Natural Coagulation Inhibitors Research Articles

Use of DOAC Stop for elimination of anticoagulants in the thrombin generation assay

Calibrated automated thrombography (CAT) is useful in monitoring the anticoagulant status of patients treated with direct oral anticoagulants (DOACs). This as well as other applications of the CAT are hampered by the wide inter-individual variation, making the diagnosis of the anticoagulant status of a patient on DOAC difficult when using normal pooled plasma as a reference. With dabigatran, the CAT is further hampered, as this direct thrombin inhibitor also inhibits the calibrator that is used in CAT. In this study we examined the added value of the universal DOAC adsorbent DOAC Stop in CAT. For this, we used normal pooled plasma spiked with apixaban, dabigatran, edoxaban or rivaroxaban, and performed CAT with 5 pM tissue factor. DOAC Stop effectively removed DOACs from plasma, leaving the DOAC Stop-treated plasma slightly more procoagulant compared to sham treated, non-anticoagulated plasma. Examining levels of natural coagulation inhibitors revealed a slight reduction in tissue factor pathway inhibitor upon DOAC Stop treatment. When DOAC Stop-treated plasma was used in the calibrator wells, normal unaffected calibration curves were observed, even when dabigatran was present. In conclusion, DOAC Stop can be used to abolish dabigatran influences of anticoagulated plasma when used in the calibrator wells. Also, the anticoagulant status of a DOAC treated patient can be diagnosed simply by comparing untreated plasma with the same plasma sample treated with DOAC Stop. Using this approach, a minor DOAC-independent increase in CAT response in the DOAC Stop-treated sample should be taken into account.

Diagnostika poruch hemostázy

Hemostasis is a complicated biological system, where the balance between procoagulation and anticoagulation processes maintains fluidity of blood through intact blood vessels and creates thrombi when it is needed to prevent bleeding from the impaired vessels. The modern model of hemostasis is divided into 2 principal phases, the first being defined as primary hemostasis which involves the platelet-vessel interplay, while the second, defined as secondary hemostasis, mainly involves coagulation factors and surfaces of activated cells. The activation and amplification of the coagulation cascade is regulated by natural inhibitors of coagulation. The blood clots which arise to prevent loss of blood must subsequently be broken down and the compact blood vessel wall must be restored. This process is called fibrinolysis. Bleeding and thromboses are manifestations of the impaired hemostatic balance. Detection of its cause is important for efficient treatment and prevention of the condition. This requires a combined evaluation of the family and personal history, a clinical anamnesis along with the evaluation of laboratory results. It is not reasonable or economical to perform all the available tests of hemostasis at the same time. It is recommendable to proceed from the global to the screening and then special tests and, through the process of elimination, obtain an explanation of the bleeding or prothrombotic phenotypes. The purpose of this report is to provide a brief overview of the principal causes of the hemostatic disorders and the practices which facilitate their diagnosis. Key words: diagnosis of hemorrhagic manifestations - diagnostics of thrombophilias - DIC diagnostics - hemophilia A - thrombopathy - von Willebrand disease.

Coagulation defects in thalassemic patients

Regular blood transfusion and compliance with iron chelation therapy has markedly improved life expectancy in thalassemia; however, this improvement is accompanied by several complications of this chronic disease including thromboembolic disorders. The objective of this work is to study natural coagulation inhibition as well as the fibrinolysis processes in thalassemic children who are otherwise in a steady state with no overt clinical manifestations of thromboembolism. In a case-control study design conducted at Sohag University Hospital, Sohag, Egypt, 50 thalassemic children and 20 age- and sex-matched healthy controls were compared as regards prothrombin concentration, international normalized ratio, partial thromboplastin time, protein C, protein S, antithrombin III, D-dimers, and thrombin activatable fibrinolysis inhibitor (TAFI). When compared to healthy controls, natural coagulation inhibitors (protein C, protein S, and antithrombin-III) were significantly lower in thalassemic children (p < 0.0001). While D-dimers showed a significant increase in thalassemic children, TAFI was significantly lower (p < 0.0001). Splenectomized thalassemic children showed significantly lower levels of protein C, protein S and TAFI (p < 0.001, p < 0.0001, p < 0.0001, respectively) when compared to nonsplenectomized thalassemic children. Significant changes in natural coagulation inhibition and fibrinolysis processes favoring thromboembolism can be detected in otherwise healthy thalassemic children. Because these changes are more pronounced in splenectomized patients, study of primary prophylactic strategies in this subgroup is warranted.

The Levels of Tissue Factor Pathway Inhibitor in Sepsis Patients Receiving Prophylactic Enoxaparin.

Objective:Sepsis syndrome is usually accompanied by activation of blood coagulation mechanisms. Earlier studies found deficiencies of the 3 main natural anticoagulants, antithrombin, protein C, and protein S. However, none of these inhibitors block tissue factor, the prime trigger of coagulation during sepsis that is controlled specifically by the tissue factor pathway inhibitor (TFPI). The aim of this study was to characterize the fluctuations in the levels of natural anticoagulants, particularly TFPI, in the course of sepsis and to find out their association with the anticoagulant action of the low-molecular-weight heparin enoxaparin.Materials and Methods:We studied 51 consecutive patients with sepsis. Blood samples were collected from patients at baseline (0 h) and at 4, 12, and 24 h after enoxaparin administration. The following assays were undertaken using commercial kits: activated partial thromboplastin time, prothrombin time, thrombin time, total and free TFPI, protein C and protein S, antithrombin, fibrinogen, and anti-factor Xa.Results:Before enoxaparin administration, there was significant prolongation of the prothrombin time and activated partial thromboplastin time, and this remained the case in the 3 subsequent samples. There was marked reduction in the levels of antithrombin, protein C, and total and free protein S to below control values throughout the study. In contrast, plasma levels of both total and free TFPI were markedly elevated and increased after enoxaparin therapy. Anti-factor Xa levels were within the therapeutic range throughout. There was no difference in TFPI levels between those patients who died and those who survived.Conclusion:Sepsis triggered marked release of TFPI from endothelial cells. This persisted and was increased further following the administration of enoxaparin. In contrast, there was marked consumption of the natural coagulation inhibitors antithrombin, protein C, and protein S. These results go some way towards explaining why the therapeutic use of recombinant TFPI fails to correct sepsis-associated coagulopathy.

Natural coagulation inhibitors in liver diseases

The hemostatic derangements accompanying liver disease are complex and affect all aspects of hemostasis. Depressed levels of the major natural anticoagulants (NAs): Antithrombin (AT), protein C (PC), protein S (PS), and tissue factor pathway inhibitor (TFPI) were reported in advanced liver disease and this reduction correlated with the severity of liver disease. Recent evidence suggests that changes in the blood levels of NAs particularly, PS and PC, were found to be more sensitive to hepatocyte dysfunction than the conventional coagulation tests prothrombin time and activated partial thromboplastin time. Depressed levels of PS and PC were found even in the mildest forms of liver disease such as chronic viral hepatitis and its carrier state when the other coagulation tests and routine liver function tests were normal. This topic did not receive enough coverage and was not described in many recent publications. The current review provides an overview of the current understanding of the pathophysiology of the major anticoagulants; AT, PC, PS, and TFPI with a particular focus on their fluctuations in different types of liver disease. It also discusses the emerging important roles of these NAs as sensitive markers of liver disease.

Molecular Basis of Thrombophilia / MOLEKULARNE OSNOVE TROMBOFILIJE

Summary Thrombophilia is a multifactorial disorder, involving both genetic and acquired risk factors that affect the balance between procoagulant and anticoagulant factors and lead to increased thrombotic tendency. The severe forms of thrombophilia are caused by a deficiency of natural anticoagulants: antithrombin, protein C and protein S. The advances in DNA technology played an important role in the identification of the exact nature of these deficiencies and opened up new possibilities in genetic research and molecular diagnostics of thrombophilia. The major breakthrough came with the discovery of activated protein C resistance and the Factor V Leiden gene mutation. Shortly afterwards, a variant in the 3’ untranslated region of the Factor II gene (FII G20210A) associated with an increased concentration of Factor II in plasma was described. These two gene variants represent the most common thrombophilic genetic risk factors. Recently, a novel prothrombin mutation (c.1787G&gt;T) was identified in a Japanese family with juvenile thrombosis. This mutation leads to impaired inhibition of mutant thrombin by antithrombin, proposing a new mechanism of thrombophilia named resistance to antithrombin. In the last decade, several prothrombotic genetic risk factors have been described, including gene variants associated with defects of natural coagulation inhibitors, increased levels of coagulation factors or their impaired inhibition and defects of the fibrinolytic system. However, most of them are not of diagnostic value, due to their minor or unknown impact on the thrombotic risk. Large-scale DNA analysis systems are now becoming available, opening a new era in the genetic studies of the molecular basis of thrombophilia.

Paired analysis of plasma proteins and coagulant capacity after treatment with three methods of pathogen reduction

The effect of photochemical pathogen reduction (PR) methods on plasma quality has been the subject of several reports but solid comparative data for the different technologies are lacking. Plasma (n = 24) photoinactivated with methylene blue (MB), riboflavin (RF), or amotosalen (AS) was compared using a pool-and-split design. Samples were taken before and after treatment with each method and tested for coagulation factors (fibrinogen, Factor [F] II, FV, FVIII, F IX, FXI), natural coagulation inhibitors (Protein C [PC], protein S [PS], antithrombin III [AT]), prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin generation (TG). The three methods were mutually compared by repeated-measures analysis of variance. All three PR methods cause significant reduction (p < 0.01) of activity of the procoagulant proteins fibrinogen, FII, FV, FVIII, F IX, and FXI. Coagulation is also affected, with significant changes in PT, APTT, and TG. RF treatment causes a significantly higher decrease in concentration of coagulation factors, PS, and AT than the other methods (p < 0.01). PT, APTT, and TG are also affected most by RF treatment. FII, FVIII, F IX, PC, AT, and PT are best preserved with the MB method and FV, FXI, and TG after AS treatment (p < 0.01). Coagulation factor loss due to the volume loss during PR treatment is more important for MB and AS than for RF. PR treatment of plasma affects coagulation proteins and coagulant capacity. For the RF method this effect is most pronounced, although to some extent compensated by a smaller volume loss.

Multiple presence of prothrombotic risk factors in Croatian children with arterial ischemic stroke and transient ischemic attack

AimTo determine the frequency of inherited and acquired prothrombotic risk factors in children with arterial ischemic stroke (AIS) and transient ischemic attacks (TIA) in Croatia.MethodsWe investigated 14 prothrombotic risk factors using blood samples from 124 children with AIS or TIA and 42 healthy children. Prothrombotic risk factors were classified into five groups: natural coagulation inhibitors (antithrombin, protein C, protein S), blood coagulation factors (FV Leiden and FII 20210), homocysteine, lipid and lipoprotein profile (lipoprotein (a), triglycerides, total, high- and low-density lipoprotein), and antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, and antiphosphatidylserine antibodies).ResultsThe most common prothrombotic risk factor was elevated lipoprotein (a), which was identified in about 31% of patients and in 24% of controls. Natural coagulation inhibitors were decreased in about 19% of patients, but not in controls. Pathological values of homocysteine, blood coagulation factor polymorphisms, and antiphospholipid antibodies were found in similar frequencies in all groups. Fourteen children with AIS and TIA (11.3%) and no children from the control group had three or more investigated risk factors.ConclusionThe presence of multiple prothrombotic risk factors in children with cerebrovascular disorder suggests that a combination of risk factors rather than individual risk factors could contribute to cerebrovascular disorders in children.

The anti-inflammatory action of Bothrops jararaca snake antithrombin on acute inflammation induced by carrageenan in mice

Antithrombin is known as the most important natural coagulation inhibitor and has been shown to have anti-inflammatory properties. The present study aimed to investigate the effects of Bothrops jararaca antithrombin on acute inflammation induced by carrageenan in mice. We evaluated the anti-inflammatory activity of antithrombin on models of paw edema formation, cell migration and leukocyte-endothelium interaction in mice (Swiss; n = 5). Acute inflammation was induced by the administration of carrageenan (15 mg kg⁻¹). Treatment with B. jararaca antithrombin (1 mg kg⁻¹) 1 h before or after carrageenan administration significantly inhibited paw edema formation, reduced cell influx to the peritoneal cavity due to reduction in the migration of polymorphonuclear cells, and attenuated leukocyte rolling in the microcirculation of the cremaster muscle.The effects of antithrombin on vascular and cellular events of inflammation were completely abolished by treatment with the cyclo-oxygenase inhibitor indomethacin (4 mg kg⁻¹), suggesting the involvement of prostacyclin in the mechanism of inflammation inhibition by B. jararaca antithrombin. This work showed for the first time the anti-inflammatory properties of B. jararaca antithrombin on vascular and cellular events of inflammation. These findings suggest that antithrombin is effective in preventing paw edema formation, cell migration and leukocyte rolling induced by carrageenan in mice.

Retinal vein occlusion

The role of systemic risk factors (age, smoking, diabetes, arterial hypertension) in the development of retinal vein occlusion (RVO) is well established. However, the association of RVO with genetic predisposition to thrombosis remains poorly understood. The aim of the study was to assess any possible additional effect of genetic predisposition to the already well known 'classical' risk factors of RVO in a cohort of elderly Greek patients. Fifty-one elderly patients with RVO and 51 healthy individuals matched for age and sex were evaluated for systemic risk factors (smoking, diabetes, dyslipidemia, arterial hypertension) and coagulation defects (lupus anticoagulant, natural inhibitors of coagulation). Additionally, genotyping was performed for mutations/polymorphisms involved in haemostasis such as: FV G1691A, FV G4070A, FIIG 20210A, MTHFR C677T and A1298C, PAI-1-675 4G/5G, F XIII exon 2G/T, EPCR A4600G and G4678C. We identified systemic risk factors in the majority of the patients Hypertension (P=0.001), dyslipidemia (P=0.029) and diabetes (P=0.01) are associated with RVO in the majority of the patients. The prevalence of prothrombotic risk factors was not significantly different in the patients with RVO compared to controls. Apart from systemic risk factors, genetic predisposition to thrombosis does not seem to have an important association with RVO in this group of elderly patients.

Aspects of platelet disturbances in haemodialysis patients

Patients with mild-to-chronic kidney disease (CKD) exhibit a variety of haemostatic disorders, ranging from an increased clotting tendency and reductions in the levels of natural inhibitors of coagulation to defective fibrinolysis. In addition, platelet (PLT) abnormalities are common. In this minireview, we report on aspects of haemodialysis (HD)-induced PLT activation. It is demonstrated that PLTs from HD patients are exhausted due to repeated stimulation of HD treatment and recurrent release of PLT degranulation products. During HD, additional aberrations of the haemostatic process occur. Besides deviations of coagulation and fibrinolysis, PLT activation and a reduction in their granule content have been observed during HD treatment. As HD treatment is carried out three times per week, month after month, chronic HD patients may suffer persistently from coagulation defects and PLT disorders on top of the alterations induced by the uraemic state itself. PLT activation occurs together with thrombin and fibrin generation. However, macro fibrin depositions in clot devices are not demonstrated, microaggregates occur not only in the extracorporeal circuit (ECC) but are also present in the blood circulation. As vascular access thrombosis is a frequent complication in patients with HD treatment, it is believed that hypercoagulability could result from vascular changes combined with PLTs and activation of coagulation factors.

Hemodialysis duration, Human platelet antigen HPA-3 and IgA Isotype of anti-β2glycoprotein I antibodies are associated with native arteriovenous fistula failure in Tunisian hemodialysis patients

IntroductionArteriovenous fistula (AVF) failure is a major cause of morbidity and mortality in hemodialysis patients. We assessed the role of a large panel of acquired and inherited thrombophilic markers in cases of AVF thrombosis among 101 Tunisians on chronic hemodialysis, all with native AVF. Materials and MethodsIn this case-control study, we considered the levels of fibrinogen, factor II, factor VII, factor VIII, factor IX, factor X, factor XI, factor XII, von Willebrand factor, natural coagulation inhibitors, D-Dimer, homocysteine, IgG, IgM and IgA anticardiolipin and anti-β2glycoprotein I (anti-β2GPI), and anti-H/PF4 antibodies; the presence of Lupus Anticoagulant; and genetic markers (Factor V Leiden, prothrombin 20210G>A, MTHFR 677C>T and 1298A>C). ResultsMultivariate analysis indicated that dialysis for >69months (OR=10.12; 95% CI, 2.53 to 40.52; p=0.001), HPA-3aa genotype (OR=3.58; 95% CI, 1.36 to 9.4; p=0.01) and anti-β2GPI IgA isotype (OR=3.4; 95% CI, 1.21 to 9.55; p=0.02) were independent risk factors for AVF thrombosis in Tunisian hemodialysis patients. Kaplan-Meier analysis showed that AVF survival was significantly lower for patients with anti-β2GPI IgA than for patients without this isotype (log-rank test, p=0.014). ConclusionsIgA anti-β2GPI may be of clinical relevance among Tunisians. Further studies on the polymorphism of β2GPI and HPA systems would be helpful for identifying patient groups at high risk of AVF failure.

Better hemostatic profiles of never-frozen liquid plasma compared with thawed fresh frozen plasma

Immediate use of thawed fresh frozen plasma (FFP) when resuscitating hemorrhagic shock patients has become more common. According to the AABB (formerly known as American Association of Blood Banks), FFP is the preferred product that can be used up to 5 days after thawing. However, limited data exist on the clinical use and hemostatic profiles of Food and Drug Administration-approved liquid plasma (LQP), which can be stored at 1 °C to 6 °C for up to 26 days. We characterized changes in LQP hemostatic potential during 26 days of cold storage. Ten FFP and 10 LQP single-donor units, matched by sex and blood group, were analyzed. FFP was thawed and kept refrigerated for 5 days and LQP for 26 days. Plasma samples were evaluated at Days 0 and 5 for thawed plasma (TP) and 0, 5, 10, 20, and 26 for LQP, by thrombelastography, thrombogram, platelet counts, platelet microparticles, clotting factors, and natural coagulation inhibitors. LQP had a better capacity to form a clot and generate thrombin compared with TP. LQP's hemostatic potential, expressed as endogenous thrombin potential (total amount of thrombin [nM] formed over time [minute]), initially exceeded that of TP (1,425 vs. 1,184, p < 0.05) but decreased to levels similar to TP by Day 26 (1,201 vs. 1,103, p = 0.15). Significantly higher platelet microparticles were found in LQP on Day 26 compared with those in LQP on Day 0 (23.6 x 10(9)/L vs. 3 x 10(9)/L, p < 0.001) or those in TP on Day 5 (2.8 x 10(9)/L). By Day 26, the majority of clotting factors and inhibitors retained more than 88% of their initial activities in LQP, with the few exceptions of factors well known to be unstable. The hemostatic profiles of LQP were better and sustained five times longer than the more commonly used TP, indicating that never-frozen plasma can be considered for use in the United States in trauma patients requiring immediate plasma resuscitation.

General mechanisms of coagulation and targets of anticoagulants (Section I)

Contrary to previous models based on plasma, coagulation processes are currently believed to be mostly cell surface-based, including three overlapping phases: initiation, when tissue factor-expressing cells and microparticles are exposed to plasma; amplification, whereby small amounts of thrombin induce platelet activation and aggregation, and promote activation of factors (F)V, FVIII and FXI on platelet surfaces; and propagation, in which the Xase (tenase) and prothrombinase complexes are formed, producing a burst of thrombin and the cleavage of fibrinogen to fibrin. Thrombin exerts a number of additional biological actions, including platelet activation, amplification and self-inhibition of coagulation, clot stabilisation and anti-fibrinolysis, in processes occurring in the proximity of vessel injury, tightly regulated by a series of inhibitory mechanisms. "Classical" anticoagulants, including heparin and vitamin K antagonists, typically target multiple coagulation steps. A number of new anticoagulants, already developed or under development, target specific steps in the process, inhibiting a single coagulation factor or mimicking natural coagulation inhibitors.

Predicting the risk of recurrent venous thromboembolism

SummaryVenous thromboembolism (VTE) is a disease, which often recurs. The recurrence risk is highest in patients with unprovoked proximal deep-vein thrombosis (VT) or pulmonary embolism. Men have a higher risk than women. The risk is low in patients with VTE related to a temporary risk factor such as surgery or estrogen use. Other risk factors include overweight, post-thrombotic syndrome, history of VTE, residual VT or a vena cava filter.Both factor V Leiden and the prothrombin mutation confer a negligible increase in recurrence risk. High clotting factor levels, deficiency of a natural coagulation inhibitor, or hyperhomocysteinaemia are also associated with an increased risk. Reasons why routine laboratory thrombophilia screening however is no longer warranted are addressed in this article. Prediction rules combining clinical characteristics and coagulation assays have recently been developed. One such model, the Vienna Prediction Model, allows predicting recurrent VTE on the basis of VTE location, sex and D-dimer. This article describes strategies to distinguish between patients with high risk of recurrent VTE from those with a lower risk, who might not benefit from long-term antithrombotic therapy.

Prediction of Recurrent Venous Thromboembolism by Clot Lysis Time: A Prospective Cohort Study

Venous thromboembolism (VTE) is a chronic disease, which tends to recur. Whether an abnormal fibrinolytic system is associated with an increased risk of VTE is unclear. We assessed the relationship between fibrinolytic capacity (reflected by clot lysis time [CLT]) and risk of recurrent VTE. We followed 704 patients (378 women; mean age 48 yrs) with a first unprovoked VTE for an average of 46 months after anticoagulation withdrawal. Patients with natural coagulation inhibitor deficiency, lupus anticoagulant, cancer, homozygosity for factor V Leiden or prothrombin mutation, or requirement for indefinite anticoagulation were excluded. Study endpoint was symptomatic recurrent VTE. For measurement of CLT, a tissue factor-induced clot was lysed by adding tissue-type plasminogen activator. Time between clot formation and lysis was determined by measuring the turbidity.135 (19%) patients had recurrent VTE. For each increase in CLT of 10 minutes, the crude relative risk (RR) of recurrence was 1.13 (95% CI 1.02–1.25; p = 0.02) and was 1.08 (95% CI 0.98–1.20; p = 0.13) after adjustment for age and sex. For women only, the adjusted RR was 1.14 (95% CI, 0.91–1.42, p = 0.22) for each increase in CLT of 10 minutes. CLT values in the 4th quartile of the female patient population, as compared to values in the 1st quartile, conferred a risk of recurrence of 3.28 (95% CI, 1.07–10.05; p = 0.04). No association between CLT and recurrence risk was found in men. Hypofibrinolysis as assessed by CLT confers a moderate increase in the risk of recurrent VTE. A weak association between CLT and risk of recurrence was found in women only.

Inherited Pro-Thrombotic Risk Factors in Children of South Moravia Region, Czech Republic

Abstract 5136 Introduction:Pro-thrombotic risk factors are associated with increased risk of thrombosis. Some of them are inherited, but clinical manifestation of thrombosis in childhood is rare. It is most likely to appear in the adulthood. When leading to thrombosis during childhood, risk factors must be either very strong (e. g. homozygous deficiency of natural coagulation inhibitors), or must act together with other, usually acquired factors. Aims:- To analyse data of children referred for thrombophilia screening to Thrombosis Haemostasis centre, Dpt. of Paediatric Haematology University Hospital Brno, Czech Republic in years 2005–09.- To specify the characteristics of that cohort and identify the reasons for referral.-To determine prevalence of respective risk factors (RF) in children within study cohort.-To analyse possible correlation between related RF findings (ProC Global and FV Leiden, Protein C, Protein S; homocystein and MTHFR C677T polymorphism). Methods:We have collected data of all consecutive children aged from 0 to 18 years referred to our out-patient clinic for assessment of inherited thrombophilia in years 2005–2009 for any reason. Data recorded for each patient were as follows: age, gender, reason for assessment, thrombotic event and its type (if applicable) and vascular anomalies. Laboratory examinations done: FV Leiden mutation, Prothrombin gene mutation G20210A, MTHFR C677T polymorphism, protein C, protein S and Antithrombin levels, coagulation activity of F VIII, ProC Global test, homocystein and lipoprotein (a) level. Data were statistically analyzed to reach the aims of the study. Results:Data of 849 Caucasian children aged 0–18 years were available for analysis, 475 girls (55. 9 %) and 374 boys (44. 1 %). Median age was 11 years at the time of referral, boys 10 years, girls 13 years. Reasons for thrombophilia screening were as follows: family history of thrombosis/thrombophilia (70. 6 %), vascular anomaly (10. 8 %), thrombotic event (8 %) and others (10. 6 %). Thrombophilia screening was in more than 70 % of children performed before 15 years of age. Thrombotic event has been recorded in 79 patients (9. 3 %), both arterial (37. 6 %) and venous (63. 3 %). Adolescent patients had significantly more thrombotic events than younger children. Most of them were venous thromboses. Ischemic strokes and other arterial events were relatively more frequent in younger children. Frequency of “positive” laboratory findings in the studied cohort were as follows: MTHFR 60. 3 %, positive ProC Global test findings 58. 1 %, FV Leiden (heterozygous)37 %, hyperlipoproteinemia (a) 28. 5 %, protein S deficiency 11. 3 %, high FVIII activity 9. 4 %, Prothrombin gene mutation (heterozygous) 7. 7 %, Antithrombin deficiency 2. 7 %, elevation of homocystein 1. 6 % and protein C deficiency 1 %. Findings have confirmed high sensitivity of ProC Global test to the pathology in protein C pathway, particularly to FV Leiden mutation (sensitivity 98. 4 %). There was no statistically significant relation between homocystein level and MTHFR polymorphism status. Prevalence of RF in study cohort was found to be similar to the literature data. Deficiencies of natural coagulation inhibitors (AT, PC and PS) were rare, pro-thrombotic mutations were more frequent. Data suggest, that role of inherited pro-thrombotic risk factors in the development of thrombotic event in children is not the major one. It is very likely, that more potent risk factors, often acquired ones, are often important for development of thrombotic event during childhood. Conclusions:In our centre, we assessed proximately 170 children referred for thrombophilia screening per year. The incidence is thus 8 children per 10000. During 2005–09the main reason for referral was positive family history, but children were often referred in younger age, than recommended. The evidence available to date suggests that it is neither necessary nor useful to examine asymptomatic children before they reach puberty. Finding of inherited thrombophilia, and thus possibility to use measures preventing eventual thrombotic event, are more important in adolescence and adulthood rather than in younger age. In children with thrombotic event, however, it is recommended to screen for inherited risks. Diagnosis and treatment of thrombotic event in children requires a specialised care and relevant expertise of the Paediatric Thrombosis Haemostasis centre. Disclosures:No relevant conflicts of interest to declare.

C0191 Acute myocardial infarction and natural coagulation inhibitors

Thrombosis is a complex multigene syndrome in which, inherited, acquired and physiological factors of increased risk may play a decisive role. Among them, important roles have the natural coagulation inhibitors.

Plasma‐derived human antithrombin attenuates ventilator‐induced coagulopathy but not inflammation in a Streptococcus pneumoniae pneumonia model in rats

Mechanical ventilation exaggerates pneumonia-associated pulmonary coagulopathy and inflammation. We hypothesized that the administration of plasma-derived human antithrombin (AT), one of the natural inhibitors of coagulation, prevents ventilator-induced pulmonary coagulopathy, inflammation and bacterial outgrowth in a Streptococcus pneumoniae pneumonia model in rats. Forty-eight hours after induction of S. pneumoniae pneumonia rats were subjected to mechanical ventilation (tidal volume 12 mL kg(-1), positive end-expiratory pressure 0 cmH(2)O and inspired oxygen fraction 40%). Rats were randomized to systemic treatment with AT (250 IU administered intravenously (i.v.) before the start of mechanical ventilation) or placebo (saline). Non-ventilated, non-infected rats and non-ventilated rats with pneumonia served as controls. The primary endpoints were pulmonary coagulation and inflammation in bronchoalveolar lavage fluid (BALF). Pneumonia was characterized by local activation of coagulation and inhibition of fibrinolysis, resulting in increased levels of fibrin degradation products and fibrin deposition in the lung. Mechanical ventilation exaggerated pulmonary coagulopathy and inflammation. Systemic administration of AT led to supra-normal BALF levels of AT and decreased ventilator-associated activation of coagulation. AT neither affected pulmonary inflammation nor bacterial outgrowth from the lungs or blood. Plasma-derived human AT attenuates ventilator-induced coagulopathy, but not inflammation and bacterial outgrowth in a S. pneumoniae pneumonia model in rats.

Infantile SVT in Consequence of a Congenital Antithrombin Deficiency

Abstract 5260The liver-made antithrombin is a natural coagulation inhibitor in human blood. Exceptionally it takes effect in inhibiting the coagulation-supporting factors IIa (thrombin) and Xa. A congenital antithrombin deficiency leads to thrombosis and has to be heterozygous, because homozygous ATIII deficiencies are incompatible with life. Unfortunately it's dominant inherited.In 1965 a congenital ATIII deficiency was first detected as a hereditary disease. There are two different types, type I describes a less produced ATIII deficiency, type II is a function loss of ATIII. Special testing can define more subclasses.In cases of congenital ATIII deficiency, vascular blockage (thrombosis) appears, especially in leg veins. Released clots can cause pulmonal embolism, rarely are other arteries affected.Although this disease is hereditary, it appears mostly between ages of 15 'til 30. Clinical trials showed that 80% of affected patient have a thrombosis or embolism until the age of 40. Has there be no kind of illness appeared until there, it's very improbable to get one becaus eof ATIII deficiency.Every hundredth below the age of 70, who comes to a health care center has a ATIII deficiency. In total population it’s a freqzuency of 1:2000 until 1:5000. Mostly there’s a deficiency nown in familary history why they are investigated. The residual activity is between 40 – 60%. Conclusion:Most cases of thrombosis are treated with heparine. Heparin binds to ATIII, so ATIII can be much more effective and inhibits thrombin and Xa much more intense. For the future we have to make sure that antithrombin deficiencies especially in childhood have to be treated with phenprocumone. Disclosures:No relevant conflicts of interest to declare.