Darlene,
The body can sometimes have an exaggerated healing response, thereby forming scar tissue around, and sometimes into, a mechanical valve. There is no known specific cause. Your doctors are doing the right thing by looking further to see how severe any obstruction might be. The most important question for you and your doctor to parse out is whether you have any symptoms.
I had a aortic valve placed (stainless steel)3 years ago, they are now saying I have scar tissue blocking 57%of my oxygen. closing off the valve from opening all the way. They are going to do a test (prob?) to look at it closer to see what can be done. My blood test are NEVER right, I take Warfarin, it goes from high to low. I watch my K intake..What would cause this scar tissue!!! Thank you
Don't worry, you can continue your active and healthy lifestyle as long as you are followed closely by your cardiologist. Many patients have trivial or mild valvular insufficiency that is of little clinical consequence, but it can evolve in some people. Also you should make sure you don't have a bicuspid aortic valve (meaning the valve has 2 cusps instead of the normal 3), but I assume your cardiologist looked for this already. Hope this helps!