I think you are right, they will probably make the valve decision once they are in there. Since you are already on coumadin they can go mechanical or tissue depending on what works best in that position.
Scar tissue is always an issue when dealing with repeat surgeries. The scar tissue surgery I had in 1982 was a bit unusual tho. I had a Bjork-Shiley single leaflet valve that seemed to be "sticking". Echos indicated the possibility of a clot but definitely showed inadequate functioning.
When the surgeon went in, he found I had grown excessive scar tissue over the leaflet which was causing it to malfunction. He cleaned out the scar tissue and that was that. After surgery I went on a quest to try and determine what caused the scar tissue buildup since everyone said it was the first time they had seen this problem.
Come to find out I had "anti-heart" antibodies which seemed to be attacking my heart tissue. Became part of a study that used long-term (1 year) prednisone to treat. Solved my problem and, when my valve was replaced in 1994, there was very little sign of scar tissue and every indication that it was old scar tissue probably from the time after surgery and before the prednisone. Just in case, it was replaced with the St. Jude bileaflet in the hopes that if scar tissue is still an issue having 2 leaflets might allow better functioning. However I have had no problems with the St. Jude valve.
Did this answer your question or way more than you wanted?