Oscar,
I have posted this information elsewhere in the past but thought you might find it useful if I repeated it directly to you. My husband's aunt had AVR replacement (pig valve) when she was 83 and again when she was 93. She lived to be 96 and died around 15 years ago. There have obviously been many advancements in OHS since then and she just used a local surgeon who, although obviously competent, had no special "high risk" skills. (I'd go for the best you can find though to raise the odds of the best outcome possible.) I remember that difficulty breathing and pronounced fatigue caused her to want the second surgery as she felt she could not tolerate living that way if there was an alternative.
Her second recovery was slower but as her mind was very clear, she frequently stated that she was glad she made the decision to have the second surgery. She was also able to be active following that surgery and drove her own car until her death. Just wanted to provide some encouragement that while not as easy, OHS on the elderly can still be successful.
Sue