I would have concerns about sedating him for 6 weeks with acepromazine. You could try it for a few days to a week just to get him acclimated to the crate and then try to wean him off of the medications. Being in the crate is a very important aspect of the treatment. It might be best to try sedating him and acclimating him to a crate before you actually get the immiticide injections so he won't cause himself any harm after the injections are given and he is in the recovery phase.

We treat TONS of heartworm positive dogs here in Tennessee. We live in the Mississippi River Valley and it is very common here.

You will have to keep him still for 6 weeks. The worms will die after the injections and they are large and live near the heart. If he were to jump, or run, sudden movements can cause a worm embolism that would result in sudden death.

If his disease is not too severe I would spend a week or so working with him and acclimating him to a small area of some sort so he won't harm himself. The treatment is usually very successful if you can follow your vet's instructions as to the 6 weeks after the injections.