I'm so sorry to hear about your ferret with cardiomyopathy, Rob!  I had a
ferret with that problem, too.  He was about five or six years old at the
time, and we managed to keep him going for about seven months (I think)
after the diagnosis.
 
The treatment we used for him was primarily Lasix (Furosemide), which is a
diuretic.  I supplemented him with banana and Pedialyte as well, to try to
make up for the potassium and electrolytes the diuretic might have been
taking out of him.  He slept a lot and didn't have much energy .. but I
don't think he was in any pain.  (The vet also said that he wasn't in any
pain ... just sleepy).
 
This was about four years ago, so cardiomyopathy treatment might have
improved a good deal since then.
 
- Ela
[Posted in FML issue 2682]