The story I read is here (You need a Medpage account to read this story)Could you clarify how you believe that he ruined his valve almost immediately?
Schwarzenegger's Aortic Valve Replacement
"Initially, things seem to be going well enough that he admitted to getting on a Lifecycle bicycle while still hooked up to all his monitors shortly after surgery (How did he get away with that?!). But later that day, because "my body was too big and too strong," the pressure on the new aortic valve (previously his pulmonary valve) was too high. He started to cough, and he became short of breath as his lungs began to fill with fluid. His physician, Vaughn Starnes, MD, told him that the surgery had failed"
Which is pulled from this interview given in 2016. starting at 2:22 he states it probably didn't help that right after waking up for surgery he got on a lifecycle. I know a key factor of the Ross procedure is blood pressure control to allow the Pulmonary valve to adapt to it's new position, I imagine hopping on an exercise bike immediately is just a recipe for destroying the valve.