Is it permissible to have grafts from pigs, for example biosynthetic heart valves and skin grafts?

Fatwa, posted 4.22.2010, from United States, in:
Religious Authority: 
Faraz Fareed Rabbani
Fatwa Question or Essay Title: 
Is it permissible to have grafts from pigs, for example biosynthetic heart valves and skin grafts?
Websites and Institutions: 
Sunni Path, (New Brunswick, New Jersey, U.S.)

If the alternatives to a pig valve aren't available or as effective (such that there will be harm or hardship), then it would be permitted to use a pig valve.