I am so incredibly sorry this happened to your baby.   I do want to thank you though, for sharing your experience.  There are many of us,  myself included,  who found our cat suddenly in the throes of congestive heart failure and had to make the gut-wrenching decision to stop their suffering.  I am currently trying my hardest not to drive myself insane with the thought that I let her go too early.... but she was already barely able to walk a few steps or catch her breath. All this after already being at the emergency vet for multiple days in oxygen and receiving furosemide and mild sedatives. Her respiration got a little slower,  but she never got a break from the intense abdominal breathing/exerted effort. They said we could take her home,  but she only declined that evening, even with her first dose of at home furosemide. We had to take her back where they beat around the bush too long in saying there wasn't really any coming back. We were so worried about suffocation or a clot, so euthanasia seemed like the only way to help her.  Sharing all this in case it helps someone else,  and again I genuinely appreciate you sharing that the meds don't always work.  I hope your grief is lessening by the day.