[snip] By some amazing twist of evolution, human heart valves and pig valves are very similar in structure and function. That said, pig valve replacement surgery is rather common. [/snip]
http://www.heart-valve-surgery.com/heart-surgery-blog/2007/09/19/pig-valve-replacement/
Yes, but they are stripped of living cells that would cause rejection, they are essentially leather valve structures, ones that are in the mechanical form of a living valve, but are utterly dead tissue.
The collagen structure is ultimately colonized by the patients own cells.
Pretty kewl.
Unfortunately, the darn pig valves only last for about ten years. My mom got one at age 78 and died at age 89 from congestive heart failure as the valve failed. She was too frail for a second operation. [1985 to 1996, maybe there have been improvements since then?]