Thought I should update my situation here because what has happened to me is strange and awesome at the same time.
I live in a hilly mountain village. We ain't no San Francisco, but when it comes to walking, running or cycling for exercise, we can do it on the streets around town, or even just outside town where there are world class hiking trails, 5 mins from my door.
So anyway, in the past month or so I've discovered I can walk or run up almost any hill around here and when I get to the top, I'm not puffing. My heart rate is up, but I don't feel short of breath. I'm talking about a 100 metre run up a steep hill and arriving at the crest, I'm breathing quietly through my nose as if I'd been walking on flat ground.
Sure my legs feel like they're about to burst into flames, but hey

Every day now I'm taking the time away from the computer to walk 2 hours or so, in all weather, and it's amazing.
I tell ya, surgeons are absolute gods. In the few months before surgery, I couldn't put a jacket on without almost collapsing from the effort. Then this man-god put his fingers into my heart, replaced the bad bit with a technological marvel and closed me back up. Now I'm fixed and I always feel like running. I literally feel like I owe him my life.