Well while I believe that heart worm prevention for cats is unnecessary, I just want to point out that a lot of 'indoor animals' still get heart worms. It only takes one mosquito to inject them, and just opening the door around here allows mosquitoes in.
Cleverly disguised as a responsible adult.
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, throughly used up, totally worn out, and loudly proclaiming --- 'WOW, WHAT A RIDE!!!!' " - Author Unknown