Fibrin Clot Strength Research Articles

New interest in fibrinogen as an ischemic risk factor.

Platelet-fibrin clot formation is a key process in acute arterial thrombosis. The relationship between thrombin-induced platelet-fibrin clot strength (P-FCS) and fibrinogen levels in patients with cardiovascular disease (CVD) and COVID-19 has not been studied. In thhe current study, the contribution of fibrinogen to P-FCS has been explored in healthy subjects (n=157), patients hospitalized with COVID-19 (n=116), and patients with CVD (n=93) using thrombelastography (TEG 6s) with citrate cartridge. We found that thrombin-induced P-FCS, fibrin clot strength (F-CS) and fibrinogen levels (FLEV) were higher among patients with CVD and COVID-19 compared to HS(p<0,05 for all) and highest among patients with COVID-19. P-FCS, an established risk factor for post-PCI ischemic event occurrences, was associated with both F-CS and FLEV (R2=0.67, p<0.001 for both comparisons.These data indicate that fibrinogen levels strongly influence the viscoelastic strength of the platelet-fibrin clot, fibrinogen may be an important driving factor for arterial thrombosis in the presence of potent platelet inhibition and may be as equally important a risk factor as high platelet reactivity. Since P-FCS is significantly associated with fibrinogen levels, the role of fibrinogen as a risk factor for arterial ischemic event occurrences should be further studied to improve antithrombotic therapy personalization.

Blood Lines: Intraspecific and Interspecific Variations in Anticoagulant Actions of Agkistrodon Viperid Venoms.

This study investigated the intraspecific and interspecific variability in the venom effects of Agkistrodon viperid snake species and subspecies (eleven venoms total) on plasma clotting times, fibrinogen levels, and fibrin clot strength. Significant delays in plasma clotting time were observed for A. conanti, A. contortrix mokasen, A. contortrix phaeogaster, A. howardgloydi, A. piscivorus leucostoma, and A. piscivorus piscivorus. Notably, the phylogenetically disjunct lineages A. conanti, A. contortrix mokasen, and A. howardgloydi exhibited the most potent anticoagulant effects, indicating the independent amplification of a basal trait. Inhibition assays with the activated clotting enzymes Factors XIa, IXa, Xa, and IIa (thrombin) revealed that FXa inhibition is another basal trait amplified independently on multiple occasions within the genus, but with A. howardgloydi, notably more potent than all others. Phospholipid degradation and zymogen destruction were identified as mechanisms underlying the variability in venom effects observed experimentally and in previous clinical reports. Thromboelastography demonstrated that the venoms did not clot fibrinogen directly but affected fibrin clot strength by damaging fibrinogen and that thrombin was subsequently only able to cleave into weak, unstable clots. The ability to activate Protein C, an endogenous anticoagulant enzyme, varied across species, with some venoms exceeding that of A. contortrix contortrix, which previously yielded the protein diagnostic agent Protac®. Phylogenetic analysis suggested that both fibrinogen degradation and Protein C activation were each amplified multiple times within the genus, albeit with negative correlation between these two modes of action. This study highlights the evolutionary, clinical, and biodiscovery implications of venom variability in the Agkistrodon species, underscoring their dynamic evolution, emphasising the need for tailored clinical approaches, and highlighting the potential for novel diagnostic and therapeutic developments inspired by the unique properties of snake venoms.

Abstract 14010: Synergistic Influence of Rivaroxaban on Platelets, Inflammation and Coagulation Biomarkers in Patients With CAD and/or PAD on Aspirin Therapy

Background: Cardiovascular benefits of 2.5 mg twice daily rivaroxaban plus aspirin therapy (RIV+ASA) has been demonstrated in patients with arterial diseases. Hypothesis: RIV+ASA is associated with reduced platelet activation and plasma inflammation and coagulation activation markers in patients with CAD and/or PAD who were on ASA. Methods: In this open-label biomarker study, patients on 81 mg/day ASA were randomized to continue ASA or RIV+ASA for 12 weeks. We assessed ADP-, α-thrombin-, and tissue factor-induced platelet aggregation (PA) using conventional aggregometry, platelet-fibrin clot strength (PFCS) by INTEM (intrinsic pathway activator) and EXTEM (extrinsic pathway activator) using thromboelastometry, shear-induced PA by platelet function analyzer-100, D-dimer and fibrinogen using coagulation analyzer, hs-CRP and interleukin-6 using ELISA method at baseline, and four weeks and 12 weeks post-randomization. Results: Data was available in 9 patients with RIV + ASA and ten patients with ASA-only therapy. Most patients were male, Caucasians, obese and older. There were no differences in baseline demographics, medications, and laboratory values between groups, except patients in RIV + ASA group had higher white blood cell counts (p=0.028) and lower baseline 2uM ADP-induced PA (p=0.03). There were no differences in other laboratory measurements between baseline and post-randomization time points within the group or at 4- and 12-week time points between groups, except D-dimer values were significantly lower at 12 weeks (p=0.038) in the RIV + ASA vs. ASA-only group. No significant adverse events were observed. Conclusions: Twelve weeks of rivaroxaban plus aspirin vs. aspirin was associated with similar levels of platelet aggregation, platelet fibrin clot strength, fibrinogen and inflammation markers, and lower d-dimer levels.

In vitro and Ex vivo Assessments of the Compatibility of Fibrin Sealant with Antimicrobial Compounds.

Background: Fibrin sealants are used as antimicrobial-releasing carriers for preventing surgical site infections; however, it is important to determine the release kinetics and antimicrobial effects of drugs added to fibrin sealants and the effects of drugs on clot/clotting properties. Materials and Methods: The antimicrobial and antibiofilm activity of cefazolin, colistin, gentamicin, oxacillin, tobramycin, and silver nitrate released from fibrin sealant were characterized using in vitro and ex vivo assays against bacteria commonly found on the skin. The effects of antimicrobial agents on the physical structure of the fibrin sealant were assessed with scanning electron microscopy (SEM) and on the clotting rate and strength of fibrin clots using run-off tests and rheology. Results: Generally, antibiotic agents were released gradually from fibrin sealant and were stable after release, with antimicrobial effects evident up to three days. Cefazolin, gentamicin, and oxacillin prevented biofilm formation of Staphylococcus aureus in porcine skin explants; gentamicin and colistin prevented biofilm formation of Pseudomonas aeruginosa. Gentamicin, cefazolin, colistin, and tobramycin did not affect the structural integrity or viscoelastic properties of fibrin sealant; changes were observed with oxacillin (SEM) and particularly silver nitrate (SEM and rheology). No antimicrobial agents caused deterioration of clotting time (run-off tests). Conclusions: From the antimicrobial agents tested, gentamicin and cefazolin showed prolonged release from fibrin sealant, sustained antimicrobial activity, and biofilm prevention properties against Staphylococcus aureus; similar results were observed for gentamicin and colistin against Pseudomonas aeruginosa. For each of these findings, the physical structure of the fibrin sealant, clotting rate, and strength of fibrin clots were unaffected.

Admission hyperglycemia as an independent predictor of clopidogrel high on-treatment platelet reactivity in ischemic stroke patients

Background: Admission hyperglycemia is a predictor of poor prognosis after ischemic stroke (IS). Previous studies have found that admission hyperglycemia was related to clopidogrel high on-treatment platelet reactivity (HTPR) in diabetic patients with myocardial infarction. However, reports on associations between admission hyperglycemia and clopidogrel HTPR remain scarce in IS patients. In this study, we assessed the correlation between admission hyperglycemia and clopidogrel HTPR in patients with IS. Methods: In this retrospective study, we included IS patients who were treated with clopidogrel for at least 5 days. Thromboelastography (TEG) was used to evaluate the platelet function. Clopidogrel HTPR was defined if adenosine diphosphate (ADP)-induced platelet fibrin clot strength (MAADP)&gt; 47 mm. Otherwise, it would be defined as clopidogrel normal on-treatment platelet reactivity (NTPR). Two groups were divided according to admission glucose of 7.8 mmol/L, consistent with previous studies on admission hyperglycemia. The independent risk factors of clopidogrel HTPR were assessed by multivariate logistic regression analysis. Results: A total of 147 patients were evaluated, and 42(28.57%) of patients were identified as clopidogrel HTPR. In the hyperglycemia group (admission glucose level ≥7.8mmol/L), 40.38% patients were defined as clopidogrel HTPR, which was significantly higher than in the normoglycemia group (22.11%, admission glucose level&lt;7.8mmol/L) (P=0.019). According to multivariate analysis, hyperglycemia was independently associated with clopidogrel HTPR (OR=8.36, 1.47-47.55, P=0.017). Admission glucose level was linearly correlated with MAADP (r=0.29, P=0.005). Furthermore, with the increase of admission glucose level tertiles, the incidence of clopidogrel HTPR increased gradually (P for trend=0.008). Conclusions: Admission hyperglycemia is an independent predictor of clopidogrel HTPR and the glucose level is linearly correlated with MAADP in IS patients. Besides, with the increase of glucose level tertiles, the incidence of clopidogrel HTPR increases gradually.

Thrombogenicity markers for early diagnosis and prognosis in COVID-19: a change from the current paradigm?

Standard biomarkers have been widely used for COVID-19 diagnosis and prognosis. We hypothesize that thrombogenicity metrics measured by thromboelastography will provide better diagnostic and prognostic utility versus standard biomarkers in COVID-19 positive patients. In this observational prospective study, we included 119 hospitalized COVID-19 positive patients and 15 COVID-19 negative patients. On admission, we measured standard biomarkers and thrombogenicity using a novel thromboelastography assay (TEG-6s). In-hospital all-cause death and thrombotic occurrences (thromboembolism, myocardial infarction and stroke) were recorded. Most COVID-19 patients were African--Americans (68%). COVID-19 patients versus COVID-19 negative patients had higher platelet-fibrin clot strength (P-FCS), fibrin clot strength (FCS) and functional fibrinogen level (FLEV) (P ≤ 0.003 for all). The presence of high TEG-6 s metrics better discriminated COVID-19 positive from negative patients. COVID-19 positive patients with sequential organ failure assessment (SOFA) score at least 3 had higher P-FCS, FCS and FLEV than patients with scores less than 3 (P ≤ 0.001 for all comparisons). By multivariate analysis, the in-hospital composite endpoint occurrence of death and thrombotic events was independently associated with SOFA score more than 3 [odds ratio (OR) = 2.9, P = 0.03], diabetes (OR = 3.3, P = 0.02) and FCS > 40 mm (OR = 3.4, P = 0.02).This largest observational study suggested the early diagnostic and prognostic utility of thromboelastography to identify COVID-19 and should be considered hypothesis generating. Our results also support the recent FDA guidance regarding the importance of measurement of whole blood viscoelastic properties in COVID-19 patients. Our findings are consistent with the observation of higher hospitalization rates and poorer outcomes for African--Americans with COVID-19.

Strength and deformability of fibrin clots: Biomechanics, thermodynamics, and mechanisms of rupture

Fibrin is the major determinant of the mechanical stability and integrity of blood clots and thrombi. To explore the rupture of blood clots, emulating thrombus breakage, we stretched fibrin gels with single-edge cracks of varying size. Ultrastructural alterations of the fibrin network correlated with three regimes of stress vs. strain profiles: the weakly non-linear regime due to alignment of fibrin fibers; linear regime owing to further alignment and stretching of fibers; and the rupture regime for large deformations reaching the critical strain and stress, at which irreversible breakage of fibers ahead of the crack tip occurs. To interpret the stress-strain curves, we developed a new Fluctuating Spring model, which maps the fibrin alignment at the characteristic strain, network stretching with the Young modulus, and simultaneous cooperative rupture of coupled fibrin fibers into a theoretical framework to obtain the closed-form expressions for the strain-dependent stress profiles. Cracks render network rupture stochastic, and the free energy change for fiber deformation and rupture decreases with the crack length, making network rupture more spontaneous. By contrast, mechanical cooperativity due to the presence of inter-fiber contacts strengthens fibrin networks. The results obtained provide a fundamental understanding of blood clot breakage that underlies thrombotic embolization. Statement of significanceFibrin, a naturally occurring biomaterial, is the major determinant of mechanical stability and integrity of blood clots and obstructive thrombi. We tested mechanically fibrin gels with single-edge cracks and followed ultrastructural alterations of the fibrin network. Rupture of fibrin gel involves initial alignment and elastic stretching of fibers followed by their eventual rupture for deformations reaching the critical level. To interpret the stress-strain curves, we developed Fluctuating Spring model, which showed that cracks render rupture of fibrin networks more spontaneous; yet, coupled fibrin fibers reinforce cracked fibrin networks. The results obtained provide fundamental understanding of blood clot breakage that underlies thrombotic embolization. Fluctuating Spring model can be applied to other protein networks with cracks and to interpret the stress-strain profiles.

Abstract 16780: Disease Severity Assessed by Thromboelastography in a Minority Population With COVID-19

Background: Thromboelastography (TEG®) is used across a wide range of clinical settings to identify patients at risk for thrombosis and coagulopathic bleeding and may be a useful diagnostic tool to guide antithrombotic treatment in patients with COVID-19. Hypothesis: TEG® identifies symptom progression in COVID -19 patients, particularly in the high-risk minority population known to have worse clinical outcomes. Methods: Whole blood from African American and Hispanic hospitalized COVID positive (n=22) and negative outpatients (n=24) was analyzed using point-of-care TEG®6s (Haemonetics, Corp). TEG® parameters including clot initiation (R), fibrin clot strength (FCS), platelet-fibrin clot strength (PFCS) and clot lysis (LY30) were compared across disease severity groups (table). Routine labs including D-Dimer, C-reactive protein (CRP), ferritin, and procalcitonin were also collected. Results: Ninety- five percent of COVID positive patients had at least one co-morbidity with the incidence of hypertension (73%), diabetes (55%), and obesity (45%) being the most frequent. R time was more rapid, and FCS and PFCS was significantly higher in COVID positive as compared to negative groups (p&lt;0.03). A stepwise increase in FCS and PFCS was observed with worsening respiratory function (table). Similarly, D-Dimer, CRP, ferritin, and procalcitonin levels were highest in patients receiving ventilator support. No differences were observed in clot lysis between the groups despite elevated D-Dimer levels. Conclusion: We have demonstrated that TEG®6s can identify a prothrombotic phenotype characterized by rapid clot initiation and increased fibrin and platelet-fibrin clot strength in a minority population with COVID-19. Future studies are warranted implementing the TEG6s® in clinical trials to personalize antithrombotic therapy in COVID-19 and improve outcomes.

Abstract 16676: Heightened Platelet Function: An Unrecognized Component of the Covid Hypercoagulability State

Introduction: Thrombo-inflammatory syndrome (TIS) characterized by a pathophysiological state of hypercoagulability, heightened platelet function, and inflammation has been observed in patients with acute myocardial infarction, and HIV. Hypothesis: The incidence of TIS is observed at a high rate in COVID-19 patients and worsens with symptom severity Methods: Blood samples from COVID-19 positive hospitalized patients (n=24) was collected for coagulation and platelet function analysis using point-of-care thromboelastography, TEG6s (Haemonetics, Corp) and routine labs were collected to measure markers of inflammation, coagulation, and organ damage (Table). Disease severity was grouped according to oxygen supplementation requirements and comparisons were made using unpaired t-test and chi-squared tests. Thrombo-inflammation was defined as the presence of both hypercoagulability by TEG [Clot initiation (R) &lt; 4.6, fibrin clot strength (FCS) &gt;32mm, and platelet fibrin clot strength (PFCS) &gt;69] and D-dimer &gt;ULN. Results: Ninety- five percent of COVID positive patients had at least one co-morbidity with the incidence of hypertension (71%), diabetes (50%), and obesity (42%) being the most frequent. A total of 63% (16/24) of patients had TIS, the incidence was significantly increased with escalating disease severity (p=0.03). A significant stepwise (p&lt;0.05) increase in FCS, D-Dimer, WBC count, lactate dehydrogenase, and procalcitonin was observed with worsening respiratory function (table). MA-ADP a measure of platelet function was in the high normal range for 81 % of patients. Conclusions: Thrombo-inflammatory is observed with most COVID patients, importantly heightened platelet function is a component of the syndrome and raises the question if antiplatelet therapy is needed in select COVID patients. Selective assessments with TEG6s may facilitate antithrombotic personalization.

Investigating the impact of M1 protein from Group A Streptococcus on fibrin clot formation, structure and fibrinolytic potential

Background: Fibrin formation is an essential part of innate immunity, sealing off infections to limit bacterial spreading.The surface-anchored M1 protein is a major virulence determinant of Group A streptococcus (GAS). During early infection M1 is cleaved from the cell surface by SpeB, a streptococcal protease regulated by CovR/S. M1 forms a supramolecular complex with fibrinogen however the impact on fibrin formation is not known. Methods: The effects of recombinant M1 (rM1) were assessed in fibrin clots made from plasma or purified fibrinogen incubated with thrombin, by confocal microscopy and scanning electron microscopy. Clotting and lysis profiles (with plasminogen activators and plasminogen) were investigated kinetically using thromboelastography (ROTEM). Results: rM1 (0.47-60 μg/ml) increased clotting rates to produce heterogeneous clots with irregular fibre bundles and compacted fibrin. Formation of the protective fibrin biofilm was also disrupted by rM1. Furthermore, mechanical strength of fibrin clots was reduced with increasing rM1 concentrations and was undetectable above 15.5 μg/ml. Purified and plasma clots formed with rM1 were more susceptible to lysis by plasmin, with a 1.4 – 2-fold reduction in lysis times. Conclusions: At sites of GAS infection, cleaved M1 may bind to fibrinogen generating fibrin clots which: lack the protective film at the clot surface; are mechanically weaker; and are less resistant to lysis by plasmin. GAS strains of M1-type are commonly associated with invasive infections; the impact of M1 on fibrin structure could contribute to the severity of GAS infection by compromising the fibrin barrier that limits bacterial proliferation and migration.

Tensile strength, growth factor content and proliferation activities for two platelet concentrates of platelet-rich fibrin and concentrated growth factor

Background/purposePlatelet-rich fibrin (PRF) can be obtained by centrifuging fresh blood in the absence of anticoagulants. Varying the centrifugation speeds may produce tougher and richer concentrated growth factors (CGF). This study examines tensile strength, growth factor content, and the potential of CGF and PRF in promoting periodontal cell proliferation. Materials and methodsBlood (40 mL/subject) was collected from 44 healthy subjects. PRF and CGF were prepared by centrifuging at 3000 rpm and switching speeds ranging within 3000 rpm, respectively. Fibrin strip was prepared and its tensile strength was measured. Transforming growth factor beta 1 (TGF-β1), platelet-derived growth factor BB (PDGF-BB), and epidermal growth factor (EGF) in the residual serum and fibrin clots were determined by enzyme-linked immunosorbent assay, and their effects on the proliferation of hFOB1.19 osteoblasts and human gingival fibroblasts were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. ResultsCompared with PRF, tensile strength of CGF was significantly higher. Concentrations and amounts of PDGF-BB and EGF in CGF were significantly higher than those in PRF. Osteoblast number was significantly higher in the cultures with fetal bovine serum (FBS, 10%) and with PRF or CGF fibrin clots (5%, 10%, and 50%) compared to that without FBS. Moreover, osteoblast number in CGF, regardless of the preparation of 10% and 50%, was significantly greater than that in PRF. Similar findings were also observed for gingival fibroblasts among the various subjects. ConclusionVarying centrifugation speeds can modify the tensile strength and biological activities of platelet fibrin clots.

The Impact of platelet-fibrin clot strength on occurrence and clinical outcomes of peripheral artery disease in patients with significant coronary artery disease.

Patients with peripheral artery disease (PAD) have shown the increased risk of cardiovascular (CV) morbidity and mortality. This study sought to evaluate the impact of clot strength on prevalence and major adverse CV events (MACE) of PAD in high-risk patients. We enrolled patients undergoing percutaneous coronary intervention (PCI) (n = 1667) with available platelet-fibrin clot strength [thrombin-induced maximal amplitude (MAthrombin) measured by thromboelastography] and inflammation [high sensitivity C-reactive protein (hs-CRP)]. PAD was defined with abnormal ankle-brachial index (≤ 0.9 or > 1.4). MACE was defined as a composite of CV death, myocardial infarction or stroke. PAD was observed in 201 patients (12.1%). In the multivariate analysis, high clot strength [MAthrombin ≥ 68mm: odds ratio (OR) 1.70, 95% confidence interval (CI) 1.20 to 2.41, p = 0.003] and enhanced inflammation (hs-CRP ≥ 3.0mg/L: OR 2.30, 95% CI 1.56 to 3.41, p < 0.001) were associated with PAD occurrence. During the follow-up post-PCI (median, 25months), MACE was more frequently occurred in patients with vs. without PAD (18.7% vs. 6.4% at 3years; hazard ratio 1.72, 95% CI 1.03 to 2.87, p = 0.039). Furthermore, combined presence of PAD and high clot strength significantly increased the risk of MACE. In conclusion, this study is the first to show the impact of clot strength on prevalence and clinical outcomes of PAD in coronary artery disease patients undergoing PCI. Whether antithrombotic strategy according to level of this biomarker can improve clinical outcomes in PAD patients deserves the further study.

Effect of Tranexamic Acid on Coagulation and Fibrin Clot Properties in Children Undergoing Craniofacial Surgery.

Craniosynostosis surgery in small children is very often associated with a high blood loss. Tranexamic acid (TXA) reduces blood loss during this procedure, although the potential underlying coagulopathy in these children is not known in detail. Objective was to determine the nature of any coagulopathy found during and after craniosynostosis surgery and to characterize the effect of TXA on fibrin clot formation, clot strength, and fibrinolysis. Thirty children received either TXA (bolus dose of 10 mg/kg followed by 8 hours continuous infusion of 3 mg/kg/h) or placebo. Dynamic whole blood clot formation assessed by thromboelastometry, platelet count, dynamic thrombin generation/thrombin-antithrombin, clot lysis assay, and fibrinogen/factor XIII (FXIII) levels were measured. Additionally, clot structure was investigated by real-time live confocal microscopy and topical data analysis. Increased ability of thrombin generation was observed together with a tendency toward shortened activated partial thromboplastin time and clotting time. Postoperative maximum clot firmness was higher among children receiving TXA. FXIII decreased significantly during surgery in both groups.Resistance toward tissue plasminogen activator-induced fibrinolysis was higher in children that received TXA, as evidenced by topical data analysis and by a significant longer lysis time. Fibrinogen levels were higher in the TXA group at 24 hours. A significant coagulopathy mainly characterized by changes in clot stability and not parameters of thrombin generation was reported. Tranexamic acid improved clot strength and reduced fibrinolysis, thereby avoiding reduction in fibrinogen levels.

P741Next generation miRNA sequencing and changes in coagulation measured by thrombelastography (TEG) in patients with cardiovascular disease

Abstract Background Thrombelastography (TEG), an ex-vivo clotting assay can identify subjects at high risk of subsequent coronary thrombotic events. Synthesis of clotting factors is subject to post-translational regulation, which is modulated at least in part by miRNA. Hypothesis We hypothesized that miRNA sequencing may identify specific miRNA linked with measures of hypercoaguability by TEG. Methods Kaolin activated thrombelastography was performed in platelet poor citrate plasma from 61 subjects referred for cardiac catheterization. Time to clot formation (R), clot stabilization time (K), and maximal fibrin clot strength (MA) was measured. Next generation miRNA sequencing was done from RNA isolated from whole blood samples, which includes miRNA derived from leukocytes and platelets. Prediction of miRNA gene targets was performed with targetscan. Results Sequencing resulted in quantification of 371 distinct miRNA from whole blood samples. We found 13 miRNA correlating with alteration in TEG-R, 33 miRNA correlating with TEG-K, and 21 miRNA correlating with TEG-MA. Coagulation factors or genes associated with coagulation were found to be among predicted targets in 49 out of these 67 miRNA. Most common predicted targets included factors II, V, VII, X, XIII, fibrinogen, plasminogen-activator inhibitor, and tissue factor. Factor XIIIA1 was highly conserved gene target by miR-96-5p (one of only 3miRNA predicted for this gene). MiR-96-5p correlated with clot stabilization time (ρ=-0.26, p=0.047) which has been shown to be dependent on FXIIIa activity. MiR-22-3p was significantly correlated with TEG-K (ρ=0.28, p=0.034) and was only miRNA with highly conserved target site for prothrombin (Factor II). Conclusions In patients with cardiovascular disease miRNA sequencing combined with coagulation phenotype in silico analysis may identify novel links to coagulation that are associated with increased thrombotic risk. Acknowledgement/Funding Charles Fisch Cardiovascular Research Award endowed by S. Knoebel

Does Tranexamic Acid Improve Clot Strength in Severely Injured Patients Who Have Elevated Fibrin Degradation Products and Low Fibrinolytic Activity, Measured by Thrombelastography?

Elevated d-dimers in injured patients with paradoxically low fibrinolysis activity measured by viscoelastic assays have been speculated to be "occult" fibrinolysis. However, an alternative explanation is that these patients have previously activated their fibrinolytic system and have shut it down by the time of blood draw, and would gain no benefit in clot strength with tranexamic acid (TXA). We hypothesize that TXA will not increase clot strength in injured patients with low fibrinolytic activity measured by thrombelastography (TEG), despite biomarkers of fibrinolysis activation. Three TEG assays (rapid, tissue plasminogen activator, and functional fibrinogen) were run on trauma patients. The tissue plasminogen activator TEG served as a functional assay to quantify depletion of fibrinolysis inhibitors (DFI). Patients were stratified by DFI vs non-DFI and then by rapid TEG lysis at 30 minutes phenotype cutoffs. Response to TXA was evaluated with functional fibrinogen TEG by calculating percent change in clot strength with the addition of exogenous TXA in the TEG cup. Six hundred and thirty patients with a median new injury severity score of 20 were analyzed. Depletion of fibrinolysis inhibitors was present in 116 (18%). The DFI patients had significantly increased d-dimer (p < 0.001) and lower fibrinogen (p < 0.001). The DFI patients had increased rates of massive transfusion (33% vs 3.3%; p < 0.001) and mortality (40% vs 6.2%; p < 0.001). Among DFI patients, TXA significantly improved fibrin clot strength with hyperfibrinolysis (+19% clot strength; p < 0.001) but not with shutdown (+1.2%) or physiologic (-2.5%). Patients with DFI have multiple abnormalities of their coagulation system, but only DFI patients with hyperfibrinolysis have improved fibrin clot strength with TXA.

Contractile forces in platelet aggregates under microfluidic shear gradients reflect platelet inhibition and bleeding risk

Platelets contract forcefully after their activation, contributing to the strength and stability of platelet aggregates and fibrin clots during blood coagulation. Viscoelastic approaches can be used to assess platelet-induced clot strengthening, but they require thrombin and fibrin generation and are unable to measure platelet forces directly. Here, we report a rapid, microfluidic approach for measuring the contractile force of platelet aggregates for the detection of platelet dysfunction. We find that platelet forces are significantly reduced when blood samples are treated with inhibitors of myosin, GPIb-IX-V, integrin αIIbβ3, P2Y12, or thromboxane generation. Clinically, we find that platelet forces are measurably lower in cardiology patients taking aspirin. We also find that measuring platelet forces can identify Emergency Department trauma patients who subsequently require blood transfusions. Together, these findings indicate that microfluidic quantification of platelet forces may be a rapid and useful approach for monitoring both antiplatelet therapy and traumatic bleeding risk.

Prediction of Ischemic Events after Percutaneous Coronary Intervention: Thrombelastography Profiles and Factor XIIIa Activity.

Background High plasma fibrin clot strength (MA) measured by thrombelastography (TEG) is associated with increased risk of cardiac events after percutaneous coronary interventions (PCIs). Factor XIIIa (FXIIIa) cross-links soluble fibrin, shortens clot formation time (TEG-K), and increases final clot strength (MA). Methods We analyzed platelet-poor plasma from patients with previous PCI. Kaolin-activated TEG (R, K, MA) in citrate platelet-poor plasma and FXIIIa were measured ( n = 257). Combined primary endpoint was defined as recurrent myocardial infarction (MI) or cardiovascular death (CVD). Relationship of FXIIIa and TEG measurements on cardiac risk was explored. Results FXIIIa correlated with TEG-MA ( p = 0.002) and inversely with TEG-K ( p < 0.001). High MA (≥35.35 mm; p = 0.001), low K (<1.15 min; p = 0.038), and elevated FXIIIa (≥83.51%; p = 0.011) were associated with increased risk of CVD or MI. Inclusion of FXIIIa activity and low TEG-K in risk scores did not improve risk prediction as compared with high TEG-MA alone. Conclusion FXIIIa is associated with higher plasma TEG-MA and low TEG-K. High FXIIIa activity is associated with a modest increase in cardiovascular risk after PCI, but is less sensitive and specific than TEG-MA. Addition of FXIIIa does not provide additional risk stratification beyond risk associated with high fibrin clot strength phenotype measured by TEG.

Fibrin Clot Strength in Patients with Diabetes Mellitus Measured by Thrombelastography.

Background Patients with diabetes mellitus (DM) exhibit increased risk of recurrent myocardial infarction. Maximal clot strength measured by thrombelastography (TEG) is a risk factor for recurrent ischemic events. We hypothesized that diabetic subjects exhibit increased fibrin clot strength in platelet-poor plasma and that glycemic control correlates with maximal fibrin clot strength. Methods We collected plasma samples from subjects with known or suspected coronary artery disease undergoing cardiac catheterization (n = 354). We measured kaolin-activated TEG in platelet-poor citrate plasma. Time to fibrin formation (R), clot formation time (K), and maximal fibrin clot strength (MA) were recorded. Results Plasma fibrin MA was increased among subjects with DM (n = 152) as compared to non-DM (n = 202) (37.0 ± 8 versus 34.1 ± 8 mm; p < 0.001). Hemoglobin A1c (HbA1c) (ρ = 0.22; p = 0.001) and fibrinogen (ρ = 0.29; p < 0.001) correlated with fibrin MA. In multivariable regression analysis, DM remained significantly associated with plasma MA after adjustment for fibrinogen level (p = 0.003). Conclusions Subjects with diabetes mellitus exhibit increased maximal fibrin clot strength measured by TEG in platelet-poor plasma.

Gastroesophageal variceal bleeding in cirrhotic patients: the possibilities of effective hemostasis

To improve the results of treatment of gastroesophageal variceal bleeding (GEVB) in cirrhotic patients with thrombocytopenia. A total experience of the clinic includes 338 GEVB patients, endoscopic variceal ligation (EVL) and transjugular intrahepatic portosystemic shunt (TIPS) were performed in 162 and 157 cases respectively. Nevertheless, just the efficacy of initial pharmacological hemostatic therapy was analyzed. Administration of serotonin adipinate 30-50 mg/day during 3-5 days in addition to standard initial therapy allowed us to achieve permanent hemostasis during initial treatment if EVL was impossible. Serotonin adipinate induces thrombocytes' adhesion and improves fibrin clot strength. This therapy markedly decreases mortality (33.3% vs 46.7%), incidence of recurrent bleeding (46.4% vs 60.0%). Also it contributes successful hemostasis with endoscopic ligation and effective portal decompression by TIPS procedure.

Thromboelastography for predicting bleeding in patients with aortic stenosis treated with transcatheter aortic valve implantation.

Bleeding complications are frequent and independently impact mortality after transcatheter aortic valve implantation (TAVI). Thromboelastography (TEG) measures viscoelastic properties of clot formation and is currently best known for perioperative management to reduce blood transfusion in cardiac surgery. We sought to determine whether TEG may be predictive of bleeding in patients treated with TAVI. Overall, 54 consecutive patients with severe aortic stenosis treated with TAVI were prospectively included. In all patients, two blood samples were obtained for TEG measurement (the first - 12 h prior to procedure tested with citrated kaolin [CK] TEG assay, and the second - immediately after prosthesis deployment tested with CK and citrated heparinised kaolin assay [CHK]). Major or life-threatening bleeding (MLTB) was diagnosed in 13 (24%) patients. In receiver-operating characteristic (ROC) curve analysis the only TEG parameters showing significant sensitivity and specific-ity for predicting MLTB were those obtained in the CK sample at the end of the procedure: R value (reaction time, time to initiation of clot formation) area under the curve (AUC) 0.69, 95% confidence interval (CI) 0.49-0.88, p = 0.04; angle (the rate of clot formation), AUC 0.75, 95% CI 0.59-0.92, p = 0.007, and maximum amplitude (MA, ultimate strength of fibrin clot), AUC 0.77, 95% CI 0.62-0.93, p = 0.003. After controlling for confounding factors on multivariate logistic regression, MA remained as the only TEG parameter that significantly correlated with bleeding after TAVI, both as a continuous variable (p = 0.004; 95% CI 0.92-0.98; odds ratio [OR] 0.95 per 1 mm increment) and after using the cut-off value derived from ROC analysis; MA < 46.6 mm (OR 10.4; 95% CI 2.1-51.8; p = 0.004). Low strength of fibrin clot measured by TEG immediately after TAVI may serve as an independent predictor of short-term major and life-threatening bleeding complications.