Induced chronic intravascular coagulation in dogs

When an emulsion of dog brain thromboplastin was infused continuously into dogs for 1--4 weeks only platelets and factor XI were consistently depressed. The remaining clotting factors fell in a dose-dependent fashion but there was a tendency toward recovery despite continued infusion of thromboplastin. Fibrinogen and factor V were unique in that with weaker emulsions of thromboplastin, they often rose without a preliminary fall.

The clinical pathology of intravascular coagulation

A variety of mechanisms may cause intravascular coagulation. Fibrinolysis is nearly always secondary to the initial clotting. In the acute form, ICF is characterized by depletion of platelets and several coagulation factors together with active fibrinolysis. There is a decrease in Factors V and VIII because they are sensitive to coagulation. The stable coagulation factors may be decreased as well because after activation they are removed from the circulation by the liver and reticuloendothelial system. Severe bleeding is the usual accompaniment of the acute syndrome, which may also occur in cancer and infection of all types. The acute syndrome may also occur in prolonged, extensive operations, after transfusion of incompatible blood, heat stroke, acute injury, certain snake bites, and with the administration of certain drugs. The chronic syndrome of intravascular coagulation is much more common and is associated with many diseases, including collagen diseases or immune diseases and malignancy. Many patients with chronic intravascular coagulation have normal or even increased levels of coagulation factors, and these patients have no unusual bleeding. The diagnosis depends on the demonstration of circulating complex of "soluble" fibrin revealed by the ethanol gel and protamine sulfate gelation tests. The secondary fibrinolysis results in elevation of FSP. Many laboratories are investigating the use of other procedures in the diagnosis of intravascular coagulation, including fibrinopeptides A and B, the VIII:C VIIIR:AG ratio, antithrombin III, PF 4, beta-thromboglobulin, D dimer, urinary FSP, and fibrinogen chromatography.

Standardization of the bleeding time

The Duke, Ivy and immersion methods for performing the bleeding time are reviewed and modifications of these methods are discussed. Certain of the automated devices are described. It is concluded that the bleeding time, when properly standardized, is an important test in the evaluation of a hemostatic disorder.

A fluorescence-conjugated immunobinding assay for the detection of P-selectin on platelets

P-selectin (GMP-140 or PADGEM) is translocated to the plasma membrane of platelets after platelet activation. P-selectin, therefore, may be a potential marker for evaluating platelet activation. A fluorescence-conjugated immunobinding assay (FCIBA) has been developed to detect specifically P-selectin on platelets. Platelets were isolated from fresh blood by centrifugation and stimulated with various doses of ADP before being fixed with 1% of paraformaldehyde. Fixed platelets were incubated with fluorescence-conjugated anti-P-selectin monoclonal antibody in the wells of fluoricon microtiter plates, and the fluorescence intensity was read on a fluorescence concentration analyzer. Once platelets were fixed, the procedures were completed in < 2 hours. The intra-assay coefficient of variation (CV) was 6.97% (n = 40), the time-based interassay CV was 8.11% (n = 16), and the sample-based inter-assay CV was 6.17% (n = 16). The FCIBA had an excellent correlation (r = 0.936, p < 0.001) with flow cytometry in the measurement of expressed P-selectin in platelets of 20 normal donors. Translocation of P-selectin in plasma-suspended platelets in response to increasing doses of adenosine diphosphate (ADP) occurred in a dose-dependent manner and correlated positively with ADP-induced platelet aggregation in terms of both stimulating doses of ADP (r = 0.99, p < 0.01) and time intervals (r = 0.92, p < 0.05). The findings show that FCIBA is a fast and convenient assay with good precision for the determination of P-selectin expression of human platelets.

Synergistic effect of storage pool deficient platelets and low plasma von Willebrand factor on the severity of the hemorrhagic diathesis in Hermansky-Pudlak syndrome

A study of 565 Puerto Rican patients with storage pool deficient (SPD) Hermansky-Pudlak syndrome (HPS) demonstrated that most HPS patients had minor bleeding episodes while others had repeated, severe hemorrhagic episodes requiring transfusion. The severity of bleeding in these latter patients could not be attributed to their SPD alone. As swine with SPD platelets and low von Willebrand factor antigen (vWF:Ag) have more severe hemorrhages than pigs with either defect alone, 146 albino patients and 46 normally pigmented patients were examined for their level of vWF:Ag. The risk of SPD HPS patients having severe, repeated bleeding episodes increased when vWF:Ag fell below 70 U/dL. Family studies indicated that low vWF:Ag levels were more frequently associated with O blood group than from a gene suppressing production or release of vWF1. HPS patients should be tested for vWF:Ag levels.

Lipid-related clotting reactions of clinical significance

Several lipid-related reactions involving coagulation and fibrinolytic mechanisms have been described. Many of these reactions have been related to the development of atherosclerosis and thromboembolism. In this article, I review the antiphospholipid antibody syndrome, the tissue factor pathway inhibitor, the involvement of fatty acids in fibrinolysis, and the Lp(a) lipoprotein.

Pigs with von Willebrand disease may be resistant to experimental infective endocarditis

Indirect evidence suggests that the blood platelet is important in the pathogenesis of experimental infective endocarditis. Mechanical injury to the endocardial surface causes deposition of fibrin and platelets; injected microorganisms quickly localize to this lesion. Endocarditis pathogens also bind to and activate platelets. We used our previously described animal model for inducing infective endocarditis in normal pigs and applied it to animals with severe von Willebrand disease. The model uses catheter-induced trauma to the aortic valve and endocardium, followed by intravenous injection of group C streptococci. Control animals all showed typical clinical and laboratory evidence of endocarditis. In contrast, in pigs with von Willebrand disease (n = 4) endocarditis failed to develop. Studies in vitro of platelet-bacteria interactions showed that platelets derived from both normal and diseased pigs were equal in their ability to bind to and be activated by group C streptococci. These data suggest that normal platelet function is important in the pathogenesis of experimental infective endocarditis.

Missense mutations and the magnitude of functional deficit: the example of factor IX

Some missense changes are compatible with normal protein function while others compromise essential aspects of protein maturation, specific activity, or stability. For those missense changes that alter function in the intact organism, how likely is it for the mutated protein to retain appreciable residual activity? By genetic analysis of patients with hemophilia B of known severity, this question can be addressed for missense mutations that reduce factor IX activity by fourfold or more below the average. We estimate that missense changes cause only 59% of moderate and severe disease, but these mutations are almost always (95%) of independent origin. In contrast, missense mutations are found in virtually all (97%) families with mild disease, but only a minority of these (41%) are of independent origin. From the aggregate data, we estimate that most (71%) of the independent deleterious missense mutations cause at least a 20-fold decrease in factor IX activity.

Impaired intracellular transport produced by a subset of type IIA von Willebrand disease mutations

Type IIA von Willebrand disease (vWD) results from abnormalities in von Willebrand factor (vWF) characterized by absence of plasma high molecular weight (HMW) vWF multimers. In this report, 5 distinct point mutations were identified in 6 Type IIA vWD families. A total of 7 mutations, all clustered within a 124-amino acid segment of the vWF A2 domain, now account for 9 of a panel of 11 Type IIA families. In COS-7 cells, 3 single amino acid substitutions, Val844----Asp, Ser743----Leu, and Gly742----Arg, impaired the transport of vWF multimers between the endoplasmic reticulum and the Golgi complex, with more profound effects on the secretion of HMW multimers than lower molecular weight forms. In contrast, 2 substitutions, Arg834----Trp and Gly742----Glu, resulted in secretion of HMW multimers similar to wild-type vWF. The vWF structure observed within patient platelets correlated closely with the synthesis pattern seen for the corresponding mutants in COS-7 cells. These findings demonstrate that structural alterations within the A2 domain of vWF can produce the characteristic phenotype of Type IIA vWD via two distinct molecular mechanisms.

Measurement of crosslinked fibrin derivatives in patients undergoing abdominal surgery: use in the diagnosis of postoperative venous thrombosis

Levels of plasma crosslinked fibrin derivatives, a sensitive and direct marker of the lysis of intravascular crosslinked fibrin, were measured serially in 135 patients undergoing major abdominal surgery to determine their behavior and their use as a screening test for postoperative venous thrombosis. Preoperative levels and levels on the first postoperative day were significantly higher by both enzyme immunoassay and latex assay in 31 patients who developed venous thrombosis (positive venography) than in 104 patients who did not (negative 125I fibrinogen leg scan). Preoperative XLFDP levels 400 ng/ml (enzyme immunoassay) had a sensitivity to the diagnosis of postoperative venous thrombosis of 58%, specificity 74%, positive predictive value 41% and negative predictive value of 85%. The sensitivity of XLFDP levels over 1200 ng/ml on the first postoperative day was 65%, specificity 73%, positive predictive value 38% and negative predictive value 89%. These cutoff values were chosen (high negative predictive value) to allow identification of patients who were unlikely to have venous thrombosis. Measurement of plasma XLFDP, a simple inexpensive test, could be used as a screen to select patients for surveillance procedures (IPG or duplex ultrasonography). A substantial increase in XLFDP levels (greater than 500 ng/ml) occurred in virtually all patients, suggesting that fibrinolysis is not 'shutdown' postoperatively and that these assays reflect lytic activity at the fibrin surface more accurately than do measurements of plasminogen activators and their inhibitors.

How to diagnose bleeding disorders

Patients with problems of hemostasis are not uncommon in the primary care setting. The bleeding history provides critical information that helps in guiding evaluation of these patients. Results of frequently used screening tests of coagulation can be abnormal in patients who have no significant hemostatic defect and can be normal in patients who do have one.

Inhibitor of the thrombin time in systemic amyloidosis: a common coagulation abnormality

Patients with primary systemic amyloidosis (AL) often experience bleeding, and we report a newly recognized coagulation abnormality in AL. Of 103 patients with primary systemic AL studied over 2 years, 41 had prolongation of the thrombin time (range, 25 to 46 seconds; normal, less than 22 seconds) and reptilase time (range, 17 to 39 seconds; normal, 14 to 16 seconds). The fibrinogen from the plasma of 36 patients was precipitated by beta-alanine and diluted to a concentration of approximately 200 mg/dL. The thrombin times of the precipitated fibrinogens were normal in 34 patients, implying that an inhibitor was responsible for the abnormal tests. The addition of patient fibrinogen-free plasma to normal plasma prolonged the thrombin times, and this result confirmed the presence of an inhibitor. The inhibitor is more likely to be present in patients with nephrotic syndrome (20 of our patients) and congestive heart failure (six). A circulating monoclonal protein (24 patients), the presence of amyloid liver involvement (eight), and the presence of amyloid neuropathy (nine) were not predisposing factors. Only one patient had deficiency of factor X. We conclude that inhibition of fibrinogen conversion to a fibrin clot rather than dysfibrinogenemia is the cause of the prolonged thrombin time in primary systemic AL.

The molecular defect in type IIB von Willebrand disease. Identification of four potential missense mutations within the putative GpIb binding domain

Type IIB von Willebrand Disease (vWD) is characterized by the selective loss of large von Willebrand Factor (vWF) multimers from plasma, presumably due to their increased reactivity with platelets and subsequent clearance from the circulation. Using the PCR, one of a panel of four potential missense mutations was identified in each of the 14 patients studied from 11 unrelated families. None of these substitutions was encountered in a large panel of normal DNAs. These changes all represent C----T transitions at CpG dinucleotides, proposed "hot spots" for mutation in the human genome. The four resulting amino acid substitutions, Arg543----Trp, Arg545----Cys, Val553----Met, and Arg578----Gln, are all clustered within the GpIb binding domain of vWF. Disruption of this latter functional domain may explain the pathogenesis of Type IIB vWD. By sequence polymorphism analysis, the Arg543----Trp substitution was shown to have occurred as at least two independent mutational events. This latter observation, along with the identification of mutations in all 14 patients studied and their localization to the GpIb binding domain, all strongly suggest that these substitutions represent the authentic defects responsible for Type IIB vWD. This panel of mutations may provide a useful diagnostic tool for the majority of patients with Type IIB vWD.

Effect of the somatostatin analogue octreotide acetate on hemostasis in humans

Octreotide acetate is a somatostatin analogue that has been shown to ameliorate the side effects of excessive secretion of hormone from benign and malignant tumors. The ability of this drug to inhibit the growth of malignant cells and to control gastrointestinal hemorrhage will prompt additional clinical trials. Because some of these patients may have thrombocytopenia, platelet dysfunction, or a coagulopathy, we studied tests of platelet function and blood coagulation in 15 patients before and after 14 days of therapy with octreotide acetate at a dosage of 500 micrograms three times daily. We found no substantial change in the results of these tests, and no patient experienced bleeding or thrombosis. These results suggest that octreotide acetate does not adversely affect platelet function or the coagulation system in humans.

Protamine-heparin-induced pulmonary hypertension in pigs: effects of treatment with a thromboxane receptor antagonist on hemodynamics and coagulation

Adverse hemodynamic reactions after protamine neutralization of heparin are an infrequent but important clinical problem. Pre-treatment of swine with a thromboxane A2 receptor antagonist has been reported to prevent the pulmonary hypertensive response occasionally seen after protamine reversal of heparin anticoagulation. In the current study, a control group of pigs (n = 9) received intravenous heparin (300 IU/kg), followed after 10 min by a neutralizing dose of protamine (3 mg/kg). A treatment group of pigs (n = 11) was treated identically, except that the thromboxane A2 receptor antagonist L-670596 (2 mg/kg) was infused intravenously 2 min after the protamine infusion. Hemodynamic and coagulation profiles were monitored during these procedures. Pulmonary hypertension developed and reached a peak within 2 min of protamine administration, often at the same time that L-670596 was administered in the treatment group. There was no statistical difference between control and treatment groups' peak pulmonary arterial pressure and peak pulmonary vascular resistance. However, the interval for return of mean pulmonary artery pressure from peak to baseline values was 11.6 +/- 3.1 versus 5.5 +/- 1.9 min (mean +/- SD) for control and treatment groups, respectively (P less than 0.01). Thromboxane B2 plasma concentrations increased in both groups and were correlated with the pulmonary hypertensive response (r = 0.86, P less than 0.01). Platelet aggregation to collagen was inhibited by the thromboxane A2 receptor antagonist (P less than 0.05). Bleeding time was prolonged beyond normal range in 50% of L-670596-treated pigs. All other coagulation tests in both groups returned to baseline after reversal of heparin with protamine and were unaffected by L-670596.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of recombinant human erythropoietin on cerebral and cutaneous blood flow and on blood coagulability

Seizures, hypertensive encephalopathy, transient ischemic attacks, and thrombosis of hemodialysis accesses occurred in early clinical trials with recombinant human erythropoietin. To determine if these events may be caused by the increased hematocrit value or some direct effect of the recombinant human hormone, 10 transfusion-dependent hemodialysis patients were divided into two groups of five according to their serum ferritin concentration: group A. less than 800 microgram/liter, and group B. greater than 800 micrograms/liter. After a month of placebo administration, recombinant human erythropoietin was given (150 U/kg intravenously thrice weekly) for four months and then stopped for one month. Hematocrit values were maintained at 0.33 +/- 0.02 (mean +/- SD) by dose adjustment in group A and at 0.26 +/- 0.02 by thrice weekly phlebotomies in group B, who received a constant dose of erythropoietin. Viscosity increased from subnormal to normal in group A (P less than 0.02) and cerebral blood flow decreased from above normal to normal (P less than 0.02). In group B minor, statistically insignificant, changes in viscosity and reciprocal changes in cerebral blood flow also occurred. There was no change in either group in transcutaneous oxygen tension. Bleeding time decreased toward normal in both groups during recombinant human erythropoietin administration but the changes did not reach statistical significance. Fibrinogen levels were increased in all patients but remained unchanged. No other significant coagulation-related changes were observed. Recombinant erythropoietin in the dosage and schedule of administration described in this study did not lead directly or indirectly to changes likely to precipitate seizures or intravascular thrombosis.

Hirudin, heparin, and placebo during deep arterial injury in the pig. The in vivo role of thrombin in platelet-mediated thrombosis

Three dosages (0.3, 0.7, and 1.0 mg/kg) of recombinant hirudin, a specific inhibitor of thrombin, were compared with heparin (50 units/kg) and placebo for reducing thrombus formation in the carotid arteries of 50 pigs after deep injury by balloon dilatation. Each drug was administered as a bolus followed immediately by a continuous infusion of the same dose per hour. Major end points were quantitative indium-111-labeled platelet and iodine-125-labeled fibrinogen deposition and the incidence of mural thrombosis. This study showed that heparin, at a dose that prolonged the activated partial thromboplastin time (APTT) to twice the control time, did not prevent mural thrombosis or significantly reduce platelet deposition compared with placebo but did reduce fibrinogen deposition. Recombinant hirudin markedly reduced platelet and fibrinogen deposition in a dose-related manner and totally eliminated mural thrombosis at an APTT of two to three times that of control. Platelet deposition (x 10(6)/cm2, mean +/- SEM) in areas of deep arterial injury for the placebo, heparin, and 0.3, 0.7, and 1.0 mg/kg hirudin groups was 54 +/- 21, 33 +/- 9, 22 +/- 6, 8 +/- 1, and 7 +/- 1, respectively; electron microscopy showed a single layer (or less) of platelets at the two highest hirudin dosages. The incidence of macroscopic mural thrombosis was 76% with placebo, 57% with heparin, 46% with 0.3 mg/kg hirudin; there were no thrombi with 0.7 or 1.0 mg/kg hirudin (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

A past mutation at isoleucine 397 is now a common cause of moderate/mild haemophilia B

Of the factor IX sequence changes that we have identified in 65 consecutive males with haemophilia B, 11 (17%) are the same mutation. This mutation is a T----C transition at base 31311 which substitutes threonine for isoleucine397 (ile397) in the factor IX molecule. The 11 patients are of Western European descent and have the same haplotype: Hinf1 (-), Xmn1 (-), Taq1 (-), BamH1 (+), Malmö allele = thr148. The frequency of this haplotype was estimated and the probability of the same mutation occurring independently 11 times in this haplotype was miniscule. We conclude that these patients have a common ancestor despite the lack of overlapping pedigrees. The clinical symptoms of the disease were consistently moderate/mild in these 11 patients, whereas factor IX coagulation values obtained from the medical records varied more than sixfold between individuals. However, when plasma from five individuals was assayed by the same laboratory concurrently, the values varied less than twofold. Thus, in routine practice, clinical severity may correlate better with the presence of a given mutation than the factor IX coagulant activity. The high frequency of the mutation at ile397 indicates that carrier testing in families of Northern European descent with moderate/mild haemophilia B can be expedited by first determining whether this particular mutation is present. We demonstrate here that the technique of polymerase chain reaction (PCR) amplification of specific alleles (PASA) can be used to rapidly perform carrier testing in families with the ile397 mutation.

Bernard-Soulier syndrome: whole blood diagnostic assays of platelets

Diagnosing Bernard-Soulier syndrome (BSS), a congenital hemorrhagic disorder of blood platelets, is complicated by the difficulty of separating the giant platelets from other blood cells to allow studies of platelet function and structure. We report on the use of three whole blood assays for diagnosing BSS. Whole blood platelet aggregation responses studied with an electrical impedance aggregometer were equivalent to those more laboriously obtained by using platelet-rich plasma prepared by unit gravity sedimentation and studied with an optical light transmittance aggregometer. Platelet aggregation responses were normal with adenosine diphosphate or collagen stimulation but absent with ristocetin or bovine plasma stimulation. Whole blood radioimmunoassay of platelet glycoprotein (GP) expression was performed by using iodinated murine monoclonal antibodies HP1-1D (anti-GP IIb/IIIa) and 6D1 (anti-GP Ib). After incubation with citrated whole blood, centrifugation was used to separate cell-bound antibody that was quantitated with a gamma counter. The patient's whole blood had a normal level of cell-bound GP IIb/IIIa but a substantially reduced level of cell-bound GP Ib (5% of normal mean). Whole blood smear immunocytochemical staining with monoclonal antibodies and qualitative analysis by light microscopy revealed a considerable reduction of GP Ib expression by the patient's giant platelets, whereas GP IIb/IIIa expression was normal. These data helped establish the diagnosis of BSS. We conclude that these three relatively simple assays of platelets in whole blood should be of particular value in the clinical laboratory differential diagnosis of patients with congenital thrombocytopenias and giant platelet syndromes.

Evaluation of preoperative hematology-coagulation screening in liver transplantation

We retrospectively reviewed the results of preoperative hematology-coagulation studies in 66 patients who underwent orthotopic liver transplantation-24 with the primary diagnosis of chronic active hepatitis (CAH), 22 with primary sclerosing cholangitis (PSC), and 20 with primary biliary cirrhosis (PBC). The mean prothrombin time was above normal in all three diagnostic groups, patients with CAH having the highest values. The mean activated partial thromboplastin time was normal in patients with PSC or PBC but elevated in those with CAH. Fibrinogen levels were above normal in patients with PBC but decreased in 1 patient (5%) with PSC and 10 (42%) with CAH. Mean platelet counts were below normal in 68% and 55% of patients with PSC and PBC, respectively, but in 96% of those with CAH. The mean Ivy bleeding time was normal in patients with PSC or PBC but prolonged in those with CAH. Patients with PSC or PBC had normal mean activity levels of factors II, V, VII, IX, and X, whereas those with CAH had below normal mean values for factors II and VII. The antithrombin III activity level was normal in patients with PSC or PBC but reduced in those with CAH. Thus, patients with CAH have a greater derangement in results of clotting studies in comparison with those who have PSC or PBC, but the use of blood did not differ among the three diagnostic groups.

Monoclonal antibodies against porcine platelet membrane glycoproteins Ib and IIb/IIIa

We prepared murine monoclonal antibodies to porcine platelet membrane glycoprotein (GP) Ib and GP IIb/IIIa for further study of the porcine hemostatic mechanism. One monoclonal antibody, designated PP3-4C, blocked Ristocetin-induced platelet agglutination and caused 80% inhibition of Ristocetin-induced 125I-von Willebrand factor (vWF) binding to porcine platelets at a concentration of greater than or equal to 12 micrograms IgG/mL. PP3-4C did not affect adenosine diphosphate (ADP)- or collagen-induced platelet aggregation. Binding of 125I-Fab fragments of PP3-4C to platelets was saturable at 3.7 x 10(4) +/- 0.8 x 10(4) molecules per platelet. Another monoclonal antibody, designated PP3-3A, blocked ADP- or collagen-induced platelet aggregation at 6 micrograms IgG/mL. At a concentration of 10 micrograms IgG/mL, PP3-3A completely inhibited binding either of 125I-fibrinogen or of 125I-vWF to ADP-stimulated platelets. PP3-3A did not affect Ristocetin-induced platelet agglutination nor 125I-vWF binding to platelets in the presence of Ristocetin. Binding of 125I-Fab' fragments of PP3-3A to platelets was saturable at 9.8 x 10(4) +/- 1.2 x 10(4) molecules per platelet. PP3-4C antibody (anti-GP Ib) did not bind to human platelets; however, PP3-3A antibody (anti-GP IIb-IIIa) had partial cross-reactivity with human platelets. Immunoaffinity chromatography of solubilized surface-radiolabeled porcine platelets and subsequent sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis demonstrated that PP3-4C recognized a GP with an apparent molecular weight of 160,000 (nonreduced), and 140,000 (reduced). PP3-3A recognized GPs with apparent molecular weights of 130,000 and 80,000 (nonreduced), and 115,000 and 95,000 (reduced). These monoclonal antibodies to porcine platelet membrane GPs, which are structural and functional analogues of human GP Ib and GP IIb/IIIa, will be useful for in vitro and in vivo studies of the mammalian hemostatic mechanism.

Molecular genetic analysis of porcine von Willebrand disease: tight linkage to the von Willebrand factor locus

von Willebrand disease (vWD), one of the most common bleeding disorders in humans, is manifested as a quantitative or qualitative defect in von Willebrand factor (vWF), an adhesive glycoprotein (GP) with critical hemostatic functions. Except for the rare severely affected patient with a gene deletion as etiology of the disease, the molecular basis for vWD is not known. We studied the molecular basis for vWD in a breeding colony of pigs with a disease closely resembling the human disorder. The porcine vWF gene is similar in size and complexity to its human counterpart, and no gross gene deletion or rearrangement was evident as the pathogenesis of porcine vWD. A restriction fragment-length polymorphism (RFLP) within the porcine vWF gene was identified with the restriction endonuclease HindIII, and 22/35 members of the pedigree were analyzed for the polymorphic site. Linkage between the vWF locus and the vWD phenotype was established with a calculated LOD score of 5.3 (1/200,000 probability by chance alone), with no crossovers identified. These findings indicate that porcine vWD is due to a molecular defect within (or near) the vWF locus, most likely representing a point mutation or small insertion/deletion within the vWF gene.

Heparin-induced thrombocytopenia and thrombosis in ischemic stroke

We reviewed the records of all patients who underwent carotid endarterectomy at our institution during the period from January 1970 through December 1986 to determine the frequency of postoperative occlusions and the role of heparin-induced thrombosis in patients with such occlusions. After 2,527 carotid endarterectomies, a total of 19 occlusions occurred in 18 patients. Of these 18 patients, 6 had an associated heparin-induced coagulation disorder, 3 of whom are described in detail. Although heparin is a useful anticoagulant, it may precipitate occlusion of vessels after an endarterectomy procedure, either at the endarterectomy site or elsewhere. Physicians should be aware of the potentially increased risk for embolic or thrombotic cerebrovascular events in patients who receive heparin therapy.

Effects of dietary supplementation with cod-liver oil on endothelium-dependent responses in porcine coronary arteries

To study the effect of dietary supplementation with fish oil on endothelium-dependent responses, Yorkshire pigs were maintained on a normal diet or on a low (0.6 ml/kg/day) or a high (1.0 ml/kg/day) dose of cod-liver oil for 4 weeks. Endothelium-dependent responses were examined in vitro in rings of proximal left anterior descending coronary arteries taken from control and treated animals studied in parallel. Endothelium-dependent relaxations in response to bradykinin, serotonin, adenosine diphosphate, and thrombin were facilitated in arteries from treated but not in those from control animals, whereas the relaxations in response to A23187 were unaltered. The facilitated relaxations were not altered by indomethacin but significantly inhibited by methylene blue. Aggregating platelets from control and treated pigs induced comparable, facilitated endothelium-dependent relaxations in rings taken from treated pigs. The platelet-induced contractions were significantly reduced in rings with endothelium taken from treated pigs, and they were comparable in rings without endothelium in both groups. Aggregating platelets from control and treated pigs released comparable amounts of serotonin and thromboxane A2. Endothelium-dependent relaxations induced by arachidonic acid and eicosapentaenoic acid were unaltered, whereas transient endothelium-dependent contractions induced by arachidonic acid were significantly reduced by the treatment with cod-liver oil. Relaxations to sodium nitroprusside or isoproterenol,and contractions to potassium chloride or serotonin were not different in rings without endothelium from control or treated pigs. These results indicate that dietary supplementation with cod-liver oil facilitates endothelium-dependent relaxations and inhibits endothelium-dependent contractions in porcine coronary arteries.

Hemostatic evaluation of patients undergoing liver transplantation

A detailed coagulation and thromboelastographic study was done on the first 50 liver transplantation procedures performed at the Mayo Clinic between March 1985 and June 1986. Most of the patients suffered from primary sclerosing cholangitis, primary biliary cirrhosis, or chronic active hepatitis. Seven patients required a second liver transplantation, and six patients died, none intraoperatively. Most of the patients had distorted hemostatic mechanisms preoperatively, as would be expected because the liver generates most of the clotting factors. The outstanding exception was factor VIII, which was usually in the high-normal range or even more elevated. Substantial deterioration of coagulation factors occurred regularly during reperfusion of the donor liver. In some instances, this trend was corrected within 1 hour, but platelet counts continued to decrease, and some coagulation factors rebounded only partially. Because thromboelastographic tracings are quickly available to the liver transplant team and because they tend to forewarn of impending hemostatic problems, we believe that thromboelastography is a reasonably effective procedure for monitoring coagulation during liver transplantation.

Parameters affecting the yield of DNA from human blood

An examination of variables affecting the yield of DNA from blood was undertaken in order to improve sample processing and to evaluate alternative methods of mailing blood samples for DNA analysis. A rapid, high-yield method was developed for the isolation of high-molecular-weight DNA from fresh and frozen blood. In addition, the following observations were made: (1) Of the anticoagulants examined, acid citrate dextrose (ACD) solution B was found to be superior to EDTA and heparin for preserving yields of DNA during incubation at room temperature. If DNA is isolated from frozen blood, high yields of undegraded DNA are achieved after incubation at 23 degrees C for 5 days with ACD solution B. (2) High yields of undegraded DNA are obtained from blood stored with ACD solution B for at least 1 day at 42 degrees C, 5 days at 0 degrees C, or 1 month at -20 degrees C. (3) Three cycles of freezing and thawing may have little if any affect on the yield of DNA. The results indicate that blood for DNA extraction may be mailed in an ambient temperature container and, in many cases, sent by first-class mail rather than by overnight delivery services.

Preoperative evaluation of hemostasis in patients with congenital heart disease

The incidence of abnormal results of coagulation tests and the risks for postoperative hemorrhage were assessed in 235 patients with congenital heart disease. Preoperatively, the prothrombin time, partial thromboplastin time, activated partial thromboplastin time, thrombin time, or platelet count was abnormal in 45 of the 235 patients (19%), a significantly higher incidence than that expected in a normal population (P less than 0.002). Prolonged values for the prothrombin time or the partial thromboplastin time or activated partial thromboplastin time were seen most frequently. Further evaluation in eight of the patients with prolonged prothrombin time or partial thromboplastin or activated partial thromboplastin time showed decreased levels of either factor VII or IX in six of them, suggesting that impaired vitamin K-dependent carboxylation is commonly present. Normal results of preoperative coagulation tests do not exclude the presence of a major bleeding diathesis (von Willebrand's disease was later diagnosed in a patient with such findings). The use of blood products during subsequent cardiac operations was not significantly different in patients with normal or abnormal test results. Two of the three patients who required reoperation and were found to have a nonsurgical cause of bleeding had abnormalities in two or more of the preoperative coagulation tests. This finding suggests that abnormal results of preoperative coagulation tests may be predictive of defective hemostasis in the postoperative period.

The capillary thrombometer and von Willebrand factor

A modified capillary thrombometer was constructed to study the rate of thrombus formation using heparinized whole blood (2 U/ml) from 4 different groups of pigs: normal, heterozygous von Willebrand's disease (vWD), homozygous vWD, and platelet storage pool disease (SPD). The median thrombosis times for the 4 groups of pigs were: 5.3 min (range = 3.0-14), 31 min (range = 4.0-47), 55 min (range = 41-60), and 60 min (range = 15-60), respectively. Significant differences were demonstrated between all pig groups (p less than .01 - p less than .001), except between the homozygous vWD pigs and the SPD pigs (p = 0.8), both of which are clinical bleeders. Cryoprecipitate was infused into 3 pigs with homozygous vWD. Partial correction of the capillary thrombometer thrombosis time and the in vivo ear bleeding time was observed. Murine monoclonal antibodies to porcine von Willebrand factor were added to normal pig whole blood samples in the capillary thrombometer. Four of six antibodies prolonged the thrombosis time and had similar effects on the ear bleeding time. Using these monoclonal antibodies, an immunoperoxidase stain demonstrated plasmatic and platelet associated von Willebrand factor in sections of thrombi from the capillary thrombometer. These experiments confirm that von Willebrand factor is important to thrombus formation in the capillary thrombometer and that measurements by this instrument may relate to in vivo hemostasis as measured by the ear bleeding time.

The capillary thrombometer revisited

A modified capillary thrombometer was constructed to study the rate of thrombus formation using heparinized whole blood (2 U/ml) obtained from normal adults (n = 22) and children (n = 20) and patients with hemophilia A (n = 10) or von Willebrand's disease (n = 8). The median thrombosis times were as follows: normal adults = 12.8 min (range = 4.5-26.0), normal children = 13.3 min (range = 5.7-29.0), patients with hemophilia A = 37.2 min (range = 20.0-60.0 min), and patients with von Willebrand's disease = 60.0 min (range = 37.2-60.0). Significant differences were demonstrated between all groups of subjects, except between normal adults and children. The capillary thrombometer appears to measure thrombus formation dependent on adequate Willebrand factor and platelets.

Transplantation of normal bone marrow into a pig with severe von Willebrand's disease

Bone marrow from a normal male pig was transplanted into a related female pig with severe homozygous von Willebrand's disease (vWd). After engraftment the circulating leukocytes were of the male karyotype, and the platelets were strongly positive for von Willebrand factor (vWF) by indirect immunofluorescence. The average level of vWF was 1.96 U/dl and of ristocetin cofactor was 2.8 U/dl. The ear immersion bleeding time before transplantation was consistently more than 15 min and afterwards varied between 5 min and more than 15 min. Transfused vWF corrected the bleeding time at a level of 10 U/dl, which is lower than that required for a von Willebrand pig. We concluded that: the plasmatic compartment is only minimally replenished by the vWF from platelets and megakaryocytes; and the platelet vWF alone only partially corrects the abnormal tests of the hemostatic mechanism in severe vWd.

Inheritance of a new bleeding disease in a herd of swine with Willebrand's disease

A herd of swine affected by Willebrand's disease was begun in 1967 at the Mayo Clinic in order to study the inherited hemostatic abnormality in swine as a model for the human disease. Affected individuals have bleeding times in excess of 15 minutes, extremely low levels of Willebrand factor (less than or equal to 0.25 percent of normal), and decreased levels of VIII coagulant activity. Individuals with long bleeding times, higher levels of Willebrand factor and normal levels of VIII coagulant activity began to appear in the colony. It is hypothesized that this new (N) condition is inherited as a simple autosomal recessive (N/n) at a locus separate and independent of the similarly autosomal recessive (A/a) von Willebrand locus. In addition, the Willebrand locus is epistatic to the N locus, i.e., individuals will only express the new condition provided there is at least one normal allele at the von Willebrand locus. Therefore, individuals with genotype aa--are all von Willebrand phenotypically, and A-nn individuals have the new disease.

Hemostatic plug formation in normal and von Willebrand pigs: the effect of the administration of cryoprecipitate and a monoclonal antibody to Willebrand factor

Hemostatic plug (HP) formation was investigated in the ear bleeding time incision in normal and von Willebrand pigs. HP volume was calculated by integrating the areas of serial sections. In normal pigs (n = 11), platelets immediately formed a layer on the surface of the cut channel. Platelet aggregates formed at the ends of transected vessels and gradually enlarged. Finally, all transected vessels were occluded by HP and bleeding stopped. In contrast, large HPs were formed in the incision in von Willebrand's disease (vWD) pigs (n = 4); these HPs did not cover the ends of the transected vessels, which continued to bleed, allowing the formation of large hemostatically ineffective platelet aggregates in the incision. Canals traversed these HPs, and bleeding from the open vessels may have continued through them. After infusion of cryoprecipitate into a vWD pig, the bleeding time shortened, and the morphological findings of the HPs were similar to those of normal pigs. In normal pigs (n = 3) infused with an anti-Willebrand factor monoclonal antibody, which prolonged the bleeding time, a large HP formed in the incision, similar to that observed in the vWD pig. The volume of the normal and vWD HPs increased with time. These in vivo findings suggest that Willebrand factor is involved in the localization of the HP to the damaged vessel and may also play a role in platelet-platelet interaction. A computerized morphometric technique was used for measuring the volume of the hemostatic plugs and the distance of sequential points on the perimeter of the HP from the center of selected bleeding vessels.

Platelet storage pool deficiency in pigs

We report a new bleeding disease--storage pool deficiency (SPD) of platelets--in pigs from the Mayo swine colony of homozygous von Willebrand's disease (vWD) and of heterozygous carriers of vWD. Levels of factor VIII, von Willebrand factor antigen (vWF:Ag), and ristocetin cofactor (RCof) were similar in the vWD carriers and SPD pigs. The latter pigs, however, had bleeding times of 15 minutes or more and were severe bleeders, in contrast to clinically normal vWD carriers. Platelet aggregation in response to collagen was reduced in most SPD pigs. Total platelet content of ADP, ATP, and serotonin was less than that of normal pigs. While the initial uptake of 14C-labeled serotonin into platelets was similar in SPD and normal pigs, retention of serotonin was reduced in platelets of SPD pigs. Transmission electron microscopy showed a large decrease of dense bodies in the platelets of SPD pigs. These findings support a diagnosis of SPD. Genetic analyses suggest an autosomal recessive mode of inheritance. A breeding program is under way to produce pigs affected only at the SPD gene, thus allowing further characterization of SPD and SPD-carrier pigs.

Isolation and study of an acquired inhibitor of human coagulation factor V

A coagulation Factor V inhibitor developed in a man 75 yr of age in association with an anaplastic malignancy and drug treatment (including the aminoglycoside antibiotic, gentamicin). The patient did not bleed abnormally, despite both surgical challenge and plasma Factor V activity of less than 1%. The inhibited plasma had grossly prolonged prothrombin and activated partial thromboplastin times, but a normal thrombin time. Mixing studies indicated progressive coagulation inhibition with normal plasma, but not with Factor V-deficient plasma, and reversal of coagulation inhibition by the addition of bovine Factor V to the patient's plasma. 1 ml of patient plasma inhibited the Factor V activity of 90 ml of normal human plasma. The inhibitor was isolated by sequential affinity chromatography on protein A-Sepharose and Factor V-Sepharose. The IgG isolate markedly inhibits the activity of prothrombinase assembled from purified Factors Xa and Va, calcium ion, and phospholipid vesicles, and partially inhibits prothrombinase assembled from purified Factor Xa, calcium ion, and normal platelets. The Factor V of platelets, however, appears relatively inaccessible to the antibody, inasmuch as platelets isolated from whole blood supplemented for 8 h with the antibody functioned normally with respect to platelet Factor V-mediated prothrombinase function. The absence of obvious hemorrhagic difficulties in the patient, the total inhibition of plasma Factor V by the inhibitor, and the apparent inaccessibility of platelet Factor V to the inhibitor specifically implicate platelet Factor V in the maintenance of hemostasis.

Hemophilia A. Detection of molecular defects and of carriers by DNA analysis

To understand the molecular basis of hemophilia A and to provide heterozygote detection and prenatal diagnosis by DNA analysis, we used cloned factor VIII:C DNA fragments to study 10 affected families. In four of these families, inhibitors of factor VIII:C had developed in affected persons. In one such family a deletion of approximately 80 kb within the factor VIII:C gene was identified. Carriers of the deletion were identified through detection of an abnormal DNA fragment located at the deletion end points. In another family a single nucleotide change in the coding region of the factor VIII:C gene produced a nonsense codon leading to premature termination of factor VIII:C synthesis. Carrier detection was performed in eight female members of this four-generation family. In a third family a small change in the size of a restriction-endonuclease fragment correlated with the presence of the mutant gene, and in the other seven families the molecular defect has not yet been identified. In addition, we used two common polymorphic sites in the factor VIII:C gene to differentiate the normal from the defective gene in four of six obligate female carriers from families with patients in whom inhibitors did not develop. Carrier detection was possible in other members of these families. These data suggest that DNA analysis of the factor VIII:C gene provides an accurate method of carrier detection and, potentially, of prenatal diagnosis in at least 50 per cent of the pedigrees affected by hemophilia A.

Factor VIII-von Willebrand factor in giant cell arteritis and polymyalgia rheumatica

Levels of three factor VIII-von Willebrand factor components (von Willebrand antigen, ristocetin cofactor, and factor VIII coagulant) were higher in specimens of plasma from 27 patients with giant cell arteritis and 18 patients with polymyalgia rheumatica than in specimens from 21 normal control subjects. Values in patients with active giant cell arteritis were higher than those in patients with either inactive giant cell arteritis or active polymyalgia rheumatica. Levels of factor VIII-von Willebrand factor components tended to decline gradually after disease activity had been suppressed by corticosteroid therapy and therefore may be indicators of vascular damage. These levels, however, did not revert to normal rapidly in response to corticosteroid therapy as did the patients' symptoms and the usual laboratory measurements indicative of inflammation; thus, measurements of these components are unlikely to be useful in day-to-day management of these diseases. Electrophoretic analysis suggested that the elevated values are due to increased amounts of normal factor VIII-von Willebrand factor rather than to the presence of an abnormal molecule.

Aortic atherosclerosis in pigs with heterozygous von Willebrand disease. Comparison with homozygous von Willebrand and normal pigs

We have reported that pigs with severe homozygous von Willebrand disease (vWd) are resistant to spontaneous and high fat, high cholesterol, diet-induced atherosclerosis. In this study we report the quantitation of aortic atherosclerotic plaques in three groups of pigs fed with a high fat, high cholesterol (2%) diet from age 3 to 9 months. Nine normal pigs (normal factor VIII antigen, VIII R:AG, and ristocetin co-factor, VIII:RWF) had a mean of 21% atherosclerotic involvement of the distal aortic surface and a 4.5% mean involvement of the entire aorta. Five homozygous vWd pigs (undetected VIII R:AG and VIII:RWF) had a mean of 4.2% atherosclerotic involvement of the distal aortic surface and 1.2% involvement of the entire aorta (p less than 0.01, rank sum test). Five heterozygous vWd pigs (approximately 35% VIII R:AG and VIII:RWF) had a mean of 25% atherosclerotic involvement of the distal aortic surface and 6% involvement of the entire aorta; the results were not significantly different from those in the normal pigs. We concluded that resistance to atherosclerosis is not found in animals with moderate reduction of VIII R:AG and VIII:RWF. This may have implications for humans, since in human vWd both factors are almost always present.

Lupus anticoagulant: an analysis of the clinical and laboratory features of 219 cases

To define clinical and laboratory characteristics of the lupus anticoagulant (LA), we reviewed our experience (219 subjects). Subjects were divided into group A, those with the LA and the diagnosis of lupus erythematosus, group B, those with the LA but nonlupus diagnoses, and group C, those with drug-related lupus syndromes. The typical laboratory findings consisted of a prolonged and inhibited plasma clot time (an average of 1.9 times control time) which was proportionately more prolonged than the partial thromboplastin time or activated partial thromboplastin time (APTT) (average 1.3 times control). Ninety-eight percent had a prolonged plasma clot time and 94% had a prolonged partial thromboplastin time. The prothrombin and thrombin times were prolonged in 33 and 25% of subjects, respectively. Washed platelets shortened the APTT in the 22 subjects so tested. Monoclonal protein peaks were seen in 7% of patients. Seventeen episodes of bleeding were observed, but in all but one instance there was another hemostatic defect present. In the 18 patients who underwent major operations, there were no hemorrhagic complications. Fifty-eight episodes of thrombosis were observed with the same incidence in group A (25%) as in group B (26%). Bleeding is rare with the LA but thrombosis is common even without SLE and lupuslike syndromes. The plasma clot time in platelet-rich plasma is more prolonged, and in our experience, is more sensitive in detecting the lupus anticoagulant than is the partial thromboplastin time.

A clinical evaluation of automated chromogenic tests as substitutes for conventional prothrombin time and activated partial thromboplastin time tests

Automated procedures involving a chromogenic substrate sensitive to thrombin-sarcosine-Pro-Arg p-nitroanilide were compared with conventional tests for prothrombin times and activated partial thromboplastin times (APTT) and with specific assays for factors V, VII, VIII, IX, X, XI, and XII. The reproducibility and sensitivity of the chromogenic tests were compared with those of the clotting tests. Further, we have confirmed that the chromogenic test for APTT is sensitive to factor VII deficiency, unlike the clotting test for APTT. This might be an advantage in monitoring orally anticoagulated patients. The ready availability of the automated equipment for performing the chromogenic tests suggests their potential for routine use. However, some discrepant results in certain patients with liver disease and in others with factor VIII inhibitors warrant caution.