Wow, how scary. Sounds like this might have been the wake up call you need. Will your cardiologist recommendation cardiac rehab? Seriously that saved me after my heart attack.
If not, talk to your doctor about what you can do. Perhaps start with one 10 min walk/day. Take it slow and build on small changes. Don't try to do it all. There is a great challenge for small changes where you get tips each day to change your life. Take it slow and make it part of your life.