I have rescued three heartworm positive dogs, all seniors. The first I had my regular vet treat. He took radiographs, did bloodwork and told me that Caoimhe would be fine to treat. Unfortunately her burden was way higher than he could know from these tests and she went into heart failure resulting from all the worms dying off. Thirteen days later I had to have Caoinhe euthanised ...
With Feidhlimidh and Duncan I decided to take them to the local vet school. They did bloodwork, radiographs and most importantly had an echocardiogram done, which as well as allowing for visualisation of the worms, gave a measure of blood pressure. Duncan's results were good - he was put on Heartgard for a month to start a slow kill, then was given the immiticide, but split, one injection on day one, and then another two a month later. he did great, and now two years on his only reminder is a very slight heart murmur.
Feidhlimidh, in contrast, had good labwork and ok rads but his echo showed he had a high burden plus hypertension. The cardiologists said they did not believe he would survive the treatment, so instead we did a slow kill with Heartgard (we elected not to give Doxycycline for the Wolbachia). Nine months later I had to euthanise Feidhlimidh. I had a necropsy done and they only found a couple of heartworms. Feidhlimidh died from metastatic cancer (brain, liver, prostate, testicular), not heartworm disease.
Cost wise, the vet school was actually cheaper than my regular vet! If you have the option of seeing a cardiologist I would recommend doing so.
Wishing your pup the best.
