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  • Title: Fainting induces an acute increase in the concentration of plasma factor VIII and von Willebrand factor.
    Author: Casonato A, Pontara E, Bertomoro A, Cattini MG, Soldera C, Girolami A.
    Journal: Haematologica; 2003 Jun; 88(6):688-93. PubMed ID: 12801845.
    Abstract:
    BACKGROUND AND OBJECTIVES: von Willebrand factor (VWF) is stored in the Weibel-Palade bodies of endothelial cells and may be released in response to different secretion stimuli such as stress, physical exercise, adrenaline, DDAVP and thrombin. DESIGN AND METHODS: We found that fainting can also induce an acute increase in plasma VWF and factor FVIII (FVIII) concentrations, following observations in two patients with von Willebrand's disease (VWD) who experienced a fainting episode during venipuncture for blood collection. RESULTS: One patient was classified as having type Vicenza VWD, the other as type 1 VWD; both had normal platelet VWF content. After the fainting episode, FVIII and VWF levels were significantly higher than the levels in blood samples collected without stress; mean increases were 4.35-fold for FVIII, 4-fold for VWF:Ag and 5.3-fold for VWF:RCo, with values overshooting the upper limit of the normal range. Moreover, the post-fainting plasma VWF multimer pattern was characterized by a significant increase in all oligomers with the appearance of unusually large VWF multimers, similar to those observed following DDAVP infusion. INTERPRETATION AND CONCLUSIONS: These findings demonstrate that fainting acts as a stimulus capable of inducing the release of VWF from endothelial cells, and further highlight the role of stress in determining hemostatic states potentially favorable to the development of thrombotic complications.
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