1: Role of DDAVP in the control of severe bleeding unresponsive to routine measures in the post-cardiopulmonary bypass (CPB) period; 2: Role of its prophylactic use in patients at risk for post-operative bleeding; 3: Etiology of this bleeding, specifically with regard to abnormalities in von Willebrand factor (vWF); and 4: Prevalence and natural history of coagulopathies associated with CHD.