Alessandra Casonato

A shorter von Willebrand factor survival in O blood group subjects explains how ABO determinants influence plasma von Willebrand factor

ABO blood groups greatly influence circulating von Willebrand factor (VWF) levels, and O group subjects have lower VWF values. In this study, we investigated whether ABO groups affect VWF survival by monitoring the post-DDAVP (1-desamino-8-d arginine vasopressin) time courses of VWF antigen (VWF:Ag), VWF collagen binding (VWF:CB), and factor VIII (FVIII) in 47 healthy subjects (28 O and 19 non-O blood groups). The elimination half-life (T1/2el) of VWF was found significantly shorter in O than in non-O subjects (10.0+/-0.8 hours vs 25.5+/-5.3 hours, respectively; P<.01), as was the T1/2el of VWF:CB (7.9+/-0.5 hours vs 20.9+/-4.5 hours; P<.01). A direct linear correlation was found between basal VWF:Ag and T1/2el, subjects with higher VWF levels having longer-surviving VWF. ABO blood groups appeared to strongly influence VWF clearance, but not its synthesis or release from endothelial cells. The VWF propeptide to VWF:Ag ratio, useful for predicting an increased VWF clearance, was found significantly higher in O than in non-O individuals (1.6+/-0.1 vs 1.2+/-0.5, P<.001), with values that correlated inversely with T1/2el (P<.001). Based on these findings, we conclude that the lower VWF values in O group individuals is attributable to a shorter VWF survival and circulating VWF values are strongly influenced by its half-life.

Abnormalities of von Willebrand factor are also part of the prothrombotic state of Cushing's syndrome

Glucocorticoids are known to increase plasma concentrations of factor VIII (FVIII) and von Willebrand factor (vWF), and their administration is associated with an increased incidence of thrombotic complications. Because Cushings syndrome is characterized by an endogenous increase in glucocorticoids, we studied levels of FVIII and vWF in 20 patients with Cushings syndrome. Plasma levels of FVIII and vWF were found to be markedly increased. Moreover, the molecular organization of plasma vWF appeared to have been altered by the presence of unusually large multimers, normally present only in the cellular compartments. Spontaneous platelet aggregation and hyperresponsiveness to ristocetin were also observed. All patients underwent therapeutic surgery. Within 1 month of the intervention, regardless of its efficacy as evaluated by the assay of plasma and urinary cortisol, an additional significant increase in levels of FVIII and vWF was observed, with a concomitant more pronounced representation of abnormally large vWF multimers in circulation. In the cured patients, a progressive decrease in the levels of FVIII and vWF was observed, beginning in the third month after surgery, with complete normalization of the pattern within 12 months of surgery; a concomitant improvement in the plasma vWF multimer pattern was also observed. In contrast, no significant changes in FVIII or vWF were found in patients with persistent Cushings syndrome. Our findings emphasize that vWF abnormalities are also part of the prothrombotic state of Cushings syndrome. Moreover, this study also identified a period of additional thrombotic risk immediately after surgery, as a result of the worsening of the hemostatic pattern.

Detection of two missense mutations and characterization of a repeat polymorphism in the factor VII gene (F7)

SummaryThe 3′ portion of the coagulation factor VII gene, containing the activation and serine protease domains, was investigated in four subjects with factor VII deficiency by temperature gradient gel electrophoresis and sequencing of polymerase chain reaction (PCR) products. Molecules displaying an altered melting behaviour were detected in three subjects, and direct sequencing showed two mutations. A G-to-T transversion causing a missense mutation, Cys-310 to Phe, suppresses a disulphide bond conserved in the catalytic domain of all serine proteases. This mutation, which in the homozygous form causes a severe reduction in protease activity (4%), was found in two patients from different Italian regions. A G-to-A transition, which gives rise to a missense mutation, Arg-304 to Gln, and is associated with the factor VII Padua variant, was found in the heterozygous form in a subject also affected by von Willebrand disease. Two polymorphic alleles, which differ in one repeat monomer element, were precisely mapped in a region spanning the exon-intron 7 border of the factor VII gene and studied in families with factor VII or X deficiency.

Platelet membrane abnormalities in myeloproliferative disorders: decrease in glycoproteins Ib and IIb/IIIa complex is associated with deficient receptor function

The number and functional activity of membrane glycoproteins (GP) Ib and IIb/IIIa were investigated in platelets from 11 patients with myeloproliferative disorders (MPD). Three patients had essential thrombocythaemia, two had chronic myeloid leukaemia and six had polycythaemia vera. The numbers of GPIb and GPIIb/IIIa molecules were detected on the platelet surface using different 125I‐labelled monoclonal antibodies. The functional properties of GPIb and GPIIb/IIIa were evaluated using purified 125I‐labelled asialo von Willebrand factor (vWF) and purified 125I‐labelled fibrinogen, respectively, in a binding assay, Binding of the anti‐GPIIb/IIIa antibody was decreased by 40% in almost all patients studied and, when measured, it was accompanied by decreased fibrinogen binding to activated platelets. Binding of anti‐GPIb antibodies to platelets was also slightly decreased or virtually the same in eight out of 11 patients. The decrease correlated with decreased binding of asialo vWF. The increased plasma glycocalicin levels, measured in four patients, depended on the high platelet count. Scatchard analysis revealed normal receptor binding affinity for all ligands tested in all but one patient. In this report we demonstrate that abnormalities in the concentrations of GPIIb/IIIa membrane proteins are commonly present in patients with MPD, while a decrease in GPIb concentration is also seen, although in fewer patients. These abnormalities are accompanied by a concurrent decrease in the respective receptor functions. These findings may explain part of the haemorrhagic tendency often encountered in MPD.

Abnormalities of von Willebrand factor in myeloproliferative disease: a relationship with bleeding diathesis

We studied factor VIII related properties in 24 patients with increased platelet number. Twenty‐one were affected by myeloproliferative disorders (eight had polycythaemia vera, 13 had essential thrombocythaemia) and three had secondary thrombocytosis. Normal levels of VIII: C and VIIIR: Ag were found while a significant (P<0.05) decrease of VIIIR:RCOF (43 ± 13%) related to a lack of larger multimers of VWF (39 ± 12%) was observed in 57% of patients with myeloproliferative disorders. A normal VWF pattern was found in the three patients with secondary thrombocytosis. The highest incidence of VWF abnormalities occurred in patients with essential thrombocythaemia (70%) in comparison with polycythaemic patients (38%). A significant (P<0.03) correlation between platelet count and the values of both VIIIR: RCOF and VWF multimeric pattern was observed only in patients with polycythaemia vera. The lowest levels of VIIIR: RCOF and the greatest loss of larger VWF multimers (less than 30%) were observed in two patients who presented bleeding symptoms at the time of study and a prolonged bleeding time. In addition, the relationship between VWF pattern and bleeding diathesis was supported by the fact that 75% of the patients with VWF abnormalities had bleeding history.

Do hemophilia A and von Willebrand disease protect against carotid atherosclerosis? A comparative study between coagulopathics and normal subjects by means of carotid echo-color Doppler scan.

Atherosclerosis is a multifactorial disease caused by genetic and environmental factors with important clinical sequelae. The aim of this study was to evaluate the degree of carotid atherosclerosis by echo-color Doppler scan in a group of patients affected by hemophilia A and von Willebrand dis ease versus a group of normal subjects apparently free of ath erosclerotic risk factors. All coagulopathics and normal patients who came to our Internal Medicine Department (Padua Hospi tal) underwent physical exam, blood analysis, standard electro cardiogram, chest x-ray, echo-color Doppler scan, and a thor ough history. We examined 156 subjects, 76 coagulopathics (46 men, 30 women) and 77 normals (37 men, 40 women). Coagulopathics were affected by hypertension in 28.9% of cases, diabetes mellitus in 6.5%, dislipidemia in 17.1%, smoke in 39.4%, and obesity in 36.8% (p < .05). Echo-color Doppler scan revealed carotid plaques in 27.2% of control patients ver sus 13.1% of coagulopathics (p < .05). Hemophilics and sub jects with von Willebrand disease with a more serious illness had fewer plaques than those with lighter defects. Coagulopath ics showed 23.6% of the plaques we revealed on the whole, versus 76.3% of control subjects (p < .01), with a lighter degree of stenosis (p < .01). Our data demonstrate that patients with hemophilia A and von Willebrand disease have fewer carotid plaques and a smaller degree of carotid stenosis than normal subjects of the same sex and age. These data seem to strengthen the hypothesis that blood coagulation defects may allow pro tection against carotid atherosclerosis and its sequelae.

Coagulopathy in Cushing’s Syndrome

A hypercoagulable state and its consequent increased incidence of thromboembolic complications are reported in patients with Cushing’s syndrome (CS). These alterations are related to cortisol excess that induces prothrombotic changes in blood by several and complex mechanisms including increased levels of clotting factors, mainly factor VIII and von Willebrand factor (VWF) and impaired fibrinolytic capacity. However, it has recently been observed that the increase in VWF levels is not a constant feature of CS and that VWF response to glucocorticoids is genetically determined and depends on the presence of particular polymorphisms in the VWF gene promoter. The risk of venous thromboembolism is moreover enhanced in patients with CS by additional endogenous and exogenous risk factors such as obesity, bed rest, surgery and invasive diagnostic procedures like inferior petrosal sinus (IPS) sampling. In line with all these data, patients with active CS should be treated as having a prothrombotic disorder and undergo antithrombotic prophylaxis during IPS sampling. Special care should be taken in the immediate perioperative period in order to avoid thromboembolic events. In the absence of prospective randomized trials, preventive antithrombotic treatment (best with heparin) during IPS sampling and low-dose heparin treatment early after surgery should be suggested.

von Willebrand factor propeptide makes it easy to identify the shorter von Willebrand factor survival in patients with type 1 and type Vicenza von Willebrand disease.

Reduced von Willebrand factor (VWF) half‐life has been suggested as a new pathogenic mechanism in von Willebrand disease (VWD). The usefulness of VWF propeptide (VWFpp) in exploring VWF half‐life was assessed in 22 type 1 and 14 type Vicenza VWD patients, and in 30 normal subjects, by comparing the findings on post‐Desmopressin (DDAVP) VWF t1/2 elimination (t1/2el). The VWFpp/VWF antigen ratio (VWFpp ratio) was dramatically increased in type Vicenza VWD (13·02 ± 0·49) when compared to normal subjects (1·45 ± 0·06), whereas it appeared to be normal in all type 1 VWD patients (1·56 ± 0·7), except for the four carrying the C1130F mutation (4·69 ± 0·67). A very short VWF t1/2el was found in type Vicenza VWD (1·3 ± 0·2 h), while all type 1 VWD patients had a t1/2el similar to that of the controls (11·6 ± 1·4 and 15·4 ± 2·5 h respectively), except for the four patients carrying the C1130F mutation, who had a significantly shorter VWF survival (4·1 ± 0·2 h). A significant inverse correlation emerged between VWFpp ratio and VWF t1/2el in both VWD patients and normal subjects. The VWFpp ratio thus seemed very useful for distinguishing between type 1 VWD cases with a normal and a reduced VWF survival, as well as for identifying type Vicenza VWD.

Arterial and venous thrombosis in patients with von Willebrand’s disease: A critical review of the literature

All patients with von Willebrand’s disease (vWD) who showed an arterial or venous thrombosis and were reported in the literature have been evaluated. 11 patients had arterial thrombosis while 19 had venous thrombosis for a total of 30 cases. 9 out the 11 cases with arterial thrombosis had myocardial infarction. Two had cerebral thrombosis. Associated risk factors for arterial thrombosis were available only for three patients who showed, respectively, smoking and dyslipidemia (2 cases) and smoking and intravenous desmopressin infusion (1 case). The majority of patients with venous thrombosis showed DVT with or without PE. Four patients presented with apparently isolated PE. In two instances thrombosis occurred in unusual sites (central retinal vein and portal vein, respectively). Several associated risk factors were present, mainly: infusion of FVIII or FVIII + vWF concentrates in 7 cases; surgery in 8 cases, pregnancy in 1, desmopressin infusion in 1, variable coagulation defects or polymorphisms in 5. More than one of these associated conditions were present in a few patients. The majority of vWD patients who showed thrombotic phenomena were type I patient, but in 6 cases were also type 3. The type of defect was not reported in 6 patients. As a conclusion of this review it seems safe to assume that both arterial and venous thrombosis appear rare in vWD. This is confirmed by the fact that arterial or venous thrombosis appears slightly more frequent in hemophilia A and B.

von Willebrand factor abnormalities in aortic valve stenosis: Pathophysiology and impact on bleeding

Acquired von Willebrand syndrome (AVWS) may complicate severe aortic valve stenosis, due to a reduction in the haemostatically more efficient large von Willebrand factor (VWF) multimers. This study was designed to analyse the relevance of VWF abnormalities and haemorrhagic diathesis in severe aortic valve stenosis. Forty-one consecutive patients undergoing valve replacement were investigated: seven had minor bleeding symptoms in their recent history; 10 (24.3%) had a reduced VWF collagen binding (VWF:CB) to VWF antigen ratio, and 33 (80.5%) had a decrease in large VWF multimers. The shortage of large multimers was not associated with any accumulation of small VWF multimers (apparently ruling out any increased VWF proteolysis), nor was there any increase in VWF propeptide, which excludes a shorter VWF survival. The risk of developing VWF abnormalities was higher in patients with rheumatic valve disease than in degenerative cases (p=0.025) and in valves with <50% of residual endothelial cells (p=0.004). Bleeders differed from non-bleeders in that they had a higher mean transvalvular gradient and a more marked decrease in large VWF multimers. VWF abnormalities did not exacerbate peri-operative blood loss, however - a finding consistent with the full correction of these VWF abnormalities, seen already on the first postoperative day and persisting for up to six months after surgery. According to the data obtained in our cohort of patients VWF abnormalities are common in severe aortic stenosis, particularly in cases of rheumatic valve disease, but loss of the largest multimers does not seem to cause clinical bleeding in most patients.