Close-up view of replacement heart valve. Sudan, Africa.

Close-up view of replacement heart valve. Sudan, Africa., There are two types of replacement valve, mechanical and biological. Mechanical valves are artificially manufactured valves made from carbon fibre. Biological valves are made from human or animal tissue (usually pig). The major difference in the valves is the length in time they last - mechanical valves can last a life time whereas biological valves last 10-15 year before needing to being replaced. (Photo by Universal Images Group via Getty Images)