I presume the hosptal has done an echo cardiogram, during your work-up to show them exactly what damage you do have.
My husband has dialated cardiomopathy, left ventricle all blown out, cause unknown, but probabaly a virus, his was so bad at the time 6 years ago that they did not think he could survive.
First get any weight issues under control, with medical help, do not go on any crazy diets, do not use food replacement sachets.
If you have a fluid issue, you must keep to what the hospital has advised you re fluid intake, it does help.
This is not a hospital recommendation, but I belive it had some postive effect, and worked, oranges, oranges, not juice the real fruit, husband craved them when he got home, from the hospital, we even got to the point where I didn;t include the fluid in his daily 1 1/2 litres of fluid, look up Vit C, and heart issues on the net, there are some theories out there saying it does help, he just loves Navel Oranges.
2nd - get yourself an Omron, blood pressure monitor, that also gives you what your heart beat rate is, about 100AUD, and when you feel off, take your readings and keep a exercise book of results.
3rd - daily weight in the morning when you first get up, add the results to your booklet, and if it changes more than say 2kilos overnight get to the hospital.
Get fit, walking, do not get too breathless, its all to do with pacing yourself, husband from not being able to walk across room in the hospital 6 yrs ago, to walking 6-7kms by 18 months.
When he got home he started walking from the easy chair up the hall way to the front door, couple of times a day, for a week, then I put a chair out the front at the letterbox in front of our house, for a couple of weeks walked to that chair, then to the neighbours letter box, and so on, as the distance increased, he drpped to doint the walking once a day, adding one letter box about every 3 - 4 days, I did the same after double hip replacement, works very well as a test to see how far you are going.
Take your medications, report to Dr's any changes in how your feel, having that little booklet all dated and timed, almost like a nurses chart, they photocopied my booklet a number of times, and seemed very impressed with my efforts.