Thank you for getting back to me. I'm sorry to hear that you won't be able to see a specialist. At age 7, your rabbit is quite elderly for a Netherland dwarf. I raised them for a number of years, and it was unusual for them to reach that age. You must take very good care of her.
I'm afraid there isn't any way to reverse such severe heart disease. Your vet is doing everything that is recommended. The Lasix will help reduce fluid and keep your rabbit more comfortable. Fluids are the standard treatment for kidney disease. In the USA, there are experimental treatments available at the larger veterinary teaching hospitals, but they are very expensive, and in an elderly rabbit, not likely to be successful.
Even in the area of supportive treatment at home, there isn't a lot you can do. A supplement called co-enzyme Q10 has been found to helpful in some cases of heart enlargement and failure. It has also been useful in kidney failure. Much of the research on it was done in Japan. It is usually available over-the-counter in pharmacies and health food stores. You could give your rabbit a capsule or two each day. I would use a needle to puncture the capsules, and then squeeze them onto her food. Other than that, about all you can do is continue regular follow-ups with the vet.
Here is an online group you may be interested in. It's for owners of rabbits with kidney disease. You would be able to talk with others to see what has helped their rabbits, and the people also offer each other emotional support.
I wish I could tell you there is a way to reverse this disease, but unfortunately, there isn't. Even the best medical care in the world can only result in management, not cure. In humans, a heart transplant is often the solution. I mention that to give you a better idea of what you are dealing with. I hope the Lasix and the fluids will keep your rabbit's illnesses under control for a long time. Give the co-enzyme Q10 a try, too - it can't hurt anything. I can tell that you love your rabbit, and I know how difficult it must be to watch her grow old and frail. I can only reassure you that you're doing the best for her. If you have more questions, just let me know by clicking on REPLY. I'll be hoping for the best possible outcome for your rabbit.