OK I'm getting a bit nervous here, I have a 6 month old female GSD that got a clean bill of health the last visit to the vet. My question is, she was laying on the floor chewing a rope and all of a sudden just started to pant really heavy? It didn't last long but she did it in her crate as well? I read that this could be heartworm but she was just tested 3 weeks ago. Please tell me something good.