I don't mess around with heartworms. I am much more lax when it comes to the flea/tick topical meds. I don't like putting chemicals on him every 30 days so I spread it out until I see a tick. (I tend to do every other month in warmer months, and not give it at all in the colder temps). But ticks/fleas are a heck of a lot easier to deal with than heartworms. I also do not believe in yearly vaccines (or even every 3 years as AAHA protocol is) and I do believe any vet who is doing yearly vaccines is in it for the money. No doubt. But heartworm meds? Doubt it.
If you are not squeamish, check out this heartworm removal surgery:
http://www.yorkietalk.com/forums/gen...g-graphic.html