You need to get in some cardio rehab and get the heart exercising. You are in more danger of them closing off from not following rehab than exercising.
Honestly, I resisted rehab, and suffered the first week, but after I got used to it I could feel the improvement.
DAN
I am 47 (was 208lbs now 183 bs) I had cabgx5 on March 30. I was somewhat active before the surgery and certainly was encouraged to do a cardiac rehab but go back to an active lifestyle. I am now running about 8 kms per day and the dr. says good.
Before and after surgery I walked 1 to 2 times per day for an hour or two and found it did wonders for me. Pace is important as you should try for about 60 steps every 30 seconds or so.
Obviously you need to check with your DR. before doing too much but after 12 weeks after surgery I am now feeling better and doing more than I have for a long time. As far as I can tell my arteries are still connected. I think though it might be a use them or lose them type of thing.
Good luck.