Acquired von Willebrand syndrome and mitral valve prosthesis leakage. A pilot study.

Background: Of patients with severe aortic stenosis, 15-25% present with bleeding episodes possibly attributable to acquired von Willebrand syndrome (AVWS). AVWS associated with mitral valve prosthesis leakage has not been reported. Methods and Results: Five patients receiving appropriate oral anticoagulation showed mitral valve prosthesis leakage and bleeding episodes; all of them required hospitalization and two blood transfusions, and a von Willebrand factor (VWF) analysis was performed. Two patients with normal functioning metallic prosthesis valves were included as controls. Before surgery, after cessation of acenocumarol, the patients had prolonged activated partial thromboplastin time; four had prolonged closure time (CT) from the platelet function analyzer. Factor VIII procoagulant activity (FVIII: C), VWF ristocetin cofactor activity (VWF:RCo), and VWF collagen binding (VWF: CB) were considerably elevated, while VWF antigen (VWF:Ag) was most elevated. Disproportionate VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios were seen with the loss of large VWF multimers. Following surgery, all parameters were markedly increased and the ratios, CT, and multimeric VWF profile became normal. Conclusions: Acquired VWF qualitative alterations in mitral valve prosthesis leakage may be associated with or contribute to bleeding diathesis. AVWS should be taken into consideration in patients with mitral valve prosthesis leakage with bleeding diathesis not explained by excessive oral anticoagulation.