Early abnormal fibrinolysis and mortality in patients with thermal injury: a prospective cohort study.

INTRODUCTION: Abnormal fibrinolysis early after injury has been associated with increased mortality in trauma patients, but no studies have addressed patients with burn injury. This prospective cohort study aimed to characterize fibrinolytic phenotypes in burn patients and to see if they were associated with mortality. METHODS: Patients presenting to a regional burn centre within 4 h of thermal injury were included. Blood was collected for sequential viscoelastic measurements using thromboelastography (RapidTEG™) over 12 h. The percentage decrease in clot strength 30 min after the time of maximal clot strength (LY30) was used to categorize patients into hypofibrinolytic/fibrinolytic shutdown (SD), physiological (PHYS) and hyperfibrinolytic (HF) phenotypes. Injury characteristics, demographics and outcomes were compared. RESULTS: Of 115 included patients, just over two thirds were male. Overall median age was 40 (i.q.r. 28-57) years and median total body surface area (TBSA) burn was 13 (i.q.r. 6-30) per cent. Some 42 (36.5 per cent) patients had severe burns affecting over 20 per cent TBSA. Overall mortality was 18.3 per cent. At admission 60.0 per cent were PHYS, 30.4 per cent were SD and 9.6 per cent HF. HF was associated with increased risk of mortality on admission (odds ratio 12.61 (95 per cent c.i. 1.12 to 142.57); P = 0.041) but not later during the admission when its incidence also decreased. Admission SD was not associated with mortality, but incidence increased and by 4 h and beyond, SD was associated with increased mortality, compared with PHYS (odds ratio 8.27 (95 per cent c.i. 1.16 to 58.95); P = 0.034). DISCUSSION: Early abnormal fibrinolytic function is associated with mortality in burn patients.

Mathematical model of thrombin generation and bleeding phenotype in Amish carriers of Factor IX:C deficiency vs. controls.

INTRODUCTION: Factor IX:C (FIX:C) levels vary in hemophilia B carriers even in pedigrees with a unifying genetic defect. Analyzing the balance between pro-and anticoagulants might increase our understanding of carriers' bleeding potential. AIM: In this research study, we evaluated bleeding scores (BS) and a novel mathematical model of thrombin generation (TG) in Amish FIX:C deficient carriers and controls. METHODS: Blood samples and BS were obtained from post-menarchal females, including 59 carriers and 57 controls from the same extended pedigree. Factors II, V, VII, VIII, IX, X, antithrombin, tissue factor pathway inhibitor and protein C were assayed to generate mathematical models of TG in response to 5pM tissue factor (TF) and for TF + thrombomodulin. BS was based on a modification of the MCMDM-1VWD scoring system. RESULTS: Carriers had a lower mean FIX:C (68% vs. 119%), von Willebrand factor antigen (108 vs.133) and Tissue activatable fibrinolysis inhibitor (103 vs. 111) compared to controls; both groups had a similar mean BS. Carriers demonstrated significantly lower TG parameters on both mathematical models compared to controls. Carriers with FIX:C ≤ 50% had lower TG curves than those >50% but similar BS. CONCLUSION: Thrombin generation showed significant differences between carriers and controls, between low (≤50%) and high (>50%) FIX:C carriers, and specifically in the TF + thrombomodulin model, between high FIX:C carriers and controls, although the BS were not different.

Effects of an acidic environment on coagulation dynamics.

Essentials Acidosis, an outcome of traumatic injury, has been linked to impaired procoagulant efficiency. In vitro model systems were used to assess coagulation dynamics at pH 7.4 and 7.0. Clot formation dynamics are slightly enhanced at pH 7.0 in blood ex vivo. Acidosis induced decreases in antithrombin efficacy offset impairments in procoagulant activity. SUMMARY: Background Disruption of hydrogen ion homeostasis is a consequence of traumatic injury often associated with clinical coagulopathy. Mechanisms by which acidification of the blood leads to aberrant coagulation require further elucidation. Objective To examine the effects of acidified conditions on coagulation dynamics using in vitro models of increasing complexity. Methods Coagulation dynamics were assessed at pH 7.4 and 7.0 as follows: (i) tissue factor (TF)-initiated coagulation proteome mixtures (±factor [F]XI, ±fibrinogen/FXIII), with reaction progress monitored as thrombin generation or fibrin formation; (ii) enzyme/inhibitor reactions; and (iii) TF-dependent or independent clot dynamics in contact pathway-inhibited blood via viscoelastometry. Results Rate constants for antithrombin inhibition of FXa and thrombin were reduced by ~ 25-30% at pH 7.0. At pH 7.0 (+FXI), TF-initiated thrombin generation showed a 20% increase in maximum thrombin levels and diminished thrombin clearance rates. Viscoelastic analyses showed a 25% increase in clot time and a 25% reduction in maximum clot firmness (MCF). A similar MCF reduction was observed at pH 7.0 when fibrinogen/FXIII were reacted with thrombin. In contrast, in contact pathway-inhibited blood (n = 6) at pH 7.0, MCF values were elevated 6% (95% confidence interval [CI]: 1%-11%) in TF-initiated blood and 15% (95% CI: 1%- 29%) in the absence of TF. Clot times at pH 7.0 decreased 32% (95% CI: 15%-49%) in TF-initiated blood and 51% (95% CI: 35%-68%) in the absence of TF. Conclusions Despite reported decreased procoagulant catalysis at pH 7.0, clot formation dynamics are slightly enhanced in blood ex vivo and suppression of thrombin generation is not observed. A decrease in antithrombin reactivity is one potential mechanism contributing to these outcomes.

Thrombin generation and bleeding in haemophilia inhibitor patients during immune tolerance induction.

BACKGROUND: Inhibitor formation complicates haemophilia treatment and requires immune tolerance induction to rid inhibitors over 5 BU. In the prospective, randomized International Immune Tolerance Study, immune tolerance induction was equally effective with high-dose (HD) (200 IU kg-1 day-1 ) and low-dose (LD) (50 IU kg-1 3× per week) factor VIII, but haemorrhages were twofold higher in the LD arm. This finding was unexpected as inhibitors neutralize FVIII activity. We hypothesized that the thrombin generation assay (TGA), a global measure of clot formation, might predict bleeding better than FVIII levels. METHODS: We evaluated TGA using relipidated tissue factor (TF) on 83 thawed, recalcified corn trypsin inhibitor/citrate plasma samples from 31 subjects (17 HD, 14 LD) who participated on the ITI study, and who had sufficient sample available and appropriate informed consent. RESULTS: There were no significant differences in peak thrombin, estimated thrombin potential, maximum rate or lag time between HD and LD arms; between pre-, during and post-ITI time points, or after FVIII spiking. In 19 subjects (12 HD, 7 LD) with anti-FVIII<1.0 BU, the prevalence of non-neutralizing antibody (NNA) and neutralizing antibody (NA) was 89.5% (17/19), and the latter strongly correlated with anti-VIII titer, r = 0.73 [95% CI: 0.55, 0.88]. CONCLUSION: In haemophilia inhibitor patients, thrombin generation is present, but does not predict bleeding risk. Following tolerance induction, NNA remains detectable in the majority.

Why does aspirin decrease the risk of venous thromboembolism? On old and novel antithrombotic effects of acetyl salicylic acid.

It is well established that aspirin, an irreversible inhibitor of platelet cyclooxygenase activity, is effective in secondary prevention of arterial thromboembolic events. The pooled results of the recent randomized, multicenter WARFASA and ASPIRE aspirin trials showed a 32% reduction in the rate of recurrence of venous thromboembolism (VTE) in patients receiving aspirin following VTE. These clinical data support evidence that platelets contribute to the initiation and progression of venous thrombosis and aspirin inhibits thrombin formation and thrombin-mediated coagulant reactions. In addition to the known acetylation of serine 529 residue in platelet cyclooxygenase-1, the postulated mechanisms of aspirin-induced antithrombotic actions also involve the acetylation of other proteins in blood coagulation, including fibrinogen, resulting in more efficient fibrinolysis. This review summarizes current knowledge on the aspirin-induced antithrombotic effects that potentially explain clinical studies showing reduced rates of VTE events in aspirin-treated subjects.

Anticoagulant effects of statins and their clinical implications.

There is evidence indicating that statins (3-hydroxy-methylglutaryl coenzyme A reductase inhibitors) may produce several cholesterol-independent antithrombotic effects. In this review, we provide an update on the current understanding of the interactions between statins and blood coagulation and their potential relevance to the prevention of venous thromboembolism (VTE). Anticoagulant properties of statins reported in experimental and clinical studies involve decreased tissue factor expression resulting in reduced thrombin generation and attenuation of pro-coagulant reactions catalysed by thrombin, such as fibrinogen cleavage, factor V and factor XIII activation, as well as enhanced endothelial thrombomodulin expression, resulting in increased protein C activation and factor Va inactivation. Observational studies and one randomized trial have shown reduced VTE risk in subjects receiving statins, although their findings still generate much controversy and suggest that the most potent statin rosuvastatin exerts the largest effect.

Models for thrombin generation and risk of disease.

Computational models can offer an integrated view of blood clotting dynamics and may ultimately be instructive regarding an individual's risk of bleeding or clotting. Appropriately, developed and validated models could allow clinicians to simulate the outcomes of therapeutics and estimate risk of disease. Computational models that describe the dynamics of thrombin generation have been developed and have been used in combination with empirical studies to understand thrombin dynamics on a mechanistic basis. The translation of an individual's specific coagulation factor composition data using these models into an integrated assessment of hemostatic status may provide a route for advancing the long-term goal of individualized medicine. This review details the integrated approaches to understanding: (i) What is normal thrombin generation in individuals? (ii) What is the effect of normal range plasma composition variation on thrombin generation in pathologic states? (iii) Can disease progression or anticoagulation be followed by understanding the boundaries of normal thrombin generation defined by plasma composition? (iv) What are the controversies and limitations of current computational approaches? Progress in these areas can bring us closer to developing models that can be used to aid in identifying hemostatic risk.

Characteristics of fibrin formation and clot stability in individuals with congenital type IIb protein C deficiency.

Many studies have shown that unregulated or excessive thrombin formation is potentially a cause of thrombosis; however, studies examining processes that contribute to fibrin stabilization in individuals predisposed to thrombosis are limited. In this study, we investigate a family with familial thrombosis via type IIb protein C (PC) deficiency. Using contact pathway inhibited whole blood, thrombin generation, fibrin clot formation and factor (f)XIII activation were monitored over time in control (n=5) and PC deficient (n=4, 34 - 69% PC by activity) subjects. The dynamics of thrombin generation varied significantly with the time required to reach the maximal rate of thrombin-antithrombin formation being much shorter in PC deficiency (5.8 ± 0.4 minutes) than in controls (9.7 ± 0.4 minutes; p < 0.001). PC deficient clots were significantly heavier than control clots (p < 0.001) and this difference could not be contributed exclusively to differences in fibrinogen levels between groups. FXIII was consumed faster in PC deficient subjects (23.7 ± 2.0 nM/minute) than in controls (5.1 ± 1.5 nM/minute; p < 0.0001) suggesting increased fXIII activation and incorporation of fXIIIa substrates into the clot. In plasma, the clot lysis time was increased in PC deficiency by both TAFIa dependent and independent mechanisms. Since PC deficient clots are both denser and show a greater degree of resistance to fibrinolysis, these clots would likely resist fibrinolysis and potentiate fibrin deposition observed in thrombosis.

Measuring the mechanical properties of blood clots formed via the tissue factor pathway of coagulation.

Thrombelastography (TEG) is a method that is used to conduct global assays that monitor fibrin formation and fibrinolysis and platelet aggregation in whole blood. The purpose of this study was to use a well-characterized tissue factor (Tf) reagent and contact pathway inhibitor (corn trypsin inhibitor, CTI) to develop a reproducible thrombelastography assay. In this study, blood was collected from 5 male subjects (three times). Clot formation was initiated in whole blood with 5 pM Tf in the presence of CTI, and fibrinolysis was induced by adding tissue plasminogen activator (tPA). Changes in viscoelasticity were then monitored by TEG. In quality control assays, our Tf reagent, when used at 5 pM, induced coagulation in whole blood in 3.93 ± 0.23 min and in plasma in 5.12 ± 0.23 min (n=3). In TEG assays, tPA significantly decreased clot strength (maximum amplitude, MA) in all individuals but had no effect on clot time (R time). The intraassay variability (CVa<10%) for R time, angle, and MA suggests that these parameters reliably describe the dynamics of fibrin formation and degradation in whole blood. Our Tf reagent reproducibly induces coagulation, making it an ideal tool to quantify the processes that contribute to mechanical clot strength in whole blood.

The influence of prophylactic factor VIII in severe haemophilia A.

Haemophilia A individuals displaying a similar genetic defect have heterogeneous clinical phenotypes. Our objective was to evaluate the underlying effect of exogenous factor (f)VIII on tissue factor (Tf)-initiated blood coagulation in severe haemophilia utilizing both empirical and computational models. We investigated twenty-five clinically severe haemophilia A patients. All individuals were on fVIII prophylaxis and had not received fVIII from 0.25 to 4 days prior to phlebotomy. Coagulation was initiated by the addition of Tf to contact-pathway inhibited whole blood ± an anti-fVIII antibody. Aliquots were quenched over 20 min and analyzed for thrombin generation and fibrin formation. Coagulation factor levels were obtained and used to computationally predict thrombin generation with fVIII set to either zero or its value at the time of the draw. As a result of prophylactic fVIII, at the time of the blood draw, the individuals had fVIII levels that ranged from <1% to 22%. Thrombin generation (maximum level and rate) in both empirical and computational systems increased as the level of fVIII increased. FXIII activation rates also increased as the fVIII level increased. Upon suppression of fVIII, thrombin generation became comparable in both systems. Plasma composition analysis showed a negative correlation between bleeding history and computational thrombin generation in the absence of fVIII. Residual prophylactic fVIII directly causes an increase in thrombin generation and fibrin cross-linking in individuals with clinically severe haemophilia A. The combination of each individual's coagulation factors (outside of fVIII) determine each individual's baseline thrombin potential and may affect bleeding risk.

Thrombin activatable fibrinolysis inhibitor activation and bleeding in haemophilia A.

Individuals with haemophilia A exhibit bleeding tendencies that are not always predicted by their factor (F)VIII level. It has been suggested that bleeding in haemophilia is due not only to defective prothrombin activation but also aberrant fibrinolysis. Thrombin activatable fibrinolysis inhibitor (TAFI) activation was measured in tissue factor (TF)-initiated blood coagulation in blood samples of 28 haemophiliacs and five controls. Reactions were quenched over time with FPRck and citrate and assayed for TAFIa and thrombin-antithrombin (TAT). The TAFIa potential (TP), TAFI activation rate and the TAFIa level at 20 min (TAFIa(20 min)) was extracted from the TAFI activation progress curve. In general, the time course of TAFI activation follows thrombin generation regardless of FVIII activity and as expected the rate of TAFI activation and TP decreases as FVIII decreases. The magnitude of TP was similar among the control subjects and subjects with <11% FVIII. In severe subjects with <1% FVIII at the time of blood collection, the TAFIa(20 min) was inversely and significantly correlated with haemarthrosis (-0.77, P = 0.03) and total bleeds (-0.75, P = 0.03). In all cases, TAFIa(20 min) was more strongly correlated with bleeding than TAT levels at 20 min. Overall, this study shows that TAFI activation in whole blood can be quantified and related to the clinical bleeding phenotype. Measuring TAFIa along with thrombin generation can potentially be useful to evaluate the differential bleeding phenotype in haemophilia A.

Activated protein C inhibitor for correction of thrombin generation in hemophilia A blood and plasma1.

BACKGROUND: Replacement therapy for hemophilic patient treatment is costly, because of the high price of pharmacologic products, and is not affordable for the majority of patients in developing countries. OBJECTIVE: To generate and evaluate low molecular weight agents that could be useful for hemophilia treatment. METHODS: Potential agents were generated by synthesizing specific inhibitors [6-(Lys-Lys-Thr-[homo]Arg)amino-2-(Lys[carbobenzoxy]-Lys[carbobenzoxy]-O-benzyl)naphthalenesulfonamide] (PNASN-1)] for activated protein C (APC) and tested in plasma and fresh blood from hemophilia A patients. RESULTS: In the activated partial thromboplastin time-based APC resistance assay, PNASN-1 partially neutralized the effect of APC. In calibrated automated thrombography, PNASN-1 neutralized the effect of APC on thrombin generation in normal and congenital factor VIII-deficient plasma (FVIII:C < 1%). The addition of PNASN-1 to tissue factor-triggered (5 pm) contact pathway-inhibited fresh blood from 15 hemophilia A patients with various degrees of FVIII deficiency (FVIII:C < 1-51%) increased the maximum level of thrombin generated from 78 to 162 nm, which approached that observed in blood from a healthy individual (201 nm). PNASN-1 also caused a 47% increase in clot weight in hemophilia A blood. CONCLUSIONS: Specific APC inhibitors compensate to a significant extent for FVIII deficiency, and could be used for hemophilia treatment.

Anticoagulation by factor Xa inhibitors.

BACKGROUND: Therapeutic agents that regulate blood coagulation are critical to the management of thrombotic disorders, with the selective targeting of factor (F) Xa emerging as a promising approach. OBJECTIVE: To assess anticoagulant strategies targeting FXa. METHODS: A deterministic computational model of tissue factor (Tf)-initiated thrombin generation and two empirical experimental systems (a synthetic coagulation proteome reconstruction using purified proteins and a whole blood model) were used to evaluate clinically relevant examples of the two available types of FXa-directed anticoagulants [an antithrombin (AT)-dependent agent, fondaparinux, and an AT-independent inhibitor, Rivaroxaban] in experimental regimens relevant to long-term (suppression of new Tf-initiated events) and acute (suppression of ongoing coagulation processes) clinical applications. RESULTS: Computational representations of each anticoagulant's efficacy in suppressing thrombin generation over a range of anticoagulant concentrations in both anticoagulation regimens were validated by results from corresponding empirical reconstructions and were consistent with those recommended for long-term and acute clinical applications, respectively. All three model systems suggested that Rivaroxaban would prove more effective in the suppression of an ongoing coagulation process than fondaparinux, reflecting its much higher reactivity toward the prothrombinase complex. CONCLUSION: The success of fondaparinux in acute settings in vivo is not explained solely by its properties as an FXa inhibitor. We have reported that FIXa contributes to the long-term capacity of clot-associated catalysts to restart a coagulation process, suggesting that the enhanced anti-FIXa activity of fondaparinux-AT may be critical to its success in acute settings in vivo.

Empirical and theoretical phenotypic discrimination.

We have developed an integrated approach that combines empirical and computational methodologies to define an individual's thrombin phenotype. We have evaluated the process of thrombin generation in healthy individuals and individuals with defined pathologies in order to develop general criteria relevant to assess an individual's propensity for hemorrhage or thrombosis. Three complementary hypotheses have emerged from our work: (i) compensation by the ensemble of other coagulation proteins in individuals with specific factor deficiencies can 'normalize' an individual's thrombin generation process and represents a rationale for their unexpected phenotype; (ii) individuals with clinically unremarkable factor levels may present thrombin generation profiles typical of individuals with hemostatic complications; and (iii) in some hemostatic disorders a specific pattern of expression of a small ensemble of coagulation factors may be sufficient to explain the overall phenotype.

Thrombin generation and bleeding in haemophilia A.

Haemophilia A displays phenotypic heterogeneity with respect to clinical severity. The aim of this study was to determine if tissue factor (TF)-initiated thrombin generation profiles in whole blood in the presence of corn trypsin inhibitor (CTI) are predictive of bleeding risk in haemophilia A. We studied factor(F) VIII deficient individuals (11 mild, 4 moderate and 12 severe) with a well-characterized 5-year bleeding history that included haemarthrosis, soft tissue haematoma and annual FVIII concentrate usage. This clinical information was used to generate a bleeding score. The bleeding scores (range 0-32) were separated into three groups (bleeding score groupings: 0, 0 and < or = 9.6, >9.6), with the higher bleeding tendency having a higher score. Whole blood collected by phlebotomy and contact pathway suppressed by 100 microg mL(-1) CTI was stimulated to react by the addition of 5 pM TF. Reactions were quenched at 20 min by inhibitors. Thrombin generation, determined by enzyme-linked immunosorbent assay for thrombin-antithrombin was evaluated in terms of clot time (CT), maximum level (MaxL) and maximum rate (MaxR) and compared to the bleeding score. Data are shown as the mean+/-SD. MaxL was significantly different (P < 0.001) between the groups: 504 +/- 114, 315 +/- 117 and 194 +/- 91 nM; with higher thrombin concentrations in the groups with lower bleeding scores. MaxR was higher in the groups with a lower bleeding score; 97 +/- 51, 86 +/- 60 and 39 +/- 16 nM min(-1) (P = 0.09). No significant difference was detected in CT among the groups, 5.6 +/- 1.3, 4.7 +/- 0.7 and 5.6 +/- 1.3 min. Our empirical study in CTI-inhibited whole blood shows that the MaxL of thrombin generation appears to correlate with the bleeding phenotype of haemophilia A.

Discordant fibrin formation in hemophilia.

BACKGROUND: The conversion of fibrinogen to fibrin and its crosslinking to form a stable clot are key events in providing effective hemostasis. OBJECTIVES: To evaluate the relationship of fibrinopeptide (FP) release and factor (F) XIII activation in whole blood from hemophiliacs. PATIENTS/METHODS: We investigated FPA and FPB release, FXIII activation and fibrin mass in tissue factor-initiated coagulation in whole blood from individuals with hemophilia and healthy subjects. RESULTS: In hemophiliacs, the rates of fibrin formation were delayed as compared to healthy individuals. FPA/FPB release and FXIII activation were decreased in hemophiliacs vs. healthy individuals: 5.4 +/- 0.7 microM min(-1) to 1.7 +/- 0.4 microM min(-1) (P = 0.003), 2.3 +/- 0.6 microM min(-1) to 0.5 +/- 0.1 microM min(-1) (P = 0.025), and 12.1 +/- 0.7 nM min(-1) to 3.1 +/- 0.7 nM min(-1) (P < 0.0005), respectively. More FPA was released in hemophiliacs (6.6 +/- 1.2 microM) prior to clot time (CT) than in healthy individuals (2.6 +/- 0.4 microM, P = 0.013), whereas FPB and activated FXIII levels remained comparable. FXIII activation, which normally coincides with FPA release, was delayed in hemophiliacs. At CT in normal blood, the FPA concentration was 2.6-fold higher than that of FPB (P = 0.003), whereas in hemophiliacs this ratio was increased to 6.6-fold (P = 0.001). CONCLUSIONS: These data suggest that essential dynamic correlations exist between the presentations of fibrin I, fibrin II, and FXIIIa. The 'discordance' of fibrin formation in hemophiliacs results in clots that are more soluble than normal (43% lower mass; P = 0.02). The resulting poor physical clot strength probably plays a crucial role in the pathology of hemophilia.

Blood coagulation dynamics in haemostasis.

Our studies involve computational simulations, a reconstructed plasma/platelet proteome, whole blood in vitro and blood exuding from microvascular wounds. All studies indicate that in normal haemostasis, the binding of tissue factor (TF) with plasma factor (F) VIIa (extrinsic FXase complex) results in the initiation phase of the procoagulant response. This phase is negatively regulated by tissue factor pathway inhibitor (TFPI) in combination with antithrombin (AT) and the protein C (PC) pathway. The synergy between these inhibitors provides a threshold-limited reaction in which a stimulus of sufficient magnitude must be provided for continuation of the reaction. With sufficient stimulus, the FXa produced activates some prothrombin. This initial thrombin activates the procofactors and platelets required for presentation of the intrinsic FXase (FVIIIa-FIXa) and prothrombinase (FVa-FXa) complexes which drive the subsequent propagation phase; continuous downregulation of which is provided by AT and the thrombin-thrombomodulin-PC complex. FXa generation during the propagation phase is largely (>90%) provided by the intrinsic FXase complex. TF is required for the initiation phase of the reaction but becomes non-essential once the propagation phase has been achieved. The propagation phase catalysts (FVIIIa-FIXa and FVa-FXa) continue to drive the reaction as blood is resupplied to the wound site by flow. Ultimately, the control of the reaction is governed by the pro- and anticoagulant dynamics and the supply of blood reactants to the site of a perforating injury. Our systems have been utilized to examine the qualities of hypothetical and novel antihaemorrhagic and anticoagulation agents and in epidemiologic studies of venous and arterial thrombosis and haemorrhagic pathology.

Thrombin generation in acute coronary syndrome and stable coronary artery disease: dependence on plasma factor composition.

BACKGROUND: Acute coronary syndrome (ACS) is associated with thrombin formation, triggered by ruptured or eroded coronary atheroma. We investigated whether thrombin generation based on circulating coagulation protein levels, could distinguish between acute and stable coronary artery disease (CAD). METHODS AND RESULTS: Plasma coagulation factor (F) compositions from 28 patients with ACS were obtained after onset of chest pain. Similar data were obtained from 25 age- and sex-matched patients with stable CAD. All individuals took aspirin. Patients on anticoagulant therapy were excluded. The groups were similar in demographic characteristics, comorbidities and concomitant treatment. Using each individual's coagulation protein composition, tissue factor (TF) initiated thrombin generation was assessed both computationally and empirically. TF pathway inhibitor (TFPI), antithrombin (AT), factor II (FII) and FVIII differed significantly (P < 0.01) between the groups, with levels of FII, FVIII and TFPI higher and AT lower in ACS patients. When thrombin generation profiles from individuals in each group were compared, simulated maximum thrombin levels (P < 0.01) and rates (P < 0.01) were 50% higher with ACS while the initiation phases of thrombin generation were shorter. Empirical reconstructions of the populations reproduced the thrombin generation profiles generated by the computational model. The differences between the thrombin generation profiles for each population were primarily dependent upon the collective contribution of AT, FII and FVIII. CONCLUSION: Simulations of thrombin formation based on plasma composition can discriminate between acute and stable CAD.

Atorvastatin and quinapril inhibit blood coagulation in patients with coronary artery disease following 28 days of therapy.

BACKGROUND: We evaluated the antithrombotic effects of statins and angiotensin-converting enzyme inhibitor (ACEI) drugs in patients with coronary artery disease (CAD). METHODS AND RESULTS: Blood coagulation at the site of microvascular injury was assessed in 26 males with CAD before and after treatment with quinapril (10 mg day-1; n=13) or atorvastatin (40 mg day-1; n=13) for 4 weeks and an additional 4 weeks of combined therapy (quinapril+atorvastatin). Rates of prothrombin and factor V activation (FVa), fibrinogen (Fbg) cleavage and FVa inactivation showed that both quinapril and atorvastatin decreased the rates of: formation of thrombin B-chain (by 30.6%, P=0.007; and by 34.3%, P=0.003), formation of thrombin-antithrombin complexes (by 30.4%, P=0.0002; and by 40%, P=0.001), FV activation (by 19.1%, P=0.03; and by 21.8%, P=0.005) and Fbg depletion (by 29.2%, P=0.004; and by 32.7%, P=0.001). Atorvastatin alone accelerated FVa inactivation (P=0.005). A further 4 weeks of combined therapy enhanced most anticoagulant effects only when atorvastatin was added to quinapril. CONCLUSIONS: In CAD patients, atorvastatin and quinapril slowed blood clotting at the site of microvascular injury after 28 days of therapy. Addition of atorvastatin to quinapril, but not quinapril to the statin, enhanced the anticoagulant effects. Our findings might help explain the reduced risk of myocardial infarction or stroke in patients treated with statins and/or ACEIs and the lack of clinical benefits from ACEI added to prior statin therapy in patients at cardiovascular risk.