Replacent valves are used from other sources than just pigs.
“I am certainly no doctor, but I would think that Coumadin would be contra-indicated for a leaking heart valve.”
True, and they even use metal valves in some cases and they can be put in through an atery. But they are not as successful and are generally reserved for person’s who cannot abide the more invasive surgery and they do not last as long as the pig valves.