Regression of deep vein thrombosis by i.v.-administration of a low molecular weight heparin--results of a pilot study.

Twenty-five patients with phlebographically confirmed deep vein thrombosis of the lower limb were treated with intravenous infusions of low molecular weight heparin for 7 to 29 days. The mean dosage was 15.2 +/- 3.0 Uanti-Xa (equivalent 7.6 +/- 1.5 U-aPTT). Phlebograms were taken before, during and after the treatment with low molecular weight heparin and evaluated using the score system of Marder. Nearly complete recanalization of the occluded veins was found in six (24%) patients, improvement of the Marder score of 60 to 90% was found in four patients and of 30 to 60% in seven patients, while eight patients remained unchanged. With an average dose of 15.2 I.U./kg/h the heptest was prolonged to 70 to 120 seconds while the aPTT-level did not significantly increase. tPA-antigen-levels increased significantly in most of the patients after the third day of treatment, while PAI-activity remained unchanged. A positive conclusion between the decrease of the Marder score and the duration of treatment was found. Thus the low molecular weight heparin used in this investigation proved to be effective and safe in treating deep vein thrombosis.

Screening of F.VIII:C antibodies by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (Elisa) method was developed in order to examine prevalence and titer of antibodies directed against the factor VIII coagulant protein (F.VIII:C) in hemophilia A and nonhemophilia A patients. Highly purified F.VIII:C was used as immunosorbent on microtiter plates with a peroxidase-conjugated goat anti human IgG antibody for F.VIII:C antibody detection. Results determined by Elisa were compared with measurements according to the Bethesda method. Initially 24 plasma samples containing an F.VIII:C inhibitory activity ranging from 0 to 7,700 Bethesda units (BU) were analysed. At plasma dilutions of 1:128 the optical density determined by our Elisa measurement and the corresponding BU showed a logarithmic correlation. The coefficient of correlation was r = 0.92 with a standard deviation of 0.002 from the regression curve. Plasma samples were analysed from 53 hemophilia A patients, from 21 nonhemophilia patients with acquired F.VIII:C antibodies and from 460 randomly selected nonhemophilia patients presenting for routine preoperative coagulation examination. F.VIII:C antibody-positive Elisa results and positive BU were found in 7 hemophilia A patients and the 2 patients with a history of acquired F.VIII:C antibodies. Positive Elisa results and negative BU were found in 1 hemophilia A patient and 25 out of 460 nonhemophilia A patients (5.43%) suggesting F.VIII:C antibodies without inhibitory potency on F.VIII:C in these cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Valproate therapy induces von Willebrand disease type I.

To investigate the increased tendency of hemorrhage in patients receiving valproate (VPA) therapy, we studied coagulation parameters in 30 randomized children of a group of 83 children receiving antiepileptic drug (AED) therapy. Besides a reduction in fibrinogen concentration and platelet count, we observed a significant decrease in factor VIII-complex. A decrease in factor VIII:C was noted in 33%, a decrease in von Willebrand factor (vWF:Ag) was noted in 83% and a decrease in ristocetin-cofactor activity (vWF:Rcof) was noted in 66% of the children. We classified a von Willebrand syndrome type I in 67% of our patients receiving VPA therapy. Sixty-three percent of patients had a history of bleeding, and 23% had a prolonged bleeding time. We compared our results with those of a control group and of a group of patients with congenital von Willebrand disease (vWD), from which patients with multimer types II and III were excluded. Because coagulation parameters in patients with congenital vWD are similar to those receiving AED therapy, we designated the increased tendency to hemorrhage as VPA-induced vWD. The decrease in coagulation parameters were not dependent on either VPA dose or period of administration. In patients receiving VPA therapy, this result must be considered, especially during surgical intervention and after traumatic events.

Fibrinogen does not protect von Willebrand factor against proteolysis by human cathepsin G.

The susceptibility of von Willebrand factor /vWF/ to digestion by human neutrophil cathepsin G in highly purified FVIII/vWF concentrate /BHS/ and in cryoprecipitate has been studied. In contrast to human neutrophil elastase, cathepsin G inactivates and degrades vWF not only in BHS but also in cryoprecipitate. Fibrinogen added in excess to purified FVIII/vWF concentrate does not protect vWF against cathepsin G proteolysis. Biological significance of this phenomena are discussed.

Effects of human elastase on von Willebrand factor in highly purified factor VIII concentrate and in cryoprecipitate.

The susceptibility of v. Willebrand factor (vWF) and F.VIII in virus-inactivated factor VIII/vWF concentrate (Behring-Haemate-HS (BHS] and in cryoprecipitate (Behring-Ristofact) to digestion by highly purified, cathepsin G free human neutrophil elastase (HNE) was compared. In Haemate-HS HNE induced a degradation of the vWF subunit. This reaction was dependent on time and enzyme concentration. It resulted in disappearance of large size vWF multimers, an anodal shift of vWF peak in crossed immunoelectrophoresis and a decrease of F.VIII:C and Ristocetin cofactor activities. In contrast in cryoprecipitate even high HNE concentration did not provoke changes of these parameters. Both Haemate-HS and Ristofact were free of alpha 1-proteinase inhibitor (alpha 1 PI) and alpha 2-macroglobulin (alpha 2 M) but they differed in the content of other contaminating proteins. In particular Haemate-HS was fibrinogen-free but Ristofact contained 6.6 mg/ml. Purified fibrinogen added to Haemate-HS was found highly effective in protecting vWF in Haemate-HS against the proteolytic degradation and loss of activity under the influence of HNE.