The Role of von Willebrand factor in Coagulation

Abstract

Perfusionists should be able to verify diagnosis and recognize the forms of von Wille brand disease (vWD) which may require specific coagulation management during open heart procedures. von Willebrand factor (vWF) plays two distinct and important roles in clot formation subsequent to vascular injury. First, it promotes platelet binding to subendothelial surfaces and other platelets (platelet aggregation). Secondly, it also functions as a transport molecule for factor VIII, protecting factor VIII from proteolysis, thus preserving its catalytic role in the coagulation cascade. von Willebrand disease is a heterogeneous group of bleeding disorders which vary in molecular basis, symptomatology, and diagnostic parameters. The great majority of vWD patients will not greatly complicate management of hemostasis during cardiac surgery. Type I vWD patients, comprising 75% of cases, require only intraoperative DDAVP infusion, with cryoprecipitate available if necessary post-surgically. Type II patients vary in response to DDAVP, and may require infusion of cryoprecipitate or purified concentrates of vWF and factor VIII. DDAVP is contraindicated in vWD Type IIB since it has been shown to induce severe thrombocytopenia.