The influence of vasovagal response on the coagulation system

Abstract

Vasovagal response (VVR) is provoked by a reduced venous blood return to the heart as a reaction to orthostatic stress and to haemorrhage. Recently, two cases were reported showing elevated plasma concentration of von-Willebrand-factor (VWF) and factor VIII (FVIII) after VVR due to venapuncture. Although the effect of epinephrine as trigger for VWF liberation is known, a connection between VVR and activation of the coagulation system has not been studied systematically. We examined 21 subjects with lower body negative pressure. We measured the plasma concentration of von-Willebrand-factor-antigen (VWF:Ag), the activity of von-Willebrand-factor-Ristocetin-Cofactor (VWF:RiCo) and FVIII at several stress-levels and consecutively split up the different VWF-multimers. In 16 of 21 subjects VVR could be induced. These subjects showed a significant increase of VWF:Ag concentration in plasma and an increase of FVIII and VWF:RiCo activity. The five individuals who experienced all stress-levels without VVR did not show any changes in their clotting factor levels. VVR leads to measurable changes in the coagulation system. This might be a further diagnostic tool in treating patients with syncope.