Anticoagulation therapy.

Despite refinements and standardization in the use of anticoagulants, many problems remain for clinicians. Dr. Crowther describes appropriate starting and maintenance doses of warfarin, factors accounting for inter- and intra-observer variability and importantly, the management of the over-anticoagulated patients and bleeding patients.

Exposure of mice to topical bovine thrombin induces systemic autoimmunity.

Bovine thrombin is used as an aid to hemostasis in medical and surgical procedures. At least 500,000 Americans are exposed to this therapeutic annually and reports suggest that exposure is associated with the development of autoreactive antibodies. To determine whether bovine thrombin can induce pathological autoimmunity we exposed nonautoimmune-prone galactose-alpha1-3-galactose-deficient mice to the two bovine thrombin preparations currently approved for use in the United States.

Antibodies to prothrombin, factor V, and beta2-glycoprotein I and vascular access thrombosis.

We studied 88 hemodialysis patients for the presence of antibodies to human factor II (hFII), bovine factor V (bFV), and human beta2-glycoprotein 1 (beta2GPI). Forty-one patients had elevated anti-hFII antibodies, 17 had elevated anti-bFV antibodies, and 9 had elevated anti-beta2GPI antibodies. Fifty-two patients had elevated antibodies to one or more protein.

Risk factors associated with thrombosis in patients with antiphospholipid antibodies.

Objective: To define risk factors associated with thrombosis in patients with antiphospholipid antibodies (aPL).

Methods: Ninety-nine patients with aPL, most of whom had prior thrombosis, were evaluated for the presence of acquired and inherited thrombophilic states. Genomic testing was performed for factor V(R506Q), 3' prothrombin (PTG) and methylene tetrahydrofolate reductase (MTHFR) polymorphisms.

Beta2-glycoprotein I-dependent anticardiolipin antibodies preferentially bind the amino terminal domain of beta2-glycoprotein I.

Many of the autoantibodies in antiphospholipid syndrome (APS) are directed against beta2-glycoprotein I (beta2-GPI). Recent studies from our laboratories have indicated that the immunodominant binding epitope(s) for high titer, affinity purified antibodies from 11 APS patients are localized to the amino terminal domain (domain 1) of beta2-GPI. The present study employed surface plasmon resonance to localize the immunodominant domain in serum samples from a large cohort of patients with GPL values ranging from 21 to 230 units (n = 106 patients).

Fine mapping of inhibitory anti-factor V antibodies using factor V C2 domain mutants. Identification of two antigenic epitopes involved in phospholipid binding.

Hemorrhagic factor V inhibitors frequently bind to the second C-type (C2) domain of factor V and interfere with phospholipid binding. To define specific residues recognized by inhibitors from four patients (one bovine thrombin-induced and three spontaneous antibodies), epitope mapping was performed using recombinant human factor V lacking most of the B-type domain (FV des B) and alanine-substituted mutants within the C2 domain (FV des B C2 mutants). FV des B C2 mutants located in the region between Lys2060 and Glu2069 were resistant to inhibition by three IgG preparations including the bovine thrombin-induced antibody in both prothrombinase and phospholipid-binding assays.

Factor VIII Arg2304 --> His binds to phosphatidylserine and is a functional cofactor in the factor X-ase complex.

Four factor VIII light chain constructs containing hemophilia A mutations at R2304 and R2307 were prepared and expressed in mammalian cells. These mutations are located in a putative phosphatidylserine binding site identified by peptide studies (spanning amino acids 2303-2332). The levels of all four mutants in conditioned medium were significantly less than wild type by immunoprecipitation and ELISA.

Immunologic impact and clinical outcomes after surgical exposure to bovine thrombin.

Objective: To determine prospectively the immunologic response and adverse clinical events in surgical patients exposed to bovine thrombin during cardiac surgical procedures.

Summary Background Data: Topical bovine thrombin is used extensively as a hemostatic agent during cardiovascular surgery. Antibodies developing after exposure to bovine thrombin have been anecdotally associated with hemorrhagic complications.

Mutation of MYH9, encoding non-muscle myosin heavy chain A, in May-Hegglin anomaly.

May-Hegglin anomaly (MHA) is an autosomal dominant macrothrombocytopenia of unclear pathogenesis characterized by thrombocytopenia, giant platelets and leukocyte inclusions. Studies have indicated that platelet structure and function are normal, suggesting a defect in megakaryocyte fragmentation. The disorder has been linked to chromosome 22q12-13.

Assessment of primary hemostasis by PFA-100 analysis in a tertiary care center.

We evaluated the utility of the PFA-100 platelet function analyzer in identifying disorders in platelet function and/or von Willebrand factor (vWF) in patients with various systemic disorders being followed at a tertiary care center. Closure times were determined with collagen/ ADP (CADP) and collagen/epinephrine (CEPI) cartridges for 305 patients, and abnormal results were further evaluated with platelet aggregometry and vWF analysis. Prolonged CADP and/or CEPI closure times were identified in 114 patients (37.

Antibodies to topical bovine thrombin correlate with access thrombosis.

Bovine thrombin is often used topically to promote hemostasis during vascular surgery, including dialysis-access placement. Patients frequently develop antibodies to bovine thrombin preparations, and some may develop antiphospholipid antibodies. We evaluated 88 hemodialysis patients for the presence of antibodies to topical bovine thrombin to determine if elevated antibody levels correlated with vascular access thrombosis.

Crystal structures of the membrane-binding C2 domain of human coagulation factor V.

Rapid and controlled clot formation is achieved through sequential activation of circulating serine proteinase precursors on phosphatidylserine-rich procoagulant membranes of activated platelets and endothelial cells. The homologous complexes Xase and prothrombinase, each consisting of an active proteinase and a non-enzymatic cofactor, perform critical steps within this coagulation cascade. The activated cofactors VIIIa and Va, highly specific for their cognate proteinases, are each derived from precursors with the same A1-A2-B-A3-C1-C2 architecture.

Partial glycosylation at asparagine-2181 of the second C-type domain of human factor V modulates assembly of the prothrombinase complex.

Thrombin-activated factor Va exists as two isoforms, factor Va(1) and factor Va(2), which differ in the size of their light chains and their affinity for biological membranes. The heterogeneity of the light chain remained following incubation of factor Va with N-glycanase. However, we found that the factor V C2 domain, which contains a single potential glycosylation site at Asn-2181, was partially glycosylated when expressed in COS cells.

Clinical and laboratory manifestations of anti-factor V antibodies.

Factor V is a large, multi-domain glycoprotein that exhibits both procoagulant and anticoagulant activity. Anti-factor V antibodies may develop by several mechanisms and, depending on their epitope specificity, may produce hemorrhagic or thromboembolic complications. The clinical laboratory is an essential component in diagnosing these antibodies, and therapeutic management depends on the predominant clinical manifestations.

Two instruments to determine activated partial thromboplastin time: implications for heparin monitoring.

Study Objective: To measure the difference in therapeutic ranges of activated partial thromboplastin time (APTT) between two laboratory devices.

Design: Prospective, controlled laboratory study.

Setting: University-affiliated hospital.

Familial antiphospholipid antibody syndrome: criteria for disease and evidence for autosomal dominant inheritance.

Objective: To develop diagnostic criteria for a familial form of antiphospholipid antibody syndrome (APS), identify families with >1 affected member, examine possible modes of inheritance, and determine linkage to potential candidate genes.

Methods: Family members of probands with primary APS were analyzed for clinical and laboratory abnormalities associated with APS. Families with > or =2 affected members were analyzed by segregation analysis and typed for candidate genetic markers.

New treatment options for heparin-induced thrombocytopenia.

A rapidly acting anticoagulant that can either inhibit thrombin generation or inhibit thrombin itself is the optimum therapy for acute thrombosis associated with heparin-induced thrombocytopenia (HIT). In this review, the newer treatment approaches that fulfill this requirement are discussed. These newer treatments include hirudin and argatroban, direct thrombin inhibitors, and danaparoid, which inhibits thrombin generation.

Recurrent thrombosis of the superior vena cava associated with activated protein C resistance: imaging findings.

The purpose of this report is to describe imaging findings in activated protein C resistance, a hereditary cause of recurrent thrombosis. The case described was unusual in that a neonate was affected, whereas the vast majority of cases occur in adulthood. This entity is important to diagnose because of the recurrent nature of thromboses and the fact that relatives are often affected.

Inhibitory anti-factor V antibodies bind to the factor V C2 domain and are associated with hemorrhagic manifestations.

Factor V inhibitors may develop as spontaneous autoantibodies, as alloantibodies after exposure to bovine thrombin preparations, or in factor V-deficient patients after plasma therapy. Clinical manifestations range from asymptomatic laboratory abnormalities to life-threatening hemorrhage. We have characterized the anti-factor V antibodies from 12 patients diagnosed with factor V inhibitors.

Disseminated thrombosis in primary antiphospholipid syndrome: MR findings.

We report the MR imaging findings in a patient with primary antiphospholipid syndrome, adrenal infarction and widespread thrombosis involving abdominal, pelvic, and pulmonary vessels. This syndrome should be suspected in patients with thromboses and organ infarctions of otherwise undetermined etiology.

Antiphospholipid antibodies: findings at arteriography.

Purpose: The purpose of this study was to determine the frequency and types of abnormalities at arteriography in patients with antiphospholipid antibodies (APA) and ischemic cerebrovascular events.

Methods: Twenty-three patients with APA and ischemic cerebrovascular events who underwent arteriography were identified. Patients over the age of 65 years were excluded.