run a mile

I have a heart condition that makes me get out of breath whilst making my bed, vacuuming…almost anything.
In middle school I walked a little over half a mile, I was the last one on the track, everyone had finished a long time before me, and I wasn’t even at 3/4… in the last curve of the track, on my 3rd lap of the 1/4 track, I passed out.
I would like to walk a mile without having to stop, without passing out. Hell, I’d like to walk across the mall without having to find a bench.