Detection of hypofibrinolysis in stable coronary artery disease using the overall haemostatic potential assay

Acute effects of high intensity interval training versus moderate intensity continuous training on haemostasis in patients with coronary artery disease

Exercise training is associated with an acute net increase in coagulation, which may increase the risk of atherothrombosis in coronary artery disease (CAD) patients. We sought to compare the acute haemostatic effects of a bout of moderate-intensity continuous (MICT) and high-intensity interval training (HIIT) in patients with CAD. Patients after a recent myocardial infarction were randomized into a HIIT or MICT session of exercise training on a stationary bike. Blood was sampled at baseline, after the exercise bout and after a one-hour resting period. We measured overall haemostatic potential (OHP), overall coagulation potential (OCP), fibrinogen, D-dimer and von Willebrand factor (vWF) and calculated overall fibrinolytic potential (OFP). Linear mixed models for repeated measures were constructed to assess the treatment effect. A total of 117 patients were included. OCP, OHP, fibrinogen, D-dimer and vWF significantly increased after exercise and returned to baseline after a one-hour rest, OFP decreased after exercise and returned to baseline levels after a one-hour rest. Linear mixed models showed a significant difference between HIIT and MICT in fibrinogen (p 0.043) and D-dimer (p 0.042). Our study has shown that an exercise bout is associated with a transient procoagulant state in patients with CAD, with similar exercise-induced haemostatic changes for HIIT and MICT.

The Fibrinolytic System and Its Measurement: History, Current Uses and Future Directions for Diagnosis and Treatment

The fibrinolytic system is a key player in keeping the haemostatic balance, and changes in fibrinolytic capacity can lead to both bleeding-related and thrombosis-related disorders. Our knowledge of the fibrinolytic system has expanded immensely during the last 75 years. From the first successful use of thrombolysis in myocardial infarction in the 1960s, thrombolytic therapy is now widely implemented and has reformed treatment in vascular medicine, especially ischemic stroke, while antifibrinolytic agents are used routinely in the prevention and treatment of major bleeding worldwide. Despite this, this research field still holds unanswered questions. Accurate and timely laboratory diagnosis of disturbed fibrinolysis in the clinical setting remains a challenge. Furthermore, despite growing evidence that hypofibrinolysis plays a central role in, e.g., sepsis-related coagulopathy, coronary artery disease, and venous thromboembolism, there is currently no approved treatment of hypofibrinolysis in these settings. The present review provides an overview of the fibrinolytic system and history of its discovery; measurement methods; clinical relevance of the fibrinolytic system in diagnosis and treatment; and points to future directions for research.

Fibrin clot properties in cardiovascular disease: from basic mechanisms to clinical practice

Fibrinogen conversion into insoluble fibrin and the formation of a stable clot is the final step of the coagulation cascade. Fibrin clot porosity and its susceptibility to plasmin-mediated lysis are the key fibrin measures, describing the properties of clots prepared ex vivo from citrated plasma. Cardiovascular disease (CVD), referring to coronary heart disease, heart failure, stroke, and hypertension, has been shown to be associated with the formation of dense fibrin networks that are relatively resistant to lysis. Denser fibrin mesh characterized acute patients at the onset of myocardial infarction or ischaemic stroke, while hypofibrinolysis has been identified as a persistent fibrin feature in patients following thrombotic events or in those with stable coronary artery disease. Traditional cardiovascular risk factors, such as smoking, diabetes mellitus, hyperlipidaemia, obesity, and hypertension, have also been linked with unfavourably altered fibrin clot properties, while some lifestyle modifications and pharmacological treatment, in particular statins and anticoagulants, may improve fibrin structure and function. Prospective studies have suggested that prothrombotic fibrin clot phenotype can predict cardiovascular events in short- and long-term follow-ups. Mutations and splice variants of the fibrinogen molecule that have been proved to be associated with thrombophilia or increased cardiovascular risk, along with fibrinogen post-translational modifications, prothrombotic state, inflammation, platelet activation, and neutrophil extracellular traps formation, contribute also to prothrombotic fibrin clot phenotype. Moreover, about 500 clot-bound proteins have been identified within plasma fibrin clots, including fibronectin, α2-antiplasmin, factor XIII, complement component C3, and histidine-rich glycoprotein. This review summarizes the current knowledge on the mechanisms underlying unfavourable fibrin clot properties and their implications in CVD and its thrombo-embolic manifestations.

Overall haemostatic potential (OHP) assay can risk stratify for venous thromboembolism recurrence in anticoagulated patients

Assessing the risk of recurrent venous thromboembolism (VTE), particularly when patients are anticoagulated, remains a major challenge largely due to the lack of biomarkers. Blood was sampled from adult VTE patients recruited between January 2018 and September 2020, while receiving therapeutic anticoagulation. Results were compared to 144 healthy subjects (34.7% male, median age 42 years). Overall haemostatic potential (OHP) assay, a spectrophotometric assay, was performed on platelet-poor plasma, in which fibrin formation (triggered by small amounts of thrombin (overall coagulation potential, OCP)) and fibrinolysis (by the addition of thrombin and tissue plasminogen activator (OHP)) are simultaneously measured. Results were obtained from 196 patients (52.6% male, mean age 57.1 years). Compared to healthy subjects, VTE patients displayed significantly higher OCP (39.6 vs 34.5 units, p < 0.001) and OHP (9.3 vs 6.4 units, p < 0.001) as well as lower overall fibrinolytic potential (75.6 v s81.1%, p < 0.001). All 16 VTE recurrences, including 11 unprovoked, occurred above an OCP cut-off of 40^th percentile (recurrence rate 4.32/100 patient-years (100PY), 95% confidence interval (CI) 2.39-7.80, p = 0.002). Of 97 patients who subsequently discontinued anticoagulation, all unprovoked VTE recurrences (n = 9) occurred above the 40^th OCP percentile (recurrence rate 9.10/100PY, 95% CI 4.74-17.49, p = 0.005) and the 40^th OHP percentile (recurrence rate 8.46/100PY, 95% CI 4.40-16.25, p = 0.009). Our pilot study demonstrates that the OHP assay can detect a hypercoagulable and hypofibrinolytic state in anticoagulated VTE patients and may be able to risk stratify VTE recurrence, allowing for more individualised decision on long-term anticoagulation. Further larger prospective studies are required.

The Correlation between the Triglyceride-Glucose Index and Coagulation Markers in Patients with Recent Acute Myocardial Infarction

Background

Metabolic abnormalities and hypercoagulability seem to have an important predictive role in patients with coronary artery disease (CAD). The triglyceride-glucose (TyG) index has emerged as a good marker for metabolic syndrome with predictive value for cardiovascular events. Overall haemostatic potential (OHP) is a reliable global haemostatic essay to identify hypercoagulability in CAD patients. The aim of our study was therefore to evaluate a possible correlation between the TyG index and haemostatic derangements in patients with CAD.

Methods

Consecutive patients referred for the first follow-up visit after acute myocardial infarction between December 1, 2018, and March 31, 2020, and did not meet exclusion criteria were included. We determined OHP, overall coagulation potential (OCP), overall fibrinolytic potential (OFP), fibrinogen, D-dimer, and von Willebrand factor from peripheral blood samples. The TyG index was calculated with the previously described and validated formula. Linear regression models were constructed for the multivariate analysis.

Results

A total of 117 patients (mean age 56 ± 10 years, 20% women) were included. A correlation was found between TyG index and OCP (r = 0.229, p = 0.026), TyG index and OHP (r = 0.202, p = 0.050), and TyG index and fibrinogen (r = 0.271, p = 0.005). In the multivariate model which accounted for sex, age, and BMI, the correlation between TyG index and OCP (R² 0.108; ANOVA for regression p = 0.035; beta 2.08 [0.79-4.01], p = 0.042) and between TyG index and fibrinogen (R² 0.11; ANOVA for regression p = 0.015; beta 0.35 [0.08-0.62], p = 0.012) emerged as statistically significant.

Conclusion

The TyG index, a marker of metabolic syndrome, has a strong correlation with a hypercoagulability state in CAD, as determined by the OCP and higher fibrinogen levels. Our findings suggest that metabolic syndrome may be an important driver of atherothrombotic risk in patients with CAD.

Association between Lipoprotein Subfractions, Hemostatic Potentials, and Coronary Atherosclerosis

Background. Dyslipidemias are associated with atherosclerotic plaque formation and a prothrombotic state, thus increasing the risk of both atherosclerotic vascular disease and atherothrombotic adverse events. We sought to explore the association between lipoprotein subfractions, overall hemostasis, and coronary calcifications in individuals at intermediate cardiovascular risk. Methods. Consecutive statin-naive individuals at intermediate cardiovascular risk referred for coronary artery calcium score (CACS) scanning were included. CACS was assessed using a 128-slice dual-source CT scanner. Traditional lipid profile, high-density lipoprotein (HDL) subfractions 2 and 3, and small dense low-density lipoproteins (sdLDL) were measured with commercially available assays. Overall hemostatic (OHP) and coagulation potentials (OCP) were measured spectrophotometrically, using fibrin aggregation curves after exposure to thrombin and recombinant tissue-type plasminogen activator, respectively. Overall fibrinolytic potential (OFP) was calculated as a difference between the two areas under curves. Results. We included 160 patients (median age 63 (interquartile range (IQR), 56-71 years, 52% women, and median CACS 8, IQR 0-173 Agatston units). HDL3 levels—but not sdLDL or hemostatic potentials—were significantly associated with CACS zero, even after adjusting for age, sex, arterial hypertension, dyslipidemia, diabetes, and smoking history (OR 0.980 (0.962-0.999), $p=0.034$ ). HDL3 was also significantly associated with OCP ( $r=-0.232$ , $p$ adjusted for age and sex 0.037). Conclusions. In patients at intermediate cardiovascular risk, HDL3 is associated with both subclinical atherosclerosis and overall coagulation. Our findings are in line with studies reporting on an inverse relationship between HDL3 and atherosclerosis and provide one possible mechanistic explanation for the association between novel lipid biomarkers and coagulation derangements.

The Need for Individualized Risk Assessment in Cardiovascular Disease

Cardiovascular disease remains the leading cause of death in the era of modern medicine despite major advancements in this field. Current available clinical surrogate markers and blood tests do not adequately predict individual risk of cardiovascular disease. A more precise and sophisticated tool that can reliably predict the thrombosis and bleeding risks at an individual level is required in order for clinicians to confidently recommend early interventions with a favorable risk–benefit profile. Critical to the development of this tool is the assessment and understanding of Virchow’s triad and its complex interactions between hypercoagulability, endothelial dysfunction and vessel flow, a fundamental concept to the development of thrombosis. This review explores the pathophysiology of cardiovascular disease stemming from the triad of factors and how individualized risk assessment can be improved through the multimodal use of tools such as global coagulation assays, endothelial biomarkers and vessel flow assessment.

Age, sex and racial differences in fibrin formation and fibrinolysis within the healthy population

Increased fibrin generation and reduced fibrinolytic potential have been detected using global coagulation assays in several hypercoagulable states including cardiovascular disease and venous thromboembolism. We aimed in this study to define the impact of age, sex and race on fibrin generation and lysis using the Overall Haemostatic Potential (OHP) assay in a group of stringently defined healthy adults. Healthy adult patients not receiving anticoagulation and without a history of thrombotic disease were prospectively recruited. Iindividuals with cardiovascular risk factors (e.g. hypertension, diabetes, smoking), receiving hormonal therapy, antiplatelet agents or with abnormal routine blood tests were also excluded. Platelet-poor plasma was obtained and the OHP assay, which evaluates fibrin formation with and without tissue plasminogen activator, was performed on all plasma samples. 144 healthy subjects (34.7% male) with median age 42 years (interquartile range 20, 77) were recruited. After multivariate analysis, age at least 50 years and female sex were associated with significantly increased fibrin generation parameters (overall coagulation potential, OHP, maximum optical density, fibrin) as well as reduced markers of fibrinolysis (overall fibrinolytic potential and time-to-50% lysis). There were no significant differences in OHP parameters between whites, East Asians and South Asians after accounting for age and sex. This study defines age, sex and racial differences of fibrin generation and fibrinolysis as measured by the OHP assay in a sample of healthy subjects. Further studies are warranted in diseased populations, where there is growing awareness of the role of global coagulation assay in defining prothrombotic and hypofibrinolytic states.

Global coagulation assays in hypercoagulable states

Thrombosis is one of the major global causes of morbidity and mortality, and predicting the risk of thrombotic and cardiovascular complications remains one of the key challenges in modern medicine. Conventional coagulation testing does not provide sufficient information, primarily because they measure the time to start of blood clotting and do not evaluate total thrombin generation. Possible adjunctive tools that may be helpful are global coagulation assays, which includes the assessment of the final products of the coagulation cascade, namely thrombin and fibrin. Whilst these assays have been more widely investigated in bleeding states, their role in thrombotic disorders is less established. We have previously investigated the use of assays such as thromboelastography, calibrated automated thrombogram and overall haemostatic potential assay in several hypercoagulable states including cardiovascular disease, haematological disorders and influence of hormone status as well as healthy controls. We provide a review of the use and limitations of global coagulation assays in healthy controls as well as hypercoagulable conditions.

Association of Global Coagulation Profiles With Cardiovascular Risk Factors and Atherosclerosis: A Sex Disaggregated Analysis From the BioHEART-CT Study

Background

Although the association between dysregulated coagulation and atherosclerosis is well recognized, individual assays have been of minimal value in understanding disease susceptibility. Here we investigated the association of global coagulation profiles with coronary artery disease with consideration of sex differences.

Methods and Results

The study included patients from the BioHEART‐CT (The BioHEART Study: Assessing Patients With Suspected Cardiovascular Disease for New Disease Markers and Risk Factors) biobank who had computed tomography coronary angiograms scored for coronary artery calcium score (CACS) and Gensini score. The cohort included 206 adult patients who were referred for clinically indicated computed tomography coronary angiography and had a median of 2 major cardiac risk factors; 50% were women and the average age was 62.6 years (±9.9 years). The overall hemostatic potential (OHP) and calibrated automated thrombography generation assays were performed on platelet‐poor plasma. CACS and Gensini score in men were significantly correlated in bivariate analysis with measures from the OHP assay, and regression models predicting disease severity by CACS or Gensini score were improved by adding the OHP assay variables in men but not in women. The calibrated automated thrombography generation assay demonstrated a more hypercoagulable profile in women than in men. The OHP assay showed hypercoagulable profiles in women with hyperlipidemia and men with obesity.

Conclusions

The OHP assay identified hypercoagulable profiles associated with different risk factors for each sex and was associated with CACS and Gensini score severity in men, emphasizing the associations between increased fibrin generation and reduced fibrinolysis with cardiac risk factors and early atherosclerosis.

Registration Information

www.anzctr.org.au. Identifier: ACTRN12618001322224.

Circulating platelet-derived extracellular vesicles are decreased after remote ischemic preconditioning in patients with coronary disease: A randomized controlled trial

BACKGROUND

Brief nonharmful ischemia, remote ischemic preconditioning (RIPC) has been proposed to confer benefit to patients with coronary artery disease via unknown mechanisms.

OBJECTIVES

We aimed to investigate the effect of RIPC on circulating levels of extracellular vesicles (EVs) and global coagulation and fibrinolytic factors in patients with coronary disease.

PATIENTS/METHODS

Blood samples were taken from 60 patients presenting for coronary angiography enrolled in a randomized, controlled trial before and after RIPC (3 × 5 min administration of 200 mmHg sphygmomanometer on the arm, n = 31) or sham (n = 29) treatment. Most patients (n = 48) had significant coronary artery disease and all were taking at least one antiplatelet agent.

RESULTS

Remote ischemic preconditioning significantly decreased circulating levels of EVs expressing platelet markers CD41 and CD61 detected by flow cytometry in plasma, whereas no such effect was found on EVs expressing phosphatidylserine, CD62P, CD45, CD11b, CD144, CD31+ /CD41- , or CD235a. RIPC had no effect on the overall hemostatic potential assay or circulating antigen levels of tissue plasminogen activator, urokinase, plasminogen activator inhibitor-1, or plasminogen. Sham treatment had no effect on any studied parameter. Statin use inhibited the effect of RIPC on CD61+ EVs, diabetes modified the effect of RIPC on CD45+ and CD11b+ EVs, and hypertension modified the effect of RIPC on CD235a+ EVs.

CONCLUSIONS

Remote ischemic preconditioning decreased circulating levels of platelet-derived EVs in patients with coronary disease taking conventional antiplatelet therapy. This may reflect increased EV clearance/uptake or change in production. Clinical variables may alter the effectiveness of RIPC.

Fibrinolysis in Acute and Chronic Cardiovascular Disease

The formation of an obstructive thrombus within an artery remains a major cause of mortality and morbidity worldwide. Despite effective inhibition of platelet function by modern antiplatelet therapies, these agents fail to fully eliminate atherothrombotic risk. This may well be related to extensive vascular disease, beyond the protective abilities of the treatment agents used. However, recent evidence suggests that residual vascular risk in those treated with modern antiplatelet therapies is related, at least in part, to impaired fibrin clot lysis. In this review, we attempt to shed more light on the role of hypofibrinolysis in predisposition to arterial vascular events. We provide a brief overview of the coagulation system followed by addressing the role of impaired fibrin clot lysis in acute and chronic vascular conditions, including coronary artery, cerebrovascular, and peripheral vascular disease. We also discuss the role of combined anticoagulant and antiplatelet therapies to reduce the risk of arterial thrombotic events, addressing both efficacy and safety of such an approach. We conclude that impaired fibrin clot lysis appears to contribute to residual thrombosis risk in individuals with arterial disease on antiplatelet therapy, and targeting proteins in the fibrinolytic system represents a viable strategy to improve outcome in this population. Future work is required to refine the antithrombotic approach by modulating pathological abnormalities in the fibrinolytic system and tailoring therapy according to the need of each individual.

Fibrinolytics for the treatment of pulmonary embolism

The use of fibrinolytic agents in acute pulmonary embolism (PE), first described over 50 years ago, hastens the resolution of RV stain, leading to earlier hemodynamic improvement. However, this benefit comes at the increased risk of bleeding. The strongest indication for fibrinolysis is in high-risk PE, or that characterized by sustained hypotension, while its use in patients with intermediate-risk PE remains controversial. Fibrinolysis is generally not recommended for routine use in intermediate-risk PE, although most guidelines advise that it may be considered in patients with signs of acute decompensation and an overall low bleeding risk. The efficacy of fibrinolysis often varies significantly between patients, which may be at least partially explained by several factors found to promote resistance to fibrinolysis. Ultimately, treatment decisions should carefully weigh the risks and benefits of the individual clinical scenario at hand, including the overall severity, the patient's bleeding risk, and the presence of factors known to promote resistance to fibrinolysis. This review aims to further explore the use of fibrinolytic agents in the treatment of PE including specific indications, outcomes, and special considerations.

A review of global coagulation assays - Is there a role in thrombosis risk prediction?

Normal haemostasis requires maintenance of a careful equilibrium between the necessity to clot when bleeding and the retention of fluid phase at all other times. Disruption of this equilibrium can result in catastrophic outcomes, e.g. acute myocardial infarction and pulmonary embolism. However, despite the significant therapeutic advances in cardiovascular medicine over recent years, our ability to provide an accurate cardiovascular risk assessment remains an unmet need. Routine coagulation testing is not a useful reflection of haemostasis and cannot be reliably used to predict bleeding and thrombosis risks. Global coagulation assays such as viscoelastic testing, thrombin and fibrin generation have been proposed as better measures of the haemostatic function. These assays, particularly viscoelastic testing, have been increasingly used to assess bleeding risks and guide blood product replacement in trauma and massive transfusion settings. However, the role of these assays in thrombosis is less well-defined but given the complexities of the coagulation system, these global coagulation assays when used in combination may provide a better assessment of cardiovascular and thrombosis risk at an individual level. Hence, we explore the role of some of the currently available global coagulation assays - the viscoelastic, thrombin generation and fibrin generation tests - and provide a review of the literature of the current evidence for these assays specifically in the field of venous thromboembolism and cardiovascular diseases.

Association of TAFI gene polymorphisms with severity of coronary stenosis in stable coronary artery disease

INTRODUCTION

Coronary stenosis is a consequence of atherosclerotic plaque progression that is associated with impaired fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) and plasminogen activator inhibitor 1 (PAI-1) are fibrinolysis inhibitors whose levels are influenced by acquired conditions and by polymorphisms. This study therefore aimed to investigate the association of TAFI and PAI-1 gene polymorphisms with severity of coronary stenosis in subjects with stable coronary artery disease (CAD).

MATERIALS AND METHODS

A total of 327 subjects suspected with CAD who underwent a coronary angiogram were recruited. Gensini score was applied to stratify the severity of coronary stenosis. Based on the Gensini score, the subjects were categorized into low-medium (<20) or high (≥20) groups. The study polymorphisms included TAFI Ala147Thr (505G/A), Thr325Ile (1040C/T), +1542C/G, +1583T/A and PAI-1 -675 4G/5G. Most polymorphisms were genotyped by allele-specific polymerase chain reaction, except for TAFI Thr325Ile that was genotyped by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

A significant increase in the Gensini score was found in TAFI 505A and +1583A allele carriers. Binary regression analysis revealed the independent association of the TAFI 505G/A and +1583T/A polymorphisms with a high Gensini score [adjusted OR = 1.67 (95% CI: 1.03, 2.73) and 1.69 (95% CI: 1.04, 2.76), respectively]. Neither the homozygous PAI-1 -675 4G/4G nor the heterozygous 4G/5G was associated with a high Gensini score.

CONCLUSIONS

The results indicated the contribution of TAFI polymorphisms to atherosclerosis progression and severity of coronary stenosis in stable CAD.

Higher Preoperative Plasma Thrombin Potential in Patients Undergoing Surgery for Aortic Stenosis Compared to Surgery for Stable Coronary Artery Disease

Aortic stenosis (AS) and coronary artery disease (CAD) influence the coagulation system, potentially affecting hemostasis during cardiac surgery. Our aim was to evaluate 2 preoperative global hemostasis assays, plasma thrombin potential and thromboelastometry, in patients with severe aortic valve stenosis compared to patients with CAD. A secondary aim was to test whether the assays were associated with postoperative bleeding. Calibrated automated thrombogram (CAT) in platelet-poor plasma and rotational thromboelastometry (ROTEM) in whole blood were analyzed in patients scheduled for elective surgery due to severe AS (n = 103) and stable CAD (n = 68). Patients with AS displayed higher plasma thrombin potential, both thrombin peak with median 252 nmol/L (interquartile range 187-319) and endogenous thrombin potential (ETP) with median 1552 nmol/L/min (interquartile range 1340-1838), when compared to patients with CAD where thrombin peak was median 174 nmol/L (interquartile range 147-229) and ETP median 1247 nmol/L/min (interquartile range 1034-1448; both P < .001). Differences persisted after adjustment for age, gender, comorbidity, and antithrombotic treatment. Differences observed in thromboelastometry between the groups did not persist after adjustment for baseline characteristics. Bleeding amount showed no relationship with plasma thrombin potential but weakly to thromboelastometry (R² = .064, P = .001). Patients with AS exhibited preoperatively increased plasma thrombin potential compared to patients with CAD. Plasma thrombin potential was not predictive for postoperative bleeding in patients scheduled for elective surgery.

The impact of frailty on coagulation and responses to warfarin in acute older hospitalised patients with atrial fibrillation: a pilot study

BACKGROUND

The evidence on coagulation changes with frailty is not consistent and clinical studies suggest that frail older people may be at an increased risk of bleeding complications with anticoagulant therapy.

AIMS

This study aims to assess the impact of frailty on coagulation function and on response to warfarin.

METHODS

Inpatients aged over 65 years with atrial fibrillation (AF) were recruited. Frailty was determined using the Reported Edmonton Frail Scale. The Overall Haemostatic Potential (OHP) and Calibrated Automated Thrombogram (CAT) were used to globally assess coagulation function.

RESULTS

Data of 95 participants were analysed, mean age 85.5 ± 6.2, 40% female, and 50.5% frail. Among participants not on anticoagulants (N = 36), there was an increased fibrin generation and decreased thrombin generation compared to the local established normal ranges in young healthy volunteers; the frail had significantly reduced fibrin generation compared to the non-frail. In the warfarin-treated group (N = 59), there was no difference on coagulation profiles between the frail and the non-frail from any of the coagulation tests.

CONCLUSION

In this cohort of acute hospitalised patients with AF, the observed decreased fibrin generation in the frail may reflect decreased acute phase response as suggested with the lower plasma fibrinogen in that group. There was no difference in coagulation profiles between the frail and the non-frail amongst those taking warfarin. Compared to young healthy volunteers, older inpatients had increased fibrin generation and decreased thrombin generation. The findings reflect the complex interaction between age, frailty, acute illness, and coagulation.

Interleukin-12 and its procoagulant effect on erythrocytes, platelets and fibrin(ogen): the lesser known side of inflammation

Inflammation, with its associated inflammatory molecules, is integral to most chronic diseases, including the various cardiovascular diseases. Interleukin 12 (IL12) is one of the inflammatory cytokines that is upregulated during inflammation; however, we know very little about its exact effect on red blood cells (RBCs), platelets and fibrin(ogen). IL12 is an important pleiotropic cytokine in early inflammatory responses and has potent immunomodulatory, antitumour and anti-infection activity. Here we investigate how low levels of circulating IL12, comparable to levels found during chronic inflammation, affect coagulation parameters, platelets and RBCs. We used thromboelastography, scanning electron microscopy, refractometery and wide-field microscopy. Our results show that IL12 caused hypercoagulation, platelet activation and spreading, as well as RBC agglutination. This phenomenon has far-reaching implications for treatment of the plethora of conditions where IL12 is upregulated, since it suggests aberrant haemorheology as agglutination affects blood flow. This information might be used in future to target the lowering of IL12 in inflammatory conditions, as well as address RBC agglutination.

Characterisation of clot microstructure properties in stable coronary artery disease

Background

Coronary artery disease (CAD) is associated with an increased prothrombotic tendency and is also linked to unfavourably altered clot microstructure. We have previously described a biomarker of clot microstructure (d_f) that is unfavourably altered in acute myocardial infarction. The d_f biomarker assesses whether the blood will form denser or looser microstructures when it clots. In this study we assessed in patients with stable chest pain whether d_f can differentiate between obstructed and unobstructed CAD.

Methods

A blood sample prior to angiography was obtained from 251 consecutive patients undergoing diagnostic coronary angiography. Patients were categorised based on angiographic findings as presence or absence of obstructive CAD (stenosis ≥50%). The blood sample was assessed using the d_f biomarker, standard laboratory markers and platelet aggregometry (Multiplate).

Results

A significant difference (p=0.028) in d_f was observed between obstructive CAD (1.748±0.057, n=83) and unobstructive CAD (1.732±0.052, n=168), where patients with significant CAD produce denser, more tightly packed clots. d_f was also raised in men with obstructive CAD compared with women (1.745±0.055 vs 1.723±0.052, p=0.007). Additionally d_f significantly correlated with the platelets response to arachidonic acid as measured by the ASPItest area under the curve readings from platelet aggregometry (correlation coefficient=0.166, p=0.008), a low value of the ASPItest indicating effective aspirin use was associated with looser, less dense clots.

Conclusions

For the first time, we characterise clot microstructure, as measured by d_f, in patients with stable CAD. d_f can potentially be used to risk-stratify patients with stable CAD and assess the efficacy of therapeutic interventions by measuring changes in clot microstructure.

Increased plasma thrombin potential is associated with stable coronary artery disease: An angiographically-controlled study

INTRODUCTION

Coagulation plays a crucial role in coronary artery disease (CAD) contributing to both atherosclerotic plaque development and acute thrombotic complications, like myocardial infarction (MI). Coagulation biomarkers have been linked with ischemic heart disease, but results are still controversial.

MATERIALS AND METHODS

D-dimer and thrombin generation, two "overall" coagulation assays, were evaluated in 775 subjects with or without angiographically-proven CAD (170 CAD-free and 605 CAD, 355 of whom with history of previous MI). Subjects taking anticoagulant drugs or with any acute illness were excluded. D-dimer plasma concentration was determined by an immuno-turbidimetric assay. Thrombin generation was assessed as the ability of plasma to generate thrombin triggered by the addition of tissue factor ex-vivo by means of a chromogenic method.

RESULTS

Both D-dimer and thrombin generation parameters were associated with several traditional cardiovascular risk factors. Lag-time, time-to-peak, peak height, and Endogenous Thrombin Potential (ETP), as well as D-dimer levels, were higher in CAD patients than in CAD-free subjects. After adjustment for all the traditional risk factors, only ETP levels remained significantly associated with CAD (the highest versus the lowest tertile: OR 2.61 with 95%CI 1.14-5.99), but without improvement of C-statistic. The association of D-dimer vanished after adjustment for inflammatory markers. No difference of either D-dimer or thrombin generation parameters was found between CAD patients with or without previous MI history.

CONCLUSIONS

Our results suggest that an increased plasma thrombin potential is characteristic in patients with clinically stable CAD, irrespective of previous MI history and independent of traditional cardiovascular risk factors.

Increased thrombin generation in a mouse model of cancer cachexia is partially interleukin-6 dependent

Essentials Cancer cachexia and cancer-associated thrombosis have not previously been mechanistically linked. We assessed thrombin generation and coagulation parameters in cachectic C26 tumor-bearing mice. C26 mice are hypercoagulable, partially corrected by blocking tumor derived interleukin-6. Coagulability and anti-inflammatory interventions may be clinically important in cancer cachexia.

SUMMARY

Background Cancer cachexia and cancer-associated thrombosis are potentially fatal outcomes of advanced cancer, which have not previously been mechanistically linked. The colon 26 (C26) carcinoma is a well-established mouse model of complications of advanced cancer cachexia, partially dependent on high levels of interleukin-6 (IL-6) produced by the tumor. Objectives To assess if cancer cachexia altered the coagulation state and if this was attributable to tumor IL-6 production. Methods In male BALB/c*DBA2 (F1 hybrid) mice with a C26 tumor we used modified calibrated automated thrombogram and fibrin generation (based on overall hemostatic potential) assays to assess the functional coagulation state, and also examined fibrinogen, erythrocyte sedimentation rate (ESR), platelet count, tissue factor pathway inhibitor (TFPI) and hepatic expression of coagulation factors by microarray. C26 mice were compared with non-cachectic NC26, pair-fed and sham control mice. IL-6 expression in C26 cells was knocked down by lentiviral shRNA constructs. Results C26 mice with significant weight loss and highly elevated IL-6 had elevated thrombin generation, fibrinogen, ESR, platelets and TFPI compared with all control groups. Fibrin generation was elevated compared with pair-fed and sham controls but not compared with NC26 tumor mice. Hepatic expression of coagulation factors and fibrinolytic inhibitors was increased. Silencing IL-6 in the tumor significantly, but incompletely, attenuated the increased thrombin generation, fibrinogen and TFPI. Conclusions Cachectic C26 tumor-bearing mice are in a hypercoagulable state, which is partly attributable to IL-6 release by the tumor. The findings support the importance of the coagulation state in cancer cachexia and the clinical utility of anti-inflammatory interventions.

The Overall Hemostatic Potential (OHP) Assay

The principle of the overall hemostatic potential (OHP) assay is the generation of a fibrin time curve by optical density readings, which represent the balance between fibrin generation, triggered by thrombin or tissue factor, and fibrinolysis, triggered by tissue plasminogen activator (tPA). OHP measures the integrated effect of procoagulant, anticoagulant, and fibrinolytic factors, and OHP assay parameters provide a means of quantifying both the coagulation and fibrinolytic potential of platelet poor plasma. In particular, the OHP assay can be used to evaluate hypercoagulable states and abnormalities of fibrinolysis which are not well defined by assays which are routinely available in the coagulation laboratory. OHP is a technically simple assay, with potential for application in the routine laboratory at minimal cost.

Variable Resistance to Plasminogen Activator Initiated Fibrinolysis for Intermediate-Risk Pulmonary Embolism

Background

We examine the clinical significance and biomarkers of tissue plasminogen activator (tPA)-catalyzed clot lysis time (CLT) in patients with intermediate-risk pulmonary embolism (PE).

Methods

Platelet-poor, citrated plasma was obtained from patients with PE. Healthy age- and sex-matched patients served as disease-negative controls. Fibrinogen, α₂-antiplasmin, plasminogen, thrombin activatable fibrinolysis inhibitor (TAFI), plasminogen activator Inhibitor 1 (PAI-1), thrombin time and D-dimer were quantified. Clotting was induced using CaCl₂, tissue factor, and phospholipid. Lysis was induced using 60 ng/mL tPA. Time to 50% clot lysis (CLT) was assessed by both thromboelastography (TEG) and turbidimetry (A405).

Results

Compared with disease-negative controls, patients with PE exhibited significantly longer mean CLT on TEG (+2,580 seconds, 95% CI 1,380 to 3,720 sec). Patients with PE and a short CLT who were treated with tenecteplase had increased risk of bleeding, whereas those with long CLT had significantly worse exercise tolerance and psychometric testing for quality of life at 3 months. A multivariate stepwise removal regression model selected PAI-1 and TAFI as predictive biomarkers of CLT.

Conclusion

The CLT from TEG predicted increased risk of bleeding and clinical failure with tenecteplase treatment for intermediate-risk PE. Plasmatic PAI-1 and TAFI were independent predictors of CLT.

Antithrombogenic Properties of Amphiphilic Block Copolymer Coatings: Evaluation of Hemocompatibility Using Whole Blood

Antithrombogenicity is one of the most critical properties required for materials used in biomedical devices, particularly in devices that contact blood. The antithrombogenicity of surfaces coated with amphiphilic block copolymers composed of hydrophobic poly(2-methoxyethyl acrylate) (M) and hydrophilic poly(N,N-dimethylacrylamide) (D) segments was investigated using plasma protein and whole blood with regard to protein adsorption, thrombus formation, platelet activation, and clotting kinetics. Three types of block copolymers and a random copolymer were synthesized using one-pot reversible addition-fragmentation chain-transfer (RAFT) polymerization under conditions of high yield and high molecular weight. Triblock and 4-arm block copolymers with MDM and (MD)₄ architecture, respectively, showed good adhesion to both organic and inorganic substrates, including polyvinyl chloride (PVC) tubes, and the resulting coated surfaces showed superior protein repellency and hemocompatibility compared to the diblock or random copolymer coatings and noncoated control. In a Chandler-loop method with whole blood, PVC tubes coated with MDM and (MD)₄ showed improved thromboresistance and adsorption resistance to blood-derived proteins. This high hemocompatibility was also confirmed with human whole blood by thrombelastography (suppression of blood-clotting behavior in both intrinsic and extrinsic coagulation pathways) and platelet function analyses (significant reductions in the aggregation activity of platelets under two types of stimulation). The antithrombogenicity has been discussed based on the structural analyses of the MDM-coated surface. The results of this study will enable the development of more effective biomedical and analytical devices with excellent antithrombogenic characteristics by using a simple and environmentally friendly approach.

Abnormal hemostatic function one year after orthotopic liver transplantation can be fully attributed to endothelial cell activation

Background: The long-term risk of thrombotic and vascular complications is elevated in liver transplant recipients compared to the general population. Patients with cirrhosis are in a hypercoagulable status during and directly after orthotopic liver transplantation, but it is unclear whether this hypercoagulability persists over time.

Aim: We aimed to investigate the hemostatic status of liver transplant recipients one year after transplantation.

Methods: We prospectively collected blood samples of 15 patients with a functioning graft one year after orthotopic liver transplantation and compared the hemostatic status of these patients with that of 30 healthy individuals.

Results: Patients one year after liver transplantation had significantly elevated plasma levels of von Willebrand factor (VWF). Thrombin generation, as assessed by the endogenous thrombin potential, was decreased in patients, which was associated with increased plasma levels of the natural anticoagulants antithrombin and tissue factor pathway inhibitor.  Plasma fibrinolytic potential was significantly decreased in patients and correlated inversely with levels of plasminogen activator inhibitor-1.

Conclusion: One year after liver transplantation, liver graft recipients have a dysregulated hemostatic system characterised by elevation of plasma levels of endothelial-derived proteins. Increased levels of von Willebrand factor and decreased fibrinolytic potential may (in part) be responsible for the increased risk for vascular disease seen in liver transplant recipients.

Abnormal hemostatic function one year after orthotopic liver transplantation can be fully attributed to endothelial cell activation

BACKGROUND

The long-term risk of thrombotic and vascular complications is elevated in liver transplant recipients compared to the general population. Patients with cirrhosis are in a hypercoagulable status during and directly after orthotopic liver transplantation, but it is unclear whether this hypercoagulability persists over time.

AIM

We aimed to investigate the hemostatic status of liver transplant recipients one year after transplantation.

METHODS

We prospectively collected blood samples of 15 patients with a functioning graft one year after orthotopic liver transplantation and compared the hemostatic status of these patients with that of 30 healthy individuals.

RESULTS

Patients one year after liver transplantation had significantly elevated plasma levels of von Willebrand factor (VWF). Thrombin generation, as assessed by the endogenous thrombin potential, was decreased in patients, which was associated with increased plasma levels of the natural anticoagulants antithrombin and tissue factor pathway inhibitor.  Plasma fibrinolytic potential was significantly decreased in patients and correlated inversely with levels of plasminogen activator inhibitor-1.

CONCLUSION

One year after liver transplantation, liver graft recipients have a dysregulated hemostatic system characterised by elevation of plasma levels of endothelial-derived proteins. Increased levels of von Willebrand factor and decreased fibrinolytic potential may (in part) be responsible for the increased risk for vascular disease seen in liver transplant recipients.