My husband developed a leak after his mitral valve implantation. He had a different scenario, though. He fainted several times, and on one occasion, he fell over without warning, flat down on his chest, and dislocated his jaw. I believe the concussion of that fall caused the leak, because soon after he developed symptoms. The valve was fairly recent surgery and prior to that, he was doing very well. It took a long time to finally get him to a repair on it, because this would then be his 3rd heart surgery. He had to be very symptomatic before the card would send him to the surgeon. Unfortunately, he did become very symptomatic and he finally forced the issue. The valve was repaired with a couple of stitches, and this surgery was done through the side, sparing his sternum. It worked out just fine.
But I do know that a fair amount of patients will have small leakage in the new valve, which eventually closes up on its own with scar tissue.