I would talk to your cardiologist about heart ranges. If you are on beta blockers, your heart range isn't the same as everyone elses. You can always have it tested in the lab. Push for cardiac rehab if you can because that is where you learn all about exercise limitations. It was really good for my ex husband. They also go over nutrition with you in that rehab setting so you will get the two for one. Pritikin is usually the diet that everyone tries to follow but everyone usually gives up because it is very low in fat (about 10% of your daily intake) and almost vegetarian. I tried to get him to follow it but it was pretty hard. He did switch from beef to salmon, so all wasn't lost there. There is a happy balance as he found. Everything in moderation...

The heart rate monitor is what helped him immensely. He was a little sketchy at first about exercise, but once he got his limits via an exercise lab, he felt more confident in it. Doesn't hurt to try it.