We all know that replacement tissue valves eventually wear out. Given that a tissue valve was good and not defective when it was placed, what causes them to wear out and calcify? I know younger people go through them faster than older people. Is it our immune systems attacking the valve? Is it because the valve can't heal itself like live tissue can? Why does the body deposit calcium on them? I sound like a little kid don't I. But why, but why, but why. I read a testimonial for the On-X valve where a guy says his tissue valve was calcifying after about 8 years. He didn't want to go through another surgery that soon so he tried to remove the calcium himself (with supplements I'm guessing). He was successful. The only problem was that the calcium was the only thing holding his tissue valve together and he went into heart failure. So much for trying to remove calcium deposits.