fibrinopeptide-a and Thrombosis

The results of experiment and clinical studies support the hypothesis that initiation and progression of arterial thrombosis are dependent on a dynamic interaction between platelet- and coagulation-dependent mechanisms. Although treatment of patients with unstable coronary syndromes acutely with glycoprotein IIb/IIIa inhibitors has already been shown to be remarkably effective in improving short- and long-term prognosis, strategies that inhibit factor thrombin and/or Xa activity may also have a role either alone or in combination with platelet inhibitors in treating patients with coronary thrombosis.

Topics: Anticoagulants; Blood Coagulation; Blood Platelets; Fibrinopeptide A; Humans; Platelet Activation; Platelet Aggregation; Platelet Glycoprotein GPIIb-IIIa Complex; Thrombolytic Therapy; Thrombosis

Cardiac surgery and hip replacement surgery (HRS) are associated with serious cardiorespiratory and vascular complications. Activation of blood coagulation and fibrinolysis in the lung vasculature seem to play a key role in the pathophysiology of this process. This article reviews the results of several experimental and clinical studies within this field. Animal studies have shown that bone traumatization induces a marked local activation of coagulation and fibrinolysis in femoral vein blood draining from the surgical area as shown by a 2.5-fold increase in plasma levels of thrombin-antithrombin complexes (TAT) and a seven-fold increase in tissue plasminogen activator (tPA) activity. A slight increase in TAT in femoral vein blood on the unoperated side has also been found and indicates increased activation of coagulation in recirculated blood, which had passed the pulmonary microvasculature. In addition, human studies have shown that bone preparation induced a 200-fold increase in systemic circulating fibrinopeptide-A during surgery and a five-fold increase in TAT (when thromboprophylaxis was stopped 1 week after surgery). Both increases are markers of thrombin generation. Furthermore, cellular studies have shown that thrombin and certain cytotoxic chemicals, such as methylmethacrylate monomer (bone cement), separately and together trigger monocytes to tissue factor (TF) expression and cause endothelial cell shape changes and detachment. This may allow pericellular fibrin formation to occur on monocytes and also transforms the nonthrombogenic endothelial coverage into a highly thrombogenic surface that triggers the conversion of fibrinogen to fibrin and releases fibrinopeptide-A. Finally, sequestration of granulocytes caused release of autodigestive proteases, which may have further strengthened this procoagulant process. Synchronous to the massive intrapulmonary activation of coagulation, an increased fibrinolytic activity was found, as evidenced by a marked drop in arterial blood tPA during surgery. This indicated tPA binding to fibrin deposits in the lung capillaries. However, this clearing process, to obtain adequate blood flow and gas exchange, was shut down several hours after surgery by an antifibrinolytic activity (PAI-1). Thus, these studies indicated that bone surgery induces a substantial intraoperative hemostatic activation in the lung capillaries, which is the primary target organ for venous blood-borne bone-marrow debris. Soft-tissue surgery

Topics: Animals; Antithrombin III; Blood Coagulation; Bone and Bones; Bone Cements; Cardiac Surgical Procedures; Cell Adhesion; Cell Size; Endothelium, Vascular; Fibrinolysis; Fibrinopeptide A; Granulocytes; Humans; Methylmethacrylates; Microcirculation; Monocytes; Peptide Hydrolases; Pulmonary Circulation; Surgical Procedures, Operative; Thrombin; Thromboplastin; Thrombosis; Tissue Plasminogen Activator

Endothelial cells (EC) interact with fibrin at sites of vascular injury, thrombosis, inflammation and tumor growth, whereas they are quiescent when exposed to circulating fibrinogen. To determine the structural basis for specific interaction with fibrin we have characterized the response of EC to fibrin of varying structure. Fibrin was prepared with thrombin, which cleaves both fibrinopeptide A (FPA) and fibrinopeptide B (FPB), with Reptilase, which cleaves only FPA, and with contortrix procoagulant to cleave only FPB. Fibrin with FPB cleavage stimulated release of von Willebrand factor from EC Weibel-Palade bodies and also supported cell spreading. Involvement of the amino terminus of the fibrin beta chain in the response was shown by stimulation of von Willebrand factor release by the peptide beta 15-42. Also, fibrin prepared from a fibrinogen derivative lacking residues 15-42 of the beta chain failed to support EC spreading. EC adhesion was unaffected by the pattern of fibrinopeptide cleavage or by the removal of peptide beta 15-42 from fibrin. The results indicate that separate sites on the fibrin molecule mediate adhesion and spreading, and that the latter requires cleavage of FPB and the new amino terminus of the beta chain. They further suggest that cellular responses to fibrin are regulated by the proteolytic cleavages and conformational changes that convert fibrinogen to fibrin and may also be modulated by plasmic or elastase degradation.

Topics: Amino Acid Sequence; Animals; Cell Adhesion; Endothelium, Vascular; Fibrin; Fibrinogen; Fibrinopeptide A; Fibrinopeptide B; Humans; Inflammation; Macromolecular Substances; Molecular Sequence Data; Neoplasms; Platelet Adhesiveness; Thrombosis; von Willebrand Factor

Topics: Animals; Antibodies, Monoclonal; Antibody Specificity; Arteriosclerosis; Dogs; Enzyme-Linked Immunosorbent Assay; Epitopes; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Humans; Kidney Diseases; Neoplasms; Pregnancy; Pregnancy Complications; Radioimmunodetection; Thrombosis

Topics: Blood Coagulation Factors; Blood Coagulation Tests; Enzyme Activation; Fibrinopeptide A; Hemostasis; Humans; Thrombosis

The interaction between blood factors and the vessel wall is important in the development of common cardiovascular diseases. Clinical markers of these interactions should be sought to help in the understanding of the processes involved, and such markers should ideally be available to identify people at risk from the disease, screen relatives, help identify appropriate treatment, and monitor the outcome of the therapy. Various aspects of platelet interaction with the vessel wall can be used, as can some changes in levels of coagulation factors, fibrinolytic proteins, and natural anticoagulants. All have their advantages and disadvantages in terms of having the attributes of the ideal marker that would identify the pathophysiological processes and be reproducible, inexpensive, and easy to perform. This review will consider the value of various clinical markers, taking account of their advantages and disadvantages.

Topics: beta-Thromboglobulin; Blood Coagulation Factors; Blood Platelets; Coronary Disease; Coronary Thrombosis; Fibrinolysin; Fibrinolysis; Fibrinopeptide A; Humans; Muscle, Smooth, Vascular; Plasminogen; Platelet Aggregation; Platelet Factor 4; Thrombosis; Thromboxane B2

The authors have studied 21 patients with Crohn's disease and have looked for signs of platelet and blood coagulation activation, by measuring platelet factor 4, beta thromboglobulin and fibrinopeptide A: a fibrinolytic system study with tissue plasminogen activator assessment has also been made. Beta thromboglobulin, platelet factor 4 and fibrinopeptide A were increased in 80 per cent, 100 per cent and 60 per cent of cases respectively. Beta thromboglobulin was significantly correlated with the Van Hees activity index. Plasminogen before venous stasis was significantly decreased and 9 patients had a plasminogen release defect. The relationship between Crohn's disease and thrombosis might partially be explained by a release of inflammation mediators and/or endotoxins: these mediators might induce thrombosis by interfering with the antithrombogenic properties of the endothelial cell. In conclusion these data prove that active Crohn's disease is currently associated with a prethrombotic state, present biologic tests that might predict a venous or arterial thrombosis at short term are not available.

Topics: Adult; Crohn Disease; Female; Fibrinolysis; Fibrinopeptide A; Hemostasis; Humans; Male; Platelet Activation; Thrombocytosis; Thrombosis

The Authors analyze the clinical and biological meanings of some markers of coagulative activity (beta thromboglobulin, PF4, fibrinogen, fibrinopeptide A) and their changes in some arterial diseases. The role of main atherosclerosis risk factors (dyslipidaemia, hypertension, smoking and diabetes) in promoting a thrombophylic state in these pathological conditions is also considered. Finally the Authors evaluate the usefulness of the markers of coagulative activity from both a diagnostic and a preventive point of view in the arteriopathies of atherosclerotic etiology.

Topics: Arteriosclerosis; beta-Thromboglobulin; Biomarkers; Fibrinogen; Fibrinopeptide A; Humans; Platelet Factor 4; Risk Factors; Thrombosis

Topics: Antithrombin III; beta-Thromboglobulin; Blood Platelets; Cell Survival; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Fibrinopeptide B; Glycoproteins; Humans; Peptide Fragments; Platelet Aggregation; Platelet Factor 4; Protein C; Thrombosis

The pharmacokinetics of heparin differ markedly from those of its fractions both in man and in experimental animal models. The route of administration determines the relative availability of different molecular species that exert the anti-Xa, anti-IIa, fibrinopeptide A generation inhibiting actions and the release of tissue plasminogen activator-like activity from the endothelial cell lining. The bioavailability of heparin fractions has proved to be much greater than heparin after subcutaneous or intraperitoneal administration. Most of the low molecular weight heparin fractions exhibit sustained antiprotease and antithrombotic actions. The pharmacokinetics of the specific anti-IIa and anti-Xa actions of heparin and its fractions is dependent on the molecular composition of these agents. Even if the fractions are standardized for identical potencies by the in vitro assays, the elimination rate of anti-Xa and anti-IIa actions are significantly different for each fraction. The antithrombotic actions of heparin and its fractions also vary widely in the rabbit stasis thrombosis model. Different fractions show variable antithrombotic actions against defined thrombogenic challenges. Moreover, selection and potency of a thrombogenic agent is of crucial importance in these studies. The primate (Macaca mulatta) model offers a useful preclinical model for the pharmacologic evaluation of the low molecular heparin fractions. Since the coagulation system and heparinizability index of this model approximate a human response, the data may be used to reflect therapeutic and prophylactic responses, as well as to assess toxic effects, such as bleeding.

Topics: Animals; Biological Availability; Bleeding Time; Chemical Phenomena; Chemistry; Disease Models, Animal; Factor X; Factor Xa; Fibrinopeptide A; Heparin; Humans; Kinetics; Macaca mulatta; Molecular Weight; Oligosaccharides; Partial Thromboplastin Time; Polymers; Prothrombin; Rabbits; Structure-Activity Relationship; Thrombosis

There are many reports in the literature of blood test abnormalities occurring in patients with venous or arterial thrombosis. Most of these have not used acceptable criteria for establishing an association between thrombosis and blood tests and, therefore, their interpretation is questionable. Recently, sensitive and specific assays have been developed for the detection of products of intravascular thrombin formation, of plasmin digests of fibrin or fibrinogen and of platelet specific proteins that are released into the plasma when platelets react with stimuli. Blood abnormalities have been sought that can either predict or detect venous thrombosis. Many of the predictive tests evaluated are nonspecific acute phase reactant responses to inflammation; of these, only reduced fibrinolytic activity has been consistently reported to be associated with postoperative venous thrombosis. Hereditary antithrombin III deficiency has been consistently shown to predispose patients to venous thrombosis. Abnormalities of the plasminogen and fibrinogen molecule have also been described in patients with familial or recurrent venous thrombosis but these are rare and the association could be coincidental. Two blood tests, the fibrinopeptide A assay and the assay for fibrin/fibrinogen fragment E are highly sensitive to acute venous thromboembolism in symptomatic patients but both are nonspecific. Elevated levels of beta thromboglobulin and platelet factor 4 have been reported in patients with arterial thromboembolism but the sensitivity and specificity of these findings is presently unknown.

Topics: Antithrombin III; Arteries; Blood Coagulation Tests; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Humans; Inflammation; Platelet Adhesiveness; Platelet Aggregation; Risk; Thrombin; Thromboembolism; Thrombophlebitis; Thrombosis; Wounds and Injuries

As knowledge of blood coagulation has advanced we have begun to examine not only the clinical entities associated with hemorrhage but also a group in which thrombosis represents the major problem. Thrombotic disorders believed to be associated with coagulation are recognized clinically but seldom investigated in the laboratory. The present approach to the problem is based on theoretical and experimental knowledge and a rapidly developing body of clinical information related to the role of platelets and antithrombin III in the initiation and control of thrombosis.

Topics: Arteries; Arteriosclerosis; Blood Coagulation; Blood Coagulation Factors; Blood Platelets; Blood Vessels; Cell Survival; Endotoxins; Factor V; Factor VIII; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinopeptide A; Humans; Thromboplastin; Thrombosis; Veins

Topics: Beta-Globulins; Blood Coagulation; Cell Survival; Fibrin; Fibrinolysin; Fibrinopeptide A; Humans; Platelet Aggregation; Platelet Factor 4; Radioimmunoassay; Thrombin; Thrombosis; Time Factors

Topics: alpha 1-Antitrypsin; alpha-Macroglobulins; Antithrombins; Blood Coagulation; Blood Coagulation Factors; Blood Platelets; Cell Survival; Factor V; Factor VII; Factor VIII; Factor XII; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Fibrinopeptide B; Humans; Kinetics; Liver; Mononuclear Phagocyte System; Platelet Aggregation; Thrombosis

Customized aortic repair (CAR) is a new concept for endovascular aortic aneurysm repair in which a non-polymerised elastomer is injected to fill the aneurysm sac around a balloon catheter. Amongst other variables, the thrombogenicity of the elastomer should be tested, before further clinical experiments can take place. The aim of this human ex vivo study was to measure the thrombogenicity of the elastomer and to compare it to expanded polytetrafluoroethylene (ePTFE).. In a validated ex vivo model, non-anticoagulated blood was drawn from the antecubital veins of 10 healthy donors with a 19-gauge needle. It was drawn through elastomer tubes and through ePTFE Gore-Tex vascular grafts, both 60 cm long and with an inner diameter of 3 mm.. Fibrinopeptide A (FPA) and P-selectin expression was measured in blood samples, collected at the end of the grafts. After the experiments, the deposition of platelets and fibrin onto the grafts was visualised by scanning electron microscopy.. For these graft types, a progressive increase in FPA production was observed in time. No significant difference was observed between the elastomer and ePTFE grafts (p > 0.05). No increase in P-selectin expression, and thereby no platelet activation, was observed in the perfusate of either grafts (p > 0.05). By scanning electron microscopy, numerous platelet aggregates were observed on the ePTFE grafts, whereas just a few adhered platelets and no aggregates were observed in the elastomer grafts.. The elastomer in its current formulation has a low thrombogenicity, comparable to ePTFE, making it an ideal substance for endovascular aneurysm sac filling. Further research should clarify the feasibility of CAR in vivo.

Topics: Adult; Aortic Aneurysm; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Dimethylpolysiloxanes; Endovascular Procedures; Fibrin; Fibrinopeptide A; Humans; Injections; Male; Microscopy, Electron, Scanning; P-Selectin; Platelet Adhesiveness; Polytetrafluoroethylene; Prosthesis Design; Silicone Elastomers; Thrombosis; Time Factors; Young Adult

Almost a third of patients who undergo peripheral bypass procedures do not have suitable veins, making the use of prosthetic materials necessary. Prosthetic materials can cause platelet adhesion and activation of the coagulation cascade on the graft. One potential strategy to reduce this thrombogenicity is to covalently bind heparin to the endoluminal surface of grafts. This human in vivo study examined systemic effects of the endoluminal heparin and addressed whether graft implantation results in (1) a measurable reduction of systemic markers of hemostasis activation compared with control grafts and (2) antibody formation against heparin, potentially responsible for heparin-induced thrombocytopenia (HIT).. The study included 20 patients undergoing femoropopliteal bypass grafting, of whom 10 received a standard Gore-Tex Thin Walled Stretch Vascular Graft (W. L. Gore & Associates, Flagstaff, Ariz) and 10 received a heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft (Gore-Tex Propaten Vascular Graft). Blood samples were drawn before and directly after the operation and at days 1, 3, 5, and week 6 after surgery. Established markers of in vivo activation of platelets and blood coagulation (prothrombin fragment 1+2, fibrinopeptide A, soluble glycoprotein V, thrombin-antithrombin complexes, and D-dimers) were measured using standard commercially available techniques. Antiplatelet factor 4/heparin antibody titers were measured using a commercially available enzyme-linked immunosorbent assay, and platelet counts were determined.. No statistical differences were observed in any of the markers of in vivo activation of platelets and blood coagulation between patients receiving Propaten or control ePTFE. Moreover, no antibodies against heparin could be demonstrated up to 6 weeks after implantation.. No measurable effect of heparin immobilization on systemic markers of hemostasis was found using a heparin-bonded ePTFE graft in vivo. Also, no antibodies against heparin could be detected up to 6 weeks after implantation.

Topics: Aged; Antibodies; Anticoagulants; Antithrombin III; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Hemostasis; Heparin; Humans; Male; Middle Aged; Peptide Fragments; Peptide Hydrolases; Peripheral Vascular Diseases; Platelet Count; Platelet Glycoprotein GPIb-IX Complex; Polytetrafluoroethylene; Prosthesis Design; Prothrombin; Thrombocytopenia; Thrombosis; Time Factors; Treatment Outcome; Vascular Patency

An elevated postprandial lipid concentration is believed to be atherogenic and to increase the risk of thrombosis.. The objective was to test whether the consumption of a stearic acid-rich structured triacylglycerol has adverse effects on postprandial fibrinolytic activity and lipemia, factor VII coagulant (FVII:c) activity, and activated FVII (FVIIa) concentrations.. A randomized crossover design was used to compare the effects on middle-aged healthy men (n = 17) and women (n = 18) of meals enriched with cocoa butter, high-oleate sunflower oil (oleate), or a structured triacylglycerol containing stearic acid.. The mean increases from fasting in plasma triacylglycerol 3 h after the oleate, cocoa butter, and structured triacylglycerol meals were 1.36 (95% CI: 1.17, 1.56), 1.39 (1.17,1.63), and 0.65 (0.50, 0.82) mmol/L, respectively. Tissue plasminogen activator activity increased and plasminogen activator type 1 activity decreased after all 3 meals. Plasma FVII:c increased after the oleate and cocoa butter meals but not after the structured triacylglycerol meal. The values 6 h after the oleate and cocoa butter meals were 11.3% (7.0%, 15.6%) and 9.9% (4.7%, 15.2%), respectively, and were significantly different (P < 0.0001 and P = 0.001, respectively) from the value after the triacylglycerol meal [2.1% (-1.1%, 5.3%)]. Plasma FVIIa increased after all 3 meals, more so after the oleate and cocoa butter meals than after the structured triacylglycerol meal.. The consumption of stearic acid in the form of a structured triacylglycerol leads to less of an increase in plasma triacylglycerol and in FVII:c than does a meal enriched in cocoa butter or oleate.

Topics: Adult; Cross-Over Studies; Dietary Fats; Factor VII; Factor VIIa; Female; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Humans; Lipids; Male; Middle Aged; Oleic Acid; Postprandial Period; Risk Factors; Stearic Acids; Thrombosis; Time Factors; Tissue Plasminogen Activator; Triglycerides

Thrombogenesis in total hip replacement (THR) begins during surgery on the femur. This study assesses the effect of two doses of unfractionated intravenous heparin administered before femoral preparation during THR on circulating markers of thrombosis.. Seventy-five patients undergoing hybrid primary THR were randomly assigned to receive blinded intravenous injection of either saline or 10 or 20 U/kg of unfractionated heparin after insertion of the acetabular component. Central venous blood samples were assayed for prothrombin F1+2 (F1+2), thrombin-antithrombin complexes (TAT), fibrinopeptide A (FPA), and D-dimer.. No changes in the markers of thrombosis were noted after insertion of the acetabular component. During surgery on the femur, significant increases in all markers were noted in the saline group (P < 0.0001). Heparin did not affect D-dimer or TAT. Twenty units per kilogram of heparin significantly reduced the increase of F1+2 after relocation of the hip joint (P < 0.001). Administration of both 10 and 20 U/kg significantly reduced the increase in FPA during implantation of the femoral component (P < 0.0001). A fourfold increase in FPA was noted in 6 of 25 patients receiving 10 U/kg of heparin but in none receiving 20 U/kg (P = 0.03). Intraoperative heparin did not affect intra- or postoperative blood loss, postoperative hematocrit, or surgeon's subjective assessments of bleeding. No bleeding complications were noted.. This study demonstrates that 20 U/kg of heparin administered before surgery on the femur suppresses fibrin formation during primary THR. This finding provides the pathophysiologic basis for the clinical use of intraoperative heparin during THR.

Topics: Aged; Anticoagulants; Antithrombin III; Arthroplasty, Replacement, Hip; Dose-Response Relationship, Drug; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Heparin; Humans; Male; Middle Aged; Peptide Hydrolases; Postoperative Complications; Thrombosis

We sought to assess the effects of antithrombotic therapy after thrombolysis for acute myocardial infarction on markers of thrombin generation and activity and to determine the relation of these markers with clinical outcomes.. Thrombin activation and generation often occur with thrombolysis for acute myocardial infarction. Antithrombotic regimens have been developed to reduce the resulting thrombotic complications.. We sampled plasma markers of thrombin generation and activity after thrombolysis in 292 patients. We assessed the relations of these markers with clinical outcomes at 30 days.. Fibrinopeptide A (FPA), a marker of thrombin activity toward fibrinogen, was elevated at baseline (12.3 ng/ml) and increased to 18.4 ng/ml by 90 min after streptokinase and subcutaneous heparin treatment. With intravenous heparin, this increase was attenuated, but intravenous heparin did not prevent thrombin generation, as measured by prothrombin fragment 1.2 (F1.2). Heparin level, measured by anti-Xa activity, correlated with activated partial thromboplastin time (aPTT, r = 0.62 to 0.67). Thrombin activity, measured by FPA, was as closely related to aPTT as to the heparin level. Baseline levels of F1.2 were significantly related to the risk of death or reinfarction at 30 days (p = 0.008); values 12 h after enrollment also were related to 30-day mortality (p = 0.05).. Although intravenous heparin partly suppresses the increased thrombin activity associated with thrombolysis, it does not inhibit thrombin generation. The aPTT was as good a measure of suppression of thrombin activity as the heparin level itself. Hematologic markers of thrombin generation were found to be related to the subsequent risk of thrombotic events.

Topics: Aged; Antithrombin III; Confounding Factors, Epidemiologic; Female; Fibrinolytic Agents; Fibrinopeptide A; Heparin; Humans; Injections, Intravenous; Injections, Subcutaneous; Male; Middle Aged; Myocardial Infarction; Peptide Hydrolases; Streptokinase; Thrombin; Thrombolytic Therapy; Thrombosis; Treatment Outcome

The activation of the clotting cascade leading to deep venous thrombosis begins during total hip arthroplasty, but few studies have assessed changes in coagulation during surgery. A better understanding of thrombogenesis during total hip arthroplasty may provide a more rational basis for treatment. In 3 separate studies, the following observations were made. Circulating indices of thrombosis and fibrinolysis: prothrombin F1.2, thrombin-antithrombin complexes, fibrinopeptide A, and D-dimer, did not increase during osteotomy of the neck of the femur or during insertion of the acetabular component, but rose significantly during insertion of the femoral component. Thrombin-antithrombin complexes, fibrinopeptide A, and D-dimer were higher after insertion of a cemented component than insertion of a noncemented femoral component. A significant decline in central venous oxygen tension was observed after relocation of the hip joint and after insertions of cemented and noncemented femoral components, providing evidence of femoral venous occlusion during insertion of the femoral component. In patients receiving a cemented femoral component, mean pulmonary artery pressure increased after relocation of the hip joint, indicating intraoperative pulmonary embolism. No changes in mean pulmonary artery pressure were noted with noncemented total hip arthroplasty. Administration of 1000 units of unfractionated heparin before insertion of a cemented femoral component blunted the rise of fibrinopeptide A. The results of these studies suggest that (1) the greatest risk of activation of the clotting cascade during total hip arthroplasty occurs during insertion of the femoral component; (2) femoral venous occlusion and use of cemented components are factors in thrombogenesis during total hip arthroplasty; and (3) measures to prevent deep venous thrombosis during total hip arthroplasty (such as intraoperative anticoagulation) should begin during surgery rather than during the postoperative period and be applied during insertion of the femoral component.

Topics: Aged; Antithrombin III; Blood Coagulation Factors; Bone Cements; Female; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Heparin; Hip Prosthesis; Humans; Intraoperative Period; Male; Middle Aged; Oximetry; Peptide Fragments; Peptide Hydrolases; Prothrombin; Pulmonary Wedge Pressure; Thrombosis

Inhibition of thrombin formation in flowing native blood reduces thrombus formation on subendothelium, dacron, or collagen fibrils at arterial wall shear rates of 450 to 650 s-1. In the present study, we have investigated the role of low levels of factor VII (FVII) in thrombus formation on collagen fibrils at arterial wall shear rates of 650 s-1 (coronary arteries), 2,600 s-1 (mildly stenosed arteries), and 10,510 s-1 (severely stenosed arteries) in parallel-plate perfusion chambers. In the perfusion chamber with the highest wall shear rate, thrombus formation took place at the apex of an eccentric stenosis, which reduced the cross-sectional area of the blood flow channel by 80%, thus simulating thrombus formation at an atherosclerotic plaque rupture. Native blood from 21 healthy volunteers and 12 homozygous FVII-deficient patients was drawn by a pump directly from an antecubital vein over a surface of fibrillar collagen positioned in the respective perfusion chambers. The patients had FVII coagulant activities ranging from 1.3% to 4.5% and FVII antigen levels of 16% to 23% of normal. Immunoaffinity purification of the patients' FVII followed by electrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]) and immunoblotting showed a protein with similar molecular mass as normal FVII. In the perfusion studies, a reduction in thrombus volume of 54% of normal (P < .007) at 10,510 s-1 was observed. The deposition of fibrin on the thrombogenic surface and the plasma level of fibrinopeptide A (FPA) in blood samples collected distal to the perfusion chamber were concomitantly reduced (P < .002 and P < .04, respectively). The plasma FPA level was also reduced at 2,600 s-1 (P < .04), but not at 650 s-1. However, at the lower shear conditions, the thrombus volume and the fibrin deposition were within the ranges observed in normal blood. The platelet-collagen adhesion was not affected at any of the three shear conditions. Thus, low plasma levels of FVII result in significantly less formation of thrombin and fibrin in and around growing platelet masses at high shear condition. This may weaken the thrombus stability and reduce platelet recruitment, thereby lowering thrombus volume. In support of this theory, one patient with afibrinogenemia had an 83% reduction in thrombus volume at this high shear condition.

Topics: Afibrinogenemia; beta-Thromboglobulin; Enzyme-Linked Immunosorbent Assay; Factor VII; Factor VII Deficiency; Female; Fibrinopeptide A; Homozygote; Humans; Male; Reference Values; Thrombosis

The goal of the present study was to investigate the effect of 7 and 14 days of daily oral administration of 75 mg clopidogrel on collagen-induced thrombogenesis in flowing non-anticoagulated human blood. Blood was drawn directly from an antecubital vein over immobilised collagen type III fibrils positioned in a parallel-plate perfusion chamber. The wall shear rates at the collagen surface were those characteristic for veins (100 s-1), and for medium sized (650 s-1) and moderately stenosed (2600 s-1) arteries. Clopidogrel ingestion reduced the thrombus volume significantly (p < 0.05) at 100 and 2600 s-1 (39 and 51% respectively). The beta-thromboglobulin plasma levels were reduced concomitantly. However, it was not possible to measure accurately the thrombus volume at 650 s-1, due to loose packing of the platelet thrombi. Transmission electron microscopy substantiated this observation and showed that clopidogrel profoundly reduced the platelet degranulation process (p < 0.005). The inhibitory effect of clopidogrel on platelet consumption by the growing thrombi resulted apparently in higher platelet concentration at the collagen surface, which enhanced the platelet-collagen adhesion at all three shear rates (p < 0.05). Despite the low deposition of fibrin on collagen, clopidogrel reduced significantly the fibrinopeptide A plasma levels and the fibrin deposition at shear rates below 650 s-1. This was apparently a consequence of the reduced platelet recruitment and the lower activation of platelets, since activated platelets in thrombi promote deposition of fibrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Anticoagulants; Blood Flow Velocity; Clopidogrel; Fibrin; Fibrinopeptide A; Hematologic Tests; Humans; Male; Platelet Activation; Platelet Adhesiveness; Platelet Aggregation Inhibitors; Platelet Count; Thrombosis; Ticlopidine

Left atrial (LA) thrombi sometimes occur in patients with mitral stenosis (MS) and may cause systemic embolization resulting in serious and fatal complications. Several clinical techniques are used to detect the presence of LA thrombi, but even echocardiography, the most widely used, has some drawbacks depending on the sizes and locations of the thrombi. This study evaluated D-dimer, fibrinopeptide A(FPA), and thrombin-antithrombin III complex (TAT) as molecular markers for diagnosing the presence of LA thrombi in 26 patients with MS who underwent cardiac surgery. Atrial fibrillation was detected in all patients. Patients with episodes of obvious thromboembolic diseases were excluded. Blood was obtained from the brachial vein before the surgery (3 +/- 1 days; mean +/- SD). The presence or absence of thrombi was confirmed at surgery in all patients. Levels of both D-dimer and TAT were significantly higher in patients with thrombi than in those without thrombi or in normal subjects. FPA levels did not differ significantly between the three groups. The levels of D-dimer and TAT correlated significantly with the weights of the LA thrombi. LA thrombi (ca > or = 2 g) were always confirmed at surgery in patients with levels of D-dimer higher than 200 ng/ml and/or levels of TAT higher than 4 ng/ml. These results indicate that D-dimer and TAT are simple and useful diagnostic markers for determining LA thrombi in patients with MS.

Topics: Antithrombin III; Biomarkers; Echocardiography; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Heart Diseases; Humans; Male; Middle Aged; Mitral Valve Stenosis; Peptide Hydrolases; Thrombosis

The therapeutic potential of the glycosaminoglycan (GAG), dermatan sulphate (DS), as an antithrombotic agent in humans has yet to be established. We have performed dose ranging studies of DS to determine its effectiveness as an antithrombotic agent in patients (n = 6-8) undergoing haemodialysis for chronic renal failure. In an initial study, Study 1, i.v. bolus doses of 2-4 mg/kg and 5-6 mg/kg DS were given to patients dialysing with polyacrylonitrile hollow fibre (PAN HF) membranes. In a second crossover study, Study 2, performed using cuprophane hollow fibre (CHF) membranes, i.v. bolus doses of 3 mg/kg and 6 mg/kg DS were compared to a standard unfractionated heparin (UFH) regime that has been shown previously to inhibit fibrin formation. Further infusion studies, Study 3 and Study 4 evaluated the antithrombotic efficacy of an i.v. DS bolus of 3 mg/kg plus an i.v. infusion of DS 0.6 mg kg-1 h-1 and a DS bolus of 5 mg/kg plus an infusion of 1 mg kg-1 h-1 over 5 h, respectively. These studies were compared to standard UFH regimes in a randomised crossover design. Plasma levels of fibrinopeptide A (FPA) and thrombin-antithrombin (TAT) were used as markers of fibrin formation and thrombin generation during dialysis using both membranes. The changes in DS concentration following administration of the different doses were similar in Studies 1 and 2. However, the effectiveness of DS as an anticoagulant appeared to depend markedly on the different dialyser types used in the two studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Aged; Aged, 80 and over; Antithrombin III; Blood Coagulation; Dermatan Sulfate; Dose-Response Relationship, Drug; Female; Fibrinolytic Agents; Fibrinopeptide A; Heparin; Humans; Kidney Failure, Chronic; Male; Middle Aged; Peptide Hydrolases; Renal Dialysis; Thrombosis

Increased thrombin generation is frequently associated with an increase in anginal activity. A cross-over, single-blind, completely randomized study was planned in order to evaluate whether the control of thrombin generation affected the increase in anginal activity. After discharge from the hospital, 24 patients (18 men and 6 women, aged 40 to 69 years) suffering from spontaneous angina were followed up to 12 months and were alternatively treated during two consecutive 6-month periods with calcium heparin, 12,500 IU by the subcutaneous route, or with placebo by the intramuscular route, in addition to the usual antianginal medications. Thrombin generation and clinical activity of angina were assessed every 15 days by measuring fibrinopeptide A (FPA) plasma levels and by grading in three classes (symptomless, mildly symptomatic, and severely symptomatic) the anginal activity on the basis of the number and the time concentration of the ischemic attacks and ECG changes. Low-dose heparin treatment significantly reduced both the FPA plasma level (from 4.1 +/- 3.7 to 2.3 +/- 1.8 ng/ml, p less than 0.001) and the clinical activity of angina. During heparin treatment, the frequency of the observations in the severely and mildly symptomatic classes decreased, respectively, by 53% and by 30%, whereas that in the symptomless class increased by 23% (p less than 0.001) in comparison with the period on placebo. Present results indicate that the control of thrombin generation obtained by low-dose heparin treatment favorably affects the degree of anginal activity in patients with spontaneous angina.

Topics: Aged; Angina Pectoris; Clinical Trials as Topic; Drug Administration Schedule; Female; Fibrinogen; Fibrinopeptide A; Heparin; Humans; Male; Patient Compliance; Random Allocation; Thrombosis

We determined the sequence of events and identified and quantitatively characterized the mobility of moving structures present during the early stages of fibrin-clot formation from the beginning of polymerization to the gel point. Three complementary techniques were used in parallel: spinning-disk confocal microscopy, transmission electron microscopy, and turbidity measurements. At the beginning of polymerization the major structures were monomers, whereas at the middle of the lag period there were monomers, oligomers, protofibrils (defined as structures that consisted of more than 8 monomers), and fibers. At the end of the lag period, there were primarily monomers and fibers, giving way to mainly fibers at the gel point. Diffusion rates were calculated from 2 different results, one based on sizes and another on the velocity of the observed structures, with similar results in the range of 3.8-0.1 μm²/s. At the gel point, the diffusion coefficients corresponded to very large, slow-moving structures and individual protofibrils. The smallest moving structures visible by confocal microscopy during fibrin polymerization were identified as protofibrils with a length of approximately 0.5 μm. The sequence of early events of clotting and the structures present are important for understanding hemostasis and thrombosis.

Topics: Blood Coagulation; Fibrin; Fibrinopeptide A; Humans; Microscopy, Confocal; Microscopy, Electron, Transmission; Nephelometry and Turbidimetry; Polymerization; Thrombosis

The consensus thrombin aptamer C15-mer is a single-stranded DNA of 15 nucleotides [d(GGTTGGTGTGGTTGG)] that was identified by the selection of thrombin-binding molecules from a large combinatorial library of oligonucleotides. It is capable of inhibiting thrombin at nanomolar concentrations through binding to a specific region within thrombin exosite 1. As has been shown in our earlier studies, the 4-thio-deoxyuridylate (s4dU)-containing oligonucleotides have high affinity for a number of proteins, due to the reduced hydrophilic character of the modified oligonucleotide.. Three different analogs of the original thrombin-inhibiting sequence, in which some of the thymidylate residues were replaced by 4-thio-deoxyuridylates, were synthesized. The inhibitory effect of modified aptamers was tested on thrombin-catalyzed fibrin clot formation and fibrinopeptide A release from fibrinogen, thrombin-induced platelet aggregation/secretion, and the formation of thrombus on coverslips coated with human collagen type III, thrombin-treated fibrinogen or subendothelial matrix of human microvascular endothelial cells.. As compared with the C15-mer, the analog with the sequence GG(s4dU)TGG(s4dU)G(s4dU)GGT(s4dU)GG (UC15-mer) showed a 2-fold increased inhibition of thrombin-catalyzed fibrin clot formation, fibrinopeptide A release, platelet aggregation and secretion in human plasma and thrombus formation on thrombin-treated fibrinogen surfaces under flow conditions. Concerning the inhibition of thrombin-induced fibrin formation from purified fibrinogen and activation of washed platelets, UC15-mer was 3-fold and twelve-fold more effective than C15-mer, respectively.. The replacement of four thymidylate residues in C15-mer by 4-thio-deoxyuridylate resulted in a new thrombin aptamer with increased anticoagulant and antithrombotic properties.

Topics: Aptamers, Nucleotide; Base Sequence; Blood Coagulation; Deoxyuracil Nucleotides; Drug Evaluation, Preclinical; Endothelial Cells; Endothelium, Vascular; Fibrinopeptide A; Humans; Perfusion; Platelet Aggregation; Structure-Activity Relationship; Thionucleotides; Thrombosis

The patency of small-diameter expanded polytetrafluoroethylene (ePTFE) grafts for vascular reconstruction is impaired by acute thrombotic occlusion. Prosthetic materials are thrombogenic and cause platelet adhesion and activation of the coagulation cascade. Heparin is a potent anticoagulant drug widely used to prevent and treat thrombosis. A new ePTFE graft with long-term bonding of heparin is now commercially available in several European countries, but a basic analysis of its mechanism of action in humans has never been performed. This study was performed to evaluate the thrombogenicity of heparin-bonded ePTFE grafts compared with standard ePTFE in a newly developed human ex vivo model.. Nonanticoagulated blood was drawn from antecubital veins of 10 healthy donors with a 19-gauge needle. The proximal end of a 60-cm ePTFE vascular graft with a diameter of 3 mm was connected to the needle while the distal end was connected to a syringe, which was placed in a syringe pump. Every volunteer served as his or her own control by using a heparin-bonded ePTFE graft on one arm and a standard ePTFE graft on the other arm. The perfusions were performed over 6 minutes with a flow rate of 20 mL/min, corresponding to a shear rate of 74/s. Serial samples were taken at the distal end of the graft for determination of prothrombin fragment 1 + 2, fibrinopeptide A, and P-selectin expression on perfused platelets. Fibrin deposition and platelet deposition were studied by using scanning electronic microscopy.. Fibrinopeptide A production over time was significantly reduced on the heparin-bonded ePTFE grafts compared with standard ePTFE grafts (P < .05). There was no increase in the production of prothrombin fragment 1 + 2 or P selectin over time on either type of graft. Scanning electronic microscopy scanning showed platelet deposition and fibrin formation on standard ePTFE grafts, whereas no platelets or fibrin were observed on heparin-bonded ePTFE grafts.. Heparin immobilization substantially reduces the thrombogenicity of small-diameter ePTFE in a newly developed human ex vivo model. In this study, we provide evidence that the mechanism of action of the heparin bonding is due not only to anticoagulant but also to antiplatelet effects. Heparin bonding may be an important improvement of ePTFE, resulting in better patency rates for vascular reconstructions.

Topics: Blood Vessel Prosthesis; Fibrin; Fibrinopeptide A; Heparin; Humans; P-Selectin; Peptide Fragments; Platelet Adhesiveness; Polytetrafluoroethylene; Prothrombin; Thrombosis

Patients with heparin-induced thrombocytopenia urgently requiring surgery with cardiopulmonary bypass (CPB) present a unique management challenge that must be addressed by the use of alternative anticoagulants. Although clinical success with the direct thrombin inhibitor hirudin has been reported, there is sparse information in the literature supporting the efficacy of this drug as an anti-thrombotic to prevent fibrin formation during CPB. In this report, we describe the efficacy of this drug to prevent thrombin-mediated fibrin formation during CPB.

Topics: Adult; Anticoagulants; Cardiopulmonary Bypass; Chondroitin Sulfates; Contraindications; Dermatan Sulfate; Endarterectomy; Fibrinolytic Agents; Fibrinopeptide A; Heparin; Heparitin Sulfate; Hirudins; Humans; Hypertension, Pulmonary; Hypothermia, Induced; Male; Peptide Fragments; Postoperative Complications; Prothrombin; Pulmonary Embolism; Purpura, Thrombocytopenic, Idiopathic; Recombinant Proteins; Thrombectomy; Thrombin; Thrombosis

We aimed to investigate plasma levels of molecular markers for platelet activity, thrombin activation and fibrinolytic status in patients with dilated cardiomyopathy (DCM) with and without left ventricular (LV) thrombus and to compare these markers between patients with DCM and control participants.. The study population comprised 60 patients with DCM who met the inclusion criteria. Patients were divided into two groups: 22 patients with LV thrombus and 38 patients without LV thrombus. The age-matched control group consisted of 23 healthy participants (18 men and five women with a mean age of 49). Patients with DCM and healthy participants were compared with respect to platelet activity, thrombin activation and fibrinolytic status. These comparisons were also performed in patients with DCM with and without LV thrombus.. Platelet factor 4 (28.2+/-4.4 ng/ml compared with 20+/-3.1 ng/ml, P<0.01) and beta-thromboglobulin (40+/-2 ng/ml compared with 17+/-3 ng/ml) levels, reflecting platelet activity, were significantly higher in patients with DCM than in control participants. Fibrinopeptide A (6.94+/-0.69 ng/ml compared with 1.96+/-0.1 ng/ml, P<0.001) and thrombin-antithrombin III complex (5.26+/-2.60 ng/ml compared with 3.17+/-1.23 ng/ml, P<0.001) levels, as markers of fibrin generation, were also higher in patients with DCM than in normal participants. Plasma levels of D-dimer (118+/-16 ng/ml compared with 85+/-3 ng/ml, P<0.001) and plasmin-alpha2-plasmin inhibitor complex (0.8+/-1.1 microg/ml compared with 0.6+/-1.7 microg/ml, P<0.001) in patients with DCM significantly exceeded those in the normal participants. There were no statistically significant differences between patients with and without LV thrombus in DCM with respect to platelet activity, thrombin activation and fibrinolytic status.. We have shown that platelet activation, thrombin activation and fibrinolytic activity are increased in patients with DCM compared to control participants. However, these markers reflecting coagulation activation in patients with LV thrombus are comparable to those in patients without LV thrombus.

Topics: Adult; Antithrombin III; beta-Thromboglobulin; Biomarkers; Blood Coagulation; Cardiomyopathy, Dilated; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Heart Ventricles; Humans; Male; Middle Aged; Peptide Hydrolases; Platelet Activation; Platelet Factor 4; Stroke Volume; Thrombin; Thrombosis; Turkey

Factor (F)Xa and thrombin bound to the clot during its formation contribute to the propensity of thrombi to activate the coagulation system. The aim of this work was to study the inhibition of clot-bound FXa and clot-bound thrombin by SanOrg123781A, a synthetic hexadecasaccharide that enhances the inhibition of thrombin and FXa by antithrombin (AT). SanOrg123781A, designed to exhibit low non-specific binding to proteins other than AT, was compared with heparin. In buffer, heparin and SanOrg123781A inhibited FXa and thrombin at similar concentrations [concentration inhibiting 50% (IC50) of Xa and IIa activity were, respectively: heparin 120 +/- 7 and 3 +/- 1 ng mL-1; SanOrg123781A 77 +/- 5 and 4 +/- 1 ng mL-1]. In human plasma, the activity of both compounds was reduced, although the activity of heparin was much more affected than that of SanOrg123781A (IC50 values for inhibition of FXa and FIIa activity were, respectively: heparin 100 +/- 5 and 800 +/- 40 ng mL-1; SanOrg123781A 10 +/- 5 and 30 +/- 3 ng mL-1). We demonstrated, in agreement with our previous results, that the procoagulant activity of the clot is essentially due to clot-bound FXa and to some extent to clot-bound thrombin. We showed that heparin and SanOrg123781A were able to inhibit fragment F1+2 generation induced by clot-bound FXa with IC50 values of 2 +/- 0.5 micro g mL-1 and 0.6 +/- 0.2 micro g mL-1, respectively. Both compounds also inhibited clot-bound thrombin activity, the IC50 values of heparin and SanOrg123781A being 1 +/- 0.01 micro g mL-1 and 0.1 +/- 0.1 micro g mL-1, respectively. Moreover, both heparin and SanOrg123781A significantly inhibited fibrinopeptide A generated by the action of clot-bound thrombin on fibrinogen but also by free thrombin generated from prothrombin by clot-bound FXa with IC50 values of 4 +/- 0.6 and 1 +/- 0.1 micro g mL-1, respectively. As with clot-bound enzymatic activities, SanOrg123781A was three times more active than heparin in vivo on fibrinogen accretion onto a pre-existing thrombus and as activators of recombinant tissue-type plasminogen activator-induced thrombolysis. In conclusion, due to the specific activities of SanOrg123781A, this compound is much more active than heparin in the presence of plasma proteins, on clot-bound enzymes and in in vivo models of thrombosis/thrombolysis.

Topics: Animals; Antithrombin III; Blood Coagulation; Factor Xa; Factor Xa Inhibitors; Fibrinopeptide A; Heparin; Humans; Inhibitory Concentration 50; Male; Peptide Fragments; Polysaccharides; Prothrombin; Rabbits; Thrombin; Thrombolytic Therapy; Thrombosis

The aim of this study was to characterize soluble fibrin(ogen) species in human, arterial, in-vivo-formed thrombi, using the immunoblotting technique. Specimens were collected via intra-arterial catheters in six patients scheduled for catheter-directed thrombolysis. Unreduced and reduced samples of the supernatants from the arterial thrombi-derived specimens were electrophoresed on polyacrylamide gels and immunoblotted, using specific mono- and polyclonal anti-fibrin(ogen) antibodies. The reduced samples disclosed substantial amounts of high molecular weight material, consistent with alpha-chain polymers and gammagamma-dimers, as well as lower molecular weight material, such as alpha-, beta- and gamma-chains. No fibrinogen with intact fibrinopeptide A was detectable, and des-AABB fibrin represented a major fibrin derivative in the soluble part of the arterial thrombi. The alpha-chains were C-terminally degraded, most of them distal to position 259. In conclusion, we have demonstrated the presence of cross-linked fibrin derivatives in soluble, arterial thrombus-related material, without signs of fibrinogen-fibrin hybrids. The fibrin derivatives were C-terminally degraded, thus representing X-oligomeric material, most probably originating from plasmin degradation of insoluble thrombus fibrin. The present study supports the hypothesis of a dynamic equilibrium between clotting and lysis in thrombi.

Topics: Aged; Antibodies, Monoclonal; Arteries; Blotting, Western; Female; Fibrin; Fibrinogen; Fibrinopeptide A; Humans; Male; Middle Aged; Molecular Weight; Oxidation-Reduction; Protein Structure, Quaternary; Solubility; Thrombosis

To clarify the sequence of alterations in the thrombotic and fibrinolytic systems after acute brain infarction, we prospectively examined sequential changes in coagulatory markers in 38 patients suffering from cardioembolic infarcts (CEI), 41 patients with atherothrombotic infarcts (ATI), 58 patients with lacunar infarcts (LI), and 32 age-matched controls. The plasma level of thrombin-antithrombin III complex (TAT), fibrinopeptide A (FpA), D-dimer, fibrin degradation products-E (FDP-E), fibrinogen, alpha2-plasmin inhibitor-plasmin complex (PIC), and percent activity of antithrombin III (AT-III) were measured within 48 h, at 1 week, and at 3 weeks after the stroke onset. Significantly elevated levels of TAT and FpA, which are both markers of thrombin formation, were observed in CEI patients, and these elevated levels were associated with increasing D-dimer levels for 3 weeks (P<0.0001). D-Dimer in CEI patients was significantly elevated compared to control, LI and ATI levels within 48 h (P<0.001). Percent activity of AT-III was significantly decreased in CEI patients for 3 weeks compared to this activity in controls, LI and ATI (P<0.001). TAT and FpA also increased significantly within 48 h in ATI subjects and declined thereafter. A significant elevation of FDP-E (P<0.001) and D-dimer (P<0.05, P<0.01) was detected in parallel with increasing fibrinogen for 3 weeks. However, there was no significant depletion of percent activity of AT-III in ATI. In LI subjects, no significant elevation of TAT, D-dimer or FDP-E were observed within 1 week. PIC increased significantly in three subtypes of brain infarcts, but did not differ significantly among the three subtypes for 3 weeks. An accurate assessment of sequential alterations in thrombotic and fibrinolytic markers in the acute stage of brain infarct should contribute to the clinical diagnosis of brain infarct subtype. Alterations in these markers in response to activation of the coagulatory system are attributable to the different pathogenesis of ischemic stroke.

Topics: Aged; alpha-2-Antiplasmin; Antifibrinolytic Agents; Antithrombin III; Brain Infarction; Female; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysin; Fibrinolysis; Fibrinopeptide A; Humans; Male; Risk Factors; Thrombin; Thrombosis

We investigated soluble, thrombin-related material in arterial thrombi and venous plasma during catheter-directed thrombolysis with alteplase. Arteriography was performed before thrombolysis and 0.5, 3, 10 and 24 h after the onset of treatment in six patients with (sub)acute lower extremity ischaemia caused by native artery or bypass occlusion. Samples were collected simultaneously from the thrombus and venous blood. After adding inhibitors of thrombin and plasmin, the centrifuged samples were assayed for prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT) and fibrinopeptide A (FPA). Levels of F1+2, TAT and FPA were extremely elevated in the thrombus-related samples before the blood flow was re-established (at 0 and 0.5 h) in all five successfully treated patients. In comparison, venous plasma levels of F1+2, TAT and FPA were moderately elevated, and reached a maximum at 3 h. In conclusion, material aspirated from lysing human thrombi formed in vivo contains large amounts of F1+2, TAT and FPA, but our methods prevented us from detecting enzymatically active thrombin.

Topics: Aged; Angiography; Antithrombin III; Blood Coagulation Factors; Catheterization; Female; Fibrinolytic Agents; Fibrinopeptide A; Humans; Ischemia; Leg; Male; Middle Aged; Peptide Fragments; Peptide Hydrolases; Protein Precursors; Prothrombin; Solubility; Thrombolytic Therapy; Thrombosis; Time Factors; Tissue Plasminogen Activator; Treatment Outcome

In this study the intrinsic thrombogenicity of the extracorporeal circuits and the benefit of heparin-bonded circuits in an extracorporeal life support system without full systemic heparinization and with minimal interference of the so called material-independent factors was tested in four calves. In two circuits (group A) all blood-contacting surfaces were coated with end-point-attached heparin and the other two were non-coated (group B). Under standardized conditions the calves were perfused at a blood flow rate of 2 L/min. After only one bolus injection of heparin (250 IU/kg body weight) before cannulation, plasma heparin activity rapidly decreased in both groups: half life of about 55 minutes. This decrease of the heparin activity was accompanied by a fall of the activated clotting time (ACT) level to baseline values. The experiments using a heparin-coated circuit, had a runtime of more than 360 minutes, whereas the experiments using a non-coated circuit had to be terminated after a runtime of 255 minutes, because massive fibrin formation was noticed in the circuit. This formation was accompanied by a rapid increase in the line pressure, measured just before the inlet of the oxygenator. The macroscopic inspections after terminating the experiments and rinsing the circuit showed a clean circuit in group A. The fibrinopeptide A (FPA) level increased faster during perfusion with the non-coated circuit than in the heparin coated circuit. Lung histopathological examinations of the lungs of the animals in group A showed no fibrin deposition, whereas most of the blood vessels of the lung preparations of the animals in group B were partially or completely occluded with fibrin. These results suggest that heparin-bonding greatly reduces the thrombogenicity of the extracorporeal circuit, and therefore it can reduce the need for systemic heparinization in an extracorporeal life support system.

Topics: Animals; Anticoagulants; Antifibrinolytic Agents; Catheterization, Peripheral; Cattle; Extracorporeal Circulation; Extracorporeal Membrane Oxygenation; Fibrin; Fibrinopeptide A; Heparin; Lung; Surface Properties; Thrombosis; Whole Blood Coagulation Time

We evaluated the contributions of coagulation factors IIa (thrombin) and Xa to small-diameter prosthetic graft thrombogenicity in vivo.. Preclotted and nonpreclotted (collagen-coated) polyester grafts were studied before and 24 hours after implantation into pig femoral arteries. After incubation of explanted grafts was performed with plasma depleted of vitamin K-dependent coagulation factors by barium chloride adsorption (Ba-plasma), graft-associated thrombin activity was determined by radioimmunoassay for fibrinopeptide A. Fibrinopeptide A levels reflect thrombin-mediated fibrin formation. Factor Xa activity was characterized by measuring activation of prothrombin added to Ba-plasma.. Thrombin and factor Xa were associated with the luminal surfaces of preclotted grafts before and 24 hours after implantation. Nonpreclotted grafts had negligible procoagulant activity before implantation. After 24 hours in vivo graft-associated factor Xa activity was similar in both nonpreclotted and preclotted grafts; however, more thrombin was bound to nonpreclotted coated grafts (p < 0.01).. The procoagulant activity of small-diameter prosthetic grafts persists for 24 hours after implantation and is attributable not only to graft-associated thrombin but also to de novo thrombin elaboration induced by factor Xa. Moreover, graft-associated procoagulant activity is not dependent on preclotting because it develops on nonpreclotted, collagen-coated grafts as well. Treatment strategies to attenuate graft thrombosis may require the inhibition of both thrombin and factor Xa.

Topics: Adsorption; Animals; Barium Compounds; Blood Coagulation; Blood Vessel Prosthesis; Chlorides; Collagen; Factor Xa; Femoral Artery; Fibrin; Fibrinopeptide A; Graft Occlusion, Vascular; Polyesters; Polyethylene Terephthalates; Prosthesis Design; Prothrombin; Surface Properties; Swine; Thrombin; Thrombosis; Vitamin K

Topics: Animals; Anticoagulants; Artifacts; Blood Coagulation Factors; Blood Specimen Collection; Disease Models, Animal; Fibrinopeptide A; Rats; Records; Reproducibility of Results; Research Design; Thrombosis

Venous thrombosis is a relatively usual but serious complication of permanent transvenous pacing. However, the pathogenesis has not been defined. To clarify underlying abnormalities in the coagulation-fibrinolysis system in patients with permanent transvenous pacemakers, we measured serum levels of fibrinopeptide A (FPA), thrombin-antithrombin III complexes (TATs), plasmin-alpha 2 plasmin inhibitor complexes (PICs), D-dimer (D-D), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4) in 53 patients with permanent transvenous pacemakers and 10 control subjects. The patients were divided into two groups, as follows, according to the presence of mural thrombus documented along the pacing lead(s) by digital subtraction angiography and transesophageal echocardiography: Group Th (-), patients without venous route thrombus; and Group Th (+), patients with venous route thrombus. FPA and TAT levels increased significantly even in Group Th (-), and further increased in Group Th (+) compared with control subjects (FPA: 7.5 +/- 4.9, 15.3 +/- 8.8 vs 3.0 +/- 1.4 ng/mL, respectively, P < 0.05; TAT: 2.9 +/- 1.3, 4.8 +/- 2.3 vs 1.7 +/- 0.6 ng/mL, respectively, P < 0.05). There were no differences in levels of D-D, PIG, beta-TG, and PF4 among control subjects, Group Th (-), and Group Th (+). These findings suggest that the hypercoagulable state appears in patients with permanent transvenous pacemakers, even without apparent venous thrombosis. The patients with permanent transvenous pacemakers are thought to be in the prethrombotic state even if they have no venous route thrombosis.

Topics: Adult; Aged; Aged, 80 and over; alpha-2-Antiplasmin; Angiography, Digital Subtraction; Antifibrinolytic Agents; Antithrombin III; beta-Thromboglobulin; Blood Coagulation; Cardiac Pacing, Artificial; Echocardiography, Transesophageal; Female; Fibrin Fibrinogen Degradation Products; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Fibrinopeptide A; Heart Diseases; Humans; Male; Middle Aged; Pacemaker, Artificial; Peptide Hydrolases; Platelet Factor 4; Serine Proteinase Inhibitors; Thrombophlebitis; Thrombosis

We report the first direct detection of a fibrinogen mutation by electrospray ionisation mass spectrometry. The propositus, from a family with a history of thrombosis, came to attention after a pulmonary embolism subsequent to a spontaneous abortion. Prolonged thrombin (41 s) and reptilase times (26 s) together with an impairment of fibrinopeptide B release suggested a mutation at the thrombin cleavage site of the Bbeta chain. Direct mass analysis of purified fibrin chains from a thrombin induced clot showed that 50% of the Bbeta chains remained uncleaved. The measured mass of the mono sialo isoform of this uncleaved chain was 54150 Da, compared to a value of 54198 Da for normal Bbeta chains. This decrease of 48 Da in the intact protein is indicative of either a Bbeta 14 Arg to Cys, or Arg to Leu substitution. Heterozygosity for the Bbeta 14 Arg --> Cys mutation was verified by PCR amplification and DNA sequence analysis.

Topics: Adult; Amino Acid Substitution; Arginine; Catalysis; Cysteine; Family Health; Female; Fibrin; Fibrinogen; Fibrinopeptide A; Fibrinopeptide B; Glycoproteins; Heterozygote; Humans; Mass Spectrometry; Molecular Weight; Mutation; Point Mutation; Polymerase Chain Reaction; Sequence Analysis; Thrombin; Thrombosis

The mechanism of anastomotic thrombosis in microvascular surgery remains poorly understood. We hypothesized that thrombin activity at anastomoses plays a major role in this process. To study this, a surgically relevant human artery anastomosis model was used to (i) measure surface thrombin activity on anastomoses and on intact vessel, (ii) determine the inhibitability of surface thrombin by heparin and recombinant hirudin (r-hirudin), and (iii) determine the anastomotic and intact vessel binding capacity for additional thrombin. Human placental artery segments were placed in chambers in which 0.2 cm2 of luminal surface was exposed to citrated platelet-poor plasma for 10 min at 37 degrees C. The fibrinopeptide A (FPA) concentration (indicating the action of thrombin on fibrinogen) in the supernatant was then measured using an ELISA assay. Intact vessels and anastomoses expressed equivalent thrombin activity that could not be inhibited by heparin at a concentration (0.3 U/ml) that is sufficient to prolong the activated partial thromboplastin time two-fold. Conversely, the concentration of heparin routinely used in intraoperative vessel irrigation solutions (50 U/ml) was able to completely block thrombin activity at both sites. r-Hirudin (0.3 heparin equivalent anti-IIa U/ml) was able to inhibit nearly all of the thrombin activity on each site. Each site was able to bind and express the activity of additional thrombin, indicating the potential for increased vessel thrombogenicity after local clot has formed and has been removed. These data indicate the presence of thrombin on dissected human vessels and its presence in equal amounts on intact and anastomosed vessels when measurement is made before blood flow resumes. Furthermore, vessel-associated thrombin is resistant to a standard systemic concentration of heparin but is susceptible to the much higher heparin concentration that can be delivered locally by the surgeon during vessel irrigation.

Topics: Anastomosis, Surgical; Arteries; Dissection; Dose-Response Relationship, Drug; Fibrinopeptide A; Heparin; Hirudins; Humans; Microcirculation; Recombinant Proteins; Thrombin; Thrombosis; Vascular Surgical Procedures

Atherosclerotic plaque rupture may trigger the formation of mural thrombus. This thrombus formation is apparently affected by very high and complex shear conditions introduced by the luminal narrowing (stenosis) of the atheroma. To study the impact of such blood flow behaviour on thrombus formation we employed a model system where collagen-induced thrombogenesis is studied at the apex of well-defined eccentric stenoses. Thrombus formation in non-anticoagulated human blood drawn directly from an antecubital vein over the collagen coated stenosis apex for periods of 0.5, 1, 3 or 5 min was quantified by morphometry. The stenoses reduced the cross-sectional area of the blood flow channel by 60, 80 and 89%, which corresponded to apex wall shear rates of 2600, 10,500 and 32,000 s-1, respectively. Platelet-collagen adhesion decreased by increasing shear at the stenosis apex. The corresponding adhesion rates were highest at 1 min, then they gradually decreased upon prolongation of the perfusion time. The platelet thrombus volume increased in concert with increasing shear rate up to 10,500 s-1, whereas, at 32,000 s-1, the volume wa decreased. The corresponding growth rates and rates of thrombus occlusion at the apex levelled off at 3 min. Significant fibrin deposition was not observed before 3 min, and was most pronounced at 10,500 and 32,000 s-1. The plasma levels of fibrinopeptide A and beta-thromboglobulin increased in concert with increasing shear and perfusion time, particularly at the two highest shear conditions. Thus, hallmarks of thrombus formation at these stenoses with increasing shear are decreased platelet-collagen adhesion, and increased platelet-platelet interaction and fibrin deposition. A fibrin tail downstream to the collagen-attached platelet thrombus is regularly observed when thrombus occlusion exceeds 40%. However, the reduced thrombus growth at the most occlusive stenosis (89%) is presumably due to the high shear stresses which may reduce the rate of platelet incorporation into the thrombus and/or tear off thrombus fragments.

Topics: Analysis of Variance; Arteriosclerosis; beta-Thromboglobulin; Case-Control Studies; Collagen; Constriction, Pathologic; Fibrin; Fibrinopeptide A; Humans; Kinetics; Platelet Adhesiveness; Regional Blood Flow; Stress, Mechanical; Thrombosis

Rethrombosis limits the efficacy of coronary thrombolysis and may result from surface-associated thrombin, de-novo prothrombin activation, or both. This study was designed to determine the relative roles of thrombin, factor Xa, and the complex of tissue factor and factor VIIa in the procoagulant activity on injured arteries with evolving thrombi.. Extensive vascular injury and platelet-rich thrombi were induced in the abdominal aorta of 25 anesthetized rabbits by applying anodal current through a transluminal electrode for 3 h. Injured vessel segments were excised and placed in a chamber permitting perfusion over the luminal surface and associated thrombus.. Vessel segments perfused with recalcified, citrated human plasma induced marked increases in the concentration of fibrinopeptide A, a marker of thrombin-induced fibrin formation, in the effluent plasma after 10 min (4636 +/- 1894% of fibrinopeptide A in the nonperfused plasma, n = 5). Perfusion with plasma depleted of vitamin K-dependent coagulation factors prevented the increase in fibrinopeptide A (122 +/- 30%, n = 4), indicating the lack of preformed functional thrombin. Furthermore, appearance of fibrinopeptide A was attenuated by perfusion with plasma containing 0.1 mumol/l recombinant tick anticoagulant peptide, a specific inhibitor of factor Xa (594 +/- 320%, n = 3), and by preincubation of vessel segments with a monoclonal antibody to rabbit tissue factor (438 +/- 220%, n = 3).. Procoagulant activity on injured vessels and associated thrombi is mediated by factor Xa, a product of the functional initiation of coagulation by factor VIIa associated with tissue factor. Accordingly, inhibition of tissue factor-mediated coagulation may be effective for attenuation of active thrombogenesis on injured vessels and during thrombolysis.

Topics: Animals; Aorta, Abdominal; Blood Coagulation; Coronary Thrombosis; Disease Models, Animal; Factor VIIa; Factor Xa; Fibrinopeptide A; Humans; Microscopy, Electron, Scanning; Prothrombin; Rabbits; Thrombin; Thrombolytic Therapy; Thromboplastin; Thrombosis

Acute thrombosis is thought to contribute to abrupt coronary occlusion during percutaneous coronary revascularization despite the administration of heparin and aspirin. This study was designed to detect the presence of heparin-resistant thrombin activity and to define its relationship to the acute ischemic complications of coronary interventions.. Plasma levels of fibrinopeptide A (FPA) and prothrombin fragment 1.2 (F1.2), markers of thrombin and factor Xa activity, respectively, were measured in the coronary sinus with heparin-bonded catheters in 58 patients undergoing coronary interventions. Activated coagulation times were maintained > 300 seconds by the Hemochron method. Mean FPA levels decreased significantly, from 7.0 +/- 0.9 nmol/L before the procedure to 5.2 +/- 0.5 nmol/L after the heparin bolus and to 2.9 +/- 0.2 nmol/L after the procedure (P = .0001). In 26 patients (45%), FPA levels remained above the threshold for suppression angioplasty of thrombin activity determined during angiography in 7 patients without coronary artery disease (> 3.0 nmol/L). FPA concentrations after coronary interventions were increased in patients with intracoronary thrombus (P = .01), abrupt coronary occlusion (P = .06), postprocedural non-Q-wave myocardial infarction (P = .04), and clinically unsuccessful procedures (P = .04). F1.2 levels were relatively low before the procedures and did not change significantly.. Heparin administration suppresses thrombin activity in most but not all patients undergoing coronary interventions. Heparin-resistant thrombin activity is associated with angiographic evidence of intracoronary thrombus and ischemic complications of coronary interventions.

Topics: Acute Disease; Aged; Angiography; Blood Specimen Collection; Cardiac Catheterization; Factor Xa Inhibitors; Female; Fibrinopeptide A; Heparin; Humans; Male; Middle Aged; Myocardial Ischemia; Peptide Fragments; Prothrombin; Reproducibility of Results; Thrombin; Thrombosis; Whole Blood Coagulation Time

Tick anticoagulant peptide (TAP) is a potent and selective inhibitor of factor Xa. TAP has shown good antithrombotic efficacy in experimental animal models of disseminated intravascular coagulation and venous and arterial thrombogenesis. In the present study we evaluated the effect of recombinant TAP (rTAP) on acute thrombus formation in human nonanticoagulated blood triggered either by tissue factor (TF) or by collagen at arterial shear conditions. The main goal was to establish the role of factor Xa in thrombus formation by use of an optimal inhibitory concentration of rTAP. Blood was drawn directly from an antecubital vein by a pump over the respective thrombogenic surfaces, which were positioned in a parallel-plate perfusion chamber. rTAP was mixed homogeneously into the flowing blood by a heparin-coated device positioned proximal to the perfusion chamber. The passage of blood through this device caused minor activation of coagulation but little activation of platelets. Fibrinopeptide A and beta-thromboglobulin levels after 5 minutes of blood perfusion were, on average, 14 ng/mL and 45 IU/mL, respectively. rTAP at a plasma concentration of 0.90 mumol/L completely inhibited TF/factor VIIa-dependent thrombus formation at wall shear rates of 650 and 2600 s-1. These shear conditions are comparable to those in medium-sized arteries and in moderately stenosed small arteries, respectively. In contrast to the TF-coated surface, rTAP was less efficient in reducing collagen-induced thrombus formation. While a significant reduction of 53% was observed at 650 s-1, thrombus formation at 2600 s-1 was not affected by rTAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Arthropod Proteins; beta-Thromboglobulin; Blood Coagulation; Blood Platelets; Collagen; Factor VIIa; Factor Xa; Factor Xa Inhibitors; Fibrinopeptide A; Humans; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Peptides; Recombinant Proteins; Thromboplastin; Thrombosis

Activated platelets provide assembly sites for coagulation enzyme complexes and in this way can mediate coagulation during hemostasis and thrombosis. In this study, we examined the procoagulant activity of platelets adhering directly to fibrillar collagen, a main thrombogenic constituent of subendothelium. For this purpose, we used a human ex-vivo thrombosis model in which collagen-coated coverslips were exposed to flowing nonanticoagulated blood (shear rate, 65/s) for 5.5 minutes, which led to the deposition of adherent platelets, platelet thrombi, and fibrin. To examine the procoagulant activity of adherent platelets only, a selective antagonist of the platelet GPIIb-IIIa complex, Ro 44-9883, was infused via a mixing device, resulting in a complete abrogation of platelet thrombus formation but leaving the collagen-adherent platelet layer intact. This platelet layer generated increased postchamber fibrinopeptide A (FPA) levels (203 +/- 33 ng/mL) as compared with control experiments without infusion of inhibitor (95 +/- 13 ng/mL). Concomitantly, fibrin deposition measured by morphometric analysis of cross-sections was also increased, as was the platelet adhesion to collagen. An immunochemical staining of fibrin fibers further showed that the adherent platelets formed the nuclei for fibrin fiber formation. This increase in fibrin deposition was mediated by the intrinsic factor X (F.X) activation complex on adherent single platelets, because almost complete inhibition of FPA generation (9 ng/mL) and fibrin deposition (0.4% +/- 0.2% coverage) was achieved upon coinfusion of the GP IIb-IIIa antagonist and active site-inhibited F.IXa. The large platelet thrombi that were deposited in control experiments contained no significant amounts of immunodetectable fibrin except at the thrombus base, where adherent platelets anchored the thrombi to the collagen surface. These results suggest that the collagen-adherent platelets are important promoters of coagulation during the initial phase of thrombogenesis by providing assembly sites for the F.X activation complex.

Topics: Acetates; Anticoagulants; Blood Coagulation; Blood Platelets; Collagen; Enzyme Activation; Factor Xa; Fibrin; Fibrinopeptide A; Hemorheology; Humans; In Vitro Techniques; Macromolecular Substances; Perfusion; Platelet Adhesiveness; Platelet Glycoprotein GPIIb-IIIa Complex; Thrombosis; Tyrosine

The role of tissue factor/factor VIIa (FVIIa) and factor VIIIa/factor IXa (FVIIIa/FIXa) complexes in thrombus formation was examined in a human ex vivo blood flow system by use of active site-blocked FVIIa (FVIIai) and FIXa (FIXai) as selective inhibitors. Blood was drawn directly from the veins of volunteers into a mixing device where FVIIai and FIXai were mixed with flowing blood. The blood then entered parallel-plate chambers containing coverslips coated with human fibrillar collagen or tissue factor-expressing cell layers of tumor necrosis factor-alpha-stimulated human endothelial cells, human smooth muscle cells, and J82 cells. Exposure of stimulated endothelial cells to blood flowing at a venous shear rate of 65/s led to fibrin deposition, which was inhibited by infusion of FVIIai (IC50, 3 nmol/L), as quantified by micro-densitometry of fibrin-stained coverslips. Whereas FIXai (600 nmol/L) was only a weak inhibitor, FVIIai (60 nmol/L) reduced fibrinopeptide A (FPA) plasma levels from 504 +/- 79 to 171 +/- 27 ng/mL and concomitantly inhibited platelet thrombus deposition. Similarly, experiments with smooth muscle cells and J82 cells showed that FVIIai but not FIXai efficiently reduced FPA levels. Conversely, with tissue factor-free collagen, ,hich induces platelet-dependent fibrin formation, infusion of FIXai but not of FVIIai inhibited fibrin deposition (IC50, 8 nmol/L) and reduced FPA levels from 55 +/- 8 to 9 +/- 5 ng/mL. However, FIXai did not affect the number of platelet thrombi deposited on collagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Sequence; beta-Thromboglobulin; Binding Sites; Blood Coagulation; Blood Platelets; Cells, Cultured; Collagen; Endothelium, Vascular; Factor VIIa; Factor XIa; Fibrin; Fibrinopeptide A; Humans; In Vitro Techniques; Molecular Sequence Data; Peptides; Platelet Activation; Rheology; Thrombosis; Time Factors

Thrombi are known to induce activation of the coagulation system, which may be a mechanism for progression of thrombosis and its recurrence after thrombolysis. This study was designed to characterize the relative role of thrombin and activated factor X (factor Xa) as mediators of procoagulant activity of whole blood clots in blood and plasma.. Clots formed from human blood were incubated in recalcified (25 mmol/L CaCl2) citrated plasma or nonanticoagulated blood with increasing concentrations of recombinant desulfatohirudin (hirudin) to inhibit thrombin activity, recombinant tick anticoagulant peptide (TAP) or recombinant tissue factor pathway inhibitor (TFPI) to inhibit factor Xa, or heparin. Fibrinopeptide A (FPA) was assayed serially as an index of procoagulant (thrombin) activity. FPA generation was greatly accelerated by addition of clots to recalcified plasma (from 1251 +/- 211 ng/mL after 15 minutes without clot to 5916 +/- 1412 ng/mL with clot, n = 7, P < .01) or whole blood (4803 +/- 761 ng/mL with clot compared with 546 +/- 233 without clot, n = 5, P < .05) and was attenuated by inhibitors of thrombin (> 90% inhibition of FPA with 0.05 mumol/L hirudin and 1.0 U/mL heparin) and factor Xa (> 90% inhibition of FPA with 1.0 mumol/L TAP and 0.15 mumol/L TFPI) in a concentration-dependent manner. Preincubation of clots with tissue-type plasminogen activator sufficient to induce partial clot lysis increased the rate of thrombin-induced FPA generation by increasing the surface area of clot exposed to plasma. However, procoagulant activity induced by partially lysed clots was attenuated by lower concentrations of both thrombin and Xa inhibitors, presumably because access of the inhibitors to bound procoagulant molecules was facilitated. Comparable results were obtained with incubations in nonanticoagulated blood.. These results indicate that factor Xa is primarily responsible for the procoagulant activity of clots in vitro and suggest a potential molecular mechanism for the observed efficacy of inhibitors of factor Xa in preventing recurrent thrombosis after coronary thrombolysis.

Topics: Arthropod Proteins; Blood Coagulation; Factor Xa; Factor Xa Inhibitors; Fibrinolysis; Fibrinopeptide A; Heparin; Hirudins; Humans; Intercellular Signaling Peptides and Proteins; Lipoproteins; Peptides; Recombinant Proteins; Thrombin; Thrombosis; Tissue Plasminogen Activator

The abrupt cessation of heparin and other thrombin inhibitors when used to treat acute coronary syndromes has been accompanied by a clustering of thrombotic events. It is unknown whether these events are the result of inadequate antithrombin therapy or whether they represent a rebound increase in thrombin activity. This study was designed to determine whether there is a true rebound, as defined by an increase followed by a subsequent decrease, in thrombin activity after discontinuation of intravenous heparin therapy.. Thirty-five patients with recent acute myocardial infarction or unstable angina who had received at least 48 hours of intravenous heparin were studied. Patients underwent ST-segment monitoring, and blood samples for determination of thrombin generation and activity were drawn at 0, 3, 6, 10, and 24 hours after heparin discontinuation. Median aPTT was 65 seconds before heparin discontinuation. Median fibrinopeptide A increased from 9.5 to 16.9 ng/mL at 3 hours (P < .0004) and returned to 10.5 by 24 hours. Prothrombin fragment 1.2 likewise transiently increased, from 0.34 to 0.51 nmol/L at 6 hours (P < .0002). Modified antithrombin III decreased over time (P < .002), and activated protein C increased from 2.3 to 4.5 ng/mL at 3 hours (P < .001). Although there were no clinical thrombotic events in the first 24 hours, 4 patients had evidence of ischemia by ST-segment monitoring at a median of 12 hours after heparin discontinuation. The degree of increase in fibrinopeptide A and prothrombin fragment 1.2 was not found to be associated with baseline diagnosis, duration of heparin therapy, baseline level of antithrombin III, or activated protein C.. This study demonstrates a transient rebound increase in thrombin activity as well as in activated protein C upon abrupt discontinuation of intravenous heparin. Clinicians should be vigilant for associated thrombotic events. Further investigation of the significance, mechanism, and possible prevention of this rebound phenomenon is needed.

Topics: Aged; Angina, Unstable; Blood Coagulation Factors; Blood Coagulation Tests; Coronary Thrombosis; Electrocardiography; Female; Fibrinopeptide A; Heparin; Humans; Infusions, Intravenous; Male; Monitoring, Physiologic; Myocardial Infarction; Myocardial Ischemia; Protein C; Substance Withdrawal Syndrome; Thrombin; Thrombosis

This study assessed three in vitro techniques designed to measure the thrombogenicity of vascular grafts. All techniques immersed vascular grafts in rotating blood. In the gravimetric analysis, the weight of adherent thrombi was recorded at 2 min intervals for 20 min. In the torque analysis, a microviscometer continuously recorded the amount of torque developed as the graft rotated for 20 min. In the thrombin analysis, the blood sample was analyzed for fibrinopeptide A production indicating fibrinogen cleavage. Expanded polytetrafluoroethylene grafts were treated by removal of air nuclei (denucleation), binding of heparin, or binding of polyethylene oxide (PEO). The gravimetric analysis determined that the time at which each group experienced clot initiation was as follows: control after 6 min, denucleation after 14 min, heparin after 18 min, and PEO after 10 min. Similarly, in the torque analysis all treatment groups significantly delayed the initial increase in torque from 8.0 min for control to 12.5 min for denucleation (P < .01), > 20 min for heparin (P < .01), and 12 min for PEO (p < .05). The thrombin analysis determined that coagulation activity was reduced relative to control at 12 min with the denucleation group (P < .05) and heparin group (P < .01) and at 18 min with all treatment groups (P < .01). The similarity of results among the techniques increases confidence that each measurement accurately predicts in vitro thrombogenicity.

Topics: Awards and Prizes; Biocompatible Materials; Blood; Blood Vessel Prosthesis; Fibrinogen; Fibrinopeptide A; Heparin; Humans; In Vitro Techniques; Polyethylene Glycols; Polytetrafluoroethylene; Stress, Mechanical; Thrombin; Thrombosis; Time Factors; Viscosity

We have studied the effect of a daily supplement of 2.4 omega-3 fatty acids (omega 3 FAs) to 16 healthy men on acute collagen-induced thrombus formation in flowing non-anticoagulated blood. The supplement was formulated as Triomar capsules, containing 60% omega-3 FAs with an eicosapentaenoic/docosahexaenoic acid ratio of 3/2. A parallel-plate perfusion chamber device was used to study thrombus formation prior to and after 3 months of omega-3 FAs supplement. The wall shear rates at the thrombogenic surface were 650, 2,600 and 10,500 s-1, which are typical for small arteries, slightly stenosed arteries and severely stenosed arteries, respectively. For the latter situation a parallel-plate perfusion chamber with an eccentric stenosis occluding 80% of the cross-sectional area of the blood flow channel was used. The dietary supplement of omega-3 FAs did not cause significant changes in platelet adhesion to collagen or in thrombus volume. However, fibrin deposition was reduced by 34% (P < 0.03) at the highest shear condition (stenosis). Plasma fibrinogen was reduced by 18% (P < 0.0006). Changes in serum concentration of triglycerides, total-cholesterol, LDL- and HDL-cholesterol were not significant. Our data suggest that a moderate intake of omega-3 FAs provides virtually no protection against acute platelet-dependent thrombus formation, irrespective of the shear conditions. However, the significant reduction in plasma levels of fibrinogen following dietary supplementation of omega-3 FAs may be important, since high levels of fibrinogen is associated with cardiovascular disease and thrombosis.

Topics: Adult; beta-Thromboglobulin; Cholesterol; Cholesterol, HDL; Cholesterol, LDL; Collagen; Dietary Fats, Unsaturated; Fatty Acids; Fatty Acids, Omega-3; Fibrinopeptide A; Humans; Male; Phospholipids; Thrombosis

Topics: Animals; Biomarkers; Cross Reactions; Fibrinopeptide A; Humans; Thrombosis

Nonionic contrast media have been considered by some to have thrombogenic properties. We prospectively assessed the effect of femoral artery catheterization and both nonionic and ionic contrast media on the coagulation parameters--fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FpA)--during clinical angiography.. Seventeen patients undergoing aortography were included. Blood samples were obtained before and after arterial puncture and before and up to 30 min after contrast administration.. An increase in FpA was observed after arterial puncture (range = 8.4 +/- 1.9 to 13.6 +/- 2.3 ng/ml, p < .004; data are written as mean +/- standard error of the mean). There was an observed increase in F1 + 2 after arterial puncture that was not statistically significant (2.0 +/- 0.4 to 2.3 +/- 0.4 nmol/l). No further increase was observed in either FpA or F1 + 2 levels after nonionic or ionic contrast media administration.. The increased activity of the coagulation system during angiography is related to the arterial puncture, and nonionic and ionic contrast media have no thrombogenic potential in vivo.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aortography; Biomarkers; Blood Coagulation; Catheterization, Peripheral; Contrast Media; Female; Femoral Artery; Fibrinopeptide A; Humans; Infusions, Intra-Arterial; Male; Middle Aged; Prospective Studies; Prothrombin; Punctures; Thrombosis

We have investigated the influence of blood flow on thrombin generation, fibrin formation, and fibrin deposition on procoagulant and nonprocoagulant surfaces. Nonanticoagulated human blood was drawn for 5 minutes directly from an antecubital vein over stimulated endothelial cells expressing tissue factor and over human type III collagen fibrils, positioned in parallel-plate perfusion chambers. The shear rates at these surfaces were 50, 650, and 2,600 s-1. Deposition of platelets and fibrin was measured by morphometry. Thrombin and fibrin formation was determined by measuring prothrombin fragments 1 + 2 (F 1 + 2), thrombin-antithrombin III complexes, (T-AT) and fibrinopeptide A (FPA) in blood effluent from the perfusion chamber at the end of the 5-minute perfusion period. On procoagulant endothelial cells, the thrombi were primarily composed of fibrin. The fibrin deposition (81%, 21%, and 2% at 50, 650, and 2,600 s-1, respectively) and plasma levels of F 1 + 2, T-AT and FPA were shear rate dependent and highest at 50 s-1. There was a positive correlation between F 1 + 2 and T-AT and the fibrin deposition (P < .01). In contrast, the collagen surface triggered primarily thrombi that were composed of platelets. The platelet thrombi and plasma levels of F 1 + 2 and T-AT were also dependent on the shear rate, but highest at 650 and 2,600 s-1. F 1 + 2 and T-AT reached the same level as observed with procoagulant endothelial cells at the higher shear rates. There was a positive correlation between F 1 + 2 and T-AT and the platelet thrombus formation (P < .05), confirming the predominant role of platelets in thrombin generation. Thus, thrombin formation is strongly influenced by the blood flow, and this effect depends on the composition of the thrombogenic surface.

Topics: Antithrombins; beta-Thromboglobulin; Collagen; Endothelium, Vascular; Enzyme Activation; Fibrinopeptide A; Humans; In Vitro Techniques; Perfusion; Platelet Activation; Prothrombin; Regional Blood Flow; Rheology; Surface Properties; Thrombin; Thrombosis

To determine whether, in patients undergoing percutaneous transluminal coronary angioplasty (PTCA), there are prothrombotic markers indicating those with a predisposition to restenosis.. Venous blood samples were obtained from patients undergoing PTCA for chronic stable angina. Patients with restenotic lesions, conduit stenoses or occlusive lesions were not included in the study. Samples were assayed for coagulation factors (fibrinopeptide A, antithrombin III, protein C), fibrinolytic factors [tissue-type plasminogen activator (t-PA), alpha 2 antiplasmin, plasminogen activator inhibitor (PAI-1)] and markers of platelet activation (platelet factor 4, beta thromboglobulin).. Of 46 patients who underwent successful PTCA, restenosis, defined as loss in absolute gain of more than 50%, occurred in 16 (35%). The minimal luminal diameter (mean +/- SD) at follow-up in those who had suffered restenosis was 1.07 +/- 0.7 mm compared with 1.73 +/- 0.5 mm in the non-restenotic patients. However, no significant differences in the levels of markers of platelet activation, coagulation factors, or fibrinolytic factors were observed between the two groups. The only significant difference between the groups was a higher platelet count in the restenotic patients [median (interquartile range): 263 (247-278) versus 224 (175-263), P < 0.05].. Our results suggest that patients who suffer restenosis following PTCA appear to have no clearly detectable pre-existing imbalance in their prothrombotic/antithrombotic status. Although the platelet count was higher in restenotic patients, the levels of markers of platelet activation were no different in the two groups. Thus, it is at present unlikely that simple blood assays before PTCA assessing an individual's 'thrombotic state' can help to predict which of the 30-40% of patients undergoing PTCA will suffer restenosis.

Topics: alpha-2-Antiplasmin; Angina Pectoris; Angioplasty, Balloon, Coronary; Antithrombin III; beta-Thromboglobulin; Biomarkers; Coronary Angiography; Coronary Disease; Female; Fibrinopeptide A; Follow-Up Studies; Humans; Male; Middle Aged; Plasminogen; Plasminogen Activator Inhibitor 1; Platelet Factor 4; Protein C; Recurrence; Risk Factors; Thrombosis; Tissue Plasminogen Activator

The common unfractionated heparin preparations (UFH) accelerate inhibition of most of the enzymes in the coagulation cascade, while low-molecular mass heparin (LMMH) mainly accelerates inhibition of activated coagulation factor X (FXa). The present study addresses the question of whether LMMH may be a weaker anticoagulant than UFH when the two preparations are added to plasma with equal FXa inhibitory activities. Normal and coagulation factor VIII (FVIII)-deficient plasma was used. Thrombin generation was determined by assaying the formation of the thrombin-antithrombin complexes (TAT) and of fibrinopeptide A (FPA), two parameters that showed a strong positive correlation. At a heparin concentration of 0.5 or 1.0 FXa-inhibiting IU/ml, the formation of TAT and FPA was substantial and always much more increased with LMMH than with UFH. At 4.0 FXa-inhibiting IU/ml, no FPA was generated, but traces of thrombin were. In recalcified FVIII-deficient plasma (one of the batches containing FVIII antibodies), more TAT was formed with 0.1 FXa-inhibiting IU/ml LMMH than with UFH with the same FXa-inhibiting activity. It is concluded that LMMH is a weaker anticoagulant than UFH, partly because of a poor thrombin inhibition capacity which facilitates acceleration of coagulation by FVIII activation and partly because of a poor inhibition of enzymes preceding the prothrombinase stage, both mechanisms leading to increased enzymatic activity above the prothrombin stage. As judged from the higher degree of thrombin generation with LMMH than with UFH, there is no support for the assumption that LMMH is as good an antithrombotic agent as UFH is, without reducing the haemostatic capacity as much as UFH does.

Topics: Antithrombin III; Blood Coagulation; Factor VIII; Factor X; Fibrinopeptide A; Heparin; Heparin, Low-Molecular-Weight; Humans; Peptide Hydrolases; Thrombin; Thrombosis

Modification of hemoglobin (Hb) by crosslinking and polymerization results in an improved oxygen release capacity and a prolonged vascular retention time. Modification improves the efficacy and prevents certain side effects. It eliminates leakage of Hb through the kidneys and accumulation in the tubuli. Another important issue is the degree of purification of Hb solutions. Traces of membrane fragments may cause immunogenic and thrombogenic side effects. To determine the contamination with erythrocyte membrane fragments, we developed assays for glycophorin-alpha and phospholipids. Special models were evaluated for testing the maximum allowable level of membrane contamination. As an in vitro model for thrombogenicity we used confluent monolayers of human umbilical vein endothelial cells. These cells were incubated with Hb solutions and subsequently tested on tissue factor (TF) procoagulant activity. TF was tested by the factor VII-catalyzed activation of factor X. The lower detection limit of this assay for endotoxin was 0.5 ng/ml. Hb did not cause any tissue factor expression even after prolonged incubation. No cooperation was found within endotoxin. As an in vivo test on thrombogenicity we developed a guinea pig model in which we can follow the generation of fibrinopeptide A (FPA). This is one of the most sensitive markers for thrombin activation in vivo. When slightly contaminated Hb solutions (phospholipid content 2 nmol/ml) were infused in the presence of factor Xa at a dose (9 micrograms/kg) which in itself did not induce FPA generation, we observed an increase in FPA levels in the plasma from 1.2 +/- 0.4 ng/ml to 5.2 +/- 0.7 ng/ml. Factor Xa is used to mimic a stressed clinical condition with activated coagulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Blood Substitutes; Cells, Cultured; Disease Models, Animal; Endothelium, Vascular; Exchange Transfusion, Whole Blood; Fibrinopeptide A; Guinea Pigs; Hemoglobins; Humans; Models, Biological; Solutions; Thrombosis

Coagulation and fibrinolysis were investigated in 14 claudicants undergoing percutaneous transluminal angioplasty (PTA) for femoropopliteal artery lesions. Cross-linked fibrin degradation products (XL-FDP), tissue plasminogen activator (t-PA) antigen, fibrinopeptide A (FPA), and plasminogen activator inhibitor-1 (PAI-1) activity were measured in peripheral blood. XL-FDP and t-PA increased, and FPA and PAI-1 decreased significantly after angioplasty. XL-FDP increased from baseline 266 +/- 72 ng/ml to 481 +/- 239 ng/ml (p < 0.0005) 30 min after PTA, indicating mural thrombus formation in spite of the significant fall in FPA influenced by heparin. A groin haematoma developed after PTA in 4/6 patients, who received more than 5600 IU heparin and in 1/8 patients receiving smaller dosages. The alterations in PAI-1 showed no correlation with those of t-PA, whereas heparin had a sparing effect on PAI-1 consumption. These findings may indicate that PAI-1 acts as a thrombin inhibitor following deep vessel wall injury by angioplasty. In two patients, who had signs of rethrombosis on the next day, residual FPA was relatively high, XL-FDP peaked at 3530 +/- 1170 ng/ml, and t-PA increased by 2.6 +/- 1.0 ng/ml. The corresponding values in patients with an uncomplicated course were 406 +/- 89 ng/ml (p < 0.0001) and 0.1 +/- 0.5 ng/ml (p < 0.02). We conclude that thrombin promotes activation of coagulation and fibrinolysis in femoropopliteal PTA. Instability between these counteracting systems resulting in thrombosis is not prevented by conventional heparin administration at dosages causing bleeding complications.

Topics: Aged; Angioplasty, Balloon; Blood Coagulation; Female; Femoral Artery; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Hematoma; Heparin; Humans; Intermittent Claudication; Male; Middle Aged; Plasminogen Activator Inhibitor 1; Popliteal Artery; Thrombosis; Tissue Plasminogen Activator

Cigarette smoking is a known risk factor for cardiovascular disease in men and women, and it has been suggested that this risk is linked to enhanced formation of platelet thromboxane A2 (TxA2). This led us to investigate the effect of cigarette smoking and TxA2 formation on collagen-induced thrombogenesis in flowing nonanticoagulated human blood. Thrombus formation in blood from smokers and nonsmokers was compared before and 2 hours after ingestion of a single oral dose of 990 mg aspirin, which is sufficient to block platelet TxA2 formation. Nonanticogulated blood was drawn directly from an antecubital vein over collagen fibrils in a parallel-plate perfusion chamber by a peristaltic roller pump placed distally to the chamber. Wall shear rates at the collagen surface were characteristic for medium-sized (650 s-1) and moderately stenosed (2600 s-1) arteries. Blood-collagen interactions were morphologically quantified, and markers of platelet release, beta-thromboglobulin (beta-TG), and activation of coagulation, fibrinopeptide A (FPA), were measured immediately distal to the perfusion chamber. The thrombus volume in blood from cigarette-smoking individuals was nearly twofold larger than in blood from nonsmokers at 2600 s-1 (37.4 and 19.4 microns 3/microns 2; P < .03). However, ingestion of aspirin reduced the thrombus volume in blood from smokers by 61.8% (P < .01), which was substantially more than the 37.6% reduction in blood from nonsmokers (P < .03). Neither cigarette smoking nor aspirin ingestion affected thrombus formation at 650 s-1. The plasma levels of FPA and beta-TG were slightly lower in nonsmokers and after aspirin ingestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Arteries; Aspirin; beta-Thromboglobulin; Blood Platelets; Cell Adhesion; Collagen; Constriction, Pathologic; Female; Fibrin; Fibrinopeptide A; Hematocrit; Humans; Male; Middle Aged; Platelet Count; Smoking; Thrombosis

A novel thrombin inhibitor based on single-stranded (ss) deoxynucleotides with the sequence GGTTGGTGTGGTTGG (thrombin aptamer) has been recently discovered. In this study, we tested its efficacy in inhibiting clot-bound thrombin activity and platelet thrombus formation in an ex vivo whole artery angioplasty model. The thrombin aptamer showed a specific dose-dependent inhibition of thrombin-induced platelet aggregation (0.5 U/mL) in human platelet-rich plasma, with an IC50 of approximately 70 to 80 nmol/L. In an in vitro clot-bound thrombin assay system, heparin, used at clinically relevant concentrations of 0.2 U/mL and 0.4 U/mL, was ineffective in inhibiting clot-bound thrombin (6.5% and 34.9% inhibition at 0.2 U/mL and 0.4 U/mL, respectively). In contrast, the thrombin aptamer at an equivalent anticoagulant concentration inhibited clot-bound thrombin (79.7% inhibition). In an ex vivo whole artery angioplasty model, the thrombin aptamer markedly suppressed the generation of fibrinopeptide A (FPA), whereas heparin at 2 U/mL was ineffective. Compared with a scrambled ssDNA control, the thrombin aptamer reduced platelet deposition by 34.5% +/- 5% (mean +/- SEM, n = 4, P = .09) at low shear rates (approximately 200 s-1) and 61.3% +/- 11% (mean +/- SEM, n = 4, P = .05) at high shear rates (approximately 850 s-1). Thrombin aptamers based on ssDNA molecules represent a new class of thrombin inhibitors with potent anticoagulant and antithrombotic properties.

Topics: Angioplasty; Anticoagulants; Aptamers, Nucleotide; Base Sequence; Dose-Response Relationship, Drug; Fibrinopeptide A; Humans; Molecular Sequence Data; Oligonucleotides; Platelet Aggregation; Platelet Aggregation Inhibitors; Polynucleotides; Thrombin; Thrombosis

A preparation of low molecular weight heparin (Fragmin) was administered to patients with multiorgan failure receiving continuous venovenous hemodialysis. Three patients received a high-dose regimen (35 IU/kg bolus followed by 13 IU/kg infusion), and 7 received a low-dose regimen (8 and 5 IU/kg, respectively) for 36 h. High-dose Fragmin was associated with minimal clotting in the extracorporeal circuit. Plasma fibrinopeptide A levels declined, and mean anti-Xa activity was in the range 0.47-0.79 IU/ml. The urea equilibration coefficient (UEC) (100% at initiation) remained above 90% throughout. All 3 patients had mild bleeding episodes, which led to discontinuation of Fragmin in 1. During all low-dose treatments, marked thrombus formation occurred in the extracorporeal circuit, and in 2, the circuit clotted within the study period. Fibrinopeptide A levels further increased in 4 patients, and mean anti-Xa activity was in the range 0.27-0.53 IU/ml. UEC declined appreciably in 3 treatments (including the 2 in which early circuit clotting occurred). One patient experienced a mild bleeding episode. The low-dose Fragmin regimen produced safer anticoagulation in patients at risk from bleeding and is suitable for prolonged renal support although the tendency to thrombosis may necessitate more frequent circuit changes.

Topics: Acute Kidney Injury; Adult; Aged; Blood Coagulation; Critical Care; Dalteparin; Female; Fibrinopeptide A; Hemorrhage; Humans; Male; Middle Aged; Renal Dialysis; Thrombosis

Leech antiplatelet protein (LAPP) is a specific inhibitor of collagen-induced human platelet aggregation and adhesion to collagen under static conditions. Recombinant LAPP (rLAPP) and L-366,763 (acetylated-Cys-Asn-Pro-Arg-Gly-Asp-Cys-NH2), a peptidyl fibrinogen receptor antagonist, were evaluated in an anesthetized baboon thrombosis model using a collagen-coated graft segment of an arteriovenous shunt to elicit thrombus formation. Animals were randomized to receive systemic intravenous administration of rLAPP (100 micrograms.kg-1 x min-1; n = 5), L-366,763 (8.5 micrograms.kg-1 x min-1; n = 3), or saline (n = 3). Despite complete and selective inhibition of type I collagen-induced ex vivo aggregation of platelets, rLAPP had no significant effect on the rate or the extent of 111-In-labeled platelet deposition onto the collagen graft and no effect on template bleeding time. In contrast, L-366,763 completely prevented platelet deposition, maintained blood flow, and significantly prolonged bleeding time at the dosage that inhibited ex vivo aggregation in response to all agonists studied. In this study, the absence of an antithrombotic benefit of rLAPP contrasted sharply with the efficacy of the fibrinogen receptor antagonist. These results demonstrate that specific inhibition of collagen-mediated platelet aggregation alone is not sufficient to prevent platelet-dependent thrombosis in this baboon model.

Topics: Amino Acid Sequence; Animals; Arteriovenous Shunt, Surgical; Bleeding Time; Collagen; Fibrinopeptide A; Kinetics; Male; Molecular Sequence Data; Oligopeptides; Papio; Partial Thromboplastin Time; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Recombinant Proteins; Salivary Proteins and Peptides; Thrombosis

Compared with the therapy of venous thromboembolism, there is little consensus regarding guidelines for heparin anticoagulation of patients with arterial thrombosis. This study aimed to identify the quantitative differences in the activation of the coagulation cascade and platelets in these two syndromes and to characterize their specific biological responses to heparin therapy.. Eighteen patients receiving intravenous heparin to treat venous (n = 9) or arterial (n = 9) thromboembolism were prospectively studied for an average of 4 days each. Clinical responses to treatment, activated partial thromboplastin time (aPTT), and molecular markers for thrombosis were measured regularly. Although both groups received equivalent doses of heparin (approximately 1100 units/h), the resulting aPTTs and plasma heparin activity were significantly lower in the arterial patients (P < .05 and P < .01, respectively). The plasma levels of beta-thromboglobulin (a marker for platelet activation and granule release) were significantly higher in the arterial patients (109 +/- 9.5 versus 79 +/- 7.1 ng/mL, mean +/- SEM, P < .05). In vivo fibrin formation, as evidenced by plasma levels of fibrinopeptide A, was less effectively suppressed in the patients with arterial versus venous thrombosis (18.5 +/- 3.2 versus 10.4 +/- 2 ng/mL, P < .05). Prothrombin fragments 1 + 2, a marker for prothrombinase complex activity, was nearly normal in both heparinized groups.. The anticoagulant response to heparin is blunted in patients with arterial thrombosis, at least in part by the antagonistic actions of increased platelet activation. Comparing arterial with venous thrombosis, higher doses of heparin on the average may be required to achieve comparable aPTTs, plasma heparin activity, and comparable suppression of fibrin formation.

Topics: Aged; beta-Thromboglobulin; Enzyme-Linked Immunosorbent Assay; Fibrinopeptide A; Heparin; Humans; Male; Middle Aged; Partial Thromboplastin Time; Peptide Fragments; Prospective Studies; Protein Precursors; Prothrombin; Pulmonary Embolism; Thrombosis

The effects on thrombosis and hemostasis of thrombin-induced activation of endogenous protein C (PC) were evaluated in baboons. Thrombosis was induced by placing into arteriovenous shunts a segment of Dacron vascular graft, which generated arterial platelet-rich thrombus, followed by an expansion region of low-shear blood flow, which in turn accumulated fibrin-rich venous-type thrombus. Thrombosis was quantified by 111In-platelet imaging and 125I-fibrinogen accumulation. Intravenous infusion of alpha-thrombin, 1-2 U/kg-min for 1 h, increased baseline activated PC levels (approximately 5 ng/ml) to 250-500 ng/ml (P < 0.01). The lower thrombin dose, which did not deplete circulating platelets, fibrinogen, or PC, reduced arterial graft platelet deposition by 48% (P < 0.05), and platelet and fibrin incorporation into venous-type thrombus by > 85% (P < 0.01). Thrombin infusion prolonged the activated partial thromboplastin clotting time, elevated fibrinopeptide A (FPA), thrombin-antithrombin III complex (T:AT III), and fibrin D-dimer plasma levels (P < 0.01), but did not affect bleeding times. Thrombin's antithrombotic effects were blocked by infusing a monoclonal antibody (HPC-4) which prevented PC activation in vivo, caused shunt occlusion, increased the consumption of platelets and fibrinogen, elevated plasma FPA and T:AT III levels, and reduced factor VIII (but not factor V) procoagulant activity (P < 0.05). We conclude that activated PC is a physiologic inhibitor of thrombosis, and that activation of endogenous PC may represent a novel and effective antithrombotic strategy.

Topics: Animals; Arteriovenous Shunt, Surgical; Blood Platelets; Factor V; Factor VII; Fibrin; Fibrinogen; Fibrinopeptide A; Male; Papio; Partial Thromboplastin Time; Polyethylene Terephthalates; Protein C; Thrombin; Thrombosis

Hematological changes occurring during use of left ventricular assist devices (LVADs) were evaluated in 3 patients suffering from postcardiotomy cardiogenic shock. LVAD treatment ranged from 6 to 9 days. During the procedure, no anticoagulants were used in the first two cases, while in the third case, a protease-inhibiting agent, nafamostat mesilate (FUT-175), was used. In the first two cases without any anticoagulants, fibrinopeptide A (FPA) and thrombin-antithrombin III complex (TAT) increased markedly over the course of LVAD treatment, suggesting the excessive activation of the coagulatory system. The fibrinolytic system also became activated during LVAD treatment as was indicated by a marked increase in FDP-D-dimer and alpha 2 plasmin inhibitor-plasmin complex (PIC). Continual decreases observed in Factor XII and prekallikrein indicate that the coagulofibrinolytic activation occurring during LVAD treatment is presumably the result of contact activation of these factors due to interaction of blood with the internal surface of the LVAD. In the third case with FUT-175, both coagulation and fibrinolysis were successfully maintained at minimum levels as was demonstrated by the extremely low levels of these molecular markers. There was also no significant consumption of any contact factors. FUT-175 looks promising as an anticoagulant during the use of cardiac assist devices.

Topics: Aged; Anticoagulants; Antithrombin III; Benzamidines; Blood Coagulation; Female; Fibrinopeptide A; Guanidines; Heart-Assist Devices; Hemostasis; Humans; Japan; Male; Middle Aged; Peptide Hydrolases; Shock, Cardiogenic; Thrombosis

Some traditional coagulation assays and several new molecular markers of hemostatic activation were measured in 37 patients with spinal cord injury (SCI). Twenty one of the patients (57%) developed deep vein thrombosis (DVT). The radiofibrinogen uptake test (RFUT) was used to diagnose DVT. Thirty eight percent of quadriplegic and 88% of paraplegic patients developed DVT (p < 0.005). No significant differences were found in platelet counts, mean platelet volumes, fibrinogen levels, von Willebrand factor (Ag) levels, platelet factor 4 and beta thromboglobulin concentrations between the groups with and without DVT. Fibrinopeptide A, thrombin/antithrombin III (TAT) complexes and plasma D-dimer levels were significantly higher in the patients with thrombosis. Most patients with DVT had elevated TAT complex levels up to three days before the RFUT became positive. D-dimer levels were highest after the diagnosis had been made.

Topics: Adolescent; Adult; Aged; Antithrombin III; Biomarkers; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Humans; Male; Middle Aged; Multienzyme Complexes; Paraplegia; Platelet Count; Quadriplegia; Spinal Cord Injuries; Thrombin; Thrombin Time; Thrombosis

A non-stasis rodent model of thrombogenicity has been used for dose-ranging studies with a conventional prothrombin complex concentrate (PCC) and to evaluate high purity factor IX concentrates from different manufacturers. Fibrin monomer (soluble fibrin) and fibrinopeptide A (FPA) were monitored before and after infusion of test solution. FPA was found to be the more sensitive and reproducible indicator of thrombogenicity and exhibited a dose-related elevation after infusion of the PCC at doses of between 100-300 IU/kg. In contrast the amounts of FPA generated after 300 IU/kg of the high purity factor IX products were similar to control infusions of albumin.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Factor IX; Female; Fibrin; Fibrinopeptide A; Prothrombin; Rats; Rats, Sprague-Dawley; Thrombosis

Thrombus extension in patients with venous thromboembolism is due to the accretion of fibrin onto existing thrombi. Extension is promoted by both circulating and thrombus-bound thrombin, which convert fibrinogen to fibrin. Heparin is an effective antithrombotic agent, but it requires continuous administration to achieve persistent inhibition of thrombus extension. Heparin is highly effective in inhibiting fluid phase thrombin, but is a relatively ineffective inhibitor of thrombus-bound thrombin. Hirudin, unlike heparin, inactivates both circulating and fibrin-bound thrombin and, therefore, has the potential to prevent thrombus extension even after a short course of treatment. The aim of this study was to evaluate the time course of the accretion of new fibrin onto preexisting rabbit jugular vein thrombi after a 3-hour infusion of saline, heparin, and hirudin. Heparin and recombinant (r)-hirudin (CGP 39399) were infused at doses that doubled the activated partial thromboplastin time (aPTT). At the end of the 3-hour infusions in rabbits treated with saline, heparin (0.75 mg/kg), or r-hirudin (1.25 mg/kg), accretion of 125I-fibrinogen was 59 +/- 5 micrograms, 34 +/- 4 micrograms, and 21 +/- 2 micrograms, respectively (heparin and r-hirudin v saline, P less than .01; r-hirudin v heparin, P less than .01). Three hours after the end of the infusions, the accreted 125I-fibrinogen in the saline-, heparin-, and hirudin-treated animals was 89 +/- 6 micrograms, 51 +/- 7 micrograms, and 23 +/- 3 micrograms, respectively; 9 hours after the end of the infusions, the accreted 125I-fibrinogen was 112 +/- 9 micrograms, 82 +/- 7 micrograms, and 25 +/- 3 micrograms, respectively. aPTT and thrombin clotting time (TCT) returned to the baseline value 90 minutes after the end of heparin or r-hirudin infusion. During in vitro experiments, human fibrin clots previously incubated in human plasma containing r-hirudin did not promote fibrinopeptide A (FPA) generation when washed and then incubated in human plasma in the absence of thrombin inhibitors. This persistent inhibition of FPA production was not observed after incubation in human plasma of human plasma clots preincubated with heparin. We conclude that heparin is effective in inhibiting thrombus extension while it is present in the circulation, but that this effect is rapidly lost after its plasma clearance. In contrast, the antithrombotic activity of r-hirudin is sustained beyond its plasma clearance, presumably because of i

Topics: Animals; Female; Fibrin; Fibrinogen; Fibrinopeptide A; Heparin; Hirudin Therapy; Hirudins; Humans; Jugular Veins; Kinetics; Male; Partial Thromboplastin Time; Rabbits; Recombinant Proteins; Thrombin Time; Thrombosis

Fibrinopeptide A was determined in 75 middle aged male patients, five control subjects and a control group of young medical students, divided into nine subsets. The FPA levels were significantly elevated in the patient group, particularly among the diabetics, when compared with the medical students and also age matched controls. Diabetic patients who smoked and had vascular pathology had high FPA levels even after they stopped smoking.

Topics: Angina Pectoris; Biomarkers; Coronary Artery Disease; Diabetic Angiopathies; Fibrinopeptide A; Humans; Male; Middle Aged; Smoking; Thrombosis

We examined the changes of haemostatic molecular markers after antithrombin III (AT III) administration in a 22-year-old woman with congenital AT III deficiency in the third trimester of pregnancy who did not have thrombosis. Various markers including fibrinopeptide A (FPA), thrombin-antithrombin III complex (TAT), prothrombin fragment F1 + 2 (F1 + 2), plasmin-alpha 2antiplasmin, D-dimer, beta-thromboglobulin, and platelet factor 4 were measured before and just after 3,000 U of AT III concentrate, which was given three times per week from the 34 week of pregnancy until delivery. Just after AT III administration, F1 + 2 and FPA levels decreased on most occasions, while TAT sometimes increased. Plasma FPA levels were markedly decreased on all 8 occasions when the plasma FPA levels was above 2.0 ng/ml before AT III administration. Plasma FPA levels were always greater than or equal to 6.4 ng/ml before AT III administration on the 4 occasions when TAT increased to above 115%. The changes of plasma F1 + 2 levels were significantly correlated with the AT III level. These results suggest that prophylactic AT III administration in the third trimester immediately inactivates intravascular thrombin to form TAT and reduce the plasma FPA level. Thus, the transient TAT elevation following AT III administration may not only be due to extraction of thrombin from the fibrin clots of thrombi but also to intravascular thrombin which is not attached to thrombi. FPA is the best molecular marker for thrombin hyperactivity and it should be monitored in AT III-deficient pregnant women in the third trimester.

Topics: Adult; Antithrombin III; Antithrombin III Deficiency; Biomarkers; Blood Coagulation Factors; Female; Fibrinopeptide A; Humans; Incidence; Peptide Hydrolases; Pregnancy; Pregnancy Complications, Hematologic; Thrombosis

In 107 asymptomatic and untreated patients with inherited syndromes associated with thrombophilia (antithrombin III, protein C and protein S deficiencies), we compared in parallel two plasma peptides which reflect activation of the common coagulation pathway: the prothrombin fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FPA). Both F1 + 2 and FPA were measured with simple, commercially available ELISA methods. High levels of F1 + 2 or FPA were found in about one fourth of the patients as a whole. When patients were divided according to the type of inherited thrombophilic syndrome, it appeared that F1 + 2 was more frequently elevated in protein C and protein S deficiencies than in antithrombin deficiency; and that, in general, it was no more frequently elevated than FPA. Although our data confirm the existence of a procoagulant imbalance in inherited thrombophilic syndromes due to defects of natural anticoagulant proteins, they do not confirm that such imbalance can be more frequently diagnosed by measuring F1 + 2 levels, particularly in patients with antithrombin deficiency.

Topics: Adolescent; Adult; Aged; Antithrombin III Deficiency; Biomarkers; Blood Proteins; Disease Susceptibility; Fibrinopeptide A; Glycoproteins; Humans; Middle Aged; Peptide Fragments; Protein C Deficiency; Protein S; Prothrombin; Syndrome; Thrombosis

Left atrial (LA) thrombi sometimes occur in patients with mitral stenosis (MS) and the systemic embolization due to thrombi causes a serious, occasionally fatal complication. Several clinical techniques have been used to estimate the presence of LA thrombi. However, the hitherto available methods, even an echocardiography which has been most widely used, still have some drawbacks, depending on the size and location of thrombi. The author measured D-dimer, fibrinopeptide A (FPA) and thrombin-antithrombin III complex (TAT) in the patients with MS and evaluated the diagnostic value of these molecular markers to estimate the presence of LA thrombi. Twenty six patients with MS who had undergone cardiac operation were studied. Atrial fibrillation was found in all the patients. Episode of obvious thromboembolic diseases is a criteria of exclusion. Blood was drawn from the brachial vein several days (3 +/- 1 days: mean +/- SD) before the operation. The presence or absence of thrombus was confirmed at the surgery in all the cases. 1) Both levels of D-dimer and TAT were significantly higher in the patients with thrombi than those in the patients without thrombus or those in normal controls (mean: 378, 93 and 64 ng/ml, respectively; p less than 0.01 for both and 9.1, 2.0 and 1.7 ng/ml, respectively; p less than 0.01 for both). However, levels of FPA were not significantly different among the three groups (mean: 7.9, 4.9 and 3.7 ng/ml, respectively; NS for both). 2) both levels of D-dimer and TAT were significantly correlated with the weights of LA thrombus (r = 0.87, p less than 0.01: r = 0.79, p less than 0.01, respectively). 3) LA thrombi (ca. greater than or equal to 2 g) were always confirmed at the surgery in the patients who had levels of D-dimer higher than 200 ng/ml and/or TAT higher than 4 ng/ml. The plasma levels of D-dimer and TAT were further followed after the surgery in the same 18 patients (8 patients who had thrombus, the rest who didn't). 1) In the patients who had thrombi, levels of D-dimer were significantly decreased after the surgery (mean: from 267 ng/ml to 73 ng/ml, p less than 0.05). Levels of TAT were slightly but not significantly decreased (mean: from 82 ng/ml to 76 ng/ml, NS).(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Aged; Antithrombin III; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Heart Atria; Heart Diseases; Heart Valve Prosthesis; Humans; Male; Middle Aged; Mitral Valve Stenosis; Peptide Hydrolases; Thrombosis; Warfarin

Artificial insemination with frozen semen was used to breed beagles homozygous for a deficiency in clotting factor VII, with plasma concentrations of 2-3% of normal adult beagle pooled plasma. The factor VII-deficient beagles were used to determine if factor VII activity has a role in the thrombogenic activity of prothrombin complex concentrates (PCCs) containing factors II, IX and X by evaluating changes in selected indicators of thrombogenicity. No differences were seen between the responsiveness of the factor VII-deficient and normal beagles, indicating that the thrombogenic activities of PCCs are mediated via effects on the intrinsic clotting system.

Topics: Animals; Blood Coagulation Factors; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Factor VII Deficiency; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Partial Thromboplastin Time; Thrombosis

Elevated levels of fibrin peptide A were found in venous occlusion only in the patients unconsuming C protein, which indicates that there is a relationship between the thrombin production processes during venous occlusion and the C protein system functioning, the anticoagulant function of the endothelium in particular. Moreover, this makes it possible to employ the standard venous occlusion test to make an integral assessment of endothelial function.

Topics: Adult; Blood Coagulation; Coronary Disease; Female; Fibrinopeptide A; Humans; Male; Middle Aged; Protein C; Thrombin; Thrombophlebitis; Thrombosis; Tissue Plasminogen Activator

Platelet function and the clinical course of the disease were prospectively investigated in 29 patients with myeloproliferative disorders. Serial determinations (median: 5 investigations per patient within 17 months) of platelet aggregation, plasma and intraplatelet concentrations of beta-thromboglobulin (beta TG) and platelet factor 4 (PF4), and of fibrinopeptide A (FPA) plasma levels were carried out. In the chronic phase of polycythaemia vera, patients with thrombohaemorrhagic complications during the study period had higher platelet count, more severe platelet aggregation defects, and increased plasma levels of beta TG and FPA compared to patients without complications. However, thrombohaemorrhagic complications were not predicted by changes in these parameters in the individual patient during the chronic disease phase. When patients with chronic myelogenous leukaemia entered blast crisis, bleeding complications were related to thrombocytopenia, impaired platelet function and low intraplatelet concentrations of beta TG and PF4. Cytoreduction by chemotherapy in the chronic phase of CML did not alter beta TG and PF4 plasma levels, whereas treatment of polycythaemia rubra vera by venesection favourably influenced platelet alpha-granule secretion and increased intraplatelet concentrations of beta TG and PF4.

Topics: Adult; Aged; beta-Thromboglobulin; Blood Platelets; Female; Fibrinopeptide A; Hemorrhage; Hemostasis; Humans; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukocyte Count; Male; Middle Aged; Myeloproliferative Disorders; Platelet Aggregation; Platelet Count; Platelet Factor 4; Polycythemia Vera; Primary Myelofibrosis; Prospective Studies; Thrombocythemia, Essential; Thrombosis

Using two-dimensional echocardiography, we studied the pathophysiology of intracardiac thrombus regression accompanied by anticoagulant therapy in 82 consecutive patients with acute cardiogenic cerebral embolism. We noted intracardiac thrombus in 15 patients; nine of the 15 were started on anticoagulant therapy with warfarin potassium to maintain the prothrombin time between 2.5 and 3.5 (international normalized ratio). Serial two-dimensional echocardiograms were obtained for these nine patients before and after anticoagulation, with the plasma levels of fibrinopeptide A, fibrinopeptide B beta 15-42, and D-dimer measured at the same time. In eight of the nine patients the intracardiac thrombi gradually decreased in size while the plasma level of fibrinopeptide A fell to within the normal range and the plasma levels of fibrinopeptide B beta 15-42 and D-dimer remained above the normal ranges. In the other patient the thrombus disappeared, with embolization to the right arm immediately after starting anticoagulant therapy. Mobile or small thrombi regressed earlier than nonmobile or large ones. We conclude that regression of intracardiac thrombi after anticoagulation may be based on the relative predominance of plasma fibrinolytic activity over anticoagulation-inhibited thrombin activity.

Topics: Aged; Anticoagulants; Echocardiography; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Fibrinopeptide B; Heart Diseases; Humans; Intracranial Embolism and Thrombosis; Male; Middle Aged; Prothrombin Time; Thrombosis

Although the mechanisms involved in the pathophysiology of primary pulmonary hypertension have not yet been delineated, thrombosis has been implicated. This study was designed to determine whether thrombin activity as reflected by plasma concentrations of fibrinopeptide A (FPA), a marker of the action of thrombin on fibrinogen, is increased in patients with primary pulmonary hypertension. To evaluate fibrinolytic activity, we measured plasma concentrations of tissue-type plasminogen activator, plasminogen activator inhibitor-1, and cross-linked fibrin degradation products. We studied 31 patients with primary pulmonary hypertension. Plasma FPA concentrations measured by radioimmunoassay, were elevated to 87.4 +/- 36.9 ng/ml (mean +/- SEM). Fifteen minutes after administration of heparin (5,000 U), FPA concentrations decreased to 6.8 +/- 1.4 ng/ml (p less than 0.001 compared with preheparin levels). In 21 of 30 patients (70%), FPA concentrations after heparin administration were less than half the preheparin levels, a response consistent with inhibition of thrombin by heparin and the short half-life of FPA. Despite evidence for marked thrombin activity, plasma concentrations of cross-linked fibrin degradation products were normal in all but four patients. Plasminogen activator inhibitor-1 activity was elevated in 19 of the 27 patients in whom it was measured, potentially limiting the fibrinolytic response. The elevations of FPA indicate that thrombin activity is increased in vivo in patients with primary pulmonary hypertension. Thus, sequential assays of plasma markers of thrombosis and fibrinolysis in vivo may help identify those patients who may benefit from treatment with anticoagulants.

Topics: Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Humans; Hypertension, Pulmonary; Lung Diseases; Plasminogen Inactivators; Prospective Studies; Thrombosis

Plasma fibrinopeptide A levels, beta-thromboglobulin levels and platelet factor 4 levels were estimated by enzyme-linked immunosorbent assay before and after hyperventilation in 12 patients with coronary vasospastic angina and in 12 control subjects matched for age and gender. In all 12 study patients, anginal attacks accompanied by electrocardiographic (ECG) changes (ST elevation in 11 patients and ST depression in 1 patient) were induced by hyperventilation. Coronary angiography was performed on 11 of the 12 patients, and coronary artery spasm with the same ECG changes was induced by intracoronary injection of acetylcholine in all 11. The plasma fibrinopeptide A levels increased significantly from 2.0 +/- 0.4 to 10.0 +/- 2.4 ng/ml during the attack (p less than 0.001) in the study patients, but remained unchanged before and after hyperventilation in the control subjects. The plasma levels of beta-thromboglobulin and platelet factor 4 remained unchanged after hyperventilation in both groups. Our data indicate that coronary artery spasm may induce thrombin generation and trigger thrombus formation in the coronary artery.

Topics: Aged; beta-Thromboglobulin; Coronary Angiography; Coronary Vasospasm; Electrocardiography; Female; Fibrinogen; Fibrinopeptide A; Heart Diseases; Humans; Hyperventilation; Male; Middle Aged; Thrombosis

Topics: Amino Acid Sequence; Disseminated Intravascular Coagulation; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinopeptide A; Fibrinopeptide B; Humans; Immunoassay; Molecular Sequence Data; Peptide Fragments; Reference Values; Thrombosis

Topics: Antithrombin III; Blood Coagulation; Blood Coagulation Tests; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Hemostasis; Humans; Peptide Hydrolases; Platelet Aggregation; Platelet Factor 4; Thrombosis

Topics: beta-Thromboglobulin; Blood Preservation; Cardiolipins; Fibrinopeptide A; Freezing; Hematologic Tests; Humans; Immunoglobulin G; Immunoglobulin M; In Vitro Techniques; Plasma; Platelet Factor 4; Thrombosis

Polyethylene tubings, 2-mm inner diameter and the length of 1 m, untreated or furnished with a covalently bonded heparin surface layer, were inserted as arteriovenous shunts bilaterally in dogs. By compressing the middle part, the initial blood flow was adjusted to 10 or 40 mL/min. The thrombogenicity of the tubings was assessed by the patency of the shunts and by assaying the generation of fibrinopeptide A (FPA) in arterial blood and in blood after its passage through the shunts. In untreated shunts clotting rapidly occurred preceded by high FPA generation in blood passing through the shunts. The blood flow in heparinized shunts remained unchanged throughout the test period. At the low flow rate a certain degree of FPA generation in the shunts occurred. At the high flow rate no changes in FPA levels occurred. The function of the heparin surface is thus flow rate dependent. Systematic heparinization and subsequent neutralization with protamine or administration of protamine alone did not interfere with the function of the heparin surface.

Topics: Animals; Arteriovenous Shunt, Surgical; Blood Circulation; Dogs; Female; Fibrinopeptide A; Heparin; Male; Protamines; Thrombosis

Patients with heparin-induced platelet activation who are reexposed to heparin may have recurrent thrombocytopenia, intravascular thrombosis, arterial emboli, or sudden death. To permit carotid endarterectomy in two patients with confirmed heparin-induced platelet activation, we compared the efficacies of aspirin and iloprost, a stable analogue of prostacyclin, in preventing heparin-induced platelet activation. In the first patient, although aspirin prevented both in vitro heparin-induced platelet aggregation (70% without and 7.5% with aspirin) and 14C serotonin release (48% without and 0% with aspirin), intraoperative administration of heparin resulted in an increase in plasma levels of platelet factor 4 from 8 to 260 ng/ml and beta-thromboglobulin levels from 29 to 39 ng/ml. In addition, the circulating platelet count decreased from 221,000 to 174,000 microliters, and 15% spontaneous platelet aggregation was observed. Fortunately, fibrinopeptide A levels remained less than 10 ng/ml intraoperatively, and no thrombotic complications occurred. In the second patient, aspirin did not prevent heparin-induced platelet aggregation in vitro (65% without and 41% with aspirin); however, iloprost (0.01 mumol/L) prevented both in vitro heparin-induced platelet aggregation (59.5% without and 0.0% with iloprost) and 14C serotonin release (56.7% without and 0.0% with iloprost). Therefore, a continuous infusion of iloprost was begun before administration of heparin and was continued until 20 minutes after reversal of heparin with protamine. After intraoperative administration of heparin, plasma levels of platelet factor 4 increased from 19 to 200 ng/ml, and beta-thromboglobulin levels increased from 56 to 76 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aged; Aspirin; beta-Thromboglobulin; Cardiovascular Agents; Carotid Arteries; Drug Evaluation; Endarterectomy; Epoprostenol; Fibrinopeptide A; Heparin; Humans; Iloprost; Male; Platelet Activating Factor; Platelet Aggregation; Platelet Count; Platelet Factor 4; Preoperative Care; Thrombosis

Arterial thrombi and atherosclerotic lesions were analyzed immunochemically and examined histologically. The extent of in vivo proteolytic cleavage of the amino-terminal end of fibrinogen by thrombin and plasmin was determined and quantitated by specific radioimmunoassays. The samples were treated with cyanogen bromide (CNBr), and the total amount of fibrinogen and fibrin-derived protein was determined as NDSK, the NH2-terminal disulfide knot of fibrinogen. Thrombin-releasable fibrinopeptides A and B were used to quantitate fibrinogen and fibrin I. Previous plasmin cleavage of the B beta chain was inferred from the amount of B beta 1-42 and B beta 15-42 in undigested NDSK. The results obtained in both acute and organized thrombi indicate that approximately 60% of the total protein (as determined by amino acid analysis) was fibrinogen-derived and that 70% to 80% of the fibrinogen-derived material was fibrin II. These findings support the hypothesis that fibrin II as distinct from fibrin I is the predominant component in a thrombus. In samples from normal and atherosclerotic aortas, fibrinogen-derived protein comprised less than 10% of the total protein. Samples from grossly normal aortas contained only fibrinogen and fibrin I. Fibrinogen concentration decreased and fibrin II concentration increased with increasing severity of the lesions, suggesting that increased fibrin II formation is associated with progression of atheromas.

Topics: Aorta; Arteriosclerosis; Fibrin; Fibrinogen; Fibrinolysin; Fibrinopeptide A; Fibrinopeptide B; Humans; Thrombin; Thrombosis

Levels of the platelet degranulation product beta-thromboglobulin (BTG) and the fibrinogen degradation product fibrinopeptide A (FPA) were measured in 26 asymptomatic subjects (group 1), 17 patients with peripheral vascular disease (PVD) (group 2), and 12 patients with PVD and bypass grafts (group 3). Mean BTG and FPA levels were elevated in both groups 2 and 3, indicating increased thrombotic activity in patients with PVD. Results of serial BTG and FPA assays in group 3 patients suggested a trend downward. These markers may be useful for estimating disease severity and prognosis, extent of graft healing and patency, and efficacy of therapeutic intervention.

Topics: Arterial Occlusive Diseases; beta-Thromboglobulin; Blood Vessel Prosthesis; Female; Fibrinogen; Fibrinopeptide A; Humans; Male; Prognosis; Radioimmunoassay; Thrombosis; Time Factors; Wound Healing

Bulk heparinized catheters (1 mm internal diameter) containing 10% heparin ionically bound, were tested in four human volunteers. Catheters containing 0% and 10% heparin were compared in each individual using ultrasound microflow velocimetry, permeability test, sequential determinations of activated partial thromboplastin time, heparin levels and generation of Fibrinopeptide A, beta thromboglobulin and Platelet factor 4. Although the release of heparin expressed by its anti-IIa activity is of similar range in the four individuals the release of anti-Xa activity is variable and generally of greater magnitude, suggesting a privileged migration of low molecular weight components of heparin. These antiproteasic activities of heparin are sufficient to inhibit fibrin formation and blood coagulation despite their relative inability to prevent platelet activation.

Topics: beta-Thromboglobulin; Catheters, Indwelling; Delayed-Action Preparations; Factor Xa; Female; Fibrinopeptide A; Heparin; Humans; Male; Materials Testing; Partial Thromboplastin Time; Platelet Factor 4; Prothrombin; Serine Proteinase Inhibitors; Thrombosis

Topics: Aged; Antithrombins; Arginine; Disseminated Intravascular Coagulation; Drug Therapy, Combination; Female; Fibrinopeptide A; Heparin; Humans; Male; Middle Aged; Pipecolic Acids; Platelet Aggregation Inhibitors; Renal Dialysis; Sulfonamides; Thrombocytopenia; Thrombosis

Thrombosis has been observed with unusual frequency in patients receiving acetohydroxamic acid (AHA) for treatment of struvite nephrolithiasis. Because this clinical observation suggests a low-grade state of diffuse intravascular coagulation, standard clinical coagulation assays, platelet counts, and plasma fibrinopeptide A (FPA) levels were measured in patients before and during treatment with AHA. Coagulation assays, fibrinogen, and fibrin-split products were not significantly different when pretreatment and treatment values were compared. FPA levels were significantly elevated and platelet counts were significantly reduced in the treatment period, indicating augmented thrombin activity and consumption of platelets into thrombi or platelet microaggregates. FPA levels were elevated within 24 hours of the initiation of AHA therapy whereas platelet counts did not change significantly within the first 4 days of treatment. The data are consistent with low-grade intravascular coagulation with AHA treatment and suggest that patients treated with this agent should be observed cautiously for signs of thrombosis.

Topics: Blood Coagulation; Fibrinopeptide A; Humans; Hydroxamic Acids; Kidney Calculi; Middle Aged; Platelet Count; Thrombosis

We investigated the effect of oral contraceptives on thrombogenesis induced by subendothelium of rabbit aorta (SE), exposed to flowing non-anticoagulated blood in an annular flow chamber. Six healthy women on sequential contraceptive drugs (0.05 mg aethinylestradiol/day, 0.125 mg desogestrel/day) were compared with 6 women without hormonal contraception and 6 men. On contraceptive drug treatment, blood values were significantly increased for fibrinogen (2.6 +/- 0.2 vs 1.9 +/- 0.1 g/l) and fibrinopeptide A (3.9 +/- 0.9 vs 0.9 +/- 0.1 ng/ml), whereas antithrombin III was decreased (81 +/- 4 vs 97 +/- 6%). Fibrin deposition on vascular subendothelium was more than four-fold increased when measured morphologically (63.4 +/- 2.5 vs 14.6 +/- 6.8% coverage of SE surface with fibrin) as well as immunologically (29.3 +/- 2.2 vs 4.5 +/- 1.9 micrograms fibrin/cm2 of SE). Thrombus volumes were more than two-fold increased in women with contraceptives (9.0 +/- 1.4 vs 3.7 +/- 1.0 micron 3/micron 2). Our study shows that during contraceptive drug treatment the exposure of flowing blood to vascular subendothelium leads to excessive deposition of fibrin and platelet thrombi. Measurement of blood interactions with subendothelium might be of predictive value in hypercoagulable states such as contraceptive treatment.

Topics: Adult; Animals; Antithrombin III; Blood Cell Count; Blood Platelets; Contraceptives, Oral; Endothelium; Female; Fibrin; Fibrinopeptide A; Humans; Male; Methods; Platelet Aggregation; Rabbits; Thrombosis

Over a 2-month period, 40 patients with untreated malignancy were studied for protein-C (PRC), antithrombin-III (AT-III), fibrinopeptide A (FPA), routine hemostatic screens, and presence of liver metastases to determine pretreatment changes of hemostasis and relate them to subsequent development of thrombotic or hemorrhagic complications. These patients were observed for a mean period of 18 months. There were 23 males and 17 females with a median age of 64 years. Nine patients had lung carcinoma, 8 colon carcinoma, 7 lymphoma, 5 breast carcinoma, 5 head and neck carcinoma, 2 acute leukemia, 2 prostate carcinoma, 1 adenocarcinoma of unknown primary, and 1 sarcoma. Eight patients had liver metastases. PRC was measured by ELISA, AT-III by radial immunodiffusion, and FPA by RIA. Four patients had decreased AT-III, 28 had decreased levels of PRC, and 39 had elevated levels of FPA. All patients with liver metastases had low PRC. Albumin levels were lower in patients with low PRC (mean 3.3 g/dL v 4.0 g/dL for others). Eight patients, five with liver metastases, developed thrombotic (4), hemorrhagic (3), or both (1) complications. Statistically significant associations were found between (1) presence of liver metastases and development of thrombotic and hemorrhagic complications (P less than .001), (2) presence of liver metastases and decreased PRC (P = .001), and (3) lower albumin levels and decreased PRC (P = .0001). Our study documents early changes of hemostasis in untreated malignancy. We extend previous observations that decreased PRC levels in malignancy may be due to poor synthetic functions of liver. Presence of liver metastases was the only factor associated with subsequent development of thrombotic and hemorrhagic complications. Biochemical markers of hemostatic abnormalities, even though encountered frequently at the time of presentation, are of little predictive value for development of thrombotic and hemorrhagic complications.

Topics: Adult; Aged; Aged, 80 and over; Antithrombin III; Female; Fibrinopeptide A; Hemorrhage; Hemostasis; Humans; Liver Neoplasms; Male; Middle Aged; Neoplasms; Protein C; Prothrombin Time; Thrombosis

A congenitally abnormal fibrinogen was isolated from blood of a young man with deep-vein thrombosis. Two other affected members of his family had three episodes of severe arterial thrombosis. The fibrinogen showed a delayed clotting by thrombin, but a normal clotting by Arvin, Reptilase, and prothrombin-staphylocoagulase complex. Analysis of the fibrinopeptides A and B by High Performance Liquid Chromatography did not reveal an abnormal peptide structure. The rate of release of A and B peptides by thrombin was strongly delayed, whereas the rate of release of fibrinopeptide A by Arvin appeared to be normal. The fibrin polymerization rate was normal. Interactions between the abnormal fibrinogen, platelets and the fibrinolytic system were also normal. Evidence is presented that the defective interaction between fibrinogen Milano II and thrombin is associated with a defective binding of thrombin to the fibrin moiety of the abnormal fibrinogen.

Topics: Adult; Blood Coagulation Disorders; Fibrin; Fibrinogen; Fibrinogens, Abnormal; Fibrinopeptide A; Fibrinopeptide B; Humans; Male; Pedigree; Platelet Aggregation; Thrombin; Thrombophlebitis; Thrombosis

In tumor cell thrombosis thrombin does not only act as clotting enzyme but also as tissue hormone stimulating the proliferation of malignant cells indicated by an increase of cell count and thymidine uptake in cell cultures. Spontaneous and by cytostatic treatment induced decay of tumor cells induces the release of tumor cell thromboplastins which activate locally the clotting system and liberate thrombin. This local liberation of thrombin in tumor cell thrombosis stimulates again tumor cell proliferation and represents a biochemical substrate of tumor spread and growth in tumor cell thrombosis.

Topics: Cell Division; DNA Replication; Fibrinopeptide A; Growth Substances; Humans; Neoplasms; Thrombin; Thromboplastin; Thrombosis; Thymidine; Tritium

Fibrinogen New York 1 (NY-1) was identified in a family with a thrombotic tendency. Studies on fibrinogen NY-1 and the fibrinogen from her brother, designated NY-1a, showed that both have abnormal thrombin-nonclottable fibrinogen (50% of the total fibrinogen in NY-1 and 35-40% in NY-1a) and that the trait is heterozygous and autosomal codominant. The abnormal fibrinogen polymerizes in the presence of calcium and can be further cross-linked by Factor XIIIa. The release rates of fibrinopeptides A and B by thrombin from both (NY-1 and NY-1a) were slower than those from normal fibrinogen. Two mol of fibrinopeptide A but only 0.6-1.0 (NY-1) or 1.0-1.3 (NY-1a) mol of fibrinopeptide B were released per mol of fibrinogen. Additionally, only 1.0 (NY-1) or 1.3 (NY-1a) mol of the B beta(1-42) peptide were released by plasmin/mol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the reduced fibrinogen revealed two protein bands in the B beta-chain region (Mr = 54,000 as compared with 57,300 for the normal). When NY-1a fibrinogen was treated with CNBr, two sizes of the NH2-terminal disulfide knot were obtained (Mr = 59,000 and 49,000). The Mr = 49,000 component is consistent with an abnormal NH2-terminal disulfide knot with two defective NH2-terminal B beta-chains. Amino acid sequence analyses demonstrated that the abnormal B beta-chain is the result of a deletion in the sequence from residues 9 to 72. This deletion corresponds exactly to exon 2 of the gene. Since this family has a thrombotic tendency, the defect in the fibrinogen may be important in the pathogenesis of thrombosis in this family.

Topics: Amino Acid Sequence; Base Sequence; Cyanogen Bromide; DNA; Electrophoresis, Polyacrylamide Gel; Fibrinogen; Fibrinogens, Abnormal; Fibrinolysin; Fibrinopeptide A; Fibrinopeptide B; Humans; Molecular Weight; Pedigree; Thrombosis

Topics: Aged; Assisted Circulation; Blood Coagulation Tests; Blood Platelets; Fibrinopeptide A; Heparin; Humans; Male; Platelet Count; Quaternary Ammonium Compounds; Thrombosis; Time Factors

Plasma Fibrinopeptide A (FPA) and beta-thromboglobulin (beta-TG) were measured in patients with various thrombogenic diseases. Plasma FPA levels were also measured in patients with malignant neoplasm and in patients who had open heart surgery. The following results were obtained. Measurement of FPA using Bentonite absorption method was simple and sensitive for clinical application. Plasma FPA and beta-TG levels were elevated in various thrombogenic diseases. Plasma FPA level correlated neither with plasma beta-TG level nor with plasma fibrinogen level. Measurement of FPA is a useful tool in the diagnosis of thromboembolic diseases, and is more trustworthy when combined with beta-TG measurement. Diagnosis of thromboembolism may be made when FPA levels are over 5 ng/ml or beta-TG over 50 ng/ml. Diagnosis of venous thrombosis was possible by the assay of FPA with a sensitivity of 100 per cent. Diagnosis of arterial thrombosis was made by the assay of beta-TG with a sensitivity of 64 per cent. In patients with gastric cancer, levels of plasma FPA tended to correlate with the size of the tumor, indicating that the progression and the activity of the tumor may be estimated by plasma FPA levels. The mean FPA level at the late stage of cardiopulmonary bypass was 14.2 +/- 6.8 ng/ml, indicating that fibrinogen is consumed during the bypass despite the systemic heparinization.

Topics: Adult; Aged; beta-Thromboglobulin; Cardiopulmonary Bypass; Female; Fibrinogen; Fibrinopeptide A; Humans; Male; Middle Aged; Radioimmunoassay; Stomach Neoplasms; Thrombosis

A simple nonisotopic method for the quantitation of FPA in biologic samples has been developed utilizing a competitive enzyme immunoassay technique. The performance characteristics of these assays have been investigated in both the experimental and clinical settings and were found to be satisfactory for the routine clinical application. This method is comparable to a commercially available RIA kit (Mallinckrodt, St. Louis, MO) in both the clinical and normal samples. This assay can be used in the diagnosis of hypercoagulable states associated with various diseases. Subclinical activation of coagulation can be readily assessed when the global tests, such as the prothrombin time, partial thromboplastin time, and thrombin time, have no value. This test is of value in the monitoring of the newer antithrombotic agents, such as the low molecular weight heparin fractions that do not effect the global assays, such as the partial thromboplastin time. Similarly, the risk of thrombosis associated with the use of procoagulant therapy, such as the activated prothrombin complex concentrates, can be readily assessed using this assay. It is proposed that the FPA measurement may also provide useful information on the quality control of various plasma-based therapeutic products, such as plasma concentrates or activated prothrombin complex concentrates. FPA generation tests are currently proposed for the screening of antithrombotic and prohemostatic agents.

Topics: Blood Coagulation Tests; Cardiovascular Diseases; Evaluation Studies as Topic; Fibrinogen; Fibrinopeptide A; Humans; Immunoenzyme Techniques; Neoplasms; Radioimmunoassay; Reference Values; Thrombosis

The assay of fibrinopeptide A (FPA) has stimulated particular interest because of its high sensitivity and unique specificity for the action of thrombin. It has proved to be an extremely useful tool in research studies concerning the pathophysiology of thrombotic disease. Use of FPA in the diagnosis and treatment of deep venous thrombosis and pulmonary embolism is reviewed, and the potential usefulness of measuring FPA in the monitoring of the effectiveness of anticoagulant therapy is discussed.

Topics: Blood Preservation; Fibrinogen; Fibrinopeptide A; Humans; Pulmonary Embolism; Specimen Handling; Thrombophlebitis; Thrombosis

Topics: Adsorption; Animals; Blood Platelets; Dogs; Endothelium; Fibrinogen; Fibrinopeptide A; Glutaral; Heparin; Humans; Platelet Count; Polysaccharides; Surface Properties; Thrombin; Thrombosis

Topics: Animals; Biocompatible Materials; Catheters, Indwelling; Dogs; Fibrinogen; Fibrinopeptide A; Heparin; Surface Properties; Thrombosis

Topics: Disseminated Intravascular Coagulation; Electrophoresis, Polyacrylamide Gel; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Fibrinopeptide B; Hemorrhage; Humans; Models, Chemical; Molecular Weight; Thrombosis

This study was made to know the significance of fibrinopeptide A(FPA) as an indicator for coagulative analysis in thrombotic diseases. In normal control subjects (n=21), values of FPA by the radioimmunoassay were 0.5 +/- 1.4 ng/ml (mean +/- SD). In animal models, using Lyoplastin (tissue thromboplastin, n=5) or Ancrod (n=5) to piglets, plasma FPA levels elevated rapidly as a reflection of fibrin formation, and these changes of FPA were found to be most rapid and sensitive among the indicators for coagulation and fibrinolysis. In patients with thrombosis (n=32), elevated FPA levels (14.7 +/- 13.8 ng/ml) and beta-thromboglobulin (beta-TG)(86.1 +/- 65.6 ng/ml) were found. FPA levels in these patients positively correlated to beta-TG (r=0.5539, P less than 0.05) and inversely to fibrinogen (fbg) (r= -0.3622, P less than 0.05). In patients with acute myelocytic leukemia (AML, n=112), acute promyelocytic leukemia (APL, n=18) and acute lymphocytic leukemia (ALL, n=15), mean FPA levels in patients with active signs and symptoms were significantly higher (AML: 13.5 ng/ml, APL: 20.8 ng/ml, ALL: 12.4 ng/ml) than those examined during remission states (AML: 7.7 ng/ml, P less than 0.02, APL: 3.9 ng/ml, P less than 0.01, ALL: 2.7 ng/ml, P less than 0.01). FPA levels in patients with APL inversely correlated to fbg (r= -0.6399, P less than 0.01). In patients with lung cancer (n=75), mean FPA level in advanced stage (17.7 ng/ml, n=67) were significantly higher than those examined in early stage 6.5 ng/ml, n=8, P less than 0.001). In patients with acute disseminated intravascular coagulation (n=12), prolonged prothrombin time and activated partial thromboplastin time, severely reduced fbg and platelets, and remarkably elevated fibrin degradation product were found. Elevated FPA and beta-TG levels were also found (FPA: 23.5 +/- 15.0 ng/ml, beta-TG: 100.0 +/- 63.0 ng/ml). In five patients with thrombotic diseases who were treated successfully with 12500 IU of heparin per 12 hours (subcutaneous injection), plasma FPA levels were reduced to near normal levels quicker than changes of other indicators. These clinical and experimental data suggested that FPA was an useful indicator for active coagulation process.

Topics: Adult; Animals; Blood Coagulation; Disseminated Intravascular Coagulation; Female; Fibrin; Fibrinogen; Fibrinopeptide A; Heparin; Humans; Leukemia, Lymphoid; Leukemia, Myeloid; Leukemia, Myeloid, Acute; Lung Neoplasms; Male; Radioimmunoassay; Swine; Thrombosis

The concentration of heparin in plasma was measured using a chromogenic substrate. It appeared that the measurement of heparin concentration in plasma was important in therapeutic control and evaluation of heparin. There was a correlation between the activated partial thromboplastin time (APTT) and heparin concentration in plasma, but since the gradients of regression line differed in each of the cases, measurement of APTT alone would give a different estimate of heparin concentration in each case. Fibrinopeptide A (FPA) is considered as the best indicator for evaluatin of therapeutic effects of heparin. Therapeutic heparin concentrations were defined as ranging from 0.2 to 1.2 IU/ml because the normalization of FPA was observed and there happened no hemorrhagic accidents in that range.

Topics: Adult; Aged; Antithrombin III; Child; Female; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Heparin; Humans; Male; Methods; Middle Aged; Partial Thromboplastin Time; Thrombosis; Time Factors

FPA immunoreactivity was elevated in 14 out of 15 patients with disseminated neoplasia. Two of the patients showed signs of DIC, two had clinically evident thrombosis and one a positive 125I-fibrinogen uptake test suggesting thrombosis. Infusion of heparin produced a prompt fall in FPA levels. FPA immunoreactivity correlated well with the turnover of intravasal 125I-fibrinogen. The results confirm that the RIA of FPA provides a specific and quantitative index of the conversion of fibrinogen into fibrin and indirectly of the thrombin action in vivo.

Topics: Disseminated Intravascular Coagulation; Fibrinogen; Fibrinopeptide A; Heparin; Humans; Iodine Radioisotopes; Neoplasms; Radioimmunoassay; Thrombosis

Topics: Angiography; Animals; Catheterization; Dogs; Evaluation Studies as Topic; Female; Fibrinopeptide A; Male; Microscopy, Electron, Scanning; Polyethylene Terephthalates; Polyethylenes; Polytetrafluoroethylene; Polyurethanes; Radioimmunoassay; Thrombosis

Topics: Cardiopulmonary Bypass; Fibrinogen; Fibrinopeptide A; Humans; Platelet Activation; Radioimmunoassay; Thrombosis; Thromboxane B2

A radioimmunoassay for measurement of canine fibrinopeptide A, which provides a quantitative index of thrombin action on canine fibrinogen, was applied to measurements of the thrombogenicity of angiographic guide wires. Benzalkonium-heparin-treated Teflon-coated, untreated Teflon-coated, and uncoated stainless steel wires were compared in an experiment in dogs which closely simulated the use of these wires in humans. During the first 4 min after insertion, the benzalkonium-heparin-treated Teflon-coated wire was associated with significantly greater systemic levels of fibrinopeptide A than were either Teflon-coated or stainless steel wires. Beyond 10 min, markedly increased levels of fibrinopeptide A were measured in association with these latter two wires compared to the benzalkonium-heparin-treated Teflon-coated wire. Both the early rises in fibrinopeptide A associated with the benzalkonium-heparin-treated Teflon-coated wire and the late increases in fibrinopeptide A associated with the Teflon-coated and uncoated stainless steel wires could be eliminated by prior systemic administration of low dose heparin (40U/kg). These studies suggest that, at least in regard to activation of the plasma clotting system, the benzalkonium-heparin treatment offered no advantages over the other wires tested in terms of reduced thrombogenicity within the critical 10 min following insertion. No difference could be discerned between uncoated stainless steel wires and Teflon-coated stainless steel guide wires in this test.

Topics: Angiography; Animals; Dogs; Female; Fibrinogen; Fibrinopeptide A; Heparin; Male; Polytetrafluoroethylene; Quaternary Ammonium Compounds; Radioimmunoassay; Stainless Steel; Thrombosis

Topics: Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Humans; Thrombosis

Topics: Animals; Anticoagulants; Disseminated Intravascular Coagulation; Dogs; Epitopes; Fibrinogen; Fibrinopeptide A; Fibrinopeptide B; Heparin; Humans; Radioimmunoassay; Thrombin; Thromboembolism; Thrombosis

Topics: Fibrinogen; Fibrinopeptide A; Humans; Pulmonary Embolism; Thrombophlebitis; Thrombosis

The formation of fibrin clots or circulating soluble fibrin is accompanied by the appearance of fibrinopeptides. Measurement of the fibrinopeptide concentration in plasma can provide important information on the rate of conversion of fibrinogen to fibrin by thrombin. This rate varies under different physiologic and pathologic conditions. Fibrinopeptide A is a better molecular marker of the conversion than fibrinopeptide B since it is the first peptide to be cleaved by thrombin. A radioimmunoassay technique has been developed for the quantitative determination of human fibrinopeptide A. The procedure detects human fibrinopeptide A at a concentration of approximately 0.05 ng/ml. The variation of fibrinopeptide A content in normal persons may reflect its rapid formation and catabolism. A significantly increased concentration of this peptide was found in a patient during defibrination therapy with a purified enzyme from the venom of Agkistrodon rhodostoma and in patients suffering from retinal vascular occlusions.

Topics: Amino Acid Sequence; Batroxobin; Fibrinogen; Fibrinopeptide A; Humans; Immune Sera; Protein Binding; Radioimmunoassay; Retinal Diseases; Retinal Vessels; Thrombophlebitis; Thrombosis; Tyrosine