Your Luke shares some of the same defects as my Katie.
Homograft and allograft are the same thing - both harvested from human cadavers.
BTW, not to scare you, but there is a recall out on Cryovac allograft tissue "items," but not the cryovac heart valves, only because the FDA doesn't consider there to be a suitable alternative. This recall, though, is from 2001-2002, so I am betting Luke's valve is perfectly safe since his surgery was so recent, but you might want to doublecheck and see who the manufacturer is of Luke's valve anyway. http://www.fda.gov/cdrh/safety/humantissue.html