If you start incorporating little tweaks into your routine, the benefits will start to add up like compound interest in a bank account.
When you go somewhere, park in the furthest spot from the door; ditch the remote control so you have to get up and physically change the channel; get a puppy - then you have to take it for a walk.
Stretching, stretching, and more stretching. In my experience, stretching actually made as much, if not more, of a difference in the way I hold and move my body.
Since you have a heart condition, it would probably be wise to start out with small things like these and perhaps a gentle workout on a treadmill or elliptical machine (if possible) rather than jumping head first into a 2 hour workout.
Consult your doctor first, of course!
If you don't already, you need to be taking in enough water. Add lemon and some herbs to it if you don't like the taste. Replace heavy pasta with lighter zucchini noodles - if you've never had it, they are absolutely delicious; you might be surprised.
These sorts of things will add up and multiply and before you know it - BAM! Lifestyle change.
Best wishes to you on your road to recovery! Every step counts.