I live in Jersey, Channel Islands, and they do not do any cardiac surgery in Jersey, we have no real option other than to fly. I had to fly to England to have my OHS, this was the day before my surgery. I travelled alone, just a lift to the airport then I was handed over to the staff there to provide me with a wheelchair. They wheeled me through to the 'plane and I was able to walk up the steps myself. I was met the other end at Gatwick in my case, by a buggy and driven through to my taxi. You do need to arrange with the airline in advance that you require assistance and they are brilliant. When I was returning to Jersey I even needed to have the wheelchair winched up to the plane as I couldn't walk due to a panic attack, not good to leave the hospital in order to travel hundreds of miles alone an hour after a person in the next bay had a cardiac arrest!
I had both mitral and aortic regurgitation. So don't worry about flying to England, as I said, if you need a wheelchair let them know in advance, and it is well worth checking just how far you need to walk, a wheelchair is the easy option especially if there is a long walk to and from the 'planes.