Heyde's syndrome is a syndrome of gastrointestinal bleeding from angiodysplasia in the presence of aortic stenosis. It is named after Dr. Edward C. Heyde, who first noted the association in 1958. It is caused by the induction of Von Willebrand disease type IIA (vWD-2A) by a depletion of Von Willebrand factor (vWF) in blood flowing through the narrowed valvular stenosis.