Faye, I am having the same issue with my senior pitbull mix. This summer, she had developed the characteristic cough and had become very, very lethargic. Took her to the vet and she tested positive for heartworms. I started her on VRM2 (3 per day) on July 20. Within 3 days she was running, playing, jumping everywhere again. That stuff is incredible! We completed 4 rounds of it (10 days on, 5 days off). I also want to thank Brenda in CA for her info/help on this forum as well! She is exceptional.
Our sweet Gretchen has now (since early October) developed abdominal swelling, and I'm guessing it's from the damage the worms had already done to her heart...I wish I had supplemented with Hawthorne, CoQ10, or some Traditional Chinese Medicine Heart/Lung Qi supplements. A vet told me they could drain the fluid, but it would come back even worse than before. She is still ravenously eating and drinking. Still playing and exploring - just a little slower because of the increased weight/fluid. I'm sorry to hear your Lasix wasn't successful. Have you tried any other herbs successfully? Is there anything out there that actually REPAIRS and strengthens damaged heart muscle?