Heartworms in Dogs?

Has anyone had a dog that developed heartworms? My dog has been coughing a lot, antibiotics haven't worked, and I'm worried at this point. The vet had mentioned possible heart disease, and I just read heartworms can cause coughing too. I'm taking her to the hospital this weekend but I just want to see if any of you guys has had a dog with heartworms. What was that like? Did they cough?