Relatively increased von Willebrand factor activity after off-pump coronary artery bypass graft surgery

SummaryHigh shear forces can induce structural changes in the shape of the von Willebrand factor (VWF) molecule, making it more sensitive for ADAMTS-13, a specific VWF protease. This leads to proteolysis of the highest-molecular-weight multimers, which are the most effective in platelet-mediated hemostasis under conditions of high shear stress. The use of cardiopulmonary bypass (CPB) is accompanied with high shear forces and could therefore lead to diminished VWF activity. Therefore, we studied VWF activity in patients undergoing myocardial revascularization. We enrolled 60 patients undergoing coronary artery bypass graft (CABG) surgery with and without CPB (30 in each group). ADAMTS-13 activity, VWF antigen (VWF:Ag) and propeptide levels were measured directly before and after the procedure. VWF activity was determined using both the ristocetin cofactor activity (VWF:Rcof) and collagen binding (VWF:CB) assays. VWF:Rcof and VWF:CB, both corrected for VWF:Ag, were significantly increased after the procedure in the off-pump group (p