Owner Robert Waley-Cohen, who bought Noble Yeats two months before the National win, said: "He looked very uncomfortable on Wednesday, so the vet came out and everybody was up all night treating him and hoping he would pull through, but unfortunately he went the other way.
"It was a grim moment.
"He was living the life of a retired horse in the field with [2011 Gold Cup winner] Long Run and [2011 Grand National runner-up] Oscar Time."