ORIGINAL: dogdr
Maybe wvvet or docE can give their experience.
I'm a Chiro, not a Vet, and I don't stay at Holiday Inn.
The final outcome depends on the degree of infestation when treatment is started. In severe cases, the heartworms can also migrate to the brain.
Heartworm treatment (NOT heartworm prevention) is extremely hard on a dog -- but not near as hard on a dog as leaving the worms in the dog.