Altered fibrin clot structure/function in patients with idiopathic venous thromboembolism and in their relatives

Real-Time Imaging of Platelet-Initiated Plasma Clot Formation and Lysis Unveils Distinct Impacts of Anticoagulants

BACKGROUND

 Fibrinolysis is spatiotemporally well-regulated and greatly influenced by activated platelets and coagulation activity. Our previous real-time imaging analyses revealed that clotting commences on activated platelet surfaces, resulting in uneven-density fibrin structures, and that fibrinolysis initiates in dense fibrin regions and extends to the periphery. Despite the widespread clinical use of direct oral anticoagulants (DOACs), their impact on thrombin-dependent activation of thrombin-activatable fibrinolysis inhibitor (TAFI) and fibrinolysis remains unclear. Here, we investigated the effects of different DOACs on the TAFI-mediated inhibition of fibrinolysis.

METHODS

 Using human platelet-containing plasma, we performed turbidimetric assays, thrombin generation assays, and confocal laser scanning microscopy to assess the effects of anticoagulants on fibrinolysis.

RESULTS AND CONCLUSION

 Activated platelets-prolonged plasma clot lysis time, shortened by activated TAFI inhibitor (TAFIaI), positively correlated with the amount of thrombin generated. Rivaroxaban (an activated factor X inhibitor) and dabigatran (a direct thrombin inhibitor) dose-dependently shortened lysis time comparably. The highest concentration of DOACs showed no further shortening of lysis time with TAFIaI. The fibrin network structures initiated by activated platelets and the localization of fluorescently labeled plasminogen were unique for these two drugs. Rivaroxaban maintained an uneven fibrin network but promoted faster plasminogen accumulation and fibrinolysis from outside dense fibrin regions. Conversely, dabigatran resulted in a more even fibrin network, with fibrinolysis starting from the activated platelets and propagating to the periphery. Visualizing and analyzing the patterns of fibrin network formation, plasminogen accumulation, and fibrinolysis provide new insights into the specific impact of anticoagulants on coagulation and fibrinolysis.

Fibrinogen Structural Changes and Their Potential Role in Endometriosis-Related Thrombosis

Endometriosis (EM), a chronic inflammatory condition predominantly affecting women of reproductive age, has been linked to an elevated risk of thrombosis, though its underlying molecular mechanisms remain incompletely understood. In this case-control study, involving 71 EM patients and 71 matched controls, we explored the structural and functional changes in fibrinogen and their potential role in thrombosis. Key oxidative stress markers, such as reactive oxygen species (ROS) levels in blood lymphocytes, monocytes, and granulocytes, along with plasma lipid peroxidation markers and total antioxidant capacity, were measured. Fibrinogen structure was examined using circular dichroism spectroscopy and intrinsic fluorescence, while functional properties were evaluated by analyzing thrombin-mediated polymerization and plasmin-induced lysis. Compared to controls, EM patients exhibited elevated ROS production and systemic oxidative stress, leading to notable fibrinogen oxidation and structural alterations. These changes were associated with impaired fibrin polymerization and enhanced resistance to plasmin-induced lysis, which are indicative of a pro-thrombotic state. These findings suggest that oxidative stress-driven fibrinogen modifications may contribute to the heightened thrombotic risk in women with EM, highlighting a potential therapeutic target to mitigate cardiovascular complications.

Comprehensive Characterization of Surface-Bound Proteins and Measurement of Fibrin Fiber Thickness on Extracorporeal Membrane Oxygenation Circuits Collected From Patients

OBJECTIVE

To characterize surface-bound proteins and to measure the thickness of fibrin fibers bound to extracorporeal membrane oxygenation (ECMO) circuits used in children.

DESIGN

Single-center observational prospective study, April to November 2021.

SETTING

PICU, Royal Children's Hospital, Melbourne, Australia.

PATIENTS

Patients aged less than 18 years on venoarterial ECMO and without preexisting disorder.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

ECMO circuits were collected from six patients. Circuit samples were collected from five different sites, and subsequently processed for proteomic and scanning electron microscopy (SEM) studies. The concentration of proteins bound to ECMO circuit samples was measured using a bicinchoninic acid protein assay, whereas characterization of the bound proteome was performed using data-independent acquisition mass spectrometry. The Reactome Over-representation Pathway Analyses tool was used to identify functional pathways related to bound proteins. For the SEM studies, ECMO circuit samples were prepared and imaged, and the thickness of bound fibrin fibers was measured using the Fiji ImageJ software, version 1.53c ( https://imagej.net/software/fiji/ ). Protein binding to ECMO circuit samples and fibrin networks showed significant intra-circuit and interpatient variation. The median (range) total protein concentration was 19.0 (0-76.9) μg/mL, and the median total number of proteins was 2011 (1435-2777). A total of 933 proteins were commonly bound to ECMO circuit samples from all patients and were functionally involved in 212 pathways, with signal transduction, cell cycle, and metabolism of proteins being the top three pathway categories. The median intra-circuit fibrin fiber thickness was 0.20 (0.15-0.24) μm, whereas the median interpatient fibrin fiber thickness was 0.18 (0.15-0.21) μm.

CONCLUSIONS

In this report, we have characterized proteins and fiber fibrin thickness bound to ECMO circuits in six children. The techniques and approaches may be useful for investigating interactions between blood, coagulation, and the ECMO circuit and have the potential for circuit design.

Fibrinolysis is impaired in patients with primary immune thrombocytopenia

BACKGROUND

Patients with primary immune thrombocytopenia (ITP) have an increased risk of thrombosis, which may be due to altered fibrinolysis.

OBJECTIVES

To elucidate the clinical impact of delayed fibrinolysis in ITP patients.

METHODS

A turbidimetric clot formation and lysis assay and a fluorometric plasmin generation (PG) assay were performed, and levels of plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA), tPA-PAI-1 complexes, α2-antiplasmin, thrombin activatable fibrinolysis inhibitor, and D-dimer were assessed in 86 adult primary ITP patients and 78 healthy controls (HCs).

RESULTS

ITP patients showed significantly delayed clot formation, increased clot density, and prolonged clot lysis time (CLT) compared with HCs, with a median (IQR) CLT of 28.0 (13.7-34.7) minutes in patients and 17.3 (12.0-28.0) minutes in HCs, while in the PG assay, only the lag time was prolonged. In ITP patients compared with controls, PAI-1 was higher (1.2 [0.8-2.6] vs 1.1 [0.6-2.1] U/mL) and tPA antigen and activity were lower (tPA antigen: 2.6 [1.1-4.4] vs 3.7 [3.2-4.7] ng/mL; tPA activity ≤ 0 U/mL: 26% vs 7%). TPA-PAI-1 complex levels were positively associated with CLT in multiple linear regression analysis (β = 0.241; P = .019), whereas PG parameters were not associated with CLT. Six patients who developed thrombosis during follow-up had higher levels of tPA-PAI-1 complexes.

CONCLUSION

Prolonged CLT and delayed onset of PG may indicate a hypofibrinolytic tendency in ITP patients, as also indicated by high PAI-1 and low tPA levels. No association was found between fibrinolytic potential and the bleeding phenotype, whereas higher tPA-PAI-1 complex levels were associated with prolonged CLT and increased in patients with future thrombosis.

Utility of Global Hemostatic Assays in Patients with Bleeding Disorders of Unknown Cause

Bleeding disorder of unknown cause (BDUC) is a diagnosis of exclusion after exhaustive evaluation of plasmatic coagulation and platelet function. This review explores the utility of global hemostatic assays as confirmatory tests and in elucidating the pathophysiology of BDUC. Unlike traditional hemostatic tests that focus on coagulation factors, global assays are conducted both in plasma and also whole blood. These assays provide a more comprehensive understanding of the cell-based model of coagulation, aid in the identification of plasmatic factor abnormalities that may reduce hemostatic capacity, and allow for the assessment of impaired platelet-endothelial interactions under shear stress, as well as hyperfibrinolytic states. While clinical tests such as skin bleeding time and global assays such as PFA-100 exhibit limited diagnostic capacity, the role of viscoelastic testing in identifying hemostatic dysfunction in patients with BDUC remains unclear. Thrombin generation assays have shown variable results in BDUC patients; some studies demonstrate differences compared with healthy controls or reference values, whereas others question its clinical utility. Fibrinolysis assessment in vitro remains challenging, with studies employing euglobulin clot lysis time, plasma clot lysis time, and fluorogenic plasmin generation yielding inconclusive or conflicting results. Notably, recent studies suggest that microfluidic analysis unveils shear-dependent platelet function defects in BDUC patients, undetected by conventional platelet function assays. Overall, global assays might be helpful for exploring underlying hemostatic impairments, when conventional hemostatic laboratory tests yield no results. However, due to limited data and/or discrepant results, further research is needed to evaluate the utility of global assays as screening tools.

Elevated plasma protein carbonylation increases the risk of ischemic cerebrovascular events in patients with atrial fibrillation: association with a prothrombotic state

INTRODUCTION

Plasma protein carbonylation that reflects oxidative stress has been demonstrated to be associated with the prothrombotic fibrin clot phenotype. However, the role of protein carbonyls (PC) in predicting ischemic stroke in atrial fibrillation (AF) is largely unknown. This study aimed to investigate whether PC increase the risk of stroke in anticoagulated AF patients during follow-up.

METHODS

In 243 AF patients on anticoagulation (median age 69 years; median CHA2DS2-VASc of 4), we measured plasma PC using the assay by Becatti, along with plasma clot permeability (Ks), clot lysis time (CLT), thrombin generation, and fibrinolytic proteins, including plasminogen activator inhibitor type 1 (PAI-1) and thrombin activatable fibrinolysis inhibitor (TAFI). Ischemic stroke, major bleeding, and mortality were recorded during a median follow-up of 53 months.

RESULTS

Plasma PC levels (median, 3.16 [2.54-3.99] nM/mg protein) at baseline showed positive associations with age (P < 0.001), CHA2DS2-VASc (P = 0.003), and N-terminal B-type natriuretic peptide (P = 0.001), but not with type of AF or comorbidities except for heart failure (P = 0.007). PC levels were correlated with CLT (r = 0.342, P < 0.001), endogenous thrombin potential (r = 0.217, P = 0.001) and weakly with Ks (r = -0.145, P = 0.024), but not with fibrinogen, PAI-1, or TAFI levels. Stroke was recorded in 20 patients (1.9%/year), who had at baseline 36% higher PC levels (P < 0.001). Elevated PC (P = 0.003) at baseline were independently associated with stroke risk.

CONCLUSION

Our findings suggest that in patients with AF enhanced protein carbonylation is associated with increased "residual" risk of stroke despite anticoagulation, which is at least in part due to unfavorably altered fibrin clot phenotype.

Reprograming Clots for In Vivo Chemical Targeting in Traumatic Brain Injury

Traumatic brain injury (TBI) is a critical public health concern, yet there are no therapeutics available to improve long-term outcomes. Drug delivery to TBI remains a challenge due to the blood-brain barrier and increased intracranial pressure. In this work, a chemical targeting approach to improve delivery of materials to the injured brain, is developed. It is hypothesized that the provisional fibrin matrix can be harnessed as an injury-specific scaffold that can be targeted by materials via click chemistry. To accomplish this, the brain clot is engineered in situ by delivering fibrinogen modified with strained cyclooctyne (SCO) moieties, which incorporated into the injury lesion and is retained there for days. Improved intra-injury capture and retention of diverse, clickable azide-materials including a small molecule azide-dye, 40 kDa azide-PEG nanomaterial, and a therapeutic azide-protein in multiple dosing regimens is subsequently observed. To demonstrate therapeutic translation of this approach, a reduction in reactive oxygen species levels in the injured brain after delivery of the antioxidant catalase, is achieved. Further, colocalization between azide and SCO-fibrinogen is specific to the brain over off-target organs. Taken together, a chemical targeting strategy leveraging endogenous clot formation is established which can be applied to improve therapeutic delivery after TBI.

Altered fibrin clot phenotype in young adults with intracerebral hemorrhage of unknown cause: A case-control study

BACKGROUND

Intracerebral hemorrhage (ICH) of undetermined etiology occurs infrequently in young and middle-aged adults. We hypothesized that slight decreases in coagulation factors and formation of less compact fibrin clots prone to faster lysis predispose to this type of ICH.

METHODS

We recruited 44 consecutive patients aged <50 years following ICH of unknown cause at least 3 months since the event. Subjects free of ICH (n = 47) matched for age, sex, BMI, and hypertension served as the control group. We assessed plasma fibrin clot permeability, turbidity and fibrinolytic capacity, along with thrombin generation, coagulation factors (F) II, FV, FVII, FVIII, FIX, FX, FXI, antithrombin, and fibrinolysis proteins.

RESULTS

ICH patients (median age 41 years, 45.5 % women) had 8.4 % lower FII (p = 0.0001) and 10.1 % lower FVII activity (p = 0.0003), 9.4 % higher antithrombin activity (p = 0.0004) and 13.5 % lower platelet count (p = 0.02). Other factors and thrombin generation did not differ between the two groups. The ICH survivors were characterized by impaired fibrin polymerization reflected by 10.1 % longer lag phase of the turbidimetry curve (p = 0.0002), decreased fiber density indicated by 11.8 % lower maximum absorbance (p = 0.004), as well as 11.1 % shorter clot lysis time (p = 0.014) and 10.0 % faster increase of maximal D-Dimer levels (p = 0.000001).

CONCLUSIONS

We demonstrated a prohemorrhagic fibrin clot phenotype, along with lower FII, FVII and higher antithrombin activity in adults below 50 years of age who suffered from ICH of unknown cause, which might indicate novel mechanisms contributing to ICH in younger individuals.

Reviewing the Rich History of Fibrin Clot Research with a Focus on Clinical Relevance

Fibrin, described on a single-lens microscopy for the first time by Malpighi in 1666 and named by de Fourcroy, has been extensively studied by biochemists, biophysicists, and more recently by clinicians who recognized that fibrin is the major component of most thrombi. Elucidation of key reactions leading to fibrin clot formation in the 1950s and 1960s grew interest in the clinical relevance of altered fibrin characteristics. Implementation of scanning electron microscopy to image fibrin clots in 1947 and clot permeation studies in the 1970s to evaluate an average pore size enabled plasma clot characterization in cohorts of patients. Unfavorably altered fibrin clot structure was demonstrated by Blombäck's group in coronary artery disease in 1992 and in diabetes in 1996. Fifteen years ago, similar plasma fibrin clot alterations were reported in patients following venous thromboembolism. Multiple myeloma was the first malignant disease to be found to lead to abnormal fibrin clot phenotype in the 1970s. Apart from anticoagulant agents, in 1998, aspirin was first shown to increase fibrin clot permeability in cardiovascular patients. The current review presents key data on the rich history of fibrin research, in particular, those that first documented abnormal fibrin clot properties in a variety of human disease states, as well as factors affecting fibrin phenotype.

Effects of dabigatran, rivaroxaban, and apixaban on fibrin network permeability, thrombin generation, and fibrinolysis

INTRODUCTION

There are important pharmacological differences between direct oral anticoagulants (DOAC) and a deeper knowledge of how they influence different aspects of hemostasis in patients on treatment is desirable.

MATERIALS AND METHODS

Blood samples from patients on dabigatran (n = 23), rivaroxaban (n = 26), or apixaban (n = 20) were analyzed with a fibrin network permeability assay, a turbidimetric clotting and lysis assay, the calibrated automated thrombogram (CAT), plasma levels of thrombin-antithrombin complex (TAT) and D-dimer, as well as DOAC concentrations, PT-INR and aPTT. As a comparison, we also analyzed samples from 27 patients on treatment with warfarin.

RESULTS

Patients on dabigatran had a more permeable fibrin network, longer lag time (CAT and turbidimetric assay), and lower levels of D-dimer in plasma, compared with patients on rivaroxaban- and apixaban treatment, and a more permeable fibrin network than patients on warfarin. Clot lysis time was slightly longer in patients on dabigatran than in patients on rivaroxaban. Warfarin patients formed a more permeable fibrin network than patients on apixaban, had longer lag time than patients on rivaroxaban (CAT assay), and lower peak thrombin and ETP compared to patients on treatment with both FXa-inhibitors.

CONCLUSIONS

Results from this study indicate dabigatran treatment is a more potent anticoagulant than apixaban and rivaroxaban. However, as these results are not supported by clinical data, they are probably more related to the assays used and highlight the difficulty of measuring and comparing the effect of anticoagulants.

Advancing Thrombosis Research: A Novel Device for Measuring Clot Permeability

Thromboembolism, a global leading cause of mortality, needs accurate risk assessment for effective prophylaxis and treatment. Current stratification methods fall short in predicting thrombotic events, emphasizing the need for a deeper understanding of clot properties. Fibrin clot permeability, a crucial parameter in hypercoagulable states, impacts clot structure and resistance to lysis. Current clot permeability measurement limitations propel the need for standardized methods. Prior findings underscore the importance of clot permeability in various thrombotic conditions but call for improvements and more precise, repeatable, and standardized methods. Addressing these challenges, our study presents an upgraded, portable, and cost-effective system for measuring blood clot permeability, which utilizes a pressure-based approach that adheres to Darcy's law. By enhancing precision and sensitivity in discerning clot characteristics, this innovation provides a valuable tool for assessing thrombotic risk and associated pathological conditions. In this paper, the authors present a device that is able to automatically perform the permeability measurements on plasma or fibrinogen in vitro-induced clots on specific holders (filters). The proposed device has been tailored to distinguish clot permeability, with high precision and sensitivity, between healthy subjects and high cardiovascular-risk patients. The precise measure of clot permeability represents an excellent indicator of thrombotic risk, thus allowing the clinician, also on the basis of other anamnestic and laboratory data, to attribute a risk score to the subject. The proposed instrument was characterized by performing permeability measurements in plasma and purified fibrinogen clots derived from 17 Behcet patients and 15 sex- and age-matched controls. As expected, our results clearly indicate a significant difference in plasma clot permeability in Behcet patients with respect to controls (0.0533 ± 0.0199 d vs. 0.0976 ± 0.0160 d, p < 0.001). This difference was confirmed in the patient's vs. control fibrin clots (0.0487 ± 0.0170 d vs. 0.1167 ± 0.0487 d, p < 0.001). In conclusion, our study demonstrates the feasibility, efficacy, portability, and cost-effectiveness of a novel device for measuring clot permeability, allowing healthcare providers to better stratify thrombotic risk and tailor interventions, thereby improving patient outcomes and reducing healthcare costs, which could significantly improve the management of thromboembolic diseases.

Mechanics and microstructure of blood plasma clots in shear driven rupture

Intravascular blood clots are subject to hydrodynamic shear and other forces that cause clot deformation and rupture (embolization). A portion of the ruptured clot can block blood flow in downstream vessels. The mechanical stability of blood clots is determined primarily by the 3D polymeric fibrin network that forms a gel. Previous studies have primarily focused on the rupture of blood plasma clots under tensile loading (Mode I), our current study investigates the rupture of fibrin induced by shear loading (Mode II), dominating under physiological conditions induced by blood flow. Using experimental and theoretical approaches, we show that fracture toughness, i.e. the critical energy release rate, is relatively independent of the type of loading and is therefore a fundamental property of the gel. Ultrastructural studies and finite element simulations demonstrate that cracks propagate perpendicular to the direction of maximum stretch at the crack tip. These observations indicate that locally, the mechanism of rupture is predominantly tensile. Knowledge gained from this study will aid in the development of methods for prediction/prevention of thrombotic embolization.

Effect of Three-Day Atorvastatin Administration on Coagulation Factors in Patients With Prior Venous Thromboembolism and Healthy Subjects: A Preliminary Study

ABSTRACT

Statins exert antithrombotic effects, which might contribute to reduced risk of venous thromboembolism (VTE). Rosuvastatin 20 mg/d administered for 4 weeks has been reported to decrease coagulation factors (F) VII, FVIII, and FXI in VTE patients. Moreover, in accordance with recent registry data in non-VTE subjects, statins usage was associated with lower FXI. We investigated whether 3 doses of a statin decrease coagulation factors activity and if such changes can alter fibrin clot properties in VTE patients and healthy subjects. We enrolled 28 consecutive first-ever prior VTE patients after 6 months of anticoagulation and 25 healthy controls well-matched for demographics and lipid profiles (aged 44 [interquartile range 34-51] years) in an interventional nonrandomized study. Before and after 3 doses of atorvastatin 40 mg/d, activity of FVII, FVIII, FIX, and FXI was measured, along with fibrin clot properties, including permeability (Ks) and clot lysis using 3 various assays. After a 3-day statin administration, we observed the decrease of FVII (by 6.2%, P = 0.046) and FXI (by 8.6%, P = 0.044), irrespective of low-density lipoprotein cholesterol reduction (by 24%, P < 0.001), whereas other coagulation factors remained unaltered. Reduction of FVII and FXI activity was inversely correlated with Ks alterations (R = -0.292, P = 0.034 and R = -0.335, P = 0.014, respectively). After adjustment for age, studied group, and fibrinogen level, the reduction of FXI was independently associated with an increase of fibrin clot permeability (B = -0.084, P = 0.027). In conclusion, a 3-day 40 mg atorvastatin administration is sufficient to reduce FVII and FXI activity in our pilot study, which is associated with favorable fibrin clot properties modification.

Reduced fibrin clot permeability on admission and elevated E-selectin at 3 months as novel risk factors of residual pulmonary vascular obstruction in patients with acute pulmonary embolism

BACKGROUND

Residual pulmonary vascular obstruction (RPVO) is common following pulmonary embolism (PE) but its association with fibrin clot properties is poorly understood. We investigated whether prothrombotic state and hypofibrinolysis markers can identify patients with RPVO.

METHODS

In 79 normotensive noncancer patients (aged 56 ± 13.3 years) with acute PE, we determined fibrin clot permeability (Ks), clot lysis time (CLT), endogenous thrombin potential (ETP), fibrinolysis proteins, oxidative stress markers, and E-selectin on admission before initiation of anticoagulant therapy, after 5-7 days, and 3 months of anticoagulation. RPVO was diagnosed using computed tomography angiography 3-6 months since PE.

RESULTS

Patients with RPVO (n = 23, 29.1%) had at baseline higher simplified Pulmonary Embolism Severity Index (sPESI) (P = 0.004), higher N-terminal brain natriuretic propeptide (P = 0.006) and higher D-dimer (P = 0.044). Patients with versus without RPVO had lower Ks (P < 0.001) and longer CLT (P < 0.05), both at baseline and 5-7 days since admission, but not at 3 months. Patients with RPVO showed 40.6% higher E-selectin (P < 0.001) solely at 3 months. By multivariable logistic regression, baseline Ks (odds ratio [OR] 0.010, 95% confidence interval [CI] 0.001-0.837, P = 0.042, per 10- 9 cm2), baseline D-dimer (OR 1.105, 95% CI 1.000-1.221, P = 0.049, per 100 ng/ml), and E-selectin levels after 3 months (OR 3.874, 95% CI 1.239-12.116, P = 0.020, per 1 ng/ml) were associated with RPVO.

CONCLUSIONS

RPVO patients despite anticoagulation characterize with the formation of denser fibrin clots on admission and higher E-selectin at 3 months. Those parameters could be the potential novel RPVO risk factors that warrant further evaluation in an independent cohort.

Maximum amplitude and mean platelet volume in the blood as biomarkers to detect lung adenocarcinoma cancer featured with ground-glass nodules

Objectives

The development and progression of malignancies are closely linked to hypercoagulability. As an early type of lung adenocarcinoma, ground glass nodules (GGNs) have been detected increasingly. Blood Maximum amplitude (MA) and mean platelet volume (MPV) are related to various conditions of hypercoagulability. Therefore, the role of MA and MPV in diagnosing lung adenocarcinoma cancer featured with GGNs was investigated in this case-control study.

Methods

The analyzed data of this study is derived from GGNs patients and healthy individuals in West China (Airport) Hospital Sichuan University. The differences between GGNs patients and healthy individuals were determined by one-way ANOVA, logistic regression or chi-squared test. The accuracy of diagnostic was performed by receiver operating characteristic curve (ROC). The relative mRNA expressions were studied by RT-qPCR.

Results

470 patients diagnosed with GGNs which benign lesions (BN group) are inflammatory and malignant lesions (LC group) are adenocarcinoma in stage IA, and 235 healthy subjects (HC group) were enrolled in this study. Levels of MA and MPV were increased in LC group compared with BN and HC group ( p < 0.001, p < 0.001). When we combined MA and MPV, MA and MPV presented a sensitivity (SEN) of 0.809 and a specificity (SPE) of 0.774. And the area under the curve (AUC) increased to 0.871 (0.837–0.900) when confidence interval was 95%.

Conclusion

This study demonstrates that there have been systemic changes in coagulation disorders in the pathogenesis of GGNs. The diagnostic ability to different lung adenocarcinoma cancer featured with GGNs from benign or healthy controls can be improved by the combination of MA and MPV. Maximum amplitude and MPV may be used as biomarkers to detect lung adenocarcinoma cancer featured with GGNs.

Tale of two systems: the intertwining duality of fibrinolysis and lipoprotein metabolism

Fibrinolysis is an enzymatic process that breaks down fibrin clots, while dyslipidemia refers to abnormal levels of lipids and lipoproteins in the blood. Both fibrinolysis and lipoprotein metabolism are critical mechanisms that regulate a myriad of functions in the body, and the imbalance of these mechanisms is linked to the development of pathologic conditions, such as thrombotic complications in atherosclerotic cardiovascular diseases. Accumulated evidence indicates the close relationship between the 2 seemingly distinct and complicated systems-fibrinolysis and lipoprotein metabolism. Observational studies in humans found that dyslipidemia, characterized by increased blood apoB-lipoprotein and decreased high-density lipoprotein, is associated with lower fibrinolytic potential. Genetic variants of some fibrinolytic regulators are associated with blood lipid levels, supporting a causal relationship between these regulators and lipoprotein metabolism. Mechanistic studies have elucidated many pathways that link the fibrinolytic system and lipoprotein metabolism. Moreover, profibrinolytic therapies improve lipid panels toward an overall cardiometabolic healthier phenotype, while some lipid-lowering treatments increase fibrinolytic potential. The complex relationship between lipoprotein and fibrinolysis warrants further research to improve our understanding of the bidirectional regulation between the mediators of fibrinolysis and lipoprotein metabolism.

ROS-driven structural and functional fibrinogen modifications are reverted by interleukin-6 inhibition in Giant Cell Arteritis

BACKGROUND

Cranial and extra-cranial vascular events are among the major determinants of morbidity and mortality in Giant Cell Arteritis (GCA). Vascular events seem mostly of inflammatory nature, although the precise pathogenetic mechanisms are still unclear. We investigated the role of oxidation-induced structural and functional fibrinogen modifications in GCA. The effects of the anti-IL6R tocilizumab in counteracting these mechanisms were also assessed.

MATERIALS AND METHODS

A cross-sectional study was conducted on 65 GCA patients and 65 matched controls. Leucocyte reactive oxygen species (ROS) production, redox state, and fibrinogen structural and functional features were compared between patients and controls. In 19 patients receiving tocilizumab, pre vs post treatment variations were assessed.

RESULTS

GCA patients displayed enhanced blood lymphocyte, monocyte and neutrophil ROS production compared to controls, with an increased plasma lipid peroxidation and a reduced total antioxidant capacity. This oxidative impairment resulted in a sustained fibrinogen oxidation (i.e. dityrosine content 320 (204-410) vs 136 (120-176) Relative Fluorescence Units (RFU), p < 0.0001), with marked alterations in fibrinogen secondary and tertiary structure [intrinsic fluorescence: 134 (101-227) vs 400 (366-433) RFU, p < 0.001]. Structural alterations paralleled a remarkable fibrinogen functional impairment, with a reduced ability to polymerize into fibrin and a lower fibrin susceptibility to plasmin-induced lysis. In patients receiving tocilizumab, a significant improvement in redox status was observed, accompanied by a significant improvement in fibrinogen structural and functional features (p < 0.001).

CONCLUSIONS

An impaired redox status accounts for structural and functional fibrinogen modifications in GCA, suggesting a potential role of tocilizumab for cardiovascular prevention in GCA.

Antithrombin Deficiency Is Associated with Prothrombotic Plasma Fibrin Clot Phenotype

BACKGROUND

 Deficiency of antithrombin increases risk of venous thromboembolism. We hypothesized that antithrombin deficiency affects fibrin clot structure and function.

METHODS

 We evaluated 148 patients (age: 38 [32-50] years; 70% women) with genetically confirmed antithrombin deficiency and 50 healthy controls. Fibrin clot permeability (Ks) and clot lysis time (CLT) along with thrombin generation capacity were assessed before and after antithrombin activity normalization in vitro.

RESULTS

 Antithrombin-deficient patients had lower antithrombin activity (-39%) and antigen levels (-23%) compared with controls (both p < 0.01). Prothrombin fragment 1 + 2 levels were 26.5% higher in patients with antithrombin deficiency than in controls along with 94% increased endogenous thrombin potential (ETP) and 108% higher peak thrombin (all p < 0.01). Antithrombin deficiency was associated with 18% reduced Ks and 35% prolonged CLT (both p < 0.001). Patients with type I (n = 65; 43.9%) compared with type II antithrombin deficiency (n = 83; 56.1%) had 22.5% lower antithrombin activity (p < 0.001) and despite similar fibrinogen levels, 8.4% reduced Ks, 18% prolonged CLT, and 30% higher ETP (all p < 0.01). Reduced Ks was associated with lower antithrombin antigen level (β = - 6.1, 95% confidence interval [CI]: -1.7 to -10.5), while prolonged CLT was associated with lower antithrombin antigen (β = - 69.6, 95% CI: -9.6 to -129.7), activity (β = - 2.4, 95% CI: -0.3 to -4.5), higher PAI-1 (β = 12.1, 95% CI: 7.7-16.5), and thrombin-activatable fibrinolysis inhibitor levels (β = 3.8, 95% CI: 1.9-5.7). Addition of exogenous antithrombin reduced ETP (-42%) and peak thrombin (-21%), and improved Ks (+8%) and CLT (-12%; all p < 0.01).

CONCLUSION

 Our study suggests that enhanced thrombin generation and prothrombotic plasma fibrin clot phenotype can contribute to increased risk of thrombosis in patients with antithrombin deficiency.

Effect of high-dose statin therapy on coagulation factors: Lowering of factor XI as a modifier of fibrin clot properties in coronary artery disease

BACKGROUND

Multiple pleiotropic effects of statins include antithrombotic properties with formation of looser fibrin networks more susceptible to lysis. Recently, rosuvastatin 20 mg/d has been reported to decrease coagulation factors (F) VII, FVIII and FXI in venous thrombosis patients.

OBJECTIVES

We investigated how high-dose statin therapy recommended in coronary artery disease (CAD) alters plasma levels of coagulation factors and if such changes might affect fibrin clot properties.

METHODS

We studied 130 advanced CAD patients, who initially did not achieve the target low-density lipoprotein cholesterol (LDL-C). Before high-dose statin therapy (rosuvastatin 40 mg/d or atorvastatin 80 mg/d) and 6-12 months after its initiation, FII, FV, FVII, FVIII, FIX, FX, FXI and fibrinogen were assessed. We evaluated the impact of statin-induced alterations to the factors on plasma fibrin clot permeability (Ks) reflecting a fibrin pore size, and clot lysis time (CLT) reflecting fibrinolytic potential.

RESULTS

At baseline LDL-C (median 3.2, interquartile range 2.7-3.7 mmol/L) was independently associated solely with FXI (β = 0.58, P < 0.001). Median LDL-C reduction by 25% (P < 0.001) on high-dose statin treatment was accompanied by lowering of FVII, FVIII, and FXI (for all P < 0.001). On high-dose statin treatment, Ks (R = 0.65, P < 0.001) inversely associated with CRP (β = -0.41, P < 0.001), LDL-C (β = -0.26, P = 0.001), and FXI (β = -0.18, P = 0.016). In turn, CLT (R = 0.45, P < 0.001) was positively associated with LDL-C (β = 0.19, P = 0.043) and FXI (β = 0.17, P = 0.049).

CONCLUSIONS

High-dose statin therapy in CAD patients decreases FVII, FVIII, and FXI. The statin-induced reduction in FXI may contribute to less prothrombotic fibrin clot phenotype, indicating additional antithrombotic effect of high-dose statins.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Therapy with high-dose statins reduces soluble P-selectin: The impact on plasma fibrin clot properties

OBJECTIVE

Studies on the effect of statins on platelets in patients with coronary artery disease (CAD) yielded inconsistent results. We sought to investigate whether high-dose statin therapy reduces plasma concentrations of soluble P-selectin (sP-selectin), a well-established platelet activation marker and if such changes can affect fibrin clot properties, which are unfavorably altered in CAD patients.

METHODS

We studied 130 consecutive patients with advanced CAD who did not achieve the target LDL cholesterol on statins. At baseline and after 6-12 months of treatment with atorvastatin 80 mg/day or rosuvastatin 40 mg/day, soluble plasma sP-selectin, along with plasma fibrin clot permeability (Ks), clot lysis time (CLT), thrombin generation and fibrinolysis proteins were determined.

RESULTS

Before high-intensity statin treatment, lower Ks and longer CLT values were associated with increased sP-selectin (β -0.27 [95% CI -0.44 to -0.10] and β 0.21 [95% CI 0.01 to 0.41]; both p < 0.05, respectively) also after adjustment for potential confounders. sP-selectin, alongside fibrin features and other variables at baseline showed no association with lipid profile. On high-dose statin therapy, there was 32% reduction in sP-selectin levels (p < 0.001). On-treatment change (Δ) in sP-selectin correlated with ΔKs and ΔCLT (r = -0.32, p < 0.001 and r = 0.22, p = 0.011, respectively), but not with cholesterol and C-reactive protein lowering. We did not observe any associations between post-treatment sP-selectin levels and lipids, fibrin clot properties or thrombin generation.

CONCLUSIONS

High-dose statin therapy reduces markedly sP-selectin levels in association with improved fibrin clot phenotype, which highlights the contribution of platelet-derived proteins to a prothrombotic state in hypercholesterolemia and statin-induced antithrombotic effects.

Translational insights into mechanisms underlying residual venous obstruction and the role of factor XI, P-selectin and GPVI in recurrent venous thromboembolism

BACKGROUND

Residual venous obstruction (RVO) after deep vein thrombosis (DVT) is considered a risk factor of recurrent venous thromboembolism (VTE), arterial events and post-thrombotic syndrome (PTS). We hypothesized thrombo-inflammatory markers might be associated with RVO and clinical outcomes.

MATERIALS AND METHODS

In a DVT cohort with routine RVO-assessment and 5-year follow-up, patients were invited for blood withdrawal after stopping anticoagulants. Thrombin generation potential, coagulation enzyme:inhibitor complexes, soluble platelet markers and clinical markers were measured in platelet-poor plasma. Associations were represented as odds ratio (OR) or hazard ratio (HR) per standard deviation.

RESULTS

Patients with RVO (102/306, 33 %) had higher rates of PTS (24 vs. 12 %, p = 0.008), but similar rates of recurrence (16 vs. 15 %, p = 0.91) and arterial events (7 vs. 4 %, p = 0.26). RVO was associated with thrombin peak height (OR 1.40 [1.04-1.88]), endogenous thrombin potential (ETP, OR 1.35 [1.02-1.79]), and CRP (OR 1.74 [1.10-2.75]). Recurrent VTE was associated with ETP (HR 1.36 [1.03-1.81]), FXIa:C₁-inhibitor (HR 1.34 [1.04-1.72]), thrombin:antithrombin (HR 1.36 [1.16-1.59]), soluble P-selectin (HR 2.30 [1.69-3.11]), soluble glycoprotein VI (sGPVI, HR 1.30 [1.01-1.69]), D-dimer (HR 1.56 [1.31-1.86]), and factor VIII (HR 1.44 [1.15-1.82]). Arterial events were associated with sGPVI (HR 1.80 [1.25-2.59]). PTS was not associated with any marker.

CONCLUSIONS

Our findings indicate RVO was associated with thrombo-inflammation, but this did not predict clinical outcomes in this setting. Importantly, we found recurrent VTE was associated with ongoing coagulation and platelet activation in patients well beyond the acute phase of DVT. Furthermore, sGPVI indicated an increased risk of arterial events, highlighting the role of platelets in arterial thrombosis following DVT.

Protocol for the Investigation of Plasma and Whole Blood Clot Property of Fibrin Fiber Thickness Using Scanning Electron Microscopy

Blood clot formation represents a key component of the coagulation process for preventing excessive hemorrhage. The structural characteristics of blood clots are associated with their strength and susceptibility to fibrinolysis. Scanning electron microscopy is a technique that allows for state-of-the-art image capture of blood clots, providing visualization of topography, fibrin thickness, fibrin network density, and blood cell involvement and morphology. In this chapter, we provide a detailed protocol for characterization of plasma and whole blood clot structure using SEM, covering the spectrum from blood collection, in vitro clot formation, sample preparation for SEM, imaging, and image analysis, specifically focusing on the measurement of fibrin fiber thickness.

Prothrombotic state, endothelial injury, and echocardiographic changes in non-active sarcoidosis patients

Sarcoidosis is a multisystem inflammatory granulomatous disease of unknown cause that most commonly affects lungs and lymph nodes, with frequent yet asymptomatic cardiac involvement. The epidemiologically associated cardiovascular risk suggests an underlying prothrombotic state and endothelial dysfunction, currently understudied in the available literature. Therefore, we aimed to investigate prothrombotic plasma properties together with selected echocardiographic and laboratory biomarkers of cardiovascular injury in that disease. N = 53 patients with pulmonary sarcoidosis in clinical remission and N = 66 matched controls were assessed for inflammatory and endothelial injury biomarkers, plasma thrombin generation profile, and echocardiographic and lung function parameters. Sarcoidosis cases had impaired systolic and diastolic left ventricular function, higher concentrations of inflammatory markers, D-dimer and factor VIII activity compared to the controls. The coexistence of extrapulmonary disease was associated with elevated circulating vascular cell adhesion molecule 1, while cases with hypercalcemia had higher thrombomodulin concentration. Sarcoidosis was characterized by the unfavorably altered thrombin generation profile, reflected by the 16% higher endogenous thrombin potential (ETP), 24% increased peak thrombin concentration, and 12% shorter time to thrombin peak in comparison to the control group. ETP was higher in cases with proxies of pulmonary restriction, extrapulmonary-extracutaneous manifestation, and need for corticosteroids use. Despite the clinical remission, sarcoidosis is related to prothrombotic plasma properties and signs of endothelial injury, likely contributing to the higher risk of cardiovascular events. In addition, subclinical cardiac involvement may play an additional role, although further clinical and experimental studies are needed to verify these findings.

GnRH Antagonist Protocol Enhances Coagulation During Controlled Ovarian Stimulation for IVF

Changes in coagulation and fibrinolysis have been reported in women undergoing controlled ovarian hyperstimulation (COH) supporting a potential hypercoagulable condition related to this treatment. This study aimed at evaluating the changes in fibrin clot properties and thrombin generation induced by two different COH protocols: long with gonadotropin-releasing hormone agonist (GnRH-a) and GnRH antagonist (GnRH-ant). Primary outcomes included determination of plasma fibrin clot properties, including clot permeability (K_s) and efficiency of fibrinolysis using clot lysis time (CLT), along with thrombin generation (prothrombin fragments 1 + 2) and endogenous thrombin potential (ETP) and fibrinolysis inhibitor levels. One hundred twenty-nine infertile women were included in the final analysis. The GnRH-ant protocol resulted in increased ETP (+ 9.8%) and reduced K_s (- 2.4%). Conversely, COH with the GnRH-a protocol reduced thrombin generation by decreasing both ETP (- 6.6%) and F1 + 2 (- 30.8%) together with favorably altered fibrin clot properties represented by increased K_s (+ 21.7%) and reduced CLT (- 13.8%) as well as decreased PAI-1 levels (by 2.5 times). The GnRH-ant compared to the GnRH-a protocol increased PAI-1 levels (+ 77.3%), thrombin generation (9.3% higher ETP), and K_s (+ 13.7%). In the GnRH-a group, post-COH K_s was 14.3% higher (K_s ≥ 7.92 × 10^-9 cm²) in women with positive vs. negative pregnancy outcomes. Our results show that the GnRH-ant protocol enhanced thrombin generation and slightly decreased fibrin clot density. COH with the GnRH-a reduced thrombin generation and improved fibrin clot features. This trial was registered (NCT04166825). Clinical Trial Registration Number: NCT04166825.

Mass-spectrometric identification of oxidative modifications in plasma-purified plasminogen: Association with hypofibrinolysis in patients with acute pulmonary embolism

OBJECTIVES

Mechanisms behind disturbed fibrinolysis in pulmonary embolism (PE) are poorly understood. We hypothesized that oxidative stress-induced changes in plasminogen contribute to impaired fibrinolysis in patients with acute PE.

METHODS

Oxidative and other modifications were investigated using mass-spectrometry in plasminogen purified from pooled plasma of 5 acute PE patients on admission and after 3 months of anticoagulant treatment, along with plasma clot lysis time, a measure of global efficiency of fibrinolysis, and a stable oxidative stress marker, plasma 8-isoprostane.

RESULTS

Twenty sites of oxidation, 3 sites of carbonylation and 4 sites of S-nitrosylation were identified in plasminogen. The intensity of peptides oxidized at cysteine residues with respect to unmodified peptides decreased after 3 months of anticoagulation (p = 0.018). This was not observed for oxidized methionine residues (p = 0.9). Oxidized tryptophan (n = 4) and proline (n = 2), as well as carbonylation at 3 threonine residues were selectively identified in acute PE episode, not after 3 months. This was accompanied by 12.8% decrease in clot lysis time (p = 0.043). Deamidation occurred at the arginine, previously identified to undergo the cleavage by plasminogen activator. Methylated were two lysine-binding sites important for an interaction of plasminogen with fibrin. Other identified modifications involved: glycation, acetylation, phosphorylation, homocysteinylation, carbamylation and dichlorination (88 modifications at 162 sites).

CONCLUSIONS

Data suggest that oxidative stress-induced changes in plasminogen molecules may contribute to less effective global fibrinolysis in patients with acute PE. The comprehensive library of posttranslational modifications in plasminogen molecules was provided, including modifications of sites reported to be involved in important biological functions.

Hemostasis Disturbances in Continuous-Flow Left Ventricular Assist Device (CF-LVAD) Patients—Rationale and Study Design

Left ventricular assist devices are a treatment option for end-stage heart failure patients. Despite advancing technologies, bleeding and thromboembolic events strongly decrease the survival and the quality of life of these patients. Little is known about prognostic factors determining these adverse events in this group of patients. Therefore, we plan to investigate 90 consecutive left ventricular assist device (LVAD) patients and study in vitro fibrin clot properties (clot lysis time, clot permeability, fibrin ultrastructure using a scanning electron microscope) and the calibrated automated thrombogram in addition to the von Willebrand factor antigen, fibrinogen, D-dimer, prothrombin time/international normalized ratio (PT/INR), and activated partial thromboplastin time (APTT) to identify prognostic factors of adverse outcomes during the course of therapy. We plan to assess the hemostasis system at four different time points, i.e., before LVAD implantation, 3–4 months after LVAD implantation, 6–12 months after LVAD implantation, and at the end of the study (at 5 years or at the time of the adverse event). Adverse outcomes were defined as bleeding events (bleeding in general or in the following subtypes: severe bleeding, fatal bleeding, gastrointestinal bleeding, intracranial bleeding), thromboembolic events (stroke or transient ischemic attack, pump thrombosis, including thrombosis within the pump or its inflow or outflow conduits, arterial peripheral thromboembolism), and death.

Fibrinogen and Factor XIII in Venous Thrombosis and Thrombus Stability

As the third most common vascular disease, venous thromboembolism is associated with significant mortality and morbidity. Pathogenesis underlying venous thrombosis is still not fully understood. Accumulating data suggest fibrin network structure and factor XIII-mediated crosslinking are major determinants of venous thrombus mass, composition, and stability. Understanding the cellular and molecular mechanisms mediating fibrin(ogen) and factor XIII production and function and their ability to influence venous thrombogenesis and resolution may inspire new anticoagulant strategies that target these proteins to reduce or prevent venous thrombosis in certain at-risk patients. This article summarizes fibrinogen and factor XIII biology and current knowledge of their function during venous thromboembolism.

Aberrant Fibrin Clot Structure Visualized Ex Vivo in Critically Ill Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Infection

OBJECTIVES

Disseminated fibrin-rich microthrombi have been reported in patients who died from COVID-19. Our objective is to determine whether the fibrin clot structure and function differ between critically ill patients with or without COVID-19 and to correlate the structure with clinical coagulation biomarkers.

DESIGN

A cross-sectional observational study. Platelet poor plasma was used to analyze fibrin clot structure; the functional implications were determined by quantifying clot turbidity and porosity.

SETTING

ICU at an academic medical center and an academic laboratory.

PATIENTS

Patients admitted from July 1 to August 1, 2020, to the ICU with severe acute respiratory syndrome coronavirus 2 infection confirmed by reverse transcription-polymerase chain reaction or patients admitted to the ICU with sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood was collected from 36 patients including 26 ICU patients with COVID-19 and 10 ICU patients with sepsis but without COVID-19 at a median of 11 days after ICU admission (interquartile range, 3-16). The cohorts were similar in age, gender, body mass index, comorbidities, Sequential Organ Failure Assessment (SOFA) score, and mortality. More patients with COVID-19 (100% vs 70%; p = 0.003) required anticoagulation. Ex vivo fibrin clots formed from patients with COVID-19 appeared to be denser and to have smaller pores than those from patients with sepsis but without COVID-19 (percent area of fluorescent fibrin 48.1% [SD, 16%] vs 24.9% [SD, 18.8%]; p = 0.049). The turbidity and flow-through assays corroborated these data; fibrin clots had a higher maximum turbidity in patients with COVID-19 compared with patients without COVID-19 (0.168 vs 0.089 OD units; p = 0.003), and it took longer for buffer to flow through these clots (216 vs 103 min; p = 0.003). In patients with COVID-19, d-dimer levels were positively correlated with percent area of fluorescent fibrin (ρ = 0.714, p = 0.047). Denser clots (assessed by turbidity and thromboelastography) and higher SOFA scores were independently associated with delayed clot lysis.

CONCLUSIONS

We found aberrant fibrin clot structure and function in critically ill patients with COVID-19. These findings may contribute to the poor outcomes observed in COVID-19 patients with widespread fibrin deposition.

Risk factors for preoperative deep venous thrombosis in hip fracture patients: a meta-analysis

STUDY DESIGN

A meta-analysis.

BACKGROUND

Hip fracture (HF), as common geriatric fracture, is related to increased disability and mortality. Preoperative deep vein thrombosis (DVT) is one of the most common complications in patients with hip fractures, affecting 8-34.9% of hip fracture patients. The study aimed to assess the risk factors of preoperative DVT after hip fractures by meta-analysis.

METHODS

An extensive search of the literature was performed in the English databases of PubMed, Embase, and the Cochrane Library; and the Chinese databases of CNKI and WAN FANG. We collected possible predictors of preoperative DVT from included studies, and data analysis was conducted with RevMan 5.3 and STATA 12.0.

RESULTS

A total of 26 English articles were included, and the rate of DVT was 16.6% (1627 of 9823 patients) in our study. Our findings showed that advanced age [p = 0.0003, OR = 0.13 95% CI (0.06, 0.21)], female patients [p = 0.0009, OR = 0.82 95% CI (0.72, 0.92)], high-energy injury [p = 0.009, OR = 0.58 95% CI (0.38, 0.87)], prolonged time from injury to admission [p < 0.00001, OR = 0.54 95% CI (0.44, 0.65)], prolonged time from injury to surgery [p < 0.00001, OR = 2.06, 95% CI (1.40, 2.72)], hemoglobin [p < 0.00001, OR = - 0.32 95% CI (- 0.43, - 0.21)], coronary heart disease [p = 0.006, OR = 1.25 95% CI (1.07, 1.47)], dementia [p = 0.02, OR = 1.72 95% CI (1.1, 2.67)], liver and kidney diseases [p = 0.02, OR = 1.91 95% CI (1.12, 3.25)], pulmonary disease [p = 0.02, OR = 1.55 95% CI (1.07, 2.23)], smoking [p = 0.007, OR = 1.45 95% CI (1.11, 1.89)], fibrinogen [p = 0.0005, OR = 0.20 95% CI (0.09, 0.32)], anti-platelet drug [p = 0.01, OR = 0.51 95% CI (0.30, 0.85)], C-reactive protein [p = 0.02, OR = 5.95 95% CI (1.04, 10.85)], < 35 g/l albumin [p = 0.006, OR = 1.42 95% CI (1.1, 1.82)], and thrombosis history [p < 0.00001, OR = 5.28 95% CI (2.85, 9.78)] were risk factors for preoperative DVT.

CONCLUSIONS

Many factors, including advanced age, female patients, high-energy injury, prolonged time from injury to admission, prolonged time from injury to surgery, patients with a history of coronary heart disease, dementia, liver and kidney diseases, pulmonary disease, smoking, and thrombosis, fibrinogen, C-reactive protein, and < 35 g/l albumin, were found to be associated with preoperative DVT. Our findings suggested that the patient with above characteristics might have preoperative DVT.

LEVEL OF EVIDENCE

Level III.

Properties of Plasma Clots in Adult Patients Following Fontan Procedure: Relation to Clot Permeability and Lysis Time-Multicenter Study

Objectives: thromboembolic complications are a major cause of morbidity and mortality following Fontan (FO) surgery. It is also well established that altered FO circulation results in systemic complications, including liver and endothelium damage. We sought to evaluate whether dysfunctions of these sources of hemostatic factors may result in changes of fibrin clot properties. Methods: a permeation coefficient (K_s) and clot lysis time (CLT) were assessed in 66 FO patients, aged 23.0 years [IQR 19.3–27.0], and 59 controls, aged 24.0 years [IQR 19.0–29.0]. K_s was determined using a pressure-driven system. CLT value was measured according to assay described by Pieters et al. Endothelium and liver-derived hemostatic factors along with liver function parameters were evaluated. The median time between FO operation and investigation was 20.5 years [IQR 16.3–22.0]. Results: FO patients had lower K_s (p = 0.005) and prolonged CLT (p < 0.001) compared to that of controls. K_s correlated with CLT (r = −0.28), FVIII (r = −0.30), FIX (r = −0.38), fibrinogen (r = −0.41), ALT (r = −0.25), AST (r = −0.26), GGTP (r = −0.27) and vWF antigen (r = −0.30), (all p < 0.05). CLT correlated with the time between FO operation and investigation (r = 0.29) and FIX (r = 0.25), (all p < 0.05). After adjustment for potential cofounders, TAFI antigen and GGTP were independent predictors of reduced K_s (OR 1.041 per 1% increase, 95% CI 1.009–1.081, p = 0.011 and OR 1.025 per 1 U/L increase, 95% CI 1.005–1.053, p = 0.033, respectively). Protein C and LDL cholesterol predicted prolonged CLT (OR 1.078 per 1% increase, 95% CI 1.027–1.153, p = 0.001 and OR 6.360 per 1 μmol/L increase, 95% CI 1.492–39.894, p = 0.011, respectively). Whereas elevated tPA was associated with lower risk of prolonged CLT (OR 0.550 per 1 ng/mL, 95% CI 0.314–0.854, p = 0.004). GGTP correlated positively with time between FO surgery and investigation (r = 0.25, p = 0.045) and patients with abnormal elevated GGTP activity (n = 28, 42.4%) had decreased K_s, compared to that of the others (5.9 × 10⁻⁹ cm² vs. 6.8 × 10⁻⁹ cm², p = 0.042). Conclusion: our study shows that cellular liver damage and endothelial injury were associated with prothrombotic clot phenotype reflected by K_s and CLT.

Novel venous thromboembolism mouse model to evaluate the role of complete and partial factor XIII deficiency in pulmonary embolism risk

BACKGROUND

Venous thrombosis (VT) and pulmonary embolism (PE), collectively venous thromboembolism (VTE), cause high mortality and morbidity. Factor XIII (FXIII) crosslinks fibrin to enhance thrombus stability and consequently may influence PE risk. Elucidating mechanisms contributing to PE is limited by a lack of models that recapitulate human PE characteristics.

OBJECTIVE

We aimed to develop a mouse model that permits embolization of red blood cell (RBC)- and fibrin-rich VT and determine the contribution of FXIII to PE risk.

METHODS AND RESULTS

In a thrombin-infusion PE model, F13a+/+ , F13a+/- , and F13a-/-  mice had similar incidence of microthrombi in the lungs; however, thrombi were small, with low RBC content (≤7%), unlike human PEs (~70%). To identify a model producing PE consistent with histological characteristics of human PE, we compared mouse femoral vein electrolytic injury, femoral vein FeCl3 injury, and infrarenal vena cava (IVC) stasis models of VT. Electrolytic and FeCl3  models produced small thrombi with few RBCs (5% and 4%, respectively), whereas IVC stasis produced large thrombi with higher RBC content (68%) that was similar to human PEs. After IVC stasis and ligature removal (de-ligation) to permit thrombus embolization, compared to F13a+/+ mice, F13a+/-  and F13a-/-  mice had similar and increased PE incidence, respectively.

CONCLUSIONS

Compared to thrombin infusion-, electrolytic injury-, and FeCl3 -based models, IVC stasis produces thrombi that are more histologically similar to human thrombi. IVC stasis followed by de-ligation permits embolization of existing RBC- and fibrin-rich thrombi. Complete FXIII deficiency increases PE incidence, but partial deficiency does not.

Accelerated fibrin clot degradation is associated with arterial thromboembolism in patients following venous thrombosis: a cohort study

Several lines of evidence have suggested that patients following venous thromboembolism (VTE) are at higher risk of arterial thromboembolism (ATE). Prothrombotic fibrin clot characteristics were reported in individuals with cardiovascular risk factors. We investigated whether specific fibrin clot properties measured after 3-4 months of anticoagulation characterize VTE patients with subsequent ATE. We enrolled 320 patients following VTE aged below 70 years (median age, 46). Ten patients were lost to follow-up. ATE occurred in 21 individuals after a median 54 (31-68) months during a follow-up of 87.5 months (incidence 0.94%; 95% confidence interval [CI], 0.59-1.4 per patient-year). Patients with ATE had faster fibrin clot degradation, reflected by maximum rate of D-dimer increase during plasma clot lysis induced by tissue-type plasminogen activator (D-D_rate) at baseline. Clot permeability, turbidimetric variables, clot lysis time, and thrombin generation were unrelated to ATE. Univariable Cox proportional hazards analysis showed that age, diabetes, and D-D_rate were risk factors for subsequent ATE. Increased D-D_rate (by 0.001 mg/L/min; hazard ratio, 1.08; 95% CI 1.02-1.14) was an independent predictor of ATE after adjustment for potential confounders. Faster fibrin clot degradation at 3 months since VTE may increase the risk of ATE among VTE patients during follow-up.

Evaluation of coagulation status using clot waveform analysis in general ward patients with COVID-19

Coronavirus disease (COVID-19)-related systemic cytokine response induces the production of procoagulant factors, which predisposes patients to a prothrombotic state. Viscoelastic testing can identify the degree of hypercoagulability, which is related to outcomes. We aimed to study the changes in clot waveform analysis (CWA) parameters in COVID-19 patients on hospital admission compared to those in a group of healthy individuals. We conducted a retrospective study of COVID-19 patients admitted to general wards and evaluated demographic and clinical parameters as well as laboratory parameters, including coagulation parameters. CWA data from patients (n = 62) with COVID-19 prior to the initiation of anticoagulation therapy were compared with those from healthy controls (n = 67). The measured CWA parameters were min1, min2, max2, and delta change. CWA, fibrinogen, and D-dimer values were higher in COVID-19 patients than in healthy controls (p < 0.001). CWA profiles were consistent with hypercoagulability and characterized by an increase in density, velocity, and acceleration of clot formation. Activated partial thromboplastin time, fibrinogen, D-dimer, and C-reactive protein (CRP) values were higher in patients in whom all CWA parameters were raised than in patients with just a few elevated CWA parameters, while Sequential Organ Failure Assessment scores, prothrombin time, fibrin degradation product levels and platelet counts did not differ between the two groups. CWA variables showed hypercoagulopathy on admission in COVID-19 patients who were hospitalized in the general ward, and this pattern was more pronounced in critically ill patients with elevated fibrinogen, D-dimer, and CRP levels. Our results may help identify patients at high risk of thromboembolism.

Fibrin Network Porosity and Endo-/Exogenous Thrombin Cross-talk

The earliest assessment of fibrin network porosity used a liquid permeation system and confocal 3D microscopy, which was later replaced by scanning electron microscopy. Although the methods have extensively been applied in studies of health or disease, there remains debate on the choice of a proper clotting trigger. In this review, we assess published data and convey our opinions with regard to several issues. First, when the coagulation process is initiated by recombinant tissue factor (rTF) and phospholipids, the fibrin network porosity is regulated by the endogenous thrombin based on enzymatic activations of multiple coagulants. If purified thrombin (1.0 IU/mL) is employed as the clotting trigger, fibrin network porosity may be affected by exogenous thrombin, which directly polymerizes fibrinogen in plasma, and additionally by endogenous thrombin stemming from a "positive feedback loop" action of the added thrombin. Second, with use of either endogenous or exogenous thrombin, the concentration and clotting property of available fibrinogen both influence the fibrin network porosity. Third, in the assay systems in vitro, exogenous thrombin but not rTF-induced endogenous thrombin seems to be functional enough to activate factor XIII, which then contributes to a decrease in the fibrin network porosity. Fourth, fibrin network porosity determines the transport of fibrinolytic components into/through the clots and therefore serves as an indicator of the fibrinolysis potential in plasma.

Psoriatic disease is associated with systemic inflammation, endothelial activation, and altered haemostatic function

Psoriasis is a chronic, immune-mediated inflammatory skin disease, affecting approximately 2% of the general population, which can be accompanied by psoriatic arthritis (PsA). The condition has been associated with an increased cardiovascular burden. Hypercoagulability is a potential underlying mechanism that may contribute to the increased risk of major cardiovascular events in psoriatic individuals. Whole blood samples were collected from 20 PsA patients and 20 healthy individuals. The concentrations of inflammatory molecules (C-reactive protein, serum amyloid A, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and soluble P-selectin) were determined by enzyme-linked immunosorbent assays. In addition, clotting efficiency was evaluated by thromboelastography. The fibrin network architecture was also assessed by scanning electron microscopy. Elevated levels of circulating inflammatory molecules were significantly associated with the presence of psoriatic disease. Furthermore, an increased tendency towards thrombus formation was significantly predictive of disease presence. Scanning electron microscopy revealed that fibrin clots were denser in psoriatic individuals, compared to healthy controls, with an increased fibrin fibre diameter associated with psoriatic disease. Our results add to the accumulating evidence of the systemic nature of psoriasis and the subsequent risk of cardiovascular comorbidities, potentially due to an acquired hypercoagulability. We suggest that haemostatic function should be monitored carefully in psoriatic patients that present with severe disease, due to the pre-eminent risk of developing thrombotic complications.

Fibrin Clot Formation under Oxidative Stress Conditions

During coagulation, the soluble fibrinogen is converted into insoluble fibrin. Fibrinogen is a multifunctional plasma protein, which is essential for hemostasis. Various oxidative posttranslational modifications influence fibrinogen structure as well as interactions between various partners in the coagulation process. The aim was to examine the effects of oxidative stress conditions on fibrin clot formation in arterial atherothrombotic disorders. We studied the changes in in vitro fibrin network formation in three groups of patients-with acute coronary syndrome (ACS), with significant carotid artery stenosis (SCAS), and with acute ischemic stroke (AIS), as well as a control group. The level of oxidative stress marker malondialdehyde measured by LC-MS/MS was higher in SCAS and AIS patients compared with controls. Turbidic methods revealed a higher final optical density and a prolonged lysis time in the clots of these patients. Electron microscopy was used to visualize changes in the in vitro-formed fibrin network. Fibers from patients with AIS were significantly thicker in comparison with control and ACS fibers. The number of fibrin fibers in patients with AIS was significantly lower in comparison with ACS and control groups. Thus, oxidative stress-mediated changes in fibrin clot formation, structure and dissolution may affect the effectiveness of thrombolytic therapy.

Fibrinolysis in Venous Thromboembolism

Fibrinolysis is of paramount importance in maintaining or regaining the patency of veins and pulmonary arteries obstructed by thrombi. Growing experimental and clinical evidence indicates that impaired fibrinolysis mediated by multiple complex mechanisms is involved in venous thromboembolism (VTE). Global plasma fibrin clot lysis markers, especially clot lysis time, have been reported to predict recurrent deep-vein thrombosis and pulmonary embolism. The current overview summarizes available data linking fibrinolysis to VTE and its long-term sequelae.

Fibrin clot properties among women with endometriosis and the impact of ovarian stimulation

RESEARCH QUESTION

Is there a difference in fibrin clot phenotype in women with endometriosis before and after ovarian stimulation?

DESIGN

Prospective study including 73 infertile women in two age-matched groups: (i) with confirmed endometriosis (n = 29); (ii) without endometriosis (n = 44). Assessments of plasma fibrin clot permeability (K_s), efficiency of fibrinolysis using clot lysis time (CLT), along with thrombin generation (prothrombin fragments 1+2 [F1+2] and endogenous thrombin potential [ETP]) and fibrinolysis inhibitors were performed together with clinical pregnancy rate.

RESULTS

Endometriosis was associated with increased thrombin generation, reflected by both higher F1+2 (+96.1%, P = 0.005) and ETP (+14.2%, P = 0.014) along with unfavourably altered fibrin clot properties represented by lower K_s (-31%, P < 0.001) and prolonged CLT (+13.5%, P = 0.02), compared with the non-endometriosis group. Moreover, women with endometriosis had higher plasminogen activator inhibitor-1 (PAI-1; +272%, P = 0.004) concentrations and alpha-2-antiplasmin activity (+39.9%, P < 0.001) in contrast to the other group. Ovarian stimulation led to reduction in F1+2 (-48.1%, P < 0.001), improvement of fibrin clot phenotype reflected by higher K_s (+25.9%, P < 0.001) and shortened CLT (-11.9%, P < 0.001), along with lower PAI-1 (-54%, P = 0.016) compared with the baseline in women with endometriosis.

CONCLUSIONS

Endometriosis is associated with the prothrombotic fibrin clot phenotype and increased thrombin generation. Ovarian stimulation favourably alters fibrin clot properties and leads to comparable pregnancy outcomes to those in women without endometriosis.

The treatment effect of rivaroxaban on clot characteristics in patients who present acutely with first time deep vein thrombosis

BACKGROUND

The acute vascular disease deep vein thrombosis (DVT) requires oral anticoagulants to prevent progression. Monitoring therapeutic efficacy of direct oral anticoagulants (DOAC), including rivaroxaban, is problematic as no reliable test is available. Advances in rheometry have led to the development of a functional coagulation biomarker using Gel Point (GP) analysis which assesses clot structure formation. The biomarker measures incipient clot formation time (TGP) and quantifies fibrin clot structure in terms of fractal dimension (df).

OBJECTIVE

This study aimed to investigate clot structure formation in first time DVT and the effect of rivaroxaban treatment.

METHODS

This prospective observational cohort study measured the GP and standard laboratory markers at three sample points: pre-treatment and at 20 and 60 days following 15 mg BD and 20 mg OD rivaroxaban respectively.

RESULTS

Forty DVT patients (mean age 64 years [SD±14.8]; 23 males, 17 female) were recruited. The results show that DVT vs non-DVT patients did not have a significantly different GP profile (df: 1.72±0.06 vs 1.70±0.06 and TGP: 267±68 sec vs 262±73 sec) with both within the defined healthy index. In addition, rivaroxaban therapy increased TGP to 392 s (±135 s) after 20 days, and subsequently increased to 395 s (±194 s) at 60 days but did not significantly increase df (from 1.69±0.05 to 1.71±0.06).

CONCLUSIONS

The results indicate in this cohort of DVT patients there was no underlying hypercoagulable effect as determined by gel point analysis. Furthermore, the anticoagulant effect of rivaroxaban prolonged clotting, suggesting a protective effect against clot formation, without significantly reducing clot microstructural properties.

Factor XIII and Fibrin Clot Properties in Acute Venous Thromboembolism

Coagulation factor XIII (FXIII) is converted by thrombin into its active form, FXIIIa, which crosslinks fibrin fibers, rendering clots more stable and resistant to degradation. FXIII affects fibrin clot structure and function leading to a more prothrombotic phenotype with denser networks, characterizing patients at risk of venous thromboembolism (VTE). Mechanisms regulating FXIII activation and its impact on fibrin structure in patients with acute VTE encompassing pulmonary embolism (PE) or deep vein thrombosis (DVT) are poorly elucidated. Reduced circulating FXIII levels in acute PE were reported over 20 years ago. Similar observations indicating decreased FXIII plasma activity and antigen levels have been made in acute PE and DVT with their subsequent increase after several weeks since the index event. Plasma fibrin clot proteome analysis confirms that clot-bound FXIII amounts associated with plasma FXIII activity are decreased in acute VTE. Reduced FXIII activity has been associated with impaired clot permeability and hypofibrinolysis in acute PE. The current review presents available studies on the role of FXIII in the modulation of fibrin clot properties during acute PE or DVT and following these events. Better understanding of FXIII’s involvement in the pathophysiology of acute VTE might help to improve current therapeutic strategies in patients with acute VTE.

Role, Laboratory Assessment and Clinical Relevance of Fibrin, Factor XIII and Endogenous Fibrinolysis in Arterial and Venous Thrombosis

Diseases such as myocardial infarction, ischaemic stroke, peripheral vascular disease and venous thromboembolism are major contributors to morbidity and mortality. Procoagulant, anticoagulant and fibrinolytic pathways are finely regulated in healthy individuals and dysregulated procoagulant, anticoagulant and fibrinolytic pathways lead to arterial and venous thrombosis. In this review article, we discuss the (patho)physiological role and laboratory assessment of fibrin, factor XIII and endogenous fibrinolysis, which are key players in the terminal phase of the coagulation cascade and fibrinolysis. Finally, we present the most up-to-date evidence for their involvement in various disease states and assessment of cardiovascular risk.

Impact of epicatechin on fibrin clot structure

Fibrin clot structure and function are major determinants of thromboembolic diseases. The study aim was to determine the impact of epicatechin (a flavonoid with cardiovascular protective effects) on fibrin clot structure and permeability. Plasma samples from 12 healthy subjects were incubated with increasing concentrations of epicatechin. Turbidity of fibrin clot was analyzed by absorbance measurement at 405 nm. The fibrin clot nanostructure was determined by scanning spectrometry (wavelength from 500 to 800 nm) and fibrin fiber size by electron microscopy. Permeability was analyzed to assess the fibrin clot functional properties. Epicatechin addition increased the maximum absorbance from 0.34 ± 0.066 (vehicle) to 0.35 ± 0.077 (P = 0.1), 0.35 ± 0.072 (P < 0.05) and 0.34 ± 0.065 (P = 0.5) for 1, 10 and 100 μM epicatechin, respectively. Epicatechin increased the fibrin clot fiber radius (nm) from 109.2 ± 3.2 (vehicle) to 108.9 ± 4.3 (P = 0.9), 110.0 ± 3.6 (P < 0.05) and 109.5 ± 3.3 (P = 0.4), and the distance between protofibrils (nm) from 22.2 ± 1.5 (vehicle) to 22.1 ± 2.3 (P = 0.9), 22.6 ± 1.8 (P < 0.05) and 22.3 ± 1.8 (P = 0.9) for 1, 10 and 100 μM epicatechin respectively. Electron microscopy confirmed these changes. Fibrin clot permeability, expressed as Darcy's constant (Ks, cm²), increased from 2.97 ± 1.17 (vehicle) to 3.36 ± 1.21 (P < 0.05), 3.81 ± 1.41 (P < 0.01) and 3.38 ± 1.33 (P = 0.9). Upon epicatechin addition, the fibrin clot structure became less dense and more permeable.

Loose Fibrin Clot Structure and Increased Susceptibility to Lysis Characterize Patients with Central Acute Pulmonary Embolism: The Impact of Isolated Embolism

BACKGROUND

 Prothrombotic fibrin clot properties are associated with higher early mortality risk in acute pulmonary embolism (PE) patients. It is unknown whether different types of PE are associated with particular clot characteristics.

METHODS

 We assessed 126 normotensive, noncancer acute PE patients (median age: 59 [48-70] years; 52.4% males), who were categorized into central versus peripheral PE with or without concomitant deep vein thrombosis (DVT). Plasma fibrin clot permeability (K _s), clot lysis time (CLT), thrombin generation, platelet-derived markers, and fibrinolytic parameters were measured on admission. Plasma fibrin clot morphology was assessed by scanning electron microscopy (SEM).

RESULTS

 Patients with central PE (n = 76; 60.3%) compared with peripheral PE (n = 50; 39.7%) had 17.8% higher K _s and 14.3% shortened CLT (both p < 0.01 after adjustment for potential confounders including fibrinogen), with no differences between segmental and subsegmental PE. SEM analysis demonstrated larger fibrin fiber diameter and pore size in central PE compared with peripheral PE (both p < 0.01). For isolated PE, there was 23.3% higher K _s in central PE than in peripheral PE (n = 24; 19%) with no differences in other variables. Central PE combined with DVT (n = 45; 35.7%), as compared with central isolated PE (n = 31; 24.6%), was associated with shortened CLT (all p < 0.05).

CONCLUSION

 Our findings suggest that looser fibrin networks composed of thicker fibers with increased susceptibility to lysis characterize patients with central PE, suggesting that fibrin clot phenotype affects the size of thrombi occluding the pulmonary arteries, highlighting the role of fibrin structures in thrombus formation and stability.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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