Emergency care of patients receiving non-vitamin K antagonist oral anticoagulants.

Non-vitamin K antagonist oral anticoagulants (NOACs), which inhibit thrombin (dabigatran) and factor Xa (rivaroxaban, apixaban, edoxaban) have been introduced in several clinical indications. Although NOACs have a favourable benefit-risk profile and can be used without routine laboratory monitoring, they are associated-as any anticoagulant-with a risk of bleeding. In addition, treatment may need to be interrupted in patients who need surgery or other procedures. The objective of this article, developed by a multidisciplinary panel of experts in thrombosis and haemostasis, is to provide an update on the management of NOAC-treated patients who experience a bleeding episode or require an urgent procedure. Recent advances in the development of targeted reversal agents are expected to help streamline the management of NOAC-treated patients in whom rapid reversal of anticoagulation is required.

Founder effect is responsible for the p.Leu131Phe heparin-binding-site antithrombin mutation common in Hungary: phenotype analysis in a large cohort.

BACKGROUND: Antithrombin (AT) is a key regulator of the coagulation. In type II deficiency, the heparin-binding-site defect (type II HBS) is considered to be relatively low thrombosis risk. OBJECTIVES: Our aims were to search for SERPINC1 mutation(s) and to describe the clinical and laboratory phenotype of a large number of AT Budapest3 (ATBp3, p.Leu131Phe) carriers and confirm the presence of a founder effect. PATIENTS/METHODS: AT-deficient patients were recruited and carriers of ATBp3, n = 102 (63 families) were selected. To investigate the founder effect, eight intragenic single nucleotide polymorphisms, a 5'-length dimorphism, and five microsatellite markers were detected. Clinical and laboratory data of the patients were collected and analyzed. RESULTS: In AT deficiency, 16 different causative mutations were found, and the great majority of patients were of type II HBS subtype. Most of them (n = 102/118, 86.5%) carried the ATBp3 mutation. The ATBp3 mutant allele was associated with one single haplotype, while different haplotypes were detected in the case of normal allele. The anti-factor Xa-based AT activity assay that we used could detect all ATBp3 patients with high sensitivity in our cohort. ATBp3 homozygosity (n = 26) was associated with thrombosis at a young age and conferred a high thrombotic risk. Half of the heterozygotes (n = 41/76, 53.9%) also had venous and/or arterial thrombosis, and pregnancy complications were also recorded. CONCLUSION: In Hungary, the founder mutation, ATBp3, is the most common AT deficiency. Our study is the first in which the clinical characterization of ATBp3 mutation was executed in a large population.

Anti-factor V auto-antibody in the plasma and platelets of a patient with repeated gastrointestinal bleeding.

Development of autoantibody against coagulation factor V (FV) is a rare clinical condition with hemorrhagic complications of varying severity. The aim of this study was to establish the pathomechanism of an acquired FV deficiency and characterize the FV inhibitor responsible for the clinical symptoms. A 78-year-old female was admitted to hospital with severe gastrointestinal bleeding. General clotting tests and determination of clotting factors were performed by standard methods. FV antigen and FV containing immune complexes were measured by ELISA. The FV molecule was investigated by Western blotting and by sequencing the f5 gene. The binding of patient's IgG to FV and activated FV (FVa) was demonstrated in an ELISA system and its effect on the procoagulant activity of FVa was tested in clotting tests and in a chromogenic prothrombinase assay. Localization of the epitope for the antibody was performed by blocking ELISA. FV activity was severely suppressed both in plasma and platelets. FV antigen levels were normal by ELISA using polyclonal anti-FV antibody or monoclonal antibody against the connecting region of FV, but depressed when HV1 monoclonal antibody against the C2 domain in the FV light-chain was used as capture antibody. The FV molecule was found intact. An IgG reacting with both FV and FVa was present in the patient's plasma and its binding to FV was inhibited by HV1 antibody. FV-containing immune complexes were detected in the patient's plasma and platelet lysate. The patient's IgG inhibited the procoagulant function of FVa. An anti-FV IgG was present in the patient's plasma and platelets. The autoantibody reacted with an epitope in the C2 domain of FV light chain and neutralized the procoagulant function of FVa.

Platelet factor XIII becomes active without the release of activation peptide during platelet activation.

The potentially active A subunit of factor XIII of blood coagulation has also been detected in platelets and monocytes/macrophages through the exact function of this cellular protransglutaminase has not yet been elucidated. In physiological conditions the first step in the activation of plasma factor XIII is the removal of an activation peptide from the N-terminal end of subunit A by thrombin. The A subunit then, in the presence of Ca2+, dissociates from the inhibitory B subunit and assumes an active conformation. Cellular factor XIII, which lacks B subunit, can be proteolytically activated in vitro by thrombin and the intracellular Ca2+ sensitive protease, calpain, in the same way as plasma factor XIII subunit A, and calpain has been suggested as the intracellular protease involved in the activation of cellular factor XIII in platelets. In the present experiments it was shown by SDS PAGE that during long-term stimulation of platelets with thrombin nondisulfide-crosslinked high M(r) protein polymers not penetrating the concentrating gel were formed. The lack of these polymers in thrombin-stimulated factor XIII deficient platelets clearly indicated that their formation in normal platelets was due to factor XIII that became active during platelet activation. However, no release of the activation peptide could be detected by Western blotting during this process. Similarly, no proteolytic cleavage of factor XIII was detectable when platelets were stimulated by Ca2+ ionophore through this stimulus activated calpain as it was clearly demonstrated by the breakdown of major intracellular calpain substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the O'Brien filter test and the PFA-100 platelet analyzer in the laboratory diagnosis of von Willebrand's disease.

Von Willebrand's disease (vWD) is the most common congenital haemorrhagic diathesis, characterized by the quantitative or qualitative disorder of von Willebrand factor (vWF). A number of methods have been used for the diagnosis of the disease, and the bleeding time determination is widely accepted as a screening test in spite of its low sensitivity. Our aim was to evaluate and compare the performance of two high shear systems (the O'Brien filter test and the PFA-100 device) in the screening and diagnosis of vWD. Thirty patients (n=13 type 1 with mild symptoms, n = 9 type 1 with severe symptoms, n = 2 type 2A, n = 3 type 2B and n = 3 type 3 vWD) and twenty controls were investigated. In mild vWD the platelet retention in the second phase of the filter test with citrated blood showed the highest sensitivity (91.6%). The sensitivity of the PFA-100 method with collagen-epinephrine cartridges in this group was 76.9%, while the bleeding time was prolonged only in 15.4% of the cases. In severe type 1, in type 2A and type 3 all functional tests reflected the bleeding tendency of the patients. In type 2B disease the bleeding time was prolonged only when the patient was thrombocytopenic, but both high shear systems revealed the disease independently of the presence of thrombocytopenia. The overall sensitivity of the bleeding time determination was 50% compared to the 80-90% sensitivity of the O'Brien filter test and the PFA-100 system. The sensitivity values of the filter test and the PFA-100 device with collagen-epinephrine cartridges were in the same range, but the collagen-ADP cartridges showed a lower (65.5%) sensitivity, though the results were specific and had high positive predictive value. We conclude that both high shear systems are suitable for the screening of vWD, and that they are superior to the traditional bleeding time determination in case of mild disease or type 2B vWD.

Monocytes of patients congenitally deficient in plasma factor XIII lack factor XIII subunit a antigen and transglutaminase activity.

Monocytes isolated from patients with severe deficiency in plasma Factor XIII of blood coagulation (FXIII) were tested for FXIII antigen and transglutaminase activity. By immunoperoxidase method the patients' monocytes, in contrast to normal controls, showed no reaction with a monospecific antibody against FXIII subunit a. This result was confirmed by immunoblotting technique, as well. In addition, tissue macrophages tested in one of the patients were also exempt of FXIII subunit a antigen. The transglutaminase activity in FXIII deficient monocytes was below the limit of the detection of the dansylcadaverine incorporation assay. The results suggest that FXIII subunit a of monocytes/macrophages and its plasma and platelet counterparts are closely related or identical proteins and demonstrate that the transglutaminase activity in monocytes is of FXIII origin and tissue transglutaminase is present, if at all, only in insignificant amount.

Promotion of the crosslinking of fibrin and alpha 2-antiplasmin by platelets.

Factor XIII (FXIII) is of high importance in the regulation of fibrinolysis. It crosslinks alpha 2-antiplasmin (alpha 2AP) and fibrin and by this way protects fibrin from the prompt elimination by plasmin. Although FXIII of platelets has been implicated in this protective mechanism, the role of platelets and platelet FXIII in the crosslinking process is far from being elucidated. As demonstrated by SDS PAGE and by immunoblotting for alpha 2AP, intact normal platelets resuspended in FXIII-free plasma or FXIII-free fibrinogen solution catalyzed the crosslinking of fibrin chains and also the crosslinking of alpha 2AP to fibrin alpha-chains. With FXIII-deficient platelets no crosslinking reaction could be observed indicating that the crosslinking with normal platelets was, indeed, due to platelet FXIII and not to another, putative platelet transglutaminase. However, the crosslinking of alpha 2AP to fibrin induced by the FXIII of intact platelets resuspended in FXIII-free plasma was considerably less extensive than the crosslinking carried out by the FXIII of normal plasma in the presence of FXIII-free platelets. Furthermore, the replacement of FXIII-free platelets by normal platelets in normal FXIII-containing plasma resulted in little, if any, difference in the crosslinking process. When crosslinking was induced by highly purified plasma FXIII the presence of intact FXIII-free platelets significantly accelerated the formation of alpha-chain polymers as well as the incorporation of alpha 2AP-fibrin alpha-chain hetero-dimer into these polymers. The results indicate that, in physiological conditions, platelet FXIII plays only a minor role in the crosslinking of alpha 2AP and fibrin; however, platelets, independently of their FXIII content, promote the crosslinking reaction by providing a catalytic surface on which the formation of highly crosslinked fibrin polymers is accelerated.

Safety of low-molecular-weight heparin in pregnancy: a systematic review.

Unfractionated heparin (UFH) remains the anticoagulant of choice during pregnancy. Low-molecular-weight heparins (LMWH) are an attractive alternative to UFH due to their logistic advantages and their association with a lower incidence of osteoporosis and HIT. We reviewed all published clinical reports concerning the use of LMWH during pregnancy. In addition, participants of an international interest group contributed a cohort of pregnant women treated with LMWH. Pregnancies were divided into two groups; those with and those without maternal comorbid conditions. The number of adverse fetal outcomes and the occurrence of maternal complications were evaluated in the two groups. In the group of women with comorbid conditions (n = 290), 13.4% of the pregnancies were associated with an adverse fetal outcome. In contrast, in the group of women without comorbid conditions (n = 196), 3.1% were associated with an adverse outcome, which is comparable to that seen in the normal population. We conclude that LMWH appear to be a safe alternative to unfractionated heparin as an anticoagulant during pregnancy.

Alterations of primary haemostasis in mixed connective tissue disease (MCTD).

Willebrand-factor antigen level and structure analysis, ristomycin-cofactor assay, beta-thromboglobulin and thromboxane metabolite estimations were performed in 22 patients with mixed connective tissue disease to evaluate the incidence and the possible role of haemostatic alterations in the complications occurring during the course of the disease. High levels of Willebrand-factor antigen and ristomycin-cofactor activity were detected in patients with thrombocytopenia, previous thrombotic event, pulmonary vascular lesions and usually in the presence of circulating anti-endothelial antibodies. Increased platelet activation could have been found in antibody positive cases and in patients with thrombocytopenia as well. The documented alterations of endothelial and platelet functions may play important role in the vascular complications of mixed connective tissue disease.

Plasma levels of beta-thromboglobulin and factor VIII-related antigen in diabetic children and adults.

In order to investigate the relationship between the in vivo platelet activation in diabetes mellitus and the endothelial damage connected with the diabetic micro- and/or macroangiopathy, plasma levels of beta-thromboglobulin (B-TG) and of factor VIII-related antigen (VIII R:Ag) were studied (1) in juvenile-onset (Type I) diabetics without clinical signs of angiopathy (age under 12 years) and (2) in mostly maturity-onset (Type II) diabetics with and without overt angiopathy (age between 14 and 60 years). Normal controls and nondiabetics with atherosclerosis were also studied. Plasma levels of both proteins were found to be elevated in all the groups of diabetic and atherosclerotic patients in comparison with the controls. Highest levels were found in adult diabetics with angiopathy and in atherosclerotics even without diabetes, but values of the diabetic children were also elevated. The data suggest a causal relationship between the vascular damage and the enhanced platelet reactivity in which the former may play the primary role.

Studies of the platelet filter test (shear dependent platelet aggregation) in patients with uncommon haemorrhagic disorders.

Platelets of anticoagulated whole blood forced at 40 mmHg through a fine filter are activated, aggregated and retained, so block the filter (platelet filter test, O'Brien JR, Salmon GP. Blood 1987; 1354-1361). Our clinical experiences with this simple and quick haemostasis test are summarized. Patients were investigated with different types of vWD (type-1 = 35, type-2A = 7, type-2B = 7, type-3 = 1), Glanzmann's thrombasthenia, congenital deficiency of cyclo-oxygenase, acquired Bernard-Soulier syndrome, FXII-, FXIII-deficiency and a control group. The cumulative drop count and the platelet retention were carefully measured during two phases of the filter test. Platelet count, bleeding time, vWF:Ag and vWF:Rcof activity were measured along with the platelet filter test. The filter was not blocked and the platelet retention was abnormally low in all patients with thrombasthenia, type-2a, type-2B, type-3 vWD. Treatment with 1-desamino-8-D-arginine-vasopressin (DDAVP) caused enhanced platelet retention in 16 patients with type-1 vWD. The test is simple, quick and cheap, has good reproducibility, and may be useful in clinical haemostasis laboratories for examination of high shear induced platelet functions.

Treatment of the severe bleeding episode in type III von Willebrand's disease by simultaneous administration of cryoprecipitate and platelet concentrate.

A severe, life-threatening bleeding episode in a 24-year-old woman suffering from type III von Willebrand's disease was treated by large doses of cryoprecipitate with unsatisfactory results. Bleeding ceased and the bleeding time normalized only after concomitant administration of platelet concentrates. In the treatment of von Willebrand's disease patients possessing platelets with absent or insufficient von Willebrand factor activity the administration of plasma concentrates together with platelets appears to be justified.

Cyclic relapses of thrombotic thrombocytopenic purpura.

A 24-year-old male patient was first observed with full-blown acute thrombotic thrombocytopenic purpura in 1991. Complete remission was achieved with plasma and plasmapheresis therapy, but in spite of continuous corticosteroid and aspirin administration, thrombocytopenic (megakaryocytic) relapses were observed every 26-30 days. Splenectomy and danazol failed to prevent the recurrence of the disease. Surprisingly, cyclosporin A (5 mg/kg/day) administration resulted in a complete transitional remission, but after dose reduction a less regular pattern of repeated milder recurrences was observed. Cryopreserved plasma, obtained from the patient during remission also proved to be effective in treating the last two thrombocytopenic episodes.

The use of polybrene for heparin neutralization in protein C activity assay.

The protein C activity assay of Francis and Patch (Thromb Res 1983; 32: 605-613) is based on the prolongation of the activated partial thromboplastin time in the presence of activated protein C isolated from the test samples. The assay was modified and standardized by Rapaport et al. (Am J Clin Pathol 1987; 87: 491-497), but could still only be used in patients on heparin therapy after chromatographic removal of the heparin. In this study we attempted to eliminate the heparin separation step without losing the advantages of the modified (Rapaport) method. Heparin was added to the isolated protein C to obtain a rapid and complete antithrombin effect after the thrombin activation step and polybrene was subsequently used to neutralize the excess heparin. Using this modified assay protein C activity ranged from 67 to 133% in the normal population, and from 9 to 25% in coumarin-treated patients. Precision of the modified method was acceptable in both normal and pathological PC ranges: within- and between-batch variations were 5.6 and 3.6%, and 8 and 14%, respectively. The assay correlated well (r = 0.84) with the ELISA technique in both healthy donors and non-coumarin-treated patients.

Coumarin-induced skin necrosis following heparin-induced thrombocytopenia and thrombosis. A case report.

A severe thrombotic thrombocytopenic status, induced by heparin in a sixty-nine-year-old woman undergoing total hip joint arthroplasty, was treated by switching the anticoagulant therapy to coumarin, which induced skin necrosis. There appeared to be a possible causal relation between the severe immune reaction to heparin and the condition that predisposed to skin necrosis in the presence of coumarin. In patients who express a strong immune response to heparin, a different anticoagulant approach other than use of coumarin congeners appears to be justified.

[Fibrinogen as an independent cardiovascular risk factor and the question of treatment with fibrinogen-lowering drugs]. / A fibrinogen, mint önálló cardiovascularis rizikótényezö és gyógyszeres befolyásolásának kérdései.

The atherosclerotic vascular disease is a progressive condition of multifactorial origin. Among cardiovascular risk factors alterations of lipid metabolism are of central role. But the haemostatic system, first of all the plasmatic fibrinogen is also highly implicated. Increased fibrinogen condition can be regarded as a strong and independent predictor of cardiovascular risk. Total cholesterol, LDL-cholesterol and plasma fibrinogen concentration as risk factors are compared. Fibrinogen lowering treatments are also summarized.

[Subcutaneous heparin-calcium therapy: clinical and laboratory experience]. / Subcutan heparin-calcium kezelés: klinikai és laboratóriumi tapasztalatok.

Fifty patients with acute deep vein thrombosis, pulmonary embolism, acute myocardial infarct and priapism were treated with subcutaneous calcium heparin. Laboratory control was based on the examination of APTT. On the first day of heparin therapy only 52% of patients's APTT was 1.5 times greater than control value but the ratio increased to 82% on the fifth day of treatment. The importance of initial venous sodium heparin bolus (5-10,000 U) followed immediately by subcutaneous calcium heparin is emphasized. Injection of 500 U/kg/day calcium heparin divided in two equal doses is recommended. Four thrombotic and two haemorrhagic complications were observed. Subcutaneous calcium heparin can substitute the intravenous form of heparin (either bolus or continuous) in the treatment of thromboembolism.

[Fibrinolysis and vascular diseases]. / Fibrinolysis és érbetegségek.

A wide array of in vitro fibrinolysis tests had been performed for a long period, suggesting defective fibrinolysis, mainly impaired tPA response and reserve as major, frequent abnormality, predecessor or causative factor of venous thromboembolism. However, these abnormalities were troublesome to reproduce, and more recently fibrinolytic activators and inhibitors received growing attention as rather atherogenic and less thrombogenic risk factors. Even if it is still not settled, lipoprotein(a) may interfere with fibrinolysis, and seems to carry atherogenic risk, too. The genetic polymorphism of fibrinogen, plasminogen, PAI-1 and some other compounds modifying circulating fibrinogen levels are also discussed in this review.

[Clinical aspects of heparin induced thrombocytopenia]. / Tennivalók az immun eredetü heparin indukált thrombocytopeniában.

Heparin induced thrombocytopenia has remained the major complication of therapy or prophylaxis with heparin. Although low molecular weight heparins seem to confer much lesser chance to induce thrombocytopenia, the danger is still considerable, and the fatal outcome is not rare. A lot of new data have been published about the origin, binding, physicochemical properties of the antibodies, the responsive platelet membrane receptors, and laboratory diagnosis in particular, however, many issues are still unresolved. The anticoagulant treatment of cases, in which heparin induced thrombocytopenia in associated with progressive, frequently arterial thrombosis still needs great skills, experience and the use of new generation antithrombotic agents. This review summarizes briefly the internationally accepted standard diagnostic and therapeutic protocols with heparin induced thrombocytopenia.