) were used. Statistical analysis examined relationships between assay results, and clinical parameters.

Results

CTI treatment was required to obtain TEG and CAT results representative of baseline hemostatic activity. Weak activity was observed in assays with low TF concentrations (0.5–2 pM), and most but not all samples approached normal activity levels at high TF concentrations (10–20 pM). A significant positive correlation was observed between results of TEG and CAT‐PRP assays. Correlations were not detected between hemostatic assay results and clinical parameters.

Conclusions

In vitro hemostatic assay results of samples containing platelets showed concordance. Assay results were not predictive of FVIII requirements or correlated with other clinical parameters. SHA patient heterogeneity is influenced by factors other than baseline hemostatic activity.

Exogenous human α-Synuclein acts in vitro as a mild platelet antiaggregant inhibiting α-thrombin-induced platelet activation

α-Synuclein (αSyn) is a small disordered protein, highly conserved in vertebrates and involved in the pathogenesis of Parkinson’s disease (PD). Indeed, αSyn amyloid aggregates are present in the brain of patients with PD. Although the pathogenic role of αSyn is widely accepted, the physiological function of this protein remains elusive. Beyond the central nervous system, αSyn is expressed in hematopoietic tissue and blood, where platelets are a major cellular host of αSyn. Platelets play a key role in hemostasis and are potently activated by thrombin (αT) through the cleavage of protease-activated receptors. Furthermore, both αT and αSyn could be found in the same spatial environment, i.e. the platelet membrane, as αT binds to and activates platelets that can release αSyn from α-granules and microvesicles. Here, we investigated the possibility that exogenous αSyn could interfere with platelet activation induced by different agonists in vitro. Data obtained from distinct experimental techniques (i.e. multiple electrode aggregometry, rotational thromboelastometry, immunofluorescence microscopy, surface plasmon resonance, and steady-state fluorescence spectroscopy) on whole blood and platelet-rich plasma indicate that exogenous αSyn has mild platelet antiaggregating properties in vitro, acting as a negative regulator of αT-mediated platelet activation by preferentially inhibiting P-selectin expression on platelet surface. We have also shown that both exogenous and endogenous (i.e. cytoplasmic) αSyn preferentially bind to the outer surface of activated platelets. Starting from these findings, a coherent model of the antiplatelet function of αSyn is proposed.

A correlation of thrombin generation assay and clot waveform analysis in patients on warfarin

OBJECTIVES

Thrombin generation assays and activated partial thromboplastin time (aPTT)-based clot waveform analysis (CWA), are some examples of global coagulation assays. Each modality evaluates different aspects of the clot forming process to globally define haemostasis with exclusive measurement parameters. Data on CWA are emerging, but its performance against other haemostatic assays is yet to be ascertained. This study evaluates the correlation between aPTT-based CWA and CAT parameters across a range of INR in warfarin-treated patients.

PATIENTS/METHODS

A prospective study consisting of patients on warfarin anticoagulation with varying INR levels. CWA and CAT were performed for the study subjects.

RESULTS

54 samples were included covering an INR range from 1.33-6.89, with a mean of 4.31 +/- 1.13. For CAT parameters, endogenous thrombin potential (ETP) and peak thrombin were assessed. Both unadjusted and adjusted (adjusted for final plateau transmittance) aPTT-based CWA were evaluated for parameters min1 (maximum velocity), min2 (maximum acceleration) and max2 (maximum deceleration). Peak thrombin showed significant correlation with all CWA parameters (min1: r = 0.435, P<0.001; min2: r = 0.485, P<0.001; max2: r = 0.578, P<0.001; adjusted min1: r = 0.734, P<0.001, adjusted min2: r = 0.693, P<0.001; adjusted max2: r = 0.751, P<0.001). ETP correlated significantly with all CWA parameters except unadjusted min1 (min1: r = 0.235, P = 0.087; min2: r = 0.326, P = 0.016; max2: r = 0.437, P<0.001; adjusted min1: r = 0.610, P<0.001, adjusted min2: r = 0.563, P<0.001; adjusted max2: r = 0.642, P<0.001).

CONCLUSION

We demonstrated a modest correlation between CAT and CWA parameters. Adjusted CWA improved this correlation. These findings provide additional understanding of CWA and it's role in the evaluation of global haemostatic function.

Polymeric Materials for Hemostatic Wound Healing

Hemorrhage is one of the greatest threats to life on the battlefield, accounting for 50% of total deaths. Nearly 86% of combat deaths occur within the first 30 min after wounding. While external wound injuries can be treated mostly using visual inspection, abdominal or internal hemorrhages are more challenging to treat with regular hemostatic dressings because of deep wounds and points of injury that cannot be located properly. The need to treat trauma wounds from limbs, abdomen, liver, stomach, colon, spleen, arterial, venous, and/or parenchymal hemorrhage accompanied by severe bleeding requires an immediate solution that the first responders can apply to reduce rapid exsanguinations from external wounds, including in military operations. This necessitates the development of a unique, easy-to-use, FDA-approved hemostatic treatment that can deliver the agent in less than 30 s and stop bleeding within the first 1 to 2 min at the point of injury without application of manual pressure on the wounded area.

Lidocaine effects on coagulation assessed by whole blood rotational thromboelastometry

Lidocaine may be beneficial when added in solutions for the preservation of vascular grafts or solid organs as it has anti-inflammatory, endothelial protective, and antithrombotic effects. However, the mechanisms of lidocaine-induced changes in hemostasis were not elucidated until now. The aim of the study was to examine the effect of increasing concentrations of lidocaine on coagulation parameters and blood-clotting kinetics using velocity curves of clot formation assessed by rotational thromboelastometry. Ex-vivo blood coagulation using whole blood from healthy volunteers was studied with rotational thromboelastometry. For each volunteer, four assays were performed: saline control and samples with lidocaine end blood concentrations of 0.3, 0.6, and 0.9%. In this in-vitro study, whole blood from 15 healthy volunteers was used. Lidocaine concentration of 0.3% prolonged the initiation phase of clotting without significant differences in the propagation phase or clot stability and inhibited clot lysis compared with the control group. Higher lidocaine concentrations (0.6 and 0.9%) resulted in prolongation of both initiation and propagation phases and decreased clot firmness compared with the control group. Lysis was significantly increased only in the 0.6% lidocaine group compared with control. Although lidocaine concentration of 0.3% only delays coagulation initiation, the 0.6% concentration inhibits all phases of hemostasis and increases clot lysis compared with control. Higher lidocaine concentration results in very weak clot formation with very low lysis visible on thromboelastometry. More research is needed to explain the effects of lidocaine on clotting kinetics.

Associations of NETs with inflammatory risk and atherosclerotic severity in ST-segment elevation myocardial infarction

AIM

To investigate the association between neutrophil extracellular traps (NETs) in coronary thrombus and risk profile of patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

All participants enrolled in the Optical Coherence Tomography Examination in Acute Myocardial Infarction (NCT03593928) registry from March 2017 to November 2019 were screened and 104 patients were qualified for the current analysis. Coronary aspirated materials were collected and culprit lesion characteristics were examined by optical coherence tomography. NETs in thrombus were identified by immunofluorescence as the co-localization of anti-histone H3 and myeloperoxidase, and NETs level was assessed using a semi-quantitative score. Patient-oriented composite endpoint included all-cause death, myocardial infarction, stroke, any revascularization, and re-admission for heart failure.

RESULTS

According to NETs burden, 44 patients were in the low NETs group and 60 in the high NETs group. The two groups were comparable in age, sex, and comorbidities but the high NETs group presented with significantly higher level of high-sensitivity C reactive protein than the low NETs group (median 9.3 mg/L vs 5.2 mg/L, p = 0.036). Although culprit plaque morphology did not differ between groups, the lipid arc was smaller (maximal lipid arc 320° vs 360°, p = 0.012) and the flow area was larger (median 1.85mm² vs 1.65mm², p = 0.041) in the high NETs group. No significant difference was observed between groups in patient-oriented composite endpoint.

CONCLUSION

Increased NETs in aspirated coronary thrombus appear to be associated with more elevated inflammation but less advanced atherosclerosis.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT03593928.

Standard and derived rotational thromboelastometry parameters for prediction of disseminated intravascular coagulation in septic patients

: Waiting for lab tests results for the calculation of disseminated intravascular coagulation (DIC) scores leads to unwanted delays in diagnosis. The use of rotational thromboelastometry (ROTEM) for this purpose would allow for a more rapid DIC diagnosis at the bedside. The aim of this study was to assess the ability of standard ROTEM parameters and calculated parameters from the ROTEM velocity curve to predict DIC. The retrospective observational study included 97 septic patients. Japanese Association for Acute Medicine score was used for DIC diagnosis and whole-blood ROTEM was performed at study inclusion. Univariate analysis revealed delayed coagulation initiation and propagation and reduced clot firmness and maximum elasticity in DIC patients compared with patients without DIC. To adjust for confounders, multivariable logistic regression models were created and fibrinogen levels, prothrombin time and ROTEM parameters such as maximum clot firmness, maximum clot elasticity (MCE) and total thrombus formation [area under the curve (AUC)] were identified as significant predictors of DIC. According to receiver operating characteristics analysis, MCE and total thrombus formation (AUC) were the most useful ROTEM parameters for DIC prediction. MCE less than 158 (73% sensitive, 80% specific) and AUC less than 6175 mm × 100 (73% sensitive, 76% specific) predicted DIC in septic patients. Both standard and derived ROTEM parameters are useful for rapid DIC prediction in septic patients, allowing the timely identification of patients with higher mortality risk which might benefit from additional therapies. Further studies are needed to assess the clinical relevance of these findings.

Complex and prolonged hypercoagulability in coronavirus disease 2019 intensive care unit patients: A thromboelastographic study

BACKGROUND

A high number of thrombotic complications have been reported in critically ill patients with coronavirus disease 2019 (COVID-19) and appear to be related to a hypercoagulable state. Evidence regarding detection, management, and monitoring of COVID-19-associated coagulopathy is still missing. We propose to describe the thrombus viscoelastic properties to investigate the mechanisms of hypercoagulability in patients with COVID-19.

METHODS

Thromboelastography (TEG) was performed in 24 consecutive patients admitted to a single intensive care unit for COVID-19 pneumonia, and 10 had a second TEG before being discharged alive from the intensive care unit.

RESULTS

Compared with a group of 20 healthy participants, patients with COVID-19 had significantly decreased values of reaction time, coagulation time, and lysis index and increased values of α angle, maximum amplitude, clot strength, and coagulation index. Velocity curves were consistent with increased generation of thrombin. These values persisted in surviving patients despite their good clinical course.

DISCUSSION

In patients with COVID-19, TEG demonstrates a complex and prolonged hypercoagulable state including fast initiation of coagulation and clot reinforcement, low fibrinolysis, high potential of thrombin generation, and high fibrinogen and platelet contribution. The antithrombotic strategy in patients with COVID-19 during intensive care hospitalisation and after discharge should be investigated in further studies.

Effect of intracellular uptake of nanoparticle-encapsulated trehalose on the hemocompatibility of allogeneic valves in the VS83 vitrification protocol

Trehalose is a disaccharide molecule consisting of two molecules of glucose. Industrially, trehalose is derived from corn starch and utilized as a drug. This study aims to examine whether the integration of nanoparticle-encapsulated trehalose to the Ice-Free Cryopreservation (IFC) method for preserving heart valves has better cell viability, benefits to protect the extracellular matrix (ECM), and reduce immune response after storage. For the experiment to be carried out, we obtained materials, and the procedures were carried out in the following manner. The initial step was the preparation of hydroxyapatite nanoparticles, followed by precipitation to acquire Apatite colloidal suspensions. Animals were obtained, and their tissue isolation and grouping were done ethically. All samples were then divided into four groups, Control group, Conventional Frozen Cryopreservation (CFC) group, IFC group, and IFC + T (IFC with the addition of 0.2 M nanoparticle-encapsulated Trehalose) group. Histological analysis was carried out via H&E staining, ECM components were stained with Modified Weigert staining, and the Gomori Ammonia method was used to stain reticular fibers. Alamar Blue assay was utilized to assess cell viability. Hemocompatibility was evaluated, and samples were processed for immunohistochemistry (TNFα and IL-10). Hemocompatibility was quantified using Terminal Complement Complex (TCC) and Neutrophil elastase (NE) as an indicator. The results of the H&E staining revealed less formation of extracellular ice crystals and intracellular vacuoles in the IFC + T group compared with all other groups. The CFC group’s cell viability showed better viability than the IFC group, but the highest viability was exhibited in the IFC + T group (70.96 ± 2.53, P < 0.0001, n = 6). In immunohistochemistry, TNFα levels were lowest in both IFC and IFC + T group, and IL-10 expression had significantly reduced in IFC and IFC + T group. The results suggested that the nanoparticle encapsulated trehalose did not show significant hemocompatibility issues on the cryopreserved heart valves.

Massive Hemorrhage: The Role of Whole Blood Viscoelastic Assays

Viscoelastic whole blood tests are increasingly used to guide hemostatic therapy in bleeding patients in the perioperative, trauma, and obstetric settings. Compared with standard laboratory tests of hemostasis, they have a shorter turnaround time and provide simultaneous information on various aspects of clot formation and lysis. The two available brands TEG (thromboelastography) and ROTEM (rotational thromboelastometry) provide devices that are either manually operated or fully automated. The automation allows for the assays to be used as point-of-care tests increasing their usefulness in massively bleeding patients with rapidly changing hemostatic profiles. While the number of research papers on the subject and the number of published treatment algorithms increase rapidly, the influence of the use of these devices on patient outcome needs yet to be established. In this article, we first review the technology of these devices and the parameters provided by the assays. Next, we present the problems encountered when choosing cut-off values that trigger intervention. Furthermore, we discuss the studies examining their influence on clinical outcomes, and finally, we briefly highlight some of the most important limitations and pitfalls inherent to these assays.

Cilostazol increases adenosine plasma concentration in patients with acute coronary syndrome

WHAT IS KNOWN AND OBJECTIVE

Cilostazol is a specific and strong inhibitor of phosphodiesterase (PDE) type III which can suppress the platelet aggregation by increasing cyclic adenosine monophosphate (cAMP) levels. The clinical benefit of cilostazol in ACS patients suggested that the drug may have non-platelet-directed properties. Some in vitro and animal studies also indicated that the 'pleiotropic' properties of cilostazol might be related to the interaction with adenosine metabolism. Adenosine is an important regulatory metabolite and an inhibitor of platelet activation. However, no human study has been conducted to determine whether cilostazol could increase the adenosine plasma concentration in vivo. As a result, this study aimed to investigate the impact of cilostazol on adenosine plasma concentration (APC) in acute coronary syndrome (ACS) patients.

METHODS

We prospectively analysed 149 ACS patients undergoing percutaneous coronary intervention (PCI) with drug-eluting stents. The included patients were divided into two groups according to the presence (cilostazol group, n = 64) or absence (aspirin group, n = 85) of aspirin intolerance. The inhibition of platelet aggregation (IPA), APC and cAMP concentration was measured. Patient characteristics, medications and 30-day clinical outcomes were examined.

RESULTS

Patients receiving cilostazol had a significantly higher adenosine and cAMP plasma concentration than patients receiving aspirin (3.00 ± 0.67 vs 2.56 ± 0.74 mol/L, P < .001; 28.10 ± 14.74 vs 20.48 ± 11.35 pmol/mL, P = .0014). Cilostazol was associated with a higher inhibition rate of ADP induced platelet aggregation than aspirin (63.35 ± 26.71 vs 52.2 ± 28.35, P = .036). The plasma levels of adenosine and cAMP showed a positive correlation with ADP induced platelet aggregation.

WHAT IS NEW AND CONCLUSION

Cilostazol increases adenosine concentration compared with aspirin. Its potent antiplatelet effect in ACS patients may be partly mediated by adenosine.

Association of lipoprotein(a) with platelet aggregation and thrombogenicity in patients undergoing percutaneous coronary intervention

This study aimed to evaluate the association of lipoprotein(a) levels with platelet aggregation and thrombogenicity in patients undergoing percutaneous coronary intervention (PCI), and to investigate the ischemic outcome on this population. Lipoprotein(a) and modified thrombelastography were measured in 6601 consecutive patients underwent PCI on dual antiplatelet therapy. Cox proportional regression analysis was applied to illustrate the ischemic events in a 2-year follow up. The mean levels of lipoprotein(a) were 29.0 mg/dl. Patients with higher lipoprotein(a) levels had significantly accelerated fibrin generation (lower K time and bigger α angle) and greater clot strength (higher maximum amplitude (MA)) than patients with lower lipoprotein(a) levels (P < .001). Moreover, the higher lipoprotein(a) group also exhibited significantly higher adenosine diphosphate (ADP) induced platelet aggregation (MA_ADP) by thrombelastography platelet mapping assay than lower lipoprotein(a) group. Cox regression analyzes revealed that patients with higher lipoprotein(a) levels had a 16% higher risk of major adverse cardiovascular and cerebrovascular events (HR 1.159, 95%CI: 1.005-1.337, P = .042) compared with patients with lower lipoprotein(a) levels. This association persisted after adjustment for a broad spectrum of risk factors (HR 1.174, 95%CI: 1.017-1.355, P = .028). High plasma lipoprotein(a) levels were associated with increased platelet aggregation and ischemic events in patients underwent PCI. Lipoprotein(a) might indicate the need for prolonged antiplatelet therapy.

Rewarming from accidental hypothermia enhances whole blood clotting properties in a murine model

BACKGROUND

Hypothermia triggers coagulation, which can lead to the development of a life-threatening condition. We previously reported that hypothermia induces platelet activation in the spleen, resulting in microthrombosis after rewarming. However, the changes in whole blood clotting properties that occur remain unclear. Using thromboelastography, we investigated blood clotting activity and the effects of rewarming in a murine model of hypothermia.

METHODS

C57Bl/6 mice were exposed to an ambient temperature of -20 °C under general anesthesia until their rectal temperature decreased to 15 °C. One group of mice was kept at 4 °C for 2 h and then euthanized. Another group was rewarmed, kept in normal conditions for 24 h, and then euthanized. Tissue and citrated whole blood samples were obtained from the mice for histopathological analysis, flow cytometry, and thromboelastography.

RESULTS

Hypothermia induced the activation of platelets in the spleen; however, rewarming significantly reduced the number of activated platelets in the spleen while their numbers significantly increased in peripheral blood. In hypothermic mice not subjected to rewarming, no increase in activated platelets was observed in peripheral blood. Thromboelastography analysis showed that whole blood samples from the rewarmed mice displayed an enhanced clotting strength.

CONCLUSIONS

Rewarming from hypothermia enhances whole blood coagulation activity accompanied by an increase in the number of active platelets in peripheral blood. This phenomenon may lead to formation of microthrombi and thrombotic disorders.

Thrombin generation and bleeding in cardiac surgery: a clinical narrative review

This narrative review discusses the role of thrombin generation in coagulation and bleeding in cardiac surgery, the laboratory methods for clinical detection of impaired thrombin generation, and the available hemostatic interventions that can be used to improve thrombin generation. Coagulopathy after cardiopulmonary bypass (CPB) is associated with excessive blood loss and adverse patient outcomes. Thrombin plays a crucial role in primary hemostasis, and impaired thrombin generation can be an important cause of post-CPB coagulopathy. Existing coagulation assays have significant limitations in assessing thrombin generation, but whole-blood assays designed to measure thrombin generation at the bed-side are under development. Until then, clinicians may need to institute therapy empirically for non-surgical bleeding in the setting of normal coagulation measures. Available therapies for impaired thrombin generation include administration of plasma, prothrombin complex concentrate, and bypassing agents (recombinant activated factor VII and factor eight inhibitor bypassing activity). In vitro experiments have explored the relative potency of these therapies, but clinical studies are lacking. The potential incorporation of thrombin generation assays into clinical practice and treatment algorithms for impaired thrombin generation must await further clinical development.

Association Between Residual Platelet Reactivity on Clopidogrel Treatment and Severity of Coronary Atherosclerosis: Intrinsic Hypercoagulability as a Mediator

INTRODUCTION

High on-treatment residual platelet reactivity (HRPR) was associated with greater atherosclerosis burden. We examined whether intrinsic hypercoagulability (IHC) could be attributed to that association in patients treated by drug-eluting stents.

METHODS

This retrospective observation enrolled a total of 891 coronary artery disease (CAD) subjects. Platelet and coagulant reactivity was measured by thrombelastography. At least 24 h after a 300-mg dose of clopidogrel, adenosine diphosphate (ADP)-induced maximum amplitude of clot strength (MA_adp) > 47 mm represented HRPR. Thrombin-induced platelet-fibrin clot strength (MA_thrombin) and blood fibrinogen surrogated intrinsic coagulability. Using mediation analysis to evaluate the effect of IHC on the relationship between the number of narrowed coronaries and HRPR on clopidogrel.

RESULTS

More HRPR on clopidogrel and higher intrinsic coagulability were observed in more severe coronary atherosclerosis, especially in the three-vessel disease. After adjustment for confounding factors, the number of narrowed coronaries (OR_adj = 1.343, 95% CI 1.063-1.695, p = 0.013), MA_thrombin (OR_adj = 1.106, 95% CI 1.058-1.157, p < 0.001), and fibrinogen (OR_adj = 1.003, 95% CI 1.001-1.005, p = 0.012) were all independent positive predictors for HRPR. MA_thrombin and fibrinogen were meaningful mediators for the significant positive association of the number of narrowed vessels and HRPR on clopidogrel, which were enhanced by around 30% and 43%, respectively, for this effect.

CONCLUSIONS

This is the first study to demonstrate that the positive correlation between the number of stenotic coronaries and HRPR on clopidogrel may be partly attributed to IHC, which may enhance the risk stratification, guide more precise coagulation in multi-vessel disease after drug-eluting stents, and therefore deserve further study.

Both CYP2C19 and PON1 Q192R Genotypes Influence Platelet Response to Clopidogrel by Thrombelastography in Patients with Acute Coronary Syndrome

Objective

The objective of this study is to explore the relationships of the effects of CYP2C19 and PON1 Q192R polymorphism on the activity of clopidogrel and the risk of high platelet responsiveness (HPR) by thrombelastography in patients with acute coronary syndrome (ACS).

Methods

459 ACS patients with aspirin and clopidogrel were enrolled in this observational case control study from July 13, 2015, to November 11, 2017. The patients with <30% platelet inhibition were defined as HPR group, while the others were defined as normal platelet responsiveness (NPR) group. The genotypes distribution between the groups was assessed, and the clinical impact of genetic variants was investigated by comparing the relationship between the risk of HPR and genotypes including CYP2C19⁎2, CYP2C19⁎3, CYP2C19⁎17, ABCB1, and PON1.

Results

Compared with CYP2C19⁎1/⁎1 wild type carriers, CYP2C19⁎2 and ⁎3 carriers showed a significant association with the lower platelet inhibition (P=0.048). The platelet inhibition in carriers of at least one CYP2C19 loss-of-function (LOF) alleles was obviously higher than noncarriers (P=0.031). The platelet inhibition of PON1 192R carriers was lower than PON1 192Q carriers (P=0.044). Patients with the CYP2C19⁎2 and ⁎3 alleles had a greater risk of HPR than CYP2C19 wild type carriers (adjusted P=0.018 and adjusted P=0.005). At least one PON1 192R carrier predicted a significantly higher risk of HPR than PON1 192Q carriers (adjusted P=0.021). Individual CYP2C19⁎17 and ABCB1 variants did not differ significantly between the two groups.

Conclusions

CYP2C19 and PON1 Q192R variants influence ADP-induced platelet inhibition by thrombelastography (TEG) in ACS patients with clopidogrel. In addition, both LOF CYP2C19 and PON1 192R variants are independent risk factors of HPR, which is measured by the relative platelet inhibition.

Targeting thrombogenicity and inflammation in chronic HIV infection

Persons with HIV infection (PWH) have increased risk for cardiovascular disease (CVD), but the underlying mechanisms remain unclear. Coronary thrombosis is known to provoke myocardial infarctions, but whether PWH have elevated thrombotic propensity is unknown. We compared thrombogenicity of PWH on antiretroviral therapy versus matched controls using the Badimon chamber. Measures of inflammation, platelet reactivity, and innate immune activation were simultaneously performed. Enrolled PWH were then randomized to placebo, aspirin (81 mg), or clopidogrel (75 mg) for 24 weeks to assess treatment effects on study parameters. Thrombogenicity was significantly higher in PWH and correlated strongly with plasma levels of D-dimer, soluble TNF receptors 1 and 2, and circulating classical and nonclassical monocytes in PWH. Clopidogrel significantly reduced thrombogenicity and sCD14. Our data suggest that higher thrombogenicity, interacting with inflammatory and immune activation markers, contributes to the increased CVD risk observed in PWH. Clopidogrel exhibits an anti-inflammatory activity in addition to its antithrombotic effect in PWH.

Effects of malignancy on blood coagulation in septic intensive care patients

: The objectives of the study are to examine the effect of sepsis on the coagulation profile of patients having solid cancer and to test the hypothesis that septic patients with cancer have normal or increased hemostatic capacity despite prolonged standard coagulation tests (SCTs) compared with noninfected cancer patients. Patients with solid cancer were included in the study forming two groups: study group included patients with sepsis with minimum two organ dysfunctions and control group formed by noninfected cancer patients. SCTs, platelet count, plasma levels of coagulation factors and rotation thromboelastometry (TEM International GmbH, Munich, Germany) were determined in both groups. Study group patients (n = 35) showed prolonged SCTs, thrombocytopenia, decreased coagulation factor levels and increased D-dimer compared with control group (n = 35). However, fibrinogen levels and clot firmness assessed by rotation thromboelastometry were not different between groups and clot lysis indexes at 45 and 60 min were increased in study group compared with control group. The first derivative of the clot firmness curve revealed an increased time to the maximum velocity of clot formation for study group, without differences in the maximum velocity of clot formation, or in total thrombus formation. Sepsis with organ dysfunction in cancer patients is associated with delayed initiation of coagulation and reduced fibrinolysis compared with control patients, but overall clot formation and stabilization is not different. For septic cancer patients, SCTs and plasmatic indicators of fibrinolysis do not translate well to whole blood clot formation and may be misleading indicators of thrombotic or bleeding risk.

Study of the Association of PEAR1, P2Y12, and UGT2A1 Polymorphisms with Platelet Reactivity in Response to Dual Antiplatelet Therapy in Chinese Patients

Objectives: Genetic variation is thought to contribute to considerable interindividual variability in platelet function, and there is a pressing need to identify genetic markers that can be used to predict the response to treatment. Our study investigated whether PEAR1, P2Y12, and UGT2A1 polymorphisms were associated with platelet reactivity in response to dual antiplatelet therapy in Chinese patients with acute coronary syndrome. Methods: Patients with inhibition of platelet aggregation (IPA) < 30% after treatment were classified as the high platelet reactivity (HPR) group. Patients with IPA > 30% were classified as the normal platelet reactivity (NPR) group. ADP-induced platelet aggregation was measured by thromboelastography (TEG) platelet-mapping assay. Thirteen single nucleotide polymorphisms (SNPs) of PEAR1, P2Y12 and UGT2A1 were genotyped using the Mass­ARRAY platform. Results: Seven SNPs were significantly associated with ADP-induced platelet aggregation by univariate analysis. Major allele G at rs12041331, minor allele G at rs2644592, minor allele C at rs11264580, and minor allele C at rs11249454 were significantly associated with HPR, whereas minor allele T at rs57731889, minor allele A at rs16863356, and minor allele T at rs7634096 were significantly associated with NPR. The mean IPA was significantly lower in patients suffering recurrent ischemic events than in patients without recurrent events in our study (p = 0.048). Conclusions: Our findings suggest that PEAR1, P2Y12, and UGT2A1 genetic variants may be potential biomarkers that can be used to guide clinical applications of clopidogrel and aspirin in Chinese patients.

Abnormalities of laboratory coagulation tests versus clinically evident coagulopathic bleeding: results from the prehospital resuscitation on helicopters study (PROHS)

BACKGROUND

Laboratory-based evidence of coagulopathy (LC) is observed in 25-35% of trauma patients, but clinically-evident coagulopathy (CC) is not well described.

METHODS

Prospective observational study of adult trauma patients transported by helicopter from the scene to nine Level 1 trauma centers in 2015. Patients meeting predefined highest-risk criteria were divided into CC+ (predefined as surgeon-confirmed bleeding from uninjured sites or injured sites not controllable by sutures) or CC-. We used a mixed-effects, Poisson regression with robust error variance to test the hypothesis that abnormalities on rapid thrombelastography (r-TEG) and international normalized ratio (INR) were independently associated with CC+.

RESULTS

Of 1,019 highest-risk patients, CC+ (n=41, 4%) were more severely injured (median ISS 32 vs 17), had evidence of LC on r-TEG and INR, received more transfused blood products at 4 hours (37 vs 0 units), and had greater 30-day mortality (59% vs 12%) than CC- (n=978, 96%). The overall incidence of LC was 39%. 30-day mortality was 22% vs 9% in those with and without LC. In two separate models, r-TEG K-time >2.5 min (RR 1.3, 95% CI 1.1-1.7), r-TEG mA <55 mm (RR 2.5, 95% CI 2.0-3.2), platelet count <150 x 10⁹/L (RR 1.2, 95% CI 1.1-1.3), and INR >1.5 (RR 5.4, 95% CI 1.8-16.3) were independently associated with CC+. A combined regression model was not generated because too few patients underwent both r-TEG and INR.

CONCLUSION

CC was rare compared to LC. CC was associated with poor outcomes and impairment of both clotting factor and platelet-mediated coagulation components.

Preliminary reference intervals and the impact of citrate storage time for thrombelastography in cats including delta and the velocity curve

Background

Thrombelastography is a useful tool in assessment of hemostasis. Beside the traditional variables, the velocity curve and the variable delta have lately earned attention. The velocity curve provides knowledge about the speed of clot formation including information about thrombin generation. Delta, which only reflects enzymatic coagulation, allows the determination of the origin of hypercoagulability when compared to clot rigidity, a variable that reflects both platelet and enzymatic activity. The aim was to establish preliminary reference intervals for feline thrombelastography including the velocity curve variables and delta obtained after 60 min of storage including the assessment of coefficients of variation. Furthermore, the effect of citrate storage time (30 versus 60 min) on feline thrombelastography will be determined.

Results

Prolonged storage times significantly reduced reaction (R) (P = 0.019) and clotting (K) (P = 0.008) times, split point (SP) (P = 0.019) and time to maximum rate of thrombus generation (TMRTG) (P = 0.023) values whereas maximum rate of thrombus generation (MRTG) significantly increased (P = 0.040). Preliminary reference intervals: R (min): 2.7–18.1; K (min): 0.8–3.9; alpha (°): 27.6–75.2; maximum amplitude (mm): 18.5–62.5; clot rigidity (dyn/cm²): 1.2–8.2; coagulation index: −4.6 – 2.6; SP (min): 2.4–15.4; delta (min): 0.3–3.1; thrombus generation (mm/min): 255.3–751.2; MRTG (mm/min): 4.0–19.3; TMRTG (min): 3.5–22.0; maximum rate of lysis (mm/min): 0.0–4.7 and time to maximum rate of lysis (min): 0.4–55.8.

Conclusion

Storage for 60 versus 30 min induces hypercoagulable tracings including the velocity curve, some of which variables (MRTG, TMRTG) might function as sensitive markers for changes in the coagulation activity. Because of the impact of citrate storage time on thrombelastography, reference intervals have to be established using a specific and constant storage time in each laboratory.

Optical sensing of anticoagulation status: Towards point-of-care coagulation testing

Anticoagulant overdose is associated with major bleeding complications. Rapid coagulation sensing may ensure safe and accurate anticoagulant dosing and reduce bleeding risk. Here, we report the novel use of Laser Speckle Rheology (LSR) for measuring anticoagulation and haemodilution status in whole blood. In the LSR approach, blood from 12 patients and 4 swine was placed in disposable cartridges and time-varying intensity fluctuations of laser speckle patterns were measured to quantify the viscoelastic modulus during clotting. Coagulation parameters, mainly clotting time, clot progression rate (α-angle) and maximum clot stiffness (MA) were derived from the clot viscoelasticity trace and compared with standard Thromboelastography (TEG). To demonstrate the capability for anticoagulation sensing in patients, blood samples from 12 patients treated with warfarin anticoagulant were analyzed. LSR clotting time correlated with prothrombin and activated partial thromboplastin time (r = 0.57-0.77, p<0.04) and all LSR parameters demonstrated good correlation with TEG (r = 0.61-0.87, p<0.04). To further evaluate the dose-dependent sensitivity of LSR parameters, swine blood was spiked with varying concentrations of heparin, argatroban and rivaroxaban or serially diluted with saline. We observed that anticoagulant treatments prolonged LSR clotting time in a dose-dependent manner that correlated closely with TEG (r = 0.99, p<0.01). LSR angle was unaltered by anticoagulation whereas TEG angle presented dose-dependent diminution likely linked to the mechanical manipulation of the clot. In both LSR and TEG, MA was largely unaffected by anticoagulation, and LSR presented a higher sensitivity to increased haemodilution in comparison to TEG (p<0.01). Our results establish that LSR rapidly and accurately measures the response of various anticoagulants, opening the opportunity for routine anticoagulation monitoring at the point-of-care or for patient self-testing.

Coagulopathy of Trauma

Coagulopathy is common after injury and develops independently from iatrogenic, hypothermic, and dilutional causes. Despite considerable research on the topic over the past decade, trauma-induced coagulopathy (TIC) continues to portend poor outcomes, including decreased survival. We review the current evidence regarding the diagnosis and mechanisms underlying trauma induced coagulopathy and summarize the debates regarding optimal management strategy including product resuscitation, potential pharmacologic adjuncts, and targeted approaches to hemostasis. Throughout, we will identify areas of continued investigation and controversy in the understanding and management of TIC.

Ticagrelor Compared with Clopidogrel Increased Adenosine and Cyclic Adenosine Monophosphate Plasma Concentration in Acute Coronary Syndrome Patients

Ticagrelor produces a more potent antiplatelet effect than clopidogrel and inhibits cellular uptake of adenosine, which is associated with several cardiovascular consequences. We aimed to explore the correlation between adenosine and cyclic adenosine monophosphate (cAMP) plasma concentration and antiplatelet effect by clopidogrel or ticagrelor in patients with acute coronary syndrome (ACS) receiving dual antiplatelet therapy (DAPT). We conducted a prospective, observational and single-centre cohort study enrolling 68 patients with non-ST-segment elevation ACS from January 2016 to May 2016. We monitored the inhibition of platelet aggregation (IPA) and assessed adenosine, adenosine deaminase (ADA) and cAMP plasma concentrations by immunoassay on admission and 48 hr after coronary angiography. The demographic and clinical data were collected by reviewing their medical records. The two groups exhibited similar baseline characteristics including adenosine, ADA and cAMP. The mean IPA in patients receiving ticagrelor was significantly higher than that in patients receiving clopidogrel (93.5% versus 67.2%; p = 0.000). Also, we observed that patients treated with ticagrelor had a significantly higher increase in levels of adenosine and cAMP compared with those treated with clopidogrel (1.04 (0.86; 1.41) versus 0.04 (-0.25; 0.26); p = 0.029 and 0.78 (-1.67; 1.81) versus 0.60 (-1.91; 4.60); p = 0.037, respectively). And there was a weak correlation between IPA and adenosine as well as cAMP plasma concentration (r = 0.390, p = 0.001 and r = 0.335, p = 0.005, respectively). Ticagrelor increased adenosine and cAMP plasma concentration compared with clopidogrel in patients with ACS.

Thromboelastometry and Thrombelastography Analysis under Normal Physiological Conditions - Systematic Review

BACKGROUND

Studies investigating thromboelastometry or thrombelastography analyses in a physiological context are scattered and not easy to access.

OBJECTIVE

To systematically retrieve and describe published reports studying healthy subjects and targeting at the correlation of ROTEM® and TEG® measurements with conventional parameters of hemostasis.

METHODS

Systematic Review: Papers were searched in Medline, Scopus and the Science Citation Index database. Reference lists of included studies and of reviews were screened. To be included papers had to report ROTEM or TEG data on healthy subjects. Two reviewers screened papers for inclusion, read full texts of potentially relevant papers, and extracted data of included papers.

RESULTS

Searches identified 1,721 records of which 1,713 were either excluded immediately or after reading the full text. The remaining 8 studies enrolled 632 subjects. The association of conventional parameters of hemostasis with ROTEM and with TEG was investigated in one and two studies, respectively. Overall correlation was limited and ranged from 0.0 to 0.40 (total thrombus generation vs. fibrinogen; clotting time INTEM vs. activated partial thromboplastin time).

CONCLUSIONS

Studies assessing the relationship between thromboelastometry or thromboelastography analyses and conventional parameters of hemostasis in healthy subjects remains scarce, and correlations are limited. Further research is needed to understand the physiology of thromboelastometry and thromboelastography parameters.

In vitro Anti-Thrombotic Activity of Extracts from Blacklip Abalone (Haliotis rubra) Processing Waste

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin.

Association of weight gain with coronary artery disease, inflammation and thrombogenicity

Obese individuals, despite having increased cardiovascular (CV) risk factors experience adverse CV outcomes less frequently than non-obese. Little is known about association of long-term weight gain to development of coronary artery disease (CAD), inflammation and thrombogenicity. 418 consecutive patients with suspected CAD undergoing elective cardiac catheterization were included in a sub-analysis of the multi analyte, thrombogenic, and genetic markers of atherosclerosis study. Maximum weight gain (MWG) was defined as percentage increase in weight since age 17 years to year of heaviest weight and categorized as: minor (<30 %), moderate (30-47 %), severe (>47-69 %), and extreme (>69 %). Lipid profiling was determined by vertical density gradient ultracentrifugation, thrombin-induced platelet fibrin clot strength (TIP-FCS) by thrombelastography, and urinary 11-dehydrothromboxane B2 (11-dhTxB2) by ELISA. CAD severity was defined as minimal (<20 %), moderate (20-75 %), and severe (>75 %) luminal diameter obstruction of any major coronary vessel. The mean MWG was 53 ± 33 %. Extreme MWG group had a higher incidence of diabetes mellitus (48 %), hypertension (81 %), depression (25 %), and were most often female (60 %) (p < 0.05 for all). In women, CAD severity was inversely associated to MWG (p = 0.05), whereas in men no such association was observed (p = 0.18). TIP-FCS increased in a stepwise fashion with MWG (p = 0.001). 11-dTxB2 levels were higher in the extreme MWG group, regardless of lipid lowering therapy (p < 0.05). Our data suggest that maximal weight gain since age 17 years is associated with heightened thrombogenicity, inflammation and a poorer lipid profile but not an increased risk for severe CAD development.

Dynamics of Thrombin Generation and Flux from Clots during Whole Human Blood Flow over Collagen/Tissue Factor Surfaces

Coagulation kinetics are well established for purified blood proteases or human plasma clotting isotropically. However, less is known about thrombin generation kinetics and transport within blood clots formed under hemodynamic flow. Using microfluidic perfusion (wall shear rate, 200 s^-1) of corn trypsin inhibitor-treated whole blood over a 250-μm long patch of type I fibrillar collagen/lipidated tissue factor (TF; ∼1 TF molecule/μm²), we measured thrombin released from clots using thrombin-antithrombin immunoassay. The majority (>85%) of generated thrombin was captured by intrathrombus fibrin as thrombin-antithrombin was largely undetectable in the effluent unless Gly-Pro-Arg-Pro (GPRP) was added to block fibrin polymerization. With GPRP present, the flux of thrombin increased to ∼0.5 × 10^-12 nmol/μm²-s over the first 500 s of perfusion and then further increased by ∼2-3-fold over the next 300 s. The increased thrombin flux after 500 s was blocked by anti-FXIa antibody (O1A6), consistent with thrombin-feedback activation of FXI. Over the first 500 s, ∼92,000 molecules of thrombin were generated per surface TF molecule for the 250-μm-long coating. A single layer of platelets (obtained with α_IIbβ₃ antagonism preventing continued platelet deposition) was largely sufficient for thrombin production. Also, the overall thrombin-generating potential of a 1000-μm-long coating became less efficient on a per μm² basis, likely due to distal boundary layer depletion of platelets. Overall, thrombin is robustly generated within clots by the extrinsic pathway followed by late-stage FXIa contributions, with fibrin localizing thrombin via its antithrombin-I activity as a potentially self-limiting hemostatic mechanism.

Assessment of Functional Fibrinolysis in Cord Blood Using Modified Thromboelastography

BACKGROUND

The fibrinolytic system in newborns is immature and probably impaired. The aim of this study was to prospectively evaluate functional fibrinolytic capacity of newborn's cord blood using a new thromboelastometry (rotational thromboelastogram, ROTEM®) test.

METHODS

Infants born at Sheba Medical Center were studied prospectively. Cord blood was obtained immediately after clumping, and ROTEM parameters were assessed applying non-activated TEM (NATEM) assay with increasing concentration of tissue plasminogen activator (tPA, 0-200 U/ml). Baseline clotting time (CT), clot formation time (CFT), alpha angle, and maximum clot firmness (MCF) were compared among infants versus adults. Each infant's demographic information was prospectively followed up until discharge.

RESULTS

One hundred one newborns were tested. CT and CFT values were lower and alpha angles were higher among neonate's cord blood compared to adults (n = 23; P = 0.001, 0.03, and 0.02, respectively). The addition of tPA significantly shortened CT and CFT, and reduced alpha angles and MCF in both groups. The lysis index at 30 min (LI30) and lysis onset time (LOT) decreased significantly, and fibrinolysis was more rapid in the newborns. Hematocrit and platelet counts in neonates correlated with LI30 (P = 0.035 and 0.037, respectively) and LOT (P = 0.02) when higher tPA concentrations were used. ROTEM values were unrelated to the occurrence of postnatal complications.

CONCLUSIONS

This first report of functional fibrinolysis in cord blood demonstrated that neonatal fibrinolysis may be augmented as compared to adult values. Further studies are required to validate this test and assess its predictive value and clinical relevance.

Transfusion and coagulation management in major obstetric hemorrhage

PURPOSE OF REVIEW

Major obstetric hemorrhage is a leading cause of maternal morbidity and mortality. We will review transfusion strategies and the value of monitoring the maternal coagulation profile during severe obstetric hemorrhage.

RECENT FINDINGS

Epidemiologic studies indicate that rates of severe postpartum hemorrhage (PPH) in well resourced countries are increasing. Despite these increases, rates of transfusion in obstetrics are low (0.9-2.3%), and investigators have questioned whether a predelivery 'type and screen' is cost-effective for all obstetric patients. Instead, blood ordering protocols specific to obstetric patients can reduce unnecessary antibody testing. When severe PPH occurs, a massive transfusion protocol has attracted interest as a key therapeutic resource by ensuring sustained availability of blood products to the labor and delivery unit. During early postpartum bleeding, recent studies have shown that hypofibrinogenemia is an important predictor for the later development of severe PPH. Point-of-care technologies, such as thromboelastography and rotational thromboelastometry, can identify decreased fibrin clot quality during PPH, which correlate with low fibrinogen levels.

SUMMARY

A massive transfusion protocol provides a key resource in the management of severe PPH. However, future studies are needed to assess whether formula-driven vs. goal-directed transfusion therapy improves maternal outcomes in women with severe PPH.

Thromboelastography defines late hypercoagulability after TBI: a pilot study

INTRODUCTION

Traumatic brain injury (TBI) is associated with a hypercoagulable state, the mechanism and duration of which remain unclear. We sought to determine whether thromboelastography (TEG) analysis could identify the hypercoagulable state after TBI, as defined by elevations in maximal amplitude (MA), thrombus generation (TG), G value (G), and alpha angle (αA).

METHODS

Patients with moderate-severe TBI, defined primarily as a GCS <12, admitted between 1/2012 and 8/2013 were eligible for enrolment in this prospective cohort study. TEG profiles were obtained between 0-24 h (T1), 24-48 h (T2), 48-72 h (T3), 72-96 h (T4), and 96-120 h (T5) after admission. Early TEG was defined as 0-48 h, and late TEG was defined as >48 h.

RESULTS

Twenty five patients (80 % men) and 7 age- and sex-matched control subjects were studied. Median age was 38 years (range 18-85). Early MA was [63.6 mm (60.5, 67.4)] versus late MA [69.9 mm (65.2,73.9); p = 0.02], early TG was [763.3 mm/min (712.8, 816.2)] versus late TG [835.9 mm/min (791.2,888.3); p = 0.02], and early G was [8.8 d/cm(2) (7.7,10.4)] versus late G [11.6 d/cm(2) (9.4,14.1); p = 0.02]. Study patients had higher MA (p = 0.02), TG (p = 0.03), and G (p = 0.02) values at T5 compared to controls. There was a linear increase per day of MA by 2.6 mm (p = 0.001), TG 31.9 mm/min (p ≤ 0.001), and G value by 1.3 d/cm(2) (p ≤ 0.001) when clustered by pairs in regression analysis. Lower MA values trended toward home discharge (p = 0.08).

CONCLUSION

The data suggest a progressive and delayed hypercoagulable state observed days after initial TBI. The hypercoagulable state may reflect excess platelet activity.

The simultaneous occurrence of both hypercoagulability and hypofibrinolysis in blood and serum during systemic inflammation, and the roles of iron and fibrin(ogen)

Although the two phenomena are usually studied separately, we summarise a considerable body of literature to the effect that a great many diseases involve (or are accompanied by) both an increased tendency for blood to clot (hypercoagulability) and the resistance of the clots so formed (hypofibrinolysis) to the typical, 'healthy' or physiological lysis. We concentrate here on the terminal stages of fibrin formation from fibrinogen, as catalysed by thrombin. Hypercoagulability goes hand in hand with inflammation, and is strongly influenced by the fibrinogen concentration (and vice versa); this can be mediated via interleukin-6. Poorly liganded iron is a significant feature of inflammatory diseases, and hypofibrinolysis may change as a result of changes in the structure and morphology of the clot, which may be mimicked in vitro, and may be caused in vivo, by the presence of unliganded iron interacting with fibrin(ogen) during clot formation. Many of these phenomena are probably caused by electrostatic changes in the iron-fibrinogen system, though hydroxyl radical (OH˙) formation can also contribute under both acute and (more especially) chronic conditions. Many substances are known to affect the nature of fibrin polymerised from fibrinogen, such that this might be seen as a kind of bellwether for human or plasma health. Overall, our analysis demonstrates the commonalities underpinning a variety of pathologies as seen in both hypercoagulability and hypofibrinolysis, and offers opportunities for both diagnostics and therapies.

Both PON1 Q192R and CYP2C19*2 influence platelet response to clopidogrel and ischemic events in Chinese patients undergoing percutaneous coronary intervention

Clopidogrel nonresponsiveness increases the recurrence of cardiovascular events in patients undergoing percutaneous coronary intervention (PCI). Previous studies found that genetic variants such as single nucleotide polymorphisms (SNPs) of CYP2C19 and PON1 may influence clopidogrel response, cause high platelet reactivity (HPR) and increase cardiovascular events. However, these studies were inconsistent and inconclusive, especially in the Eastern Asian population. In this study, we investigated the effects of genetic variants on clopidogrel response and clinical outcomes in Chinese patients undergoing PCI. A total of 336 acute coronary syndrome patients undergoing PCI were included, 53 (15.77%) of whom were categorized as HPR. Among the 10 SNPs studied (ABCB1, CYP2C19*2, CYP2C19*3, CYP2C19*4, CYP2C19*17, CYP3A4, CYP3A5, ITGB3, P2Y12 and PON1 Q192R), the CYP2C19*4 and P2Y12 variants were not found in our population. The PON1 192Q and CYP2C19*2 alleles were significantly higher in the HPR group compared with the normal platelet reactivity (NPR) group (P=0.033 and 0.038, respectively), while the other SNPs were not significantly different between the two groups. Platelet aggregation of the PON1 192Q allele carriers was significantly higher than that of non-carriers both at baseline and 1 month after PCI (P=0.010 and 0.024, respectively); this was the case for CYP2C19*2 allele carriers, as well (P=0.005 and 0.003, respectively). The risk of major adverse cardiovascular event (MACE) increased with the presence of the PON1 192Q and CYP2C19*2 alleles during 6-month follow-up (P=0.012 and 0.003, respectively). In conclusion, both the PON1 Q192R and CYP2C19*2 variants are associated with HPR and an increased risk of ischemic events in Chinese patients undergoing PCI.

Association of thrombelastographic parameters with post-stenting ischemic events

BACKGROUND AND PURPOSE

Thrombelastography (TEG) is widely used for the measurement of platelet function. However, few studies have investigated the TEG parameters in patients receiving extracranial or intracranial artery stenting for ischemic cerebrovascular disease. This study sought to describe the association of TEG parameters before the procedure with post-procedural ischemic events after extracranial or intracranial artery stenting.

METHODS

Patients in whom stenting was performed for extracranial or intracranial artery stenosis (70-99%) were recruited into the study. Blood samples were obtained for TEG to assess platelet function before stenting. The primary endpoint was ischemic stroke or transient ischemic attack in the territory of the stented artery.

RESULTS

A total of 218 patients were included in the study. During a mean follow-up period of 132 days (range 98-226 days), 18 (8.3%) primary endpoint events were recorded. Compared with patients without ischemic events, the ADP-induced platelet-fibrin clot strength (MA_ADP) was significantly higher (41.57±15.10 vs 33.50±13.86, p=0.020) and the ADP inhibition rate (ADP%) was significantly lower in patients with ischemic events (39.54±23.15 vs 55.29±24.43, p=0.009). Multivariate analysis identified MA_ADP and ADP% as significant independent predictors of subsequent ischemic events with HRs of 1.036 and 0.965, respectively. From receiver operating characteristic curve analysis, MA_ADP >49.95 mm had the best predictive value of ischemic events.

CONCLUSIONS

Our study suggests that TEG parameters MA_ADP and ADP% are associated with subsequent ischemic events in patients with extracranial or intracranial stents.

CLINICAL TRIAL NUMBER

NCT01925872.

Evaluation of dynamic parameters of thrombus formation measured on whole blood using rotational thromboelastometry in children undergoing cardiac surgery: a descriptive study

BACKGROUND

Total thrombus formation velocity calculated using amplitude parameters obtained at different times could be used to estimate the amplification and the propagation phases observed during coagulation processes, and therefore might be useful to predict postoperative hemostatic products administration in pediatric patients.

METHODS

We retrospectively analyzed data from 49 children <3 months of age who underwent cardiac surgery. Children ≤1 month of age routinely received fresh frozen plasma during bypass while children >1 month of age did not. The EXTEM parameters were used to calculate velocity curves using amplitudes obtained at different times, the area under the curve called total thrombus formation and the maximum rate of thrombus formation. These parameters were compared between children who received fresh frozen plasma and those who did not. Receiver operating characteristics curves were used to define variables that could be used to predict postoperative fresh frozen plasma transfusion.

RESULTS

Total thrombus formation and maximum rate of thrombus formation significantly increased in children who received fresh frozen plasma compared to those who did not. Both total thrombus formation and maximum rate of thrombus formation have a better specificity to predict postoperative fresh frozen plasma transfusion compared to clotting time or maximal clot firmness.

CONCLUSION

Based on this descriptive study, dynamic ROTEM(®) parameters of total thrombus formation could be used to estimate the amplification and the propagation phases of coagulation in children. These parameters might be used in further well-designed study to predict the need for hemostatic products in children undergoing cardiac surgery with cardiopulmonary bypass.

Global assays of hemostasis

PURPOSE OF REVIEW

There exists an imbalance between our understanding of the physiology of the blood coagulation process and the translation of this understanding into useful assays for clinical application. As technology advances, the capabilities for merging the two areas have become more attainable. Global assays have advanced our understanding of the dynamics of the blood coagulation process beyond end point assays and are at the forefront of implementation in the clinic.

RECENT FINDINGS

We will review recent advances in the main global assays with a focus on thrombin generation that have potential for clinical utility. These assays include direct (thrombogram, whole blood, purified systems) and indirect empirical measures of thrombin generation (thromboelastography) and mechanism-based computational models that use plasma composition data from individuals to generate thrombin generation profiles.

SUMMARY

Empirical thrombin generation assays (direct and indirect) and computational modeling of thrombin generation have greatly advanced our understanding of the hemostatic balance. Implementation of these types of assays and visualization approaches in the clinic will potentially provide a basis for the development of individualized patient care. Advances in both empirical and computational global assays have made the goal of predicting precrisis changes in an individual's hemostatic state one step closer.