Nanna just had her yearly checkup. The good news- she tested NEGATIVE for heartworms!
Several years ago she tested positive and, due to her size, the vet decided not to try a treatment on her. He suggested giving her a preventative so she wouldn't get more heartworms. However, her chances were iffy. The worms could die and pass out of her body or one could travel to her lungs and kill her. Lucky for me the former happened.
Give your dog heartworm preventatives! It's easy and worth the cost of the pills- as I well know.